Daily Radiology Case

Explanation

Sigmoid volvulus is a twist of the sigmoid colon around its mesentery, accounting for 5–15% of large bowel obstructions in developed countries and up to 50% in endemic regions. The elderly population, particularly males, are at highest risk, often triggered by chronic constipation, immobility, or megacolon. Radiographically, the hallmark finding is the dilated, twisted sigmoid loop (coffee bean sign on X-ray due to the tapered transition point), with an absence of distal gas reflecting complete obstruction. CT demonstrates the whirlpool sign—convergence of mesenteric vessels and twisted mesentery at the volvulus point—which can confirm diagnosis and assess for ischemia. The closed-loop mechanism creates risk for ischemia and perforation if not decompressed promptly. Management typically begins with rigid or flexible sigmoidoscopy for decompression, though recurrence rates are high without definitive surgical resection (sigmoidectomy). This case was successfully decompressed via rigid sigmoidoscopy, avoiding emergent surgery.

Source: Knipe H, Sigmoid volvulus - coffee bean and whirlpool signs. Case study, Radiopaedia.org (Accessed on 10 Mar 2026) https://doi.org/10.53347/rID-230353

Hints

• An elderly male presents with acute-onset abdominal distension and constipation; he appears uncomfortable with visible abdominal bloating.
• On exam, the abdomen is markedly distended and tympanic to percussion, with diminished or absent bowel sounds, suggesting mechanical obstruction of the colon.
• There is no palpable fecal impaction on rectal exam, and the rectum is empty. Indicating obstruction proximal to the rectosigmoid junction.
• Abdominal X-ray shows a massively dilated loop of colon in the pelvis with an abrupt transition to a narrow, decompressed distal segment and absence of rectal gas.
• The dilated bowel loop has a characteristic tapered appearance at its narrowest point, resembling a twisted loop or "coffee bean" on frontal view—the classic radiographic sign of volvulus.
• CT imaging demonstrates converging mesenteric vessels and twisted mesentery at the volvulus point, producing the "whirlpool sign" that confirms the sigmoid colon is twisted 180–360 degrees around its mesenteric axis.