Clinical Theriogenology 2022; 14: 32 Avian reproductive tract diseases and surgical resolutions Scott Echols,a,b,c Brian Speerb aEchols Veterinary Services, Salt Lake City, UT bMedical Center for Birds, Oakley, CA cParrish Creek Veterinary Hospital and Diagnostic Center, Centerville, UT Abstract Reproductive tract disease is a commonplace in avian practice, particularly among female birds. Unique anatomy and physiology of the avian reproductive tract results in a highly productive but poorly accessible organ system. Affected hens are commonly pre- sented with nonspecific lethargy, coelomic swelling and sometimes laying abnormal eggs. Reproductive diseases are less common in male birds; however, they are well described. Although many reproductive tract diseases can be managed medically, there is a definite need for surgical intervention in some cases. Because of internal location, various disease processes and even normal physiologic processes can dramatically alter patient presentations. For this reason, a clear understanding of avian female anato- my and male reproductive tracts is vital to diagnose and treat disorders. This manuscript focuses on recognition and treatment (emphasizing surgical management) of avian reproductive tract diseases. Because of the unique avian reproductive anatomy and frequent need for surgical correction of disorders, the organization of the manuscript starts with descriptions of coelom and basic surgical principles. Keywords: Birds, reproductive anatomy, ovarian and oviductal problems, testicular disease, surgical and medical treatments Introduction Primarily due to high egg producing hens, reproductive tract diseases are common in pet and even commercial avian prac- tice.1 With advances in diagnostics and therapeutics available to birds, many reproductive tract diseases can be medically managed. However, several diseases can only be treated sur- gically. Because of past literature describing procedures such as salpingohysterectomy as ‘difficult and risky’, many practi- tioners are rightfully cautious about performing avian repro- ductive tract surgery.1 As with diagnostics and therapeutics, anesthetic techniques, instrumentation, pain management, a better understanding of respiratory physiology and surgical techniques have all advanced in avian medicine. Due to med- ical and surgical progress and public awareness, avian practi- tioners are being called upon to manage more complex be- havioral, medical, and surgical related problems in birds with greater success.1 Surgeon’s experience and proper instrumentation are vital to minimize tissue trauma, bleeding, and anesthetic time and to improve outcomes. Analgesics should be considered in all surgical cases. Description of anesthetic management, post- surgical care, and analgesics are beyond the scope of this man- uscript and are adequately described. Coelomic anatomy of birds Because of avian reproductive tracts’ location, a basic under- standing of the coelom is beneficial.2,3 Coelom refers to the pri- mordial body cavity lined by mesoderm and formed by fusion of lateral body folds early in embryonic development. Within the coelomic cavity are individual and unique compartments, each lined by mesothelium and capable of producing serosal fluid. ‘Lower’ reptile species have 2 cavities (pericardial and pleuroperitoneal) and more highly developed reptiles have 3 (pericardial, pleural, and peritoneal), whereas birds have 8 distinct coelomic cavities. Interrelationship of these cavities with the respiratory tract is complex. Eight coelomic cavities of birds include, 1 pericardial and 1 intestinal peritoneal cavity (IPC), 2 pleural cavities, and 4 he- patic peritoneal cavities. All visceral organs except right and left liver lobes are contained within IPC. Pericardial cavity is situated ventrally on the midline, just dorsal to sternum and is restrained by fibrous attachments to surrounding structures, most notably sternum. Apex of the sac is intimately associated with and positioned between 2 liver lobes. Parietal pleura surrounding each lung and mesothelial coat- ing of visceral pleura applied to the lung itself form a small, Clinical Theriogenology 2022; 14: 33 potential pleural cavity due to fixed dimensions of avian lung in most species. Parietal and visceral pleura develop fibrous cross connections starting along lung’s ventromedial surface.2 Birds have 5 distinct peritoneal cavities. Four hepatic peritone- al cavities (HPC) surround right and left liver lobes. A single, midline IPC contains most of the gastrointestinal tract, gall bladder (if present), reproductive tract, and spleen. Hepatic peritoneal cavities are composed of 2 paired struc- tures, larger left and right ventral hepatic peritoneal cavities, and much smaller right and left dorsal hepatic peritoneal cavities. HPCs are divided on the midline into right and left entities by the ventral mesentery. In chicken, left dorsal hepat- ic peritoneal cavity communicates with intestinal peritoneal cavity via a small opening that is covered on the IPC side only by abdominal air sacs. A single IPC is centrally located in mid to caudal coelom and contains proventriculus, ventriculus, gall bladder (if present), spleen, intestines, and male or female reproductive tracts. The only coelomic cavity containing air sacs (left and right abdom- inal) is IPC. A ventral midline incision made caudal to the ventriculus leads directly and specifically into IPC, not into ‘coelom’ or ‘coelomic cavity’, and not into respiratory tract. Right and left subpulmonary cavities (air sacs) are structures unique to birds and strictly speaking, are not true coelomic cavities as they are not lined by mesothelium. Their intimate relationships with coelomic cavities, however, require under- standing for the purposes of surgical intervention. Subpulmo- nary cavities predominately include air sac system of birds; cervicocephalic, clavicular, cranial thoracic, and caudal tho- racic air sacs. Surgical principles and patient preparation For coeliotomy, the patient is usually placed in lateral or dorsal recumbency. Birds have a very thin epidermis that is diffusely supplied by capillaries in the dermis, unlike what is observed in mammals. There is less subcutaneous tissue, and dermis is firmly attached to the underlying muscle fascia. Compared to mammals, most blood vessels are comparatively less protected by surrounding tissues, leaving more potential for hemorrhage. Body contour feathers are easily plucked in the direction of their growth once the patient is anesthetized. Some species of bird may have particularly thin skin, predis- posing them to iatrogenic tears when feathers are plucked. Water soluble gel or masking tape may be used to keep down and contour feathers under control. Surgical preparation of the skin is performed with betadine, chlorhexidine, and/or isopropyl alcohol. Patient preparation with excessive amounts of saline or alcohol can predispose the patient to hypother- mia. Draping the patient as quickly as possible with clear plas- tic drapes helps to retain heat better than using cloth drapes. Clear, transparent plastic drapes also allow respiration to be monitored during the procedure. Supplemental heat (warm water bottles, circulating warm water blankets, heat lamps, and forced warm air) should be provided to the patient. Surgical instruments Magnification is a common and important component of many coelomic procedures, viewing the frequent small pa- tient size and resultant needs for fine instrumentation and microsurgical skills. Magnification makes hand tremors more apparent, and necessitates slow, deliberate motions for great- est efficiency. This in turn can result in a slower surgical pace for the procedure(s) that may require increased detail to an- esthesia protocols and patient support methods used during the procedure. Although magnification greatly adds to visual- ization of the direct surgical field, it limits surgeon’s ability to visualize peripheral fields. This makes an assistant necessary when utilizing the operating microscope, and helpful when utilizing magnifying loupes. Fine and delicate instruments are essential for avian surgery. Gauze pads (2 x 2) can be cut from standard 4 x 4 sponges or can be specifically purchased. A basic surgery pack should contain a long jeweler’s forceps with fine delicate tip but flat handles, round handled microsurgical forceps, a Castroviejo pen needle holder of at least 5.25 inch length, with fine jaws and rounded handles, and a spring-loaded microsurgical scis- sors of at least 7 inches with rounded handles. Sterile cotton tipped applicators should also be available for point hemosta- sis and blunt tissue retraction. Hemostatic clips are also useful and come in a variety of sizes. Right angled appliers are also available for special applications in deep cavities. Heiss blunt retractors, Alm retractors and Ring retractors are suitable for use in medium to smaller species.4 Halsted’s principles of surgery should be followed when per- forming surgery in any species. These principles are itemized below: Gentle handling of tissue Meticulous hemostasis Preservation of blood supply Strict aseptic technique Minimum tension on tissues Accurate tissue apposition Obliteration of dead space Surgical approaches to coelomic cavities Approaches commonly made include a ventral midline ap- proach, a midline-L approach, a midline-T approach, and left and right lateral approaches that may or may not include L flaps. Modifications of these basic approaches also can be used, depending on the patient and desired exposure of surgi- cal site. These surgical approaches generally require the bird to be in dorsal or lateral recumbency. If ascites or substantial or- ganomegaly is present, elevating the proximal half of the body may help reduce pressure on heart, lungs, and more cranial air sacs, improving ventilation. To specifically enter the IPC directly from the body wall with- out penetrating an air sac, use 1 of 2 approaches. A midline, paramedian or transverse incision in the ventral body wall will enter the IPC when made caudal to posthepatic septum Clinical Theriogenology 2022; 14: 34 end and medial to distal limits of caudal thoracic and abdom- inal air sacs. The other site for direct entry from the body wall to IPC is the left or right postischial approach. A small skin incision dorsal to pubis and just caudal to ischium allows a blunt puncture through the thin body wall dorsolateral to co- prodeum.2,3 Female reproductive tract diseases Understanding the avian female reproductive tract anatomy, especially, its blood supply and drainage, is vital to proper diagnosis and treatment (especially surgery). During sexual and egg laying activity, blood supply to ovary and oviduct can be substantial. Due to potential vascularity, being mindful of local blood supply and minimizing bleeding can often deter- mine the outcome. Focus will be given to basic structure and vasculature of ovary and oviduct. If possible, the following surgeries should be performed when the female is reproduc- tively inactive as blood supply is often reduced. Ovarian anatomy A right and left ovary and oviduct are present in the embry- ologic stages of all chicks, but the right half regresses due to Müllerian inhibiting substance action prior to hatch. Al- though a persistent right oviduct with or without a functional right ovary is present in some birds, most birds only have a left female reproductive system. Brown kiwi is an exception and normally has a functional left and right ovary. Interestingly, in chicken about 480,000 oocytes develop by hatching. Of these, ~ 2,000 are visible as a mass of small ova and only 250 - 500 reach maturity and ovulate within the lifespan of domestic species and even fewer mature in wild species.1 Ovarian folli- cles are arranged hierarchically. Largest follicle (F1) will ovu- late on the next day, second largest (F2) on the following day, and so on. Ovary is attached to the cranial renal division and dorsal body wall by the mesovarian ligament and receives its blood supply from ovarian artery that originates off the left cranial renal artery or directly off the aorta. Accessory ovarian arteries may also arise from other adjacent arteries. Ovarian artery further divides into many branches with the greatest blood flow di- rected to any large preovulatory follicles present. Ovarian veins unite into main anterior and posterior veins that drain into the overlying vena cava. Multiple left ovarian veins may exist and drain into the cranial oviductal vein that enter the com- mon iliac vein and finally into the caudal vena cava.5 In first author’s experience, the cranial oviductal vein is too short or poorly developed to recognize grossly. Instead, multiple short veins seem to enter the common iliac vein over the length of its contact with the dorsum (base) of the ovary. Ovarian diseases Cystic ovarian disease Although the cause is often unknown, cystic ovarian disease has been reported in several bird species. Cystic ovaries are sometimes secondary to neoplasia. Depending on their size ovarian cysts can be observed incidentally; small ovarian cysts can cause none to mild coelomic distension whereas large and/or numerous cysts can be associated with readily iden- tifiable ascites. Many cysts are large and can often be diag- nosed noninvasively using ultrasonography, CT, and/or MRI. Cysts can be treated by ultrasonography guided transabdom- inal aspiration or more directly via celiotomy or endoscopy. If collected, evaluate the fluid for evidence of infection or other abnormalities. Severe cystic disease may require partial or complete ovariectomy and should include biopsy for his- topathological evaluation. Leuprolide acetate has also been suggested to reduce or resolve ovarian cysts in birds and may offer a noninvasive treatment option.1 Use of desorelin (a GnRH agonist) has also been recommended anecdotally.6 It is important to note that no peer reviewed publications have documented the benefit of using either leuprolide acetate or deslorelin to treat ovarian cysts in birds. In authors’ experi- ence, aspiration or physical removal is the only means to re- move ovarian cysts, if clinically indicated. Oophoritis Ovarian infections can be life-threatening and are often as- sociated with septicemia. Salmonella pullorum is the etiologic agent of pullorum disease of poultry and most frequently af- fects ovary.1 Clinically affected birds usually have more severe, albeit general signs of illness and if not treated quickly, perito- nitis and death may result. Irregular follicular shapes and sizes noted on ultrasonography, MRI or CT may be related to in- fectious oophoritis or neoplastic disease. Abnormally shaped, colored or partially ruptured follicles identified during celiot- omy or endoscopy should be carefully aspirated for cytolog- ical and microbiological analysis and patients treated with broad-spectrum antibiotics, initiated pending culture results. Storz injection needle with Teflon guide (Karl Storz Veterinary Endoscopy America, Goleta, CA) is particularly useful as an endoscopic means to aspirate ovarian follicles. If possible, completely drain the abscessed follicle(s), being careful not to contaminate coelom. Partial or complete ovariectomy may be required for chronically infected and caseated follicles. Neoplasia of ovary and oviduct Ovarian neoplasia is reported with some frequency in birds and can be associated with egg retention, ascites, cystic ovar- ian disease, medullary hyperostosis, coelomic hernias, ovi- ductal impaction, and general malaise. Thirty eight percent of USDA inspection service mature fowl condemnation is the result of neoplastic disease, with most from the genital tract; ‘there is indeed a unique propensity for hens (poultry) to develop cancer of the reproductive system in the almost total absence of tumors at other sites’.7 Granulosa cell tumors and ovarian adenocarcinomas are most frequently reported but carcinomas, leiomyosarcomas/leiomyomas, adenomas, teratomas, dysgerminomas, fibrosarcomas, lipomas, and lym- phomatosis have all been identified in bird ovaries. Oviductal tumors are less common than ovarian neoplasia and include adenocarcinomas/adenomas, adenomatous hyperplasia, car- cinoma, and carcinomatosis.1 Granulosa cell tumors and possibly other reproductive tract neoplasms may be functional and cause increased plasma hormone concentrations. Granulosa cell tumors are common in older female budgerigars (Melopsittacus undulatus) and may Clinical Theriogenology 2022; 14: 35 be functional resulting in hyperestrogenism.8 Polyostotic (medullary) hyperostosis may also result as a paraneoplastic syndrome with functional ovarian and oviductal neoplasms. Interestingly, hyperestrogenism did not cause polyostotic hy- perostosis in several species of birds with various neoplastic and nonneoplastic reproductive tract diseases.9 Clinical signs vary and are nonspecific for most reproductive tract diseases and include coelomic swelling, dyspnea, ascites, poor or altered reproductive performance and lethargy. If the mass compresses the overlying lumbar or sacral nerve plexus- es, lameness (usually left sided) may be observed. Diagnosis can be further supported using radiography, ultrasonography, MRI, CT, exploratory celiotomy, endoscopy, and biopsy. Once a definitive diagnosis is made, options for therapy include chemotherapy, radiation therapy, and partial or complete ova- riectomy, but all carry a guarded prognosis if the neoplastic tissue cannot be completely removed. Ovarian surgery Partial and ‘complete’ ovariectomy Ovariectomy in hens is a challenging and oftentimes high-risk procedure. Ovariectomy has been used in many poultry stud- ies and this procedure is mentioned throughout literature. Unfortunately, most papers poorly describe specific details of ovariectomy or its complications. To cite a few examples; it was stated that ovariectomized birds ‘lost considerably more blood than sham-operated hens’.10 Incompletely ovariecto- mized turkeys (number not provided) were excluded.11 Ova- riectomy has also been described by ‘destroying ovarian tissue by local application of small pieces of dry ice.’12 Although it has been stated that the short stalk of cranial renal artery is what makes ovariectomy difficult, first author sug- gested that the intimate and lengthy attachment to the overly- ing common iliac vein is what makes this procedure risky.1 As discussed, multiple small veins often connect directly into the common iliac vein. It is often venous, and not arterial, bleed- ing from a lacerated common iliac vein that usually causes life-threatening hemorrhage during ovariectomy. As with ovi- duct, ovary can dramatically change in size and vascularity with sexual and egg laying activity. As a result, every attempt should be made to medically or behaviorally downregulate bird’s reproductive activity to reduce vascularity to ovary. Of- tentimes, diseases requiring ovariectomy do not allow attend- ing clinician’s time to ‘condition’ the avian patient prior to surgery. Ovariectomy should be reserved for ovarian diseases such as cancer, chronic recurring cysts, persistent follicular activ- ity, oophoritis and other diseases that cannot be managed medically and are life-threatening without further treatment. Whereas some birds such as cockatiels appear to stop ovu- lating after the salpingohysterectomy, other species such as ducks may continue chronic and possibly life-threatening ovulation necessitating hormonal therapy or ovariectomy.13 Behavioral and/or medical management, discussed elsewhere in literature, is necessary after a partial ovariectomy, to prevent internal or ectopic ovulation. A cranial left lateral celiotomy often provides the best left ova- ry exposure. Clean the surgical field of fluid and debris to best visualize the ovary and its vasculature. Surrounding organs may need to be gently retracted using moistened cotton-tip applicators or other nontraumatic instruments. A ventral mid- line, singly or combined with a transverse approach, can also be used to reach the ovary from a caudal approach. First step to ovariectomy is to debulk its mass, regardless of size, in order to visualize the ovarian attachment to the over- lying common iliac vein and any other vessels. If the ovary is inactive or juvenile, little debulking is needed. If present, remove large preovulatory follicles by twirling as discussed below. Aspirate and drain any cystic follicles present, being careful not to spill contents into the coelomic cavity, especial- ly if there is concern of oophoritis. When aspirating follicles, guide a small gauge (23 - 25) butterfly catheter needle into the most visibly avascular portion to reduce hemorrhage and have an assistant provide distant suction. Using this aspira- tion technique, a substantial amount of an active and/or cys- tic ovary can be debulked. Blood filled follicles may represent previously ruptured blood vessels from an invasive mass and warrants caution when attempting debulking. Alternatively, large ovarian follicles can be twirled using cot- ton tip applicators. Use the cotton tip applicators to rotate the follicle in 1 direction continuously until it separates from its pedicle. This may require 15 - 30 full rotations until the folli- cle is free. Once free, simply remove the follicle. Once the fluid component is minimized, progressively clamp or hemostatically clip the ovarian mass closer to its base. When used properly, angled DeBakey neonatal vascular clamps are atraumatic, will rest in the surgical site without obstructing view and seem to provide some hemostasis to the ovarian mass. Once a section of the mass is hemostatically clipped or clamped, surgically excise or cauterize and remove the ven- tral-most ovarian segment. Reassess the mass and move the clamp (or place new hemostatic clips) closer to the base and repeat the excision process. This process is repeated until the overlying vasculature is clearly identified, and the course of the common iliac vein is observed. Once the mass has been debulked, several options exist for complete or partial ovariectomy. An electrocautery ball elec- trode was used effectively to coagulate ovarian follicles in immature females.14 Similar procedure resulted in ovarian re- generation and subsequent ovulatory activity in mature hens. Some juvenile bird ovaries were gently ‘peeled’ in toto from caudal to cranial off its dorsal attachments with no or min- imal bleeding.6 In these cases, ovarian caudal end is grasped with angled hemostats and pulled in a cranial direction with a clear separation, and minimal effort, from the dorsally lo- cated common iliac vein. If attempting this procedure, stop if any resistance is noted to prevent tearing the overlying vein. Another technique with juvenile or sufficiently debulked ova- ries is to place hemoclips in the potential space between the ovarian base and the common iliac vein. Gently lift the ovar- ian caudal pole and place a small to medium hemostatic clip from caudal to cranial across the ovarian vascular supply. Al- though difficult without good exposure, a last hemostatic clip Clinical Theriogenology 2022; 14: 36 can be placed from cranial to caudal in the same manner in an attempt to ligate the more cranially located ovarian artery. With the blood supply adequately clamped, the ovary can be gently shaved off with precise radiosurgery using an Ellman B ‘loop’ series or blade electrode (Ellman International, Inc., New York, NY) or left to die without a blood supply. First au- thor has successfully performed ovariectomies in adult hens using this technique. Obvious complications include hemor- rhage when trying to remove the hemostatically clipped ova- ry and inadequate, blind, placement of the hemostatic clips. Second author has used another approach when the ovarian attachment to the overlying common iliac vein is too long to hemoclip or there is erosion into the overlying vessel and the entire ovary must be removed for the bird’s survival (as with otherwise untreatable cancer).6 Debulk the ovarian mass as described above. Once clearly identified, hemostatically clip the common iliac vein just caudal to the ovary and cranial to its junction with caudal renal vein. Next, hemostatically clip the common iliac vein just cranial to the ovary and caudal to its junction with caudal vena cava. If performed properly, the ovarian artery and common iliac veins are effectively clamped, allowing one to carefully dissect the entire ovary from the overlying vessel(s). If needed, the ventral wall of the common iliac vessel can be safely removed. There is the real potential of damaging left adrenal gland, substantially altering blood flow through the renal portal system and the cranial renal division and causing physical damage to overlying kidney and lumbar and/or sacral nerve plexus(es). None of the above described ovariectomy procedures have been satisfactorily studied in pet bird species and each carries a marked risk to patient. With each procedure, closure is rou- tine. More often, a partial ovariectomy is performed and only the abnormal ovarian tissue is removed. Oviductal anatomy Oviduct, or salpinx, develops from the left Müllerian duct and can be divided into 5 regions.15 Cranial most region is the infundibulum (site of fertilization) that engulfs the ovulated ovum. Next, ovum moves into the largest region, the mag- num. Magnum produces albumin that surrounds the develop- ing egg. As the ovum progresses caudally it enters the isthmus where the inner and outer shell membranes are formed. Egg is ‘plumped’ with water and solutes, calcified to form a shell and pigments are deposited during its prolonged stay in the shell gland or ‘uterus’. Shell gland transfers the complete egg through the uterovaginal sphincter and into vagina. Uterovag- inal area contains sperm storage tubules allowing many spe- cies to store viable sperm for prolonged periods (> 21 days in turkey hens).15 Vagina terminates at cloaca and coordinates with shell gland to ultimately expel egg. Oviduct is suspended within the coelomic cavity via a dorsal and ventral ligament.15,16 Cranial, middle, and caudal oviduc- tal arteries running in the dorsal mesentery, supply blood to oviduct. Origins of each vessel vary between species, but some generalization can be made.16 Cranial oviductal artery arises from the left cranial renal artery, aorta, or external iliac artery. Middle oviductal artery arises from the left ischiatic artery or its branch, the medial renal artery. Finally, the caudal oviduc- tal artery arises from the left internal iliac artery or the puden- dal artery. Veins draining the cranial oviduct empty into cau- dal vena cava (via common iliac vein), whereas those draining the caudal oviduct enter the renal portal or hepatic systems. Oviductal diseases Congenital defects Congenital defects have been identified in birds and include large cysts on a rudimentary oviduct of a budgerigar and dis- continuous or atretic oviducts in domestic fowl. Persistence of right ovary and/or oviduct has been reported in numerous species.1 First author has observed an association between the presence of right oviducts and nonspecific reproductive tract problems in hens (e.g. cystic ovarian follicles, and excessive egg laying). Cystic dilatation is common with persistent right oviducts in poultry species. Each defect should be evaluated on a case-by-case basis and may require surgical modification or removal based on associated clinical signs. Ectopic ovulation, ectopic eggs, and egg yolk peritonitis Ectopic ovulation occurs when infundibulum fails to engulf an ovum or fails to retain ovum because of oviductal rupture or reverse peristalsis. Ectopic ovum is not well developed. Po- tential causes include infundibulum failure from oviductal fat, trauma or disease, exuberant reverse peristalsis, and ovi- ductal disease. Ectopic ovulation occurs frequently and has been reported in 28.6% of necropsied birds from 9 orders.17 Authors have also observed ectopic ovulation associated with a persistent right oviduct in several avian species. Ectopic ovu- lation usually results in mild, self-resolving, sterile yolk coelo- mitis and usually requires no or minimal supportive therapy (fluid therapy, anti-inflammatories, and others). Partially and completely shelled ectopic eggs result when a de- veloping egg enters the ceolomic cavity through an oviductal rupture or via reverse peristalsis from oviductal or even cloacal disease. Anything affecting the oviduct function such as cloa- cal or oviductal masses (including egg binding, impactions, and neoplasia), salpingitis, cystic hyperplasia, and oddly shaped or large eggs can result in ectopic eggs. A large ectopic egg can cause a penguin-like stance and is often associated with ascites and varying degrees of depression in many birds. Diagnosis can often be suspected using radiography, ultraso- nography, MRI, CT, and sometimes endoscopy (depending on how much debris is in the coelom); however, celiotomy is often required for definitive diagnosis. Ectopic eggs should always be considered when conservative therapy for egg bind- ing fails. Partially and fully formed ectopic eggs should be sur- gically removed after stabilizing the patient and determining underlying cause(s). Severe sterile and life-threatening septic egg yolk peritonitis may also result from ectopic ovulation or eggs. Acute egg yolk peritonitis may result in marked depression, anorexia, and as- cites and rarely, respiratory distress and death. Secondary dis- eases resulting from sterile and septic yolk peritonitis include pancreatitis, splenitis, yolk-thromboembolic’ disease, hepati- tis, nephritis, and coelomic adhesions. Septic yolk peritonitis may obviously result in or from septicemia and has been most noted with coliforms such as Escherichia coli, Yersinia pseudo- Clinical Theriogenology 2022; 14: 37 tuberculosis and Staphylococcus spp.18 Coelomocentesis and cytologic fluid analysis and culture are used to definitively di- agnose yolk peritonitis. If needed, celiotomy and endoscopy can be used to assess the associated internal pathology. Severe egg yolk peritonitis, especially when associated with bacteria, includes aggressive supportive care, antimicrobials, identify- ing and resolving causative factors if possible and occasionally may require surgical removal, irrigation of the caudal coelo- mic cavity and placing a drain tube. If irrigation is used, be careful to prevent fluid from entering the respiratory system. Egg binding and dystocia Egg binding, dystocia and other reproductive tract diseases (e.g. egg yolk peritonitis and cystic ovary) are common prob- lems in pet bird medicine. Oviposition is the expulsion of egg from the oviduct and is conducted by vigorous contraction of the uterine muscles and peristalsis of the vagina. Egg binding is simply defined as prolonged oviposition (egg is arrested in oviduct longer than normal for the given species) whereas dys- tocia implies the developing egg is within the distal oviduct either obstructing the cloaca or prolapsed through the ovi- duct-cloacal opening. Dystocia is often more advanced than egg binding alone, has many potential causes and is common- ly associated with functional (malformed eggs, cloacal mass- es, and obesity), metabolic (calcium imbalance and nutrition- al deficiencies), environmental (temperature changes, lack of exercise and other stressors) and hereditary diseases. Captive conditions (readily available food, water, light, appro- priate temperature, and frequently a constant mate) tend to promote reproductive activity in pet birds. As a result, exces- sive egg laying, prolonged broody behavior and reproductive tract disease are common, especially, in smaller birds such as cockatiels and budgerigars. Secondary complications of exces- sive egg laying include egg binding, dystocia, egg yolk perito- nitis, acquired metabolic bone disease, pathologic fractures, prolapsed cloaca and oviduct, and salpingitis. Additionally, some of these ‘over productive’ hens are on a poor diet, are nutritionally depleted and have other underlying diseases complicating their reproductive problem. Several options are available for treatment of eggbound birds. Most birds can produce a shelled egg from a follicle in < 24 hours. Although knowledge of individual species is import- ant, most birds that have an egg present for > 24 hours are considered ‘egg bound’. Eggs place pressure on surrounding organs, especially the kidneys, and can cause progressive problems the longer egg binding continues. Smaller the bird, the more serious egg binding becomes. Stable birds can often be managed conservatively (pain management, fluid therapy, supplemental heat, nutritional and hormonal support, and others) to help the patient deliver the bound egg. If needed, the egg can be manually manipulated or crushed to facilitate removal. Following techniques should only be con- sidered if more conservative therapy fails, or pressure must be relieved immediately. Due to the potential for substantial tissue damage, antibiotics are often indicated. One can gently push the egg toward the cloaca and (hopefully) out. Prelubri- cate the cloaca with a water-soluble lubricant (H-R Lubricant, Carter Products, New York, NY) to facilitate the egg’s removal. Another option is to aspirate the egg’s contents (pass an 18 - 20 gauge needle through the cloaca if the egg is visualized, and aspirate) and then crush the egg with digital pressure. If no adhesions or oviductal torsion, masses or tear(s) are pres- ent, the bird will oftentimes pass the crushed egg within 24 hours. Aspirating the egg through the coelomic wall results in minimal to severe (laceration) trauma to the oviduct and is not recommended. Salpingohysterectomy is needed in other- wise nonresponsive cases. Once egg binding has been resolved, every attempt should be made to downregulate the bird’s reproductive system. Simple methods include removing the mate, nest box(es) or favor- ite toy(s) when present, changing the diet (usually improving quality), decreasing the photoperiod to a maximum of 10 - 12 hours a day, modifying the cage setup and toys and in general, altering the bird’s normal daily activities. GnRH agonists (le- uprolide acetate and deslorelin) may also be beneficial. The intent herein is to limit environmental influences on repro- ductive activity and stop the bird’s desire to breed. As supported in domestic fowl, once incubation behavior is established, the ovarian hormones are not required for maintenance or the readiness to brood day-old chicks.19 This implies that drugs intended to decrease production of ovar- ian hormones, such as leuprolide acetate, alone may not be sufficient to stop a bird’s reproductive behaviors. This further supports the need for environmental, dietary, and other be- havioral modifications with leuprolide acetate use to decrease reproductive activity in birds. Oviductal cystic hyperplasia Cystic oviductal hyperplasia or dilatation has been reported in budgerigars, other psittacines and poultry.1 Although little etiologic information is forwarded, cysts may occur second- ary to improper formation of the oviduct. Affected oviducts are often thickened with white to beige masses and distended with brown or white mucoid fluid. Affected birds may show no signs (and the oviductal hyperplasia is discovered inciden- tally) or signs typical of reproductive tract disease. Antimicro- bials may be tried if organisms are recovered from aspirated samples, otherwise salpingohysterectomy is indicated. Oviductal impaction An impacted oviduct is usually distended and simply con- tains caseated material and misshapen, ruptured, soft-shelled, partially, or fully formed eggs. Potential causes include excess mucin and albumin secretion secondary to inspissated egg material and cystic hyperplasia. Salpingitis is often found con- comitantly, especially in older birds. Metritis, salpingitis, egg binding, dystocia and neoplasia commonly precede oviductal impactions. Typical of most reproductive tract diseases, vague clinical signs with or without coelomic swelling and ascites are common with oviductal impaction. Some birds may show persistent ‘broodiness’ with recent cessation of egg laying. Oviductal impactions have been reported in budgerigars, cockatiels, ca- naries, African grey parrots (Psittacus erithacus) and poultry.1 Definitive diagnosis is made at celiotomy or sometimes via Clinical Theriogenology 2022; 14: 38 ultrasonography, MRI, CT, and endoscopy with aspiration of the oviductal contents. Chronic oviductal impactions may be observed incidentally during exploratory celiotomy and are often associated with a history of sudden cessation of egg lay- ing several months or years prior to presentation. Acute im- pactions may be treated by salpingotomy, culture and appro- priate antibiotic use and oviductal flushing, whereas severe or chronic disease are best treated with salpingohysterectomy. Oviductal prolapse Powerful coelomic contractions combined with the process of oviposition can result in oviductal prolapse which is often secondary to dystocia. Predisposing factors may include large or abnormally shaped eggs, malnutrition, general debilitation and systemic illness, disease of the oviduct and sometimes, normal egg laying. In turkeys selected for high meat yield, decreased vaginal collagen has been associated with uterine prolapse.1 Uterus is most commonly prolapsed; however, va- gina and other portions of oviduct may also prolapse. Cloacal prolapsed tissue, if present, should be distinguished from the oviductal prolapse. Because the exposed tissue can rapidly become devitalized and infected, aggressive treatment with warm saline flush- es, antibiotics and replacement of the prolapsed oviduct is warranted. If the prolapsed oviduct is edematous, topical dextrose, dimethyl sulfoxide (DMSO) and/or steroids may be needed to reduce the swelling. If an egg is present in the prolapsed or coelomic oviductal tissue, ovocentesis and digi- tal crushing is often needed to reduce associated pressure and aid in egg-shell removal. After stabilizing the bird, remove the egg medically if possible and replace the prolapsed tissue. Two transcloacal sutures may be required to prevent the immediate recurrence of prolapsed tissue. Surgical removal is indicated when the oviduct is necrotic and/or the egg (or its fragmented shell) cannot be removed medically or pass on its own. If an oviductal torsion is present caudal to egg (within the oviduct), attempting to force deliver the egg will often result in further damage. Oviductal torsion, neoplasia, adhesions, and other anatomic disorders should be considered if a bound egg cannot be delivered without force- ful techniques and surgical options should be pursued. Oviductal torsion Oviductal torsion has been reported infrequently as a cause of egg binding. Oviductal torsion may occur after a tear of the dorsal, and possibly ventral, oviductal ligament(s). In 4 reported cases, all birds presented with signs of egg binding and/or general lethargy and had a history of previously lay- ing ‘many eggs’ prior to the oviductal torsion.20 A cockatiel presented thin with lethargy, depression and coelomic dis- tension, and died despite emergency therapy. Of the 3 birds presented live, 2 cockatiels were treated with salpingohysterec- tomy and 1 eclectus parrot (Eclectus roratus vosmaeri) was treat- ed with a hysterotomy (salpingotomy), egg removal, torsion correction, and subsequent closure of the oviductal ligament tear. All birds recovered uneventfully from surgery. Eclectus parrot successfully laid normal clutches after surgery. Salpingitis and metritis Salpingitis, inflammation of the oviduct or salpinx, is com- mon in birds. In poultry, salpingitis has been listed as the most prevalent form of reproductive tract disease. E. coli in- fections are common in poultry and can cause salpingitis, but Streptococcus spp., Mycoplasma gallisepticum, Acinetobacter spp., Corynebacterium spp., Salmonella spp., and Pasteurella mul- tocida have all been implicated from various species.1 Some ground-nesting species, such as Anseriformes and emus, may develop nonlactose fermenting, gram negative (Pseudomonas aeruginosa, Proteus mirabilis, P. vulgaris) salpingitis. Noninfec- tious salpingitis can also occur, especially with chronic, ster- ile oviductal impactions. Metritis is inflammation within the uterine portion of the oviduct and may result from or cause egg binding, chronic oviductal impaction and rupture, coelo- mitis, and septicemia. Prosthogonimus ovatus and other related trematodes (flukes) can inhabit the oviduct of Anseriformes and Galliformes and result in salpingitis with heavy infesta- tions. Other infectious agents ascending from the vagina or cloaca or descending from air sacculitis, pneumonia and sep- ticemia can also cause salpingitis. Specifically, in poultry, vent cannibalism has been implicated as a precursor to salpingitis. Birds with nonseptic salpingitis or metritis often have vague signs of illness, whereas septic birds are usually clinically very ill. A distinctive feature is that egg-shell deformities and em- bryonic and neonatal infections are often secondary to metri- tis. Presumptive diagnosis may be made with ultrasonography, MRI, CT, and occasionally with endoscopy. Definitive diagno- sis is made during celiotomy or endoscopy with aspiration of oviductal fluid for cytologic and microbiologic analysis or if the oviduct has no liquid contents, biopsy with culture. Base antibiotic use on culture and sensitivity results. If trying to spare the oviduct, repeated endoscopic evaluation, direct and indirect oviductal flushing, and long-term antimicrobials are recommended. Salpingohysterectomy is indicated for severe cases or those nonresponsive to appropriate antimicrobials. Oviductal surgery Salpingohysterectomy Salpingohysterectomy, is the surgical removal of oviduct, from infundibulum to uterus, and is indicated for chronic egg lay- ing and any oviduct disease that cannot be medically managed and is reported as the ‘therapy of choice for overproduction of eggs.’1 Every attempt should be made to understand the bird’s overall health status prior to surgery, as the patient should ide- ally be stable. Birds with septic yolk-peritonitis generally carry a poor prognosis. Patients with underlying health problems such as various lung, liver, and kidney diseases, can also com- plicate surgery. Otherwise, healthy salpingohysterectomy can- didates typically do well and surgery is often straightforward especially when the oviduct is small and inactive. Oviductal hypertrophy occurs secondary to elevated estrogen concentra- tions during sexual activity and can take up most of the left side of the IPC. This oviductal hypertrophy includes increased vascularity and risk of bleeding during surgery. If the patient is stable, time permits, and increased reproductive tract vascular- ity is suspected, the authors will ‘condition’ the bird prior to surgery. ‘Conditioning’ includes improving nutritional status (if necessary) and attempting to downregulate the bird’s sex- Clinical Theriogenology 2022; 14: 39 ual cycle as discussed under ‘egg binding and dystocia’. This process may take weeks to months and often results in de- creased vascularity and lower patient morbidity. In first author’s experience, a left lateral approach offers the best exposure to the left ovary and oviduct, however a ventral midline approach can also be used and is best for overall re- productive tract evaluation. Perform a left lateral celiotomy. After incising through the left abdominal air sac, ovary and oviduct are readily visible. Gently retract the cranial oviduct (infundibulum area) out the incision and hemostatic clip or cauterize suspensory ligament vessels as needed. Closer the bird is to laying, the larger the vessels present. Depending on the size, the cranial, middle and/or caudal oviductal artery(ies) may need to be hemo- clipped or cauterized. Once visualized, hemoclip the base of the oviduct just proximal to its junction with the cloaca. Ex- cise the oviduct. Well-developed preovulatory follicles (F1 and F2 +/- F3, and F4) may pose a risk for intra-coelomic ovulation and can usually be easily removed as described for ‘ovarian surgery.’ If the follicle has a well-developed vascular pedicle, use hemo- clips and then excise the follicle or twirl the follicle. Domestic chickens have a pause in laying that increased with the num- ber of follicles removed compared to sham operated hens.21 Cystic follicles should either be aspirated (drained) or re- moved. Whereas normal follicles have a yellow appearance and are filled with thick yolk, cystic follicles are pale to trans- lucent and generally contain clear watery fluid. If the follicle is accidentally incised, yolk will leak into the coelom. Simply ‘mop up’ excess yolk and other fluid if present. Collect culture and samples for histopathologic evaluation as needed. An endoscopic approach to salpingohysterectomy of juvenile cockatiels has been described.22 A left lateral coelomic endo- scopic approach (left leg pulled caudally) was performed on juvenile (3 - 11 months) cockatiels. Once visualized, the sup- porting ligament of the infundibulum was carefully pulled laterally toward the coelomic entry site using flexible endo- scopic grasping forceps (Karl Storz Veterinary Endoscopy, Inc., Goleta, CA). This action broke down the supporting structures (ventral and dorsal suspensory ligaments of the cranial ovi- duct and uterus) and separated the salpinx (oviduct) from the overlying kidney, caudal vena cava and left ureter. Next, a cotton-tipped applicator was placed in the cloaca and was used to better visualize the uterus-cloacal junction and ensure the salpinx was ‘peeled’ from the surrounding tissues. Salpinx was exteriorized and then crushed and cut with microsurgi- cal forceps and scissors, respectively, at the point of exit from the coelomic cavity, just cranial to the uterovaginal sphincter. Endoscope was replaced to check for hemorrhage and closure was routine. Endoscopic salpingohysterectomy has several distinct benefits and limitations. As indicated,22 this procedure was acceptable in juvenile birds due to a poorly developed blood supply of the oviduct and that if attempted in mature, egg-producing cockatiels, may result in fatal hemorrhage. Additionally, this procedure required an endoscope and 2 surgeons. Although the endoscopic surgery was limited to young birds, there was minimal hemorrhage and could be performed safely and quickly (estimated to take < 10 minutes with experience) and offers an option for juvenile salpingohysterectomy.22 Caesarian section and reproductive tract sparing Caesarian section is indicated when the bird’s reproductive capabilities need to be spared and is typically limited to egg binding with an otherwise normal, or minimally diseased oviduct. Depending on the location of the egg, a caudal left lateral or ventral midline approach is used. Oviduct should be incised directly over the bound egg and away from prominent blood vessels. After removing the egg, inspect the oviduct for other abnormalities and collect biopsies and cultures as need- ed. Close the oviduct in a single simple interrupted or con- tinuous layer using fine (4 - 0 or smaller) absorbable suture material. Coelomic closure is standard. Authors recommend resting the hen from reproductive stimuli for 2 - 4 weeks or longer as dictated by culture and/or histopathologic results. Male reproductive tract diseases Compared to females, male reproductive diseases are less fre- quently reported; however, they are well described. A clear un- derstanding of the anatomy is essential to make a diagnosis and to properly treat conditions identified. Medical and sur- gical management of male reproductive tract diseases, capon- ization, and vasectomy are described. Testicular anatomy Reproductive anatomy of most male birds consists of 3 main gross structures: testes, epididymis, and ductus deferens. Some birds also possess a phallus. Paired testes are located ventral to their respective left or right cranial renal division. Mesor- chium connects the testes to the dorsal body wall. Left testis is typically larger than the right in most young birds, but this relationship can change as the bird ages. In seasonal breeders, such as some passerines, testes can increase 300 - 500 times in size and should not be interpreted as neoplasia. Large active testes can also be readily evident radiographically. In addition to size, the color of the testes can also change with fluctuat- ing hormone concentrations ranging from black in the sex- ually immature or inactive cockatoos to white or yellow in the chicken.1 Epididymis is located at the testicular hilus, or dorsomedial aspect of testis. Ductus deferens continue from epididymis as highly convoluted tubes running lateral to and alongside the ureters and then terminate at the urodeum as a papillae ventral to ureteral ostium. Testicular artery arises from the cranial renal artery and pro- vides most of the arterial blood supply to testis. An accesso- ry testicular artery may arise directly from the aorta. Venous drainage is returned either directly to caudal vena cava or forms a common stem with adrenal veins. In Pekin drakes (Anas platyrhynchos), 2 testicular veins empty directly into cau- dal vena cava.23 Given the diversity within the class Aves, it is likely that multiple variations of the testicular vasculature exist. Clinical Theriogenology 2022; 14: 40 Although most birds lack a copulatory organ, some birds pos- sess a nonprotrusible (Galliformes) or protrusible (ratites and Anseriformes) phallus. Domestic chickens and turkeys have a nonintromittent phallus, consisting of a median and 2 lateral phallic bodies, on the floor of the lip of the vent. Lymphatic flow through the phallic bodies and their laterally associated lymphatic folds result in tumescence. Because the lymphatic folds and lateral phallic bodies accumulate more fluid than the median body, phallus everts during tumescence producing a groove for semen to travel. Semen is deposited when phallus contacts the hen’s everted oviductal opening. Male avian reproductive system diseases Orchitis Inflammation of the testis, or orchitis, is usually due to bac- terial infections and may originate from septicemia, renal obstruction, cloacitis or even prolapsed or ulcerated phalli. Affected birds may show signs of septicemia. However, first au- thor has seen cases of focal orchitis with no associated clinical signs or reduced fertility only. Orchitis may be diagnosed via cytology and/or microbiologic analysis via aspiration through endoscopy or celiotomy when whole testis appears abnormal or, biopsy when focal lesions are seen. Ultrasonography and contrast CT or MRI may help isolate lesions within the testis. Initial treatment for bacterial orchitis should include antibi- otics based on culture and sensitivity results. If a focal gran- ulomatous lesion is observed and appropriate antimicrobials have proven ineffective, the testis can be partially ablated. Clamp with hemostats or surgically clip the testicular tissue dorsal (towards the blood supply) to the lesion(s) and remove using cold excision, laser, or radiosurgery. Avian testicular tis- sue has great regenerative capabilities and may redevelop fol- lowing partial ablation. Enbloc surgical removal of the affect- ed testicle is indicated for diffuse, nonmedically responsive orchitis. Testicular neoplasia Avian testicular neoplasia most commonly includes Serto- li and interstitial cell tumors, seminomas, teratomas, and lymphoproliferative diseases. Sertoli cell tumors appear to be more prevalent testicular neoplasm in birds. Reported neoplasms of epididymis and ductus deferens include leio- myosarcoma and carcinoma. Chronic weight loss, coelomic swelling and unilateral paresis are most commonly associated with testicular cancer. Radiographs, CT, MRI, ultrasonography may all be used to help make a diagnosis. Surgical removal of the affected testis is the treatment of choice and carries a good prognosis if metastasis is not present. As noted in literature and in authors’ experience, many testicular tumors are cystic. Cystic testicular masses can be aspirated and drained during surgery to reduce their mass and facilitate removal. Some tes- ticular tumors may metastasize as has been reported in a guin- ea fowl (Numida meleagris) with malignant seminoma.24 Cystic testicular disease Nonneoplastic cystic testicular disease is very infrequently re- ported, and its importance is unknown.1 Cystic dilatation of the seminiferous tubules (and testes) has been produced in fowl fed a diet high in sodium. Cystic testes have also been noted in chickens fed egg albumen as a source of protein. Dil- atation of seminiferous tubules, but not gross cystic testicular change, has been noted in roosters affected with epididymal cysts and stones of unknown origin. As mentioned above, consider cancer first when cystic testis is diagnosed. Cystic tes- tis should be drained, biopsied and ideally removed. Disorders of phallus Male waterfowl have a protrusible phallus, which is highly variable and particularly long and corkscrewed in the Mus- covy duck (Cairina moschata).6 Partial and complete phallic prolapses are possible in waterfowl with large phallus and are usually secondary to trauma, local infection, and masturba- tion. Over exuberant vent sexing and mating, Neisseria spp. (suspected to be sexually transmitted in geese and the cause of ‘goose gonorrhea’) and contamination have all been impli- cated causes of phallic infections.1 A prolapsed phallus may become enlarged, ulcerated and/or necrotic compounding the problem. Frostbite and resultant necrotizing dermatitis of a prolapsed phallus has been noted in ostriches. Birds with severe prolapse and infection may be substantially depressed and often lose interest in copulation. Clean exposed phallus and carefully debride abnormal tissue prior to replacement. Topical antibiotic creams, DMSO and systemic antibiotics may be beneficial, and their use is based on clinical findings. Cloaca may need partial closure (via tran- scloacal sutures) to prevent recurring prolapses. If the prolapse is prolonged and will not stay when replaced, use 4-0’ mono- filament absorbable suture to gently tack the phallus to its resting position within the cloacal mucosa. Severely necrotic phallus often needs surgical debridement. Using absorbable suture in an encircling pattern, ligate the phallus proximal to necrotic tissue. It is best if there is a clear demarcation from healthy tissue. Amputate the tissue distal to the ligature ensur- ing that all necrotic tissue is removed. Male reproductive system surgery Castration Clinical castration is infrequently discussed, especially in comparison to salpingohysterectomy, suggesting that male re- productive tract diseases are relatively uncommon. Although caponization is common in the poultry industry (performed between 1 - 2 weeks or up to 6 weeks of age depending on the breed), routine castration is rare in pet birds. As a result, there is little information regarding the behavior and physiologic altering effects of castration in pet birds. Caponized chickens (capons) have increased coelomic fat weight, total hepatic lipid content and saturated fatty acid percentage compared to intact birds. Medical consequences, if any, of this body change are not known. Castrated Gambel’s (Callipepla gambelii) and scaled (C. squa- mata) quail have reduced or eliminated courtship behaviors and lower rates of male-male threats.25 However, the castrates maintained ornate plumage, exhibited overt aggression, and Clinical Theriogenology 2022; 14: 41 frequently won contests when actually engaged. Yearling Eu- ropean starlings (Sturnus vulgaris) castrated when not actively reproductive were more aggressive compared to uncastrated controls.26 It was suggested that ‘nonreproductive aggression in yearling male starlings is independent of gonadal sex ste- roids and it even increased after castration.’26 These limited results suggest that persistent ‘male’ behaviors are either already learned at castration, result from hormones other than testosterone or another source of testicular hor- mones is still present postcastration. It is known that some species have an appendix epididymis extending from epi- didymis into adrenal gland that may secrete androgens after castration. Authors have performed castration in roosters in effort to stop crowing. Castrated roosters did exhibit reduced crowing behavior; however, it did not stop. Authors conclud- ed that castration was not appropriate or effective to eliminate crowing behavior in roosters. Until further studies are available, castration should be used judiciously to alter avian behaviors, especially in adult birds and should always be considered secondary to more conser- vative methods of behavior management. However, castration has real benefit with testicular cancer, abscesses/granulomas, cysts, and other conditions that may not respond to medical management alone. Several methods of castration have been advocated and in- clude simple extraction (caponization), laser ablation, intra- capsular suction, enbloc surgical excision and endoscopic or- chidectomy. Even with early age caponization, testis regrowth is well documented.6 This supports the need for complete removal of testis, the reason why the authors prefer enbloc surgical excision. Caponization is typically performed in young male chickens to create meat that is apparently more tender, juicier, and tastier than in the intact rooster. Heavy chicken breeds are ca- ponized at 2 - 4 weeks, whereas some slow-growing meat-type birds after 6 weeks.6 As the bird ages, tunica albuginea of the testis becomes hard making caponization more difficult and time consuming. The procedure is typically performed with- out anesthesia with the bird held or strapped to a table. A sterile preparation is given to the appropriate side and an inci- sion is made between the last 2 ribs through the lateral body wall that is then spread with a ‘spreader’. Performed correctly, specialized caponizing forceps are used to enter the incision, delicately hold entire testis, and pull with a twisting motion until testis is free and removed. Wound is disinfected and left to close by second intention. Incompletely caponized birds may regrow testis and the birds tend to develop secondary sex characteristics unlike true capons. A similar technique using standard curved forceps is described in 9 - 10 weeks Japanese quail (Coturnix coturnix japonica).27 Use a cranial left lateral approach or ventral midline incision with transverse flap to evaluate testis. Due to cranial location, the lateral celiotomy is often extended cranially by cutting the last 2 ribs to improve testicular exposure. With a left lateral approach, puncture through the caudal thoracic and/or the abdominal air sac(s) to expose left testis. Right testis may be exposed through the same incision by cutting through the midline junction of the corresponding air sacs or the process may be repeated with a right lateral celiotomy. With gentle traction, pull the testis ventrally and surgically clip the dorsal blood supply. Use of a right-angle surgical clip often makes the approach easier. If 2 clips can be placed, then incise be- tween the surgical clips and remove the testis. Otherwise, use radiosurgery to carefully free testis from the surgical clip and vascular cord. Cautery should destroy any remaining testicular cells attached to the surgical clip. Be careful to not damage the overlying blood vessels, kidney, or adrenal gland. Alternatively, if testicular blood supply is small, a hemostat can be temporarily used in the place of a surgical clip and tes- tis is pulled free. Leave the hemostat on the vascular stump for 1 - 2 minutes prior to release. Use direct pressure hemostasis as needed. Diode laser excision can also be used through this approach and may be performed without the need for direct hemostasis. Closure is routine. Multiport endoscopic orchidectomy has been described in Carneau pigeons.28 Whereas the details of the procedure are described,28 endoscopic orchidectomy produced good results in 10 of 11 pigeons with a mean surgical time of 39 minutes. Mild hemorrhage and partial necrosis of the cranial renal pole was noted in 27% of tested birds and represented the most common complication of surgery. Surgical failure (regrowth of testis) in 1 bird was considered due to surgeon’s inexpe- rience. When performed using appropriate equipment and techniques, endoscopic orchidectomy was successful and safe in pigeons. This technique could potentially be used in poul- try and waterfowl. As expected, large testes are more difficult to remove endoscopically.28 In authors’ experiences, orchidec- tomy is more often needed for clinically abnormal (cancer, cysts, and others) and often large testes requiring celiotomy. Vasectomy Vasectomy is a useful technique to produce ‘teaser males’ and aid in population control and has been described in small passerines and budgerigars.29 In anesthetized budgerigars, a 3 mm incision, 7 mm lateral to the cloacal sphincter (vent), was used for the initial approach. Careful dissection was made through the coelomic musculature and fat. An operating mi- croscope was used to find and aid in the removal of a 5 mm section of vas deferens. Only skin incision was closed. It was recommended performing left and right vasectomy 2 weeks apart.29 Two of 12 birds died postoperatively and 1 had pre- existing disease. Other complications were postoperative te- nesmus for 2 days and accumulation of droppings around the vent in 3 of the remaining 10 birds. This procedure was successful (no semen upon collection attempts) in 9 of the 10 surviving birds.30 Anesthetized Bengalese (Lonchura striata) and zebra (Taeniopy- gia guttata) finches have been vasectomized similarly to the procedure described above.29 In anesthetized finches, a 3 mm incision 5 mm lateral to the cloaca was made using an operat- ing microscope. Muscle and fat were incised to locate seminal glomera (glomus). It was noted that the seminal glomera of Bengalese finch were ‘obvious and highly accessible,’ and that of the zebra finch was ‘less obvious and in some cases difficult to locate.’ Vas deferens was carefully separated from the ureter Clinical Theriogenology 2022; 14: 42 and ‘1 or more pieces’ were removed with no ligature and the skin was closed. A single (14 days apart) and bilateral vasecto- mies were performed successfully, and was successful in 12 of 12 Bengalese and 14 of 15 zebra finches.29 In larger species, vas deferens zig zags lateral to the ureter and can be transected endoscopically or via celiotomy. Either a left, and sometimes right, lateral coelomic approaches are used. Ureter is avoided to prevent damage. In vasectomized (just distal to epididymis) roosters, spermatogenesis ceased within 5 - 7 days.31 Authors prefer endoscopic vasectomy in large birds, most commonly, as a means of population control in gallinaceous birds. Ductus deferens is identified endoscopically (as if eval- uating kidney) and grasped just distal to the epididymis and ~ 5 - 8 mm is removed with simple traction. At this location, ductus deferens is usually not closely associated with ureter.32 Depending on the species, both ductus deferens may be ap- proached through 1 endoscopic portal. Alternatively, 2 endo- scopic entry points (left and right) can be used. It should be recognized that vasectomy does not stop courtship and cop- ulation. Conflict of interest There are no conflicts of interest to declare. References 1. Echols MS: Surgery of the avian reproductive tract. Seminars in Avian and Exotic Pet Med 2002;11:177-195. 2. Taylor WM: Pleura, pericardium, and peritoneum: The coelomic cavities of birds and their relationship to the lung-air sac system. In: Speer: editor. Current Veterinary Therapy in Avian Medicine and Surgery. St Louis; Elsevier. 2016. p. 345-362. 3. Mison M, Mehler S, Echols S, et al: Approaches to the coelom and selected procedures. In: Speer: editor. Current Veterinary Therapy in Avian Medicine and Surgery. St Louis; Elsevier: 2016; p. 638-657. 4. Rubin JA, Runge JJ: Principles of microsurgery. In: Speer: editor. Current Veterinary Therapy in Avian Medicine and Surgery. St Loui; Elsevier: 2016; p. 631-638. 5. Baumel JL: Systema Cardiovasculare. In: Baumel JL, Kings AS, Breazile JE, editors. Handbook of Avian Anatomy: Nomina Anatomica Avium. 2nd edition, Cambridge; Nuttall Ornithological Club: 1993. p. 407-475. 6. Echols MS: Soft tissue surgery. In: Greenacre C, Morishita T: editors. Backyard Poultry Medicine and Surgery: A Guide for Veterinary Practitioners. Indianapolis; Wiley: 2021. p. 381-433. 7. Fredrickson TN: Ovarian tumors of the hen. Environ Health Perspect 1987;73:35-51. 8. Bauck L: Neoplasms. In: Rosskopf WJ, Woerpel RW: editors. Diseases of Cage and Aviary Birds. Baltimore; Williams and Wilkins: 1996. p. 480-489. 9. Baumgartner R, Hatt-J-M, Dobeli M, et al: Endocrinologic and pathologic findings in birds with polyostotic hyperostosis. J Avian Med Surg 1995;9:251-254. 10. Zadworny D, Etches RJ: Effects of ovariectomy or force feeding on the plasma concentrations of prolactin and luteinizing hormone in incubating turkey hens. Biol Repro 1987;36:81-88. 11. Proudman JA, Opel H: Daily changes in plasma prolactin, corticosterone, and luteinizing hormone in the unrestrained, ovariectomized hen. Poultry Sci 1989;68:177-184. 12. Terada O, Shimada K, Saito N: Effect of oestradiol replacement in ovariectomized chickens on pituitary LH concentrations and concentrations of mRNAs encoding LH β and α subunits. J Repro Fertil 1997;111:59-64. 13. Hudelson KS, Hudelson P: A brief review of the female avian reproductive cycle with special emphasis on the role of prostaglandins and clinical applications. J Avian Med Surg 1996;10:67-74. 14. Altman RB: Soft tissue surgical procedures. In: Altman RB, Clubb SL, Dorrestein GM, et al: editors. Avian Medicine and Surgery. Philadelphia; WB Saunders: 1997. p. 704-732. 15. Johnson AL: Reproduction in the female. In: Whittow GC, editor. Sturkie’s Avian Physiology. 5th edition, San Diego; Academic Press: 2000. p. 569-596. 16. Female reproductive system. In: King AS, McLelland J, editors. Birds Their Structure and Function. 2nd edition, Philadelphia; Bailliere Tindall: 1984. p. 145-165. 17. Keymer IF: Disorders of the avian female reproductive system. Avian Pathol 1980;9:405-419. 18. Romagnano A: Avian obstetrics. Sem in Avian Exotic Pet Med 1996;5:180-188. 19. Lea RW, Richard-Yris MA, Sharp PJ. The effect of ovariectomy on concentrations of plasma prolactin and LH and parental behavior in the domestic fowl. Gen Comp Endocrinol 1996;101:115-121. 20. Harcourt-Brown NH: Torsion and displacement of the oviduct as a cause of egg-binding in four psittacine birds. J Avian Med Surg 1996;10:262-267. 21. Johnson PA, Brooks C, Wang SY: Plasma concentrations of immunoreactive inhibin and gonadotropins following removal of ovarian follicles in the domestic hen. Biol Repro 1993;49:1026-1031. 22. Pye GW, Bennett RA, Plunske R: Endoscopic salpingohysterectomy of juvenile cockatiels (Nymphicus hollandicus). J Avian Med Surg 2001;15:90-94. 23. Kremer A, Budras KD: The blood supply of the testis in Pekin drakes (Anas platyryhnchos L.). Macroscopic, light microscopic, and scanning electron microscopic studies. Anat Anz 1990;171:73-87. 24. Golbar HM, Izawa T, Kuwamura M, et al: Malignant seminoma with multiple visceral metastasis in a guinea fowl (Numida mealagris) kept in a zoo. Avian Dis 2009;53:143-145. 25. Hagelin JC: Castration in Gambel’s and scaled quail: ornate plumage and dominance persist, but courtship and threat behaviors do not. Horm Behav 2001;39:1-10. 26. Pinxten R, De Ridder E, De Cock M, et al: Castration does not decrease nonreproductive aggression in yearling male European starlings (Sturnis vulgaris). Horm Behav 2003;43:394-401. 27. Busso JM, Satterlee DG, Roberts ML, et al: Testosterone manipulation postcastration does not alter cloacal gland growth differences in male quail selected for divergent plasma corticosterone stress response. Poult Sci 2010;89:2691-2698. Clinical Theriogenology 2022; 14: 43 28. Hernandez-Divers SJ, Stahl SJ, Wilson GH, et al: Endoscopic orchidectomy and salpingohysterectomy of pigeons (Columba livia): an avian model for minimally invasive endosurgery. J Avian Med Surg 2007;21:22-37. 29. Birkhead TR, Pellatt JE: Vasectomy in small passerine birds. Vet Rec. 1989;125:646. 30. Samour JH, Markham JA: Vasectomy in budgerigars (Melopsittacus undulatus). Vet Rec 1987;120:115. 31. Janssen SJ, Kirby JD, Hess RA: Identification of epididymal stones in diverse rooster populations. Poult Sci 2000;79:569-574. 32. Samour J: Vasectomy in birds: a review. J Avian Med Surg 2010;24:169-173.