What is a closed loop bowel obstruction, and what are its CT and MRI features?
A closed loop bowel obstruction is a surgical emergency and is secondary to obstruction of bowel at two separate locations along its course. This condition generally arises in the setting of volvulus, hernia, or adhesion formation, and it can rapidly progress to bowel ischemia, bowel infarction, bowel perforation, sepsis, and death.
CT and MRI findings include C-shaped or U-shaped loops of dilated bowel, often with a radial configuration and convergence of mesenteric vessels toward a central focus; mesenteric haziness and fluid related to edema; prominent engorged mesenteric vessels; a swirling appearance of the mesentery and vessels adjacent to the transition zone (“whirl” sign); and beaking and tapering of bowel loops at the sites of obstruction (“beak” sign), often spatially located in close proximity to each other.
