ORIGINAL ARTICLE Reporting the small bowel examination DJ Solomon FFRad (D) SA Levin & Partners Constantiaberg Mediclinic Cape Town Introduction Relative to the upper gastrointesti- nal tract and colon, diseases of the small intestine are relatively rare. Outside of a dedicated gastrointestinal unit requests for investigation of the small bowel are infrequent, limiting the interest and diligence of the radi- ologist performing the small bowel examination. Ultrasound, CT and more recently MR all contribute to assessment of small bowel pathology but generally the initial request is for a barium small bowel examination. Technique Many small bowel examinations are performed by conventional fol- low-through, with or without inter- mittent fluoroscopy during transit of barium through the small bowel. This procedure is limited by the narrowing of the lumen caused by drug-induced transit acceleration, causing crowding of the mucosal folds and a false appearance of nodularity. It cannot test distensibility of the lumen, and early mural infiltration or subtle stenoses may be missed. The small bowel enema (SBE) should be the investigation of choice. Discomfort caused during intuba- tion must be appreciated and the radiologist should be sensitive to the patient's need for reassurance, ade- quate topical anaesthesia and mild sedation if required. The hypotonia induced by jejunal distention allows for display of all dis- tended loops to the end of the exami- nation and folds are straightened, making it possible to determine mor- phological normality. The examina- tion is quicker and importantly more frequent fluoroscopy may show inter- mittent segmental dilatation, indicat- ing subtle stenoses (Fig. I). Fig. 1. Intermittent segmental dilatation in a patient with multiple stenoses due to small bowel lymphoma. The report Interpreting and reporting the small bowel investigation depends on a knowledge of normal morphology and understanding the clinical histo- ry. Morphologic normality is based on observation of the fold pattern (valvulae conniventes), lumen dia- meter and wall thickness. Fold density is higher in the jejunum (4 - 7 folds per inch) and gradually reduces to the ileum (2 - 4 4 SA JOURNAL OF RADIOLOGY • February 2003 folds per inch). Fold thickness is greater in the jejunum (2 mm), being thinner and shallower in the ileum (1 mm). It is important to measure fold thickness during adequate lumen distention. Lumen diameter is somewhat tech- nique-dependent but generally con- sidered to be up to 4.5 cm in the jejunum and 3.5 cm in the ileum. Wall thickness must be assessed when two adjacent loops are parallel to each other over a length of 5 cm and should be approximately 2 mm for a single wall thickness. Transit time through the small bowel is variable and may be influenced by factors such as infusion rate, presence of food con- tent and a loaded caecum. Objective criteria have been defined but should only be applied when the infusion rate can be controlled by a mechanical pump. Assesment is made after 300 ml have been infused at 75 ml/min, with normal motility regarded as the jejunum having filled with approximately one-third of loops in contraction, hypermotility when greater than two-thirds ofloops are in contraction, and hypomotility when the jejunum has not yet filled and few loops are in contraction. However, few radiologists have the use of a mechanical infusion pump and transit time is generally made subjec- tively. As with all radiological investiga- tions, reporting a study should depend on the clinical indication for the procedure and the questions asked by the referring doctor. The com- monest indications for a small bowel examination are: (i) assessment of Crohn's disease; (ii) diarrhoea or mal- absorption states; (iii) partial mechanical small bowel obstruction; and (iv) obscure GIT bleeding. ORIGINAL ARTICLE Crohn's disease To confirm the presence or absence of Crohn's disease on the basis of history or prior studies requires a dedicated and detailed examination of the terminal ileum, assessing it in varying degrees of dis- tension and compression. A normal report may state: 'Normal small bowel mucosal and fold patterns. The ter- minal ileum has a normal appearance and no features to suggest Crohn's dis- ease have been demonstrated: Having decided that the examination is abnormal the following features need to be mentioned in the report. 1. Are the abnormal features spe- cific for Crohn's disease, and if not a differential diagnosis should be given. If the changes are non-specific it is important not to make a definitive radiological diagnosis of Crohn's as the label may remain with the patient for life. (Fig. 2). 2. Describe the nature and esti- mated length of involvement. 3. Identify and characterise proxi- mal skip lesions. 4. Does the appearance of a steno- sis .suggest active inflammation which will respond to medical treatment or is it a smooth tapered fibrotic stric- ture with proximal dilatation that may require surgery. 5. Identify complications such as a fistula or features to suggest an adja- cent abscess. Each of these questions should be answered in the report as they have an important bearing on the clinician's choice of management. Fig. 2. Non-specific nodular rr:~cosal s"!elling in the terminal ileum due to Yersmla enteritis. Diarrhoea/mal- absorption states Most pathological conditions of the small bowel that cause malabsorp- tion are due to some form of mucosal infiltrate although other conditions such as lymphangectasia, jejunal diverticulosis, scleroderma and coeli- ac disease should be considered. Therefore the following points should be reflected in the report of a small bowel examination in this clin- ical setting: (i) are there diverticulae? (ii) are the folds thickened, and if so is this regular or nodular, segmental or diffuse?; (iii) abnormality of fold den- sity; and (iv) bowel shortening. Partial mechani- cal small bowel obstruction Here the aim is to identify stenotic lesions in the small bowel. Stenoses usually have a non-specific appear- ance but the likely cause may be inferred from the characteristics of the stenosis and the patient's history. The following features may help to narrow down the differential diagnosis: (i) the site of the stenosis; (ii) single or multiple stenoses; (iii) degree of prox- imal dilatation; and (iv) other small bowel abnormalities, in particular an abnormal terminal ileum which may indicate Crohn's disease. GIT bleeding The sensitivity of the small bowel examination in this clinical setting is low but a SBE is usually requested before proceeding to angiography. The report in this situation should reflect the following points: (t) is there a Meckel's diverticulum? (ii) mucosal mass and its nature, e.g. a cavitating lesion may represent melanoma, lymphoma or leiomyosarcoma whereas a polypoid lesion may reflect a benign polyp or a melanoma metas- tasis; and (iii) focal mucosal distortion as seen in the presence of a vascular malformation. Conclusion The pathological spectrum of small bowel disease is wide, and other than the pathognomonic features of Crohn's disease, all abnormalities have a differential diagnosis that should be interpreted in conjunction with the patient's clinical history and consulta- tion with the referring doctor. The report should be kept as sim- ple as possible with positive and nega- tive findings reflecting the radiolo- gist's understanding of the clinical problem. 5 SA JOURNAL OF RADIOLOGY • February2003