Volvulus of the entire small bowel with normal bowel fixation simulating malrotation and midgut volvulus

Midgut volvulus is a complication of malrotation of bowel and mesenteric malfixation. In contrast, primary volvulus of the small bowel is a distinctly different and rare entity characterized by torsion of the entire small bowel with normal mesenteric fixation. To present the clinical and imaging findings in four infants with primary small bowel volvulus and normal bowel fixation in order to improve awareness of this entity among clinicians and radiologists and to discuss the potential etiologies of this entity to distinguish it from other causes of small bowel volvulus. A retrospective review of imaging studies (two ultrasounds and four upper gastrointestinal series) in four infants (three full-term and one premature) from three institutions with surgically proven volvulus of the entire small bowel and normal bowel fixation were reviewed by three board-certified pediatric radiologists and correlated with clinical and surgical reports when available. The infants presented during the first week to 6 months of life and were acutely ill. The upper gastrointestinal series showed complete duodenal obstruction with beaking in one and partial duodenal obstruction in three. All studies were interpreted as highly suspicious for malrotation and midgut volvulus. Emergent laparotomy demonstrated primary small bowel volvulus with normal mesenteric fixation in all infants. The base of the small bowel mesentery was described by the operating surgeon as smaller than normal in one infant (case 3). There was no mesenteric defect or other abnormality predisposing to volvulus in the other three. In both infants who had abdominal US, a retroperitoneal position of the third portion of the duodenum was demonstrated. All infants survived. One infant required resection of the necrotic small bowel and currently has short gut syndrome, one has malabsorption and two were lost to follow-up. Primary small bowel volvulus with normal fixation is indistinguishable from malrotation with midgut volvulus in the acutely ill infant or child. Radiographic diagnosis can be difficult in patients with intermittent or incomplete small bowel volvulus without malrotation. In these patients, neither an upper gastrointestinal series demonstrating a normal position of the duodenojejunal junction nor the sonographic demonstration of a retromesenteric third portion of the duodenum excludes the diagnosis. In young infants, the clinical and imaging findings may mimic necrotizing enterocolitis. Sonography may be useful to evaluate the bowel for signs of bowel wall compromise or a whirlpool sign.