What causes Whirlpool sign in abdomen on CT?
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Answer:
Whirlpool-like swirling appearance of bowel loops and mesentery around the superior mesenteric artery (SMA) in midgut volvulus, a surgical emergency due to intestinal malrotation; also described in some cases of portal venous gas where gas outlines mesenteric vessels in a swirling pattern. The same descriptive sign – swirling of a twisted vascular pedicle – is also a well-established finding on ultrasound (with Doppler) in ovarian torsion and testicular torsion, where it represents the twisted vascular pedicle rather than bowel/mesentery.
Why is it called so?
Named for its resemblance to a literal whirlpool or water vortex, reflecting the characteristic rotational distortion of vascular and/or bowel structures around a central axis. The term whirlpool sign visually conveys the concentric, rotating configuration seen on CT or ultrasound.
Pathophysiology
Midgut volvulus arises from incomplete rotation and fixation of the midgut during embryonic development, allowing the small bowel mesentery to twist around the SMA axis; this produces a “corkscrew” or whirlpool configuration visible on CT as clockwise or counterclockwise swirling of bowel and mesentery superior to the SMA origin. In portal venous gas, intraluminal gas extends into mesenteric veins, accentuating the swirling vascular pattern amid edematous bowel. In ovarian or testicular torsion, twisting of the vascular pedicle produces an analogous swirled appearance of the twisted vessels and supporting tissue on grayscale/Doppler ultrasound.
Alternative names: Hurricane sign (informal synonym); corkscrew sign (near-synonymous fluoroscopic correlate on upper GI/small bowel series).
Other associated named signs: Beak sign (luminal tapering at the point of torsion – a general volvulus finding, also classically described in sigmoid and cecal volvulus, not exclusive to midgut volvulus); SMV inversion (abnormal SMV position to the left of the SMA, a supportive but nonspecific sign of malrotation).
References
Access all radiology signs posted so far: https://radiogyan.com/radiology-signs/
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