CT OF SMALL-BOWEL OBSTRUCTION - VALUE IN ESTABLISHING THE DIAGNOSIS AND DETERMINING THE DEGREE AND CAUSE

OBJECTIVE. The early diagnosis of small-bowel obstruction is critical in preventing complications, particularly strangulation. Traditionally , the clinical diagnosis of small-bowel obstruction has depended on pl ain film confirmation. Unfortunately, findings on the plain film may n ot be confirmatory in 20-52% of cases. The purpose of this study was t o determine whether CT is superior to the traditional clinical-radiogr aphic evaluation in prospectively establishing the diagnosis, severity , and cause in cases of suspected obstruction of the small bowel and t o see what impact this information might have on treatment, costs, and the need for additional gastrointestinal contrast studies. SUBJECTS A ND METHODS. Physicians from three surgical services referred all patie nts with suspected small-bowel obstruction for plain film and CT evalu ation. Eighty-five patients were evaluated on 90 occasions during an 1 1-month period. Obstruction was classified on the basis of clinical an d plain film findings as absent, indeterminate, or present (partial or complete). CT scans were obtained in all patients and were interprete d and graded without knowledge of the clinical-radiographic classifica tion. The results of gastrointestinal contrast studies (barium enema, small-bowel series, and enteroclysis) performed in 21 cases were also compared. The gold standard for the diagnosis was surgical findings in 61 cases and clinical course in 29 cases. RESULTS. On the basis of th e combined clinical-radiographic findings, the diagnosis was complete obstruction in 21 of 46 cases (sensitivity, 46%; confidence interval ( CI), 32-60%). When CT was used, the diagnosis was established in all 4 6 cases (sensitivity, 100%; CI, 86-100%). In the 25 cases in which the traditional evaluation failed, the early CT diagnosis of complete obs truction prevented a 12-72 hr delay in surgery with its attendant incr eased morbidity, mortality, and costs. On the basis of the combined cl inical-radiographic findings, partial obstruction of the small bowel w as diagnosed in six of 20 cases (sensitivity, 30%), whereas all cases were detected with CT. False-positive CT findings for complete obstruc tion of the small bowel occurred in three cases of paralytic ileus (on e each due to small-bowel infarction, lower lobe pneumonia, and perito nitis due to rupture of the urinary bladder). One case of colonic obst ruction due to carcinoma in the hepatic flexure was mistakenly diagnos ed as partial obstruction of the small bower. The clinical and plain f ilm evaluation was never precise enough to provide the exact location or cause of small-bowel obstruction. Gastrointestinal contrast studies provided additional useful information regarding colonic abnormalitie s (four cases), functional grading of partial obstruction of the small bowel (six cases), and exclusion of a false positive CT diagnosis of complete obstruction in a case of reflex ileus. CONCLUSION. CT is sens itive for diagnosing complete obstruction of the small bowel and for d etermining the location and cause of obstruction. In comparison, the t raditional clinical and plain film evaluation is relatively insensitiv e. CT should be used when the results of clinical and plain film evalu ation are inconclusive. Gastrointestinal contrast studies play an impo rtant diagnostic role in partial obstruction of the small bowel and in colonic obstruction with predominant small-bowel dilatation.