"Bulb-like" sign: Small bowel closed loop obstruction in incarcerated Spigelian hernia

Abstract

A Spigelian hernia is a rare hernia, making up approximately 0.1% of all abdominal wall hernias. This hernia goes through a defect in the Spigelian fascia which is the part of the transversus abdominis aponeurosis lateral to the rectus muscle, often at the level of the arcuate line, where the fascia is widest and weakest. Clinical diagnosis is difficult in patients without obvious abdominal mass but imaging can be a valuable adjunct in diagnosis. We report the case of a 64-year-old male who presented to our hospital with small bowel obstruction secondary to an incarcerated Spigelian hernia who was pre-operatively diagnosed with ultrasound and computed tomography. At ultrasound and computed tomography a closed loop obstruction in a Spigelian Hernia was detected, resembling on both imaging modalities a "bulb-like" appearance.

Keywords: CT; Incarceration; Small bowel obstruction; Spigelian hernia; Ultrasound.

Fig. 1

(a, b). Sonographic view of the right lower quadrant of the abdomen showing the interruption in the inferior margin of the spigelian fascia, the hernial defect is clearly visible (spotted line). Axial scan of the hernial sac, obtained in supine position, shows the “bulb-like” image determined by the presence of both the afferent and efferent loop (white arrows) tapered at the point of obstruction, the hyperechoic mesenteric and omental fat (*) and the inhomogeneous hypoechoic fluid collection (black arrow).

Fig. 2

Sonographic view of the right lower quadrant of the abdomen, showing a dilated, hypokinetic, fluid-filled small bowel loop. Outer caliber, measured from wall to wall, was >25 mm.

Fig. 3

(a, b). Axial (a) and sagittal MPR reconstruction (b) contrast enhanced CT shows a right-sided lower quadrant interstitial Spigelian hernia, through a 20-mm defect located between the rectus muscle and oblique muscles, superficially covered by external oblique aponeurosis and subcutaneous/cutaneous tissues. Inside the hernial sac the “bulb” (white arrow) is composed by hypodense mesenteric and omental fat and the small bowel loops, creating a multilayered image overlapping US findings. The mildly hypodense free fluid collection is visible around the loops.