CONTACT Agustin J. Ruiz agustin.ruiz@gvequine.com.au © 2023 The Author(s). This is an Open Access article distributed under the terms of the Creative Commons Attribution-NonCommercial 4.0 International License (http:// creativecommons.org/licenses/by-nc/4.0/), permitting all noncommercial use, distribution, and reproduction in any medium, provided the original work is properly cited. Citation line: Clinical Theriogenology 2023, 15, 9641, http://dx.doi.org/10.58292/CT.v15.9641 Review Report Perineal urethrostomy in the male horse: a review of the indications, surgical technique, outcome, and complications Agustin J. Ruiz,a Eduardo Arroyob aGoulburn Valley Equine Hospital, Congupna, Victoria, Australia bCollege of Veterinary Medicine, Washington State University, Pullman, WA, USA Abstract Perineal urethrostomy is a surgical technique performed for temporary or permanent urine diversion from the penile urethra in male patients with obstructive urinary outflow disease, extensive trauma or invasive tumor affecting penis and prepuce, to access the urethra or bladder to remove uroliths, and to treat horses affected with hemospermia or hematuria secondary to urethral rents. Perineal urethrostomy has been advocated as the treatment of choice in geldings where hematuria does not resolve with conserva- tive treatment and in stallions with hemospermia caused by urethral defects. Most cases of geldings with hematuria are resolved with a single perineal urethrostomy surgery; however, stallions with hemospermia might need a second surgery. Perineal urethros- tomy also enables access to the urinary bladder in male horses with cystoliths following minimal dissection and without accessing the abdominal cavity. The most common complications directly related to this surgery are hemorrhage, urine scalding, and urethral stricture at the surgical site. The aim of this article is to review comprehensively the indications for perineal urethrostomy surgery, illustrate the surgical technique approach, and discuss outcomes and complications. Keywords: Perineal urethrostomy, corpus spongiotomy, urethral rent, hemospermia, hematuria Introduction Perineal urethrostomy (PU) is a surgical technique that entails the creation of a temporary or permanent opening of the ure- thral lumen most commonly at the level of the ischial arch in male horses. The surgery is indicated in several disorders of the equine penis, prepuce, urethra, and urinary bladder. The most common indication of PU in male horses is for resolu- tion of hemospermia in the breeding stallion and hematuria in geldings due to urethral rents. The aim of this article is to review comprehensively the indi- cations for PU surgery, illustrate the surgical technique approach, and discuss outcomes and complications. Indications Temporary PU at the level of the ischial arch is indicated for temporary urine diversion from the penile urethra in male patients with obstructive urinary outflow disease, to access the urethra or bladder to remove uroliths, and to treat horses affected with hemospermia or hematuria secondary to ure- thral rents. Permanent PU is indicated in patients with extensive trauma or invasive squamous cell carcinoma affect- ing the penis and prepuce requiring permanent urinary diversion. One of the most common primary lesions of the equine ure- thra are longitudinally oriented urethral rents that extend from the surface of the urethra to the corpus spongiosum penis (CSP) at the level of the ischial arch.1,2 Males of any age and breed are affected, although Quarter Horses have been proposed to be more predisposed.3 A retrospective study eval- uated 24 years of clinical cases presented to a referral facility and found that 33 male horses presenting with hematuria or hemospermia were diagnosed with a urethral rent on ure- throscopy (0.08% of the total gelding and stallion population admitted during the study).4 The cause of urethral rents is idiopathic; however, it has been hypothesized to be associated with a combination of factors, occurring simultaneously, favoring the onset of this lesion. These include the abrupt reduction of the urethral diameter (from 3.5–5cm to 1–1.5cm) at the level of the ischial arch and the increased hydrodynamic forces occurring during erection, ejaculation, and final stages of urination that the urethra at the level of the ischial arch is exposed to.2,5 Commonly, urethral rents clinically present as hemospermia in stallions and terminal hematuria in geldings mailto:agustin.ruiz@gvequine.com.au http://creativecommons.org/licenses/by-nc/4.0/ http://creativecommons.org/licenses/by-nc/4.0/ http://dx.doi.org/10.58292/CT.v15.9641 Citation line: Clinical Theriogenology 2023, 15, 9641, http://dx.doi.org/10.58292/CT.v15.9641 59 because of the communication between the CSP and the ure- thral lumen through the mucosal defect.6,7 In geldings, pres- ence of bright red blood exiting the urethral process at the end of urination apparently occurs when intraluminal urethral pressure decreases suddenly, secondary to forceful contrac- tions of the bulbospongiosus penis (BSP) muscle while the pressure in the CSP remains high.2 Dysuria, pollakiuria, or pain are not commonly present. In stallions, hemospermia as a result of hemorrhage during or at the end of ejaculation occurs when contraction of the BSP during ejaculation and coitus causes a 45-fold pressure increase within the CSP.2,4,8 Hemospermia can have severe economic impacts in a breed- ing program mostly associated with variable degrees of fertil- ity reduction in sires. In stallions on live-cover breeding programs, the first indication of hemospermia is reduced fer- tility rates and possibly evidence of blood on the mare’s peri- neal region or stallion’s glans penis following dismount. In stallions that are collected with an artificial vagina, hemo- spermia will be observed with a variable degree of blood- tinged ejaculate (Figure 1). The presence of significant amount of blood in the ejaculate (>50% of whole blood) is associated with severe sperm damage due to the extensive peroxidative damage induced on sperm membranes as a con- sequence of the iron released by the red blood cells.9,10 A lower degree of blood contamination on the ejaculate (between 5–20% of whole blood per volume) has been asso- ciated with decrease in fertility11 and no effect on fertility,10 respectively. In some geldings, hematuria resolves spontaneously. While sexual rest alone seems not to resolve hemospermia in stal- lions, it is imperative to alleviate the severity of the clinical signs as an adjunct to non-invasive treatment.1,3 A variety of medical treatments have been attempted on affected horses. They are aimed to stop the bleeding and promote healing. These include intravenous administration of formaldehyde solution, oral administration of methenamine, systemic administration of antimicrobial drugs and more recently top- ical treatment with 4% Policresulen solution.12–14 On the other hand, surgical treatment is aimed at decreasing pressure within the CSP to minimize or prevent hemorrhage through the rent so that it can heal.1 The most common surgical approaches include PU and corpus spongiotomy (CS). Alternative surgical options reported are direct suturing of the urethral defect via a PU with urethroscopy guidance, laser application to the edges of the defect combined with PU and buccal mucosal urethroplasty combined with PU.4,15,16 Diagnostic approach to horses presenting with hematuria or hemospermia is based on the identification of different degrees of blood in the ejaculate or urine, followed by visual- ization of a urethral rent by urethroscopy.8,17 In horses affected with hematuria/hemospermia, clinical examination is gener- ally unremarkable with the occasional presence of mild ane- mia on laboratory analysis of blood. Urine samples collected mid-stream or by bladder catheterization may appear grossly normal. Sediment examination on urinalysis or urine reagent strip may show presence of red blood cells. A thorough endo- scopic evaluation of the urethra should be performed to examine the urethra, colliculus seminalis, seminal vesicles, urinary bladder, and ureteral openings to identify any evi- dence of trauma, presence of blood, or discontinuation of the urethral mucosa.8,18 Almost exclusively, urethral rents appear as a 5–10 mm long, linear defect on the convex surface of the urethra at the level of the ischial arch (Figure 2).1 The exact location can be confirmed by inserting percutaneously a hypodermic needle shaft through the perineal area at the level of the ischial arch by an assistant, while simultaneously performing the endoscopic evaluation of the urethra. The pressure applied by the needle shaft through the perineal area will deform the urethral lumen allowing to identify the exact location of the urethral rent by visualization by endoscopic camera. In some cases, urethral rents are undetected due to the collapse of the urethra in the sedated patient and small size of the tear.4 In these cases, performing the endoscopic Figure 1. Presence of blood in the ejaculate (hemospermia) of a stallion with an urethral rent. Figure 2. Urethral rent located at the level of the ischial arch in an adult stallion. http://dx.doi.org/10.58292/CT.v15.9641 60 Citation line: Clinical Theriogenology 2023, 15, 9641, http://dx.doi.org/10.58292/CT.v15.9641 examination immediately after urination (geldings) or ejacu- lation (stallions) can aid to observe small traces of blood emanating from an otherwise undetected urethral rent.19 Further diagnostic approaches involve the elimination of other causes of bleeding, such as vesicular adenitis, penile lesions (trauma, squamous cell carcinoma of urethral process or glans penis, infection, and habronemiasis), presence of calculi within any portion of the uri nary tract, and midline cysts of the colliculus seminalis.14,20,21 The ruling out process starts with a thorough physical examination of the penis and prepuce, particularly the glans of the penis and urethral open- ing, followed by transrectal palpation and ultrasonography of accessory sex glands (particularly seminal vesicles), bladder and kidneys. Urolithiasis in horses accounts for approximately 8% of the diagnosis of equine urinary tract disease.3 Clinical examina- tion findings depend on location of the uroliths. Affected horses typically present with anuria, stranguria, pollakiuria, and/or hematuria.3 In horses with urethral uroliths, respira- tory and cardiac distress, general discomfort and straining to urinate without urine passage are commonly seen.22 Diagnosis is based on transrectal palpation of the bladder, ultrasonography of kidneys, bladder, urethra, and urethros- copy/cystoscopy.23,24 Cystoscopy allows direct visualization of uroliths in most cases; however, horses that have a history of urolithiasis may show urethral bruising consistent with recent calculus passage. Two types of equine cystoliths are recognized, both primarily composed of calcium carbon- ate.24 Type I cystoliths account for approximately 90% of the cases, are yellow-greening appearance, have a rough surface, and variable resistance to fragmentation. Type II cystoliths contain variable amounts of phosphorus, are gray-white in appearance, have a smooth surface and are more difficult to fragment.24 Complete calculi removal is the treatment of choice for cystolithiasis.6,25 In male horses, described surgical approaches for cystoliths removal include PU, pararectal cys- totomy (Gokel’s approach), cystoscopy-guided techniques, and laparoscopy techniques (standing or under general anesthesia).23,26,27 Temporary PU combined with daily topical treatment with antimicrobials and anti-inflammatory drugs has been advo- cated as the treatment of choice in geldings where hematuria does not resolve with conservative treatment and in stallions with hemospermia caused by urethral defects.1 Temporary PU enables access to the urinary bladder in male horses with cystoliths following minimal dissection and without access- ing the abdominal cavity.28 Moreover, PU can be performed standing thereby avoiding the risks and expenses of general anesthesia. Small cystoliths can be removed “en bloc” through a PU, although lithotripsy is required for removal of larger cystoliths.29 Cystolith fragmentation through a PU has been performed using long-handled bone forceps, an osteo- tome and a mallet, laser, shockwave, and a customized scaler.27 Surgical technique Preparation of the patient PU is best approached with the horse standing in stock under sedation and analgesia.12 Jugular vein catheter placement is recommended. Sedatives options include the combination of an α2-agonists (detomidine hydrochloride [0.01 mg/kg IV]) or xylazine hydrochlo ride (0.2 to 0.5 mg/kg IV) with butorphanol tartrate (0.01 mg/kg IV) in bolus to effect. In some cases, an initial bolus can be followed by a continuous detomidine hydrochloride drip infusion at 0.01–0.04 mg/ kg/h.30 The rectum is evacuated. A sterile stallion urinary catheter is advanced using sterile technique from the urethral process into the urinary bladder to assist as a landmark for identification of the urethra during surgery. Caudal epidural anesthesia is achieved by administration of 2% lidocaine (0.22 mg/kg) either alone or in combination with 10% xyla- zine hydrochloride (0.15–0.2 mg/kg) diluted to a volume of 7–10mL with sterile preservative free saline (0.9% NaCl) solution is used to desensitize the perineal region. The tail is wrapped in an obstetric sleeve or bandaged, using cohesive or support bandage material, and tied laterally. The perineal region is prepared surgically. Skin and subcutaneous tissues can be infused with local anesthetic if there is presence of sensitivity in the perineal area after placing the epidural or if preferred by the surgeon. Good-quality surgical head lights are recommended to assist on visualization of the surgical field and assist on maintaining a midline orientation throughout the surgery. Surgical approach An approximately 7–8 cm longitudinal midline skin incision is made in the perineum extending from 4–5 cm distal to the anus ventrally to the to the level of the palpable ischial tuber- osities (Figure 3).12 The longitudinal midline incision is con- tinued dividing the subcutaneous tissues, the paired retractor penis muscles and the BSP muscles (Figure 4). Careful dissec- tion technique while palpating the urinary catheter is recom- mended to maintain the correct midline orientation23,31 and Figure 3. Midline skin incision starting approximately 4–5 cm ventral to the anal sphincter. http://dx.doi.org/10.58292/CT.v15.9641 Citation line: Clinical Theriogenology 2023, 15, 9641, http://dx.doi.org/10.58292/CT.v15.9641 61 (Weitlaner muscle retractors) to maintain dissected muscle layers out of the visual field while reducing the excessive tis- sue manipulation and risk of subsequent edema (Figure 4C). The dissection is continued through the CSP that envelops the urethra allowing exposure of the urethra by retraction of these muscles (Figure 5). Increased bleeding from the CSP is expected and commonly subsides spontaneously; however, it can be controlled by ligation and digital pressure if a situa- tion warrants such measures. The length of the perineal inci- sion should progressively decrease toward the deeper layers to avoid postoperative tissue pocketing of urine. The urethra is identified and stabilized by palpation of the urinary cathe- ter. An approximately 3 cm longitudinal incision is made along the caudal surface of the urethra, and the mucosa is reflected abaxially (Figure 6). In horses with intraluminal obstructions such as uroliths or cystoliths, stay sutures using 0- polydioxanone (PDS) are placed on each edge to allow manipulation by either retrograde hydropulsion using uri- nary catheter forceps inserted through the PU incision, or urethral dilators.29,33 For temporary (6 to 10 weeks) diversion of urine (temporary PU), a Foley urinary catheter is placed through the temporary urethrostomy incision, and its balloon filled with sterile saline solution once enters the urinary bladder. The catheter is secured with stay sutures for 48 to 96 hours.12 For permanent diversion of urine (permanent PU) the CSP, BSP, and retractor penis muscles are sutured along their cut edges with a 3-0 synthetic absorbable suture in a continuous pattern. The urethral mucosa and skin are approximated (marsupialized) using a 2-0 or 3-0 synthetic monofilament absorbable or nonabsorbable suture material in an inter- rupted pattern.12 Apposition of the perineal skin and urethral mucosa is important to avoid excessive tension and minimize post-operative complications. Stallions with hemospermia and geldings with hematuria sec- ondary to urethral rents can be initially treated alternatively with incision of the CSP without incision of the urethra, called corpus spongiotomy (CS).1,3,31 This surgery dissipates the A B C D Figure 4. (A) Skin and subcutaneous tissues dissected. (B) Blunt dissection over the retractor penis muscle. (C) Exposure of the bulbospongiosum penis (BSP) muscle – The use of muscle retractors (Weitlaner) assists in improving visualization and avoid excessive tissue manipulation. (D) Blunt dissection over the bulbospongiosum penis (BSP) muscle. Figure 5. Corpus spongiosum penis muscle dissected with exposure of the catheterized urethra. avoid large branches of the external pudendal artery with pro- fuse hemorrhage and potential periurethral hematoma for- mation.32 This can be assisted by a pair of muscle retractors http://dx.doi.org/10.58292/CT.v15.9641 62 Citation line: Clinical Theriogenology 2023, 15, 9641, http://dx.doi.org/10.58292/CT.v15.9641 pressure from the CSP into the urethra to the subischial inci- sion allowing the urethral rent to heal.1 Primary closure of a urethral rent at the level of the ischial arch is performed when temporary PU or CS have not resolved the hematuria or hemospermia secondary to the urethral rent.12 Post-surgical care Temporary PU and CS are allowed to heal by second intention and are commonly healed within 2–3 weeks with minimal complications.2,33 The patient should be closely monitored to ensure that urination occurs without difficulty, particularly after PU for removal of urethral or cystic calculi. Broad spec- trum antibiotics and nonsteroidal anti-inflammatory drugs are commonly administered following surgery. The surgical site should be cleaned and disinfected daily with care not to disturb the sutures (if in place). The skin of the ventral perineum, inguinal region, and adductor surfaces of the hind- limbs should be cleansed daily and protective emollients applied due to high risk of urine soilage and urine scalding. In stallions with urethral rents, strict sexual rest for 6–8 weeks is very important because erection and contractions of the bul- bospongiosus muscle can prevent the rent from healing.4,34 Outcome In geldings presenting with hematuria, PU was shown to effec- tively resolve the vast majority of the cases after 1 surgery. In one study, PU resolved hematuria in 6 geldings after 1 surgical procedure.1 In another study, 13 out of 17 geldings underwent PU to resolve hematuria with successful results.4 Additionally on the same study, 4 more male horses underwent CS which successfully resolved hematuria. An alternative to surgery is transendoscopic use of a neodymium:yttrium-aluminum-gar- net (Nd:YAG laser) or diode laser to fuse the edges of the rent. This was successfully performed as sole treatment in one geld- ing and in combination with CS in another gelding.15 In stallions presenting with hemospermia, PU alone restored fertility in 11 out of 15 stallions after 1 surgical procedure in one study.3 In another study, PU alone resolved hemospermia in 1 out of 2 stallions.1 In another study, 6 stallions underwent PU with complete resolution and no complications in 4 of them. The remaining 2 stallions with recurrent hemospermia required a second PU with subsequent primary closure of the urethral rent with direct suturing guided by urethroscopic guidance.4 A stallion with recurrent hemospermia secondary to a urethral rent was treated with a PU and application of a buccal mucosal graft to the urethral rent successfully.16 Laser  treatment alone failed to resolve hemospermia in one stallion; however, successfully resolved hemospermia recur- rence in 4 stallions when combined with CS.15 Chemical cau- terization using 4% Policresulen, a polycondensation product of meta-cresolsulfonic acid and phenol used as a topical hemo- static  and  antiseptic (Albocresile 360 mg/g, Takeda Pharma Figure 6. Exposure of urinary catheter after incision of the ure- thral mucosa. Figure 7. Mild hemorrhage presented 2hs after corpus spon- giotomy surgery in a stallion. http://dx.doi.org/10.58292/CT.v15.9641 Citation line: Clinical Theriogenology 2023, 15, 9641, http://dx.doi.org/10.58292/CT.v15.9641 63 Ltda, Jaguariuna, SP, Brazil) daily infused (for up to 4 days) topically in the urethra efficiently resolved hemospermia in 4 stallions.13 PU is an effective technique for uroliths removal in the male horse. Recent advances on the uroliths manipulation and retrieval techniques have increased the success and signifi- cantly reduced complications and recurrence.34,35 Complications Previously reported complications with PU include rectal tear during cystic calculus manipulation, fistula formation, septic peritonitis, orchitis, postoperative tenesmus, excessive hemorrhage, urethral stricture, and dysuria.17,36,37 Most of these complications appear to be closely associated with the underlying disease process (large uroliths that require manipulation) rather than with the surgical procedure.37 The most common complications directly related to the PU are hemorrhage, urine scalding and urethral stricture at the sur- gical site. Mild, self-limiting hemorrhage caused by increased CSP pressure secondary to contraction of the BSP occurs at the end of urination for up to 2 weeks (Figure 7).37 Hemorrhage from the urethral orifice and evidence of pain during urination are not commonly observed after surgery.1 Severe hemorrhage from the PU is an uncommon complica- tion.37 Urine scalding has been reported as a delayed compli- cation of permanent PU and associated with extension of the PU incision ventral to the ischium in one report38 but not in a different study.37 The use of appropriate regular cleaning and emollients is recommended in mild cases while surgical drains might be recommended for severe cases where there is leakage of urine from the surgical site into surrounding tis- sues.12 The use of indwelling catheters left in placed postop- eratively has been regularly used with the aim to ensure patency of urine voiding; however, they have been recently associated with increased risk of additional complications including severe cystitis, urine scald, urethral stricture, and ruptured bladder when meticulous care and frequent moni- toring have not been performed.37,39 For horses undergoing temporary PU, it is currently recommended to limit the duration of catheterization and remove it within 2–3 days.39 Additionally, chances of stricture formation postoperatively may be reduced by appropriate hemostasis, tissue repair, and tissue drainage.40 Stricture formation has been reported in up to 30% of the horses undergoing perineal urethrostomy for calculi removal.36,40 It has been postulated that urethral stricture for- mation depends on the degree of trauma induced during cal- culi extraction rather than the surgical approach itself.29,41 Recent advances in cystoliths fragmentation and prevention of recurrence following cystolith removal through perineal ure- throstomy in male horses has been made.34,35 The use of ure- thral mechanical dilators and laparoscopic pouch retrieval has shown to reduce complications by protecting the urethral mucosa from mechanic trauma during instrument insertion/ manipulation and urolith removal.35,36,41 For horses with urethral rents, most of the previously described complications can be avoided by changing the surgical approach from a PU to a CS, which has been successfully used for resolving hematuria in geldings with urethral rents in one surgical procedure. However, stallions presenting with hemo- spermia may require more than 1 PU, CS, or primary closure of the rent to resolve hemospermia.4 Acknowledgments The authors are grateful to Drs. Ahmed Tibary and Allan Gunn for critical review of the manuscript. Conflict of interest None of the authors have any conflict of interest to declare. References 1. Schumacher J, Varner DD, Schmitz DG, et al: Urethral defects in geldings with hematuria and stallions with hemospermia. Vet Surg 1995;24:250–254. doi: 10.1111/j.1532-950X.1995.tb01326.x 2. Taintor J, Schumacher J, Schumacher J, et al: Comparison of pres- sure within the corpus spongiosum penis during urination between geldings and stallions. Equine Vet J 2004;36:362–364. doi: 10.2746/0425164044890571 3. Sullins KE, Bertone JJ, Voss JL, et al: Treatment of hemospermia in stallions: a discussion of 18 cases. Compend Contin Educ Pract Vet 1988;10:1396–1403. 4. 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