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The usual way to diagnose small-bowel perforation is by demonstration of free intraperitoneal air on plain abdominal or erect chest radiographs1. Contrast examination of the small bowel is seldom performed in acute cases.
A man aged 72 underwent total colectomy for uncontrol-lable ulcerative colitis. Postoperatively he developed subhepatic collections diagnosed by abdominal ultrasound examination, probably secondary to perforation of a duodenal ulcer. At that time the patient was too frail to undergo repeat laparotomy and a conservative management strategy was chosen. A Robinson drain was inserted under ultrasound guidance that initially drained offensive purulent fluid but after two days began to drain up to 2 litres per day of what appeared to be small-bowel contents. A Gastrografin follow-through examination did not reveal leakage from the small bowel (Figure 1). Drainage continued unabated overnight and clinically small-bowel perforation still seemed likely. The next morning, 18 hours after the follow-through investigation, a specimen of drain fluid was X-rayed against a control specimen of water and was seen to contain contrast agent (Figure 2). This was confirmed by densitometry—drain contents 0.81, water 0.45. A sinogram (Figure 3) then showed that the drain lay within the jejunum. The drain was removed and the patient recovered uneventfully.
In a prospective series of 1000 consecutive patients having combined upper gastrointestinal and small-bowel studies only 14% were performed to exclude perforation2. The technique is best suited to disorders presenting non-acutely, for example Crohn's disease, neoplasms, radiation enteritis, or tuberculosis1. It was chosen in this patient because the presence of free air on plain radiography was thought to be an unreliable indicator after laparotomy and drain insertion, and diagnostic laparotomy would not have been tolerated.
Why was the small-bowel perforation missed in the Gastrografin follow-through? The use of barium as a contrast agent is absolutely contraindicated when bowel perforation is suspected1. Gastrografin was chosen because it is water-soluble3. There are no published data to suggest that the choice of contrast agent influences interpretation of single-contrast small-bowel studies. Maglinte, Burney and Miller reviewed 42 small-bowel lesions missed on follow-through examination but were later demonstrated by enteroclysis (small-bowel enema) and at operation4. Most of the lesions had been missed because of technical inadequacies with the follow-through, although none of the missed lesions were perforations. Buckwalter and Herbst addressed the means of diagnosis of bowel leak in 791 patients who had undergone gastric bariatric surgery. Of the 19 patients who developed leaks, only 7 were diagnosed by Gastrografin swallow, the remainder being identified clinically or by oral dye studies, barium swallow, sinogram or at laparotomy5. The authors do not say whether enteroclysis was used in their institution at that time.
Enteroclysis is a reliable, accurate, quick means of imaging the small bowel. It is more invasive than follow-through but the radiation dose is lower6. Usually it is performed as an elective procedure on prepared bowel. Whether enteroclysis would have detected the migration of the intraperitoneal drain in our patient is debatable.
Finally, would a sinogram have been a more appropriate initial investigation? Without the information from the radiograph of the drain specimens, we believe that a sinogram would have been contraindicated in these circumstances. There is a risk of delivering contrast agent to the peritoneum, with only a small chance of making the diagnosis.
In this case, radiography of drain contents established the diagnosis of small-bowel perforation without further irradiation or invasive procedures. We have not found any previous report of such a technique.