The whirlpool sign, also known as the whirl sign, is seen when a structure twists upon itself. It is most commonly described in the abdomen where bowel rotates around its mesentery, with mesenteric vessels creating the whirls. It can also be seen in ovarian torsion.
Whirlpool sign: mesenteric
It is seen in a number of settings:
- malrotation complicated by midgut volvulus
- caecal volvulus
- sigmoid volvulus 6
- closed loop bowel obstruction 5
- enteritis: similar pattern, but in the opposite direction has been described on ultrasound 3
- omental torsion 8
Malrotation and midgut volvulus
It represents the swirling appearance of the mesentery and superior mesenteric vein around the superior mesenteric artery. The direction of swirl is clockwise on ultrasound (viewed from above so-to-speak) and counter-clockwise on CT (as if viewed from below).
It is the corollary of the corkscrew sign seen on barium studies.
Caecal volvulus can have the same appearance, with whirl occurring in the caecal mesentery.
Whirlpool sign: ovarian
Whirlpool sign of a twisted ovarian pedicle has been described as an US or CT sign of ovarian torsion 7.
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- 3. Shimanuki Y, Aihara T, Takano H et-al. Clockwise whirlpool sign at color Doppler US: an objective and definite sign of midgut volvulus. Radiology. 1996;199 (1): 261-4. Radiology (abstract) - Pubmed citation
- 4. Frank AJ, Goffner LB, Fruauff AA et-al. Cecal volvulus: the CT whirl sign. Abdom Imaging. 1993;18 (3): 288-9. - Pubmed citation
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- 6. Levsky JM, Den EI, DuBrow RA et-al. CT findings of sigmoid volvulus. AJR Am J Roentgenol. 2010;194 (1): 136-43. doi:10.2214/AJR.09.2580 - Pubmed citation
- 7. Duigenan S, Oliva E, Lee SI. Ovarian torsion: diagnostic features on CT and MRI with pathologic correlation. AJR Am J Roentgenol. 2012;198 (2): W122-31. doi:10.2214/AJR.10.7293 - Pubmed citation
- 8. Tandon AA, Lim KS. Torsion of the greater omentum: A rare preoperative diagnosis. Indian J Radiol Imaging. 2010;20 (4): 294-6. doi:10.4103/0971-3026.73540 - Free text at pubmed - Pubmed citation