The major clinical dilemma in small bowel obstruction is determining which patients require immediate laparotomy and which patients can be observed with a long-tube treatment. A combination of tests, including abdominal radiography, ultrasonography, computed tomography (CT), and enteroclysis, usually is performed to assist in this decision. Magnetic resonance imaging (MRI) has the potential to rapidly provide the required clinical information with a single investigation but has not been evaluated in an emergency situation. Matsuoka and colleagues compared preoperative assessments by various techniques, including MRI, in 27 Japanese patients who underwent laparotomy for small bowel obstruction.

Each patient was evaluated using standardized techniques with abdominal radiography, CT, and MRI. All investigations were interpreted by the same radiologist, who assessed the site of the obstruction and the cause based only on the imaging studies. These assessments were compared with the findings at laparotomy.

The mean age of the 16 women and 11 men studied was 62 years (range, 21 to 91 years), and 24 of the patients (89 percent) had a history of abdominal surgeries. Abdominal radiographs detected bowel obstructions in 22 of 27 patients (81.5 percent), CT detected obstructions in 24 of 26 patients (92.3 percent), and MRI detected obstructions in 25 of 27 patients (92.6 percent). The site of the obstruction correlated with the findings at surgery in 15 of 26 patients (57.7 percent) when CT was used and in 25 of 27 (92.6 percent) when MRI was used.

The cause of small bowel obstruction was accurately predicted with CT in 23 of 26 patients (88.5 percent) and in 25 of 27 (92.6 percent) with MRI. The patients with obstructions missed by CT and MRI had a bowel diameter of less than 2.5 cm or obstructions caused by carcinomatous peritoneal dissemination. When MRI was used, the only incorrect diagnoses of etiology occurred in patients with small carcinomas or when paralytic bowel obstruction was suspected because of enteritis, even though the bowel was strangulated. MRI was particularly useful in the diagnosis of bowel strangulation because bowel movement could be assessed. This diagnosis helped avoid bowel resection in two patients.

The authors conclude that MRI is superior to CT and other imaging modalities in the assessment of small bowel obstruction. MRI provides rapid, highly accurate identification of small bowel obstruction and localization of the site, and assists estimation of the etiology. The use of MRI could enable more accurate and timely selection of patients for operative intervention without radiation exposure. Information on relative costs of the three modalities was not provided because of the differences between the U.S. and Japanese health systems.