CT diagnosis of afferent loop syndrome.

OBJECTIVE: To report the computed tomography (CT) features of afferent loop syndrome which is often clinically unsuspected.
MATERIALS AND METHODS: The CT studies of five patients with afferent loop syndrome were reviewed. These patients had undergone gastroenterostomy and other surgical procedures, for malignant neoplasms in four and for peptic ulcer in one. Patients presented between 4 months and 15 years (average 5.5 years) after surgery. Symptoms were acute in all patients, the most common symptom being abdominal pain. In addition three of the patients had chronic symptoms including recurrent episodes of abdominal pain, recurrent ascending cholangitis, jaundice and bilious vomiting.
RESULTS: The obstructed afferent loop appeared on CT as a fluid-filled tubular mass with an average diameter of 5.3cm. Valvulae conniventes were identified in all, and small intraluminal air bubbles in four. The dilated afferent loop was opacified with oral contrast material in only one patient. The loop was located in the subhepatic area in three patients and crossed the midline between the aorta and the superior mesenteric vessels in the other two. Additional findings included biliary dilatation in all five patients and signs of pancreatitis in one. Treatment was surgical in four patients (delayed for four months in one) and conservative in one.
CONCLUSION: A fluid-filled tubular structure containing small air bubbles in the right upper quadrant or crossing the midline on CT in symptomatic patients after gastroenterostomy is characteristic of a dilated, possibly obstructed, afferent loop. The diagnosis is often not suspected clinically since patients may present many years after the initial surgery. Recognition of the characteristic CT findings will avoid both inappropriate procedures such as aspiration or drainage of an obstructed afferent loop and delay in treatment.