The “paper-thin wall” appearance in acute mesenteric ischemia

Abstract

The “paper-thin wall” describes a CT depiction of the small and large bowel that can be seen in acute mesenteric ischemia [1]. This appearance is generated by an extreme thinning of the bowel wall, caused by volume loss of intestinal tissue, vasculature, and muscular tone, resembling a “sheet of paper” (Fig. 1) [2]. Acute mesenteric ischemia can occur from arterial embolic or thrombotic obstruction (60–70%), or mesenteric venous thrombosis (5–10%), or can have a non-occlusive etiology (10–20%) [2]. Normal bowel wall thickness ranges from 3 to 5 mm depending on the degree of bowel distention [1]. In acute mesenteric ischemia, contrast-enhanced CT can reveal luminal dilatation with air-fluid levels, thrombus in the mesenteric arteries or veins, abnormal enhancement of bowel wall, and an attenuated bowel wall with a “paper-thin wall” appearance (Fig. 2) [1, 3]. While a useful clue, the paper-thin wall is a less sensitive sign of acute mesenteric ischemia [3]. Indeed, this appearance can be typically found in the setting of acute arterial occlusive mesenteric ischemia or transmural infarction [3]. However, arterial ischemia bowel wall can also be thickened, due to hematoma, edema, or inflammation [3]. In cases of reversible mesenteric arterial ischemia, or occlusions of mesenteric veins, or non-occlusive mesenteric ischemia, abnormal mural thickening (up to 15 mm) of the small bowel or colon is the most frequently observed CT finding, due to intramural hemorrhage, edema, and/or superinfection [1, 3]. The ischemic bowel segment attenuation is variable: on unenhanced CT images, hypoattenuation of the bowel wall indicates bowel wall edema; on contrast-enhanced CT, an absent or diminished bowel mural enhancement is a specific finding of ischemia, while