The “abdominal whirlpool” sign

Excerpt

A whirlpool is a large mass of swirling water and has a potential to suck even large surrounding objects within it (Fig. 1). The “abdominal whirlpool” sign (aka the whirl sign) describes the twisting of the mesenteric vessels and the small bowel loops, characteristically seen in a midgut volvulus [1]. The twisting of the superior mesenteric vein (SMV) and its tributaries, around the superior mesenteric artery (SMA), produces the characteristic whirl-like appearance (Fig. 2a–c) [2]. The surrounding bowel loops may also get involved in the twist, resulting in formation of a larger mass. A midgut volvulus is a surgical emergency and is typically seen in the pediatric population, classically presenting with bilious vomiting in the first month of life [3]. It is often associated with malrotation of the intestine, which can be diagnosed on imaging. Abnormal location of the duodeno-jejunal flexure, ileo-caecal junction and reversal of the normal orientation of the SMA and the SMV are the main indicators pointing to underlying malrotation. The severity of the volvulus is directly proportional to the degree of twisting and severe twisting can often result in catastrophic complications like bowel ischemia and perforation. Initial abdominal radiographs may be non-specific or may demonstrate dilated proximal small bowel loops. Contrast-enhanced computed tomography (CT) images are diagnostic of this condition with demonstration of the whirling of the mesenteric vessels and the small bowel loops. CT can accurately diagnose any abnormality in the SMA and SMV relationship (normally the SMV is located to the left of SMA). This abnormality in the SMA and SMV relationship can also be identified on an ultrasound doppler and can be useful as a definitive sign of a midgut volvulus [4]. CT is the modality of choice to evaluate for associated complications like ischemia or bowel necrosis and to look for any free intraperitoneal gas, which indicates perforation. Urgent surgical exploration is indicated once the diagnosis has been made, to reduce the volvulus and to salvage the involved bowel loops. Ladd’s procedure is the surgical treatment for malrotation of the intestine.

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