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Findings: CT done on admission reveals significant small bowel wall thickening with cystic appearing subserosal air. There is generalized small bowel distention with associated air fluid levels throughout the small bowel and remaining colon. Thickening of the splenic flexure colonic mucosa is suggestive of thumbprinting associated with ischemia. Although not present in this case, ascites may be an associated finding secondary to infarction.
Differential diagnosis of pneumatosis intestinalis:
Presence of subserosal or mucosal-filled cystic structures which may vary in size from a few mm to several cm and track along the bowel wall can be detected on plain films and barium studies, but CT remains the most sensitive modality and should be used if pneumatosis is suspect. CT facilitates localization of small amounts of air and localization of affected loops of bowel. If the conventional abdominal windows reveal no cystic collections of air, lung windows can be used to improve detection of small amounts of air. The presence of air in the portal vein is a very grave prognostic sign and a surgical emergency.
Clinical and radiographic findings raised the clinical suspicion of bowel infarction and the patient underwent angiographic evaluation.
Angiographic findings: AP and lateral abdominal aortogram reveals atherosclerotic changes, including mural irregularity and tortuosity. The striking (naked aorta) appearance with absence of the origins of the celiac, SMA and IMA arteries is evident. No major collaterals are visualized between the circulations. There is a tangle of collaterals in the vicinity of the celiac axis. These collaterals appear to arise from the left renal artery and subsequently reconstitute the proximal celiac axis, with filling of a hepatic proper, common hepatic, hepatic arteries and gastroduodenal artery. At no time is opacification in the splenic, SMA or IMA identified. The right renal artery is poorly opacified by collateral vessels.
The findings are compatible with mesenteric ischemia, most likely secondary to progressive atherosclerotic disease, no evidence of embolic phenomenon is noted in this case.
Diagnosis: Mesenteric Ischemia/Pneumatosis Intestinalis.
Discussion: Mesenteric ischemia is a syndrome of varying severity and causes affecting the anoxia sensitive intestinal mucosa often progressing to transmural infarction and ultimately death. It can be divided into three classes: abdominal angina, occlusive mesenteric infarction and nonocclusive mesenteric ischemia. Each is associated with its own clinical presentation, etiology and outcome. There is, however, frequently some degree of overlap. Ischemia can be related to acute or chronic arterial or venous insufficiency. Arterial insufficiency has a wide variety of causes including: atheromatous disease, fibromuscular hyperplasia, vasculitis, endotoxic shock, hypoperfusion, DIC, embolic disease and trauma.
Abdominal angina frequently presents with intermittent abdominal pain which is aggravated by the ingestion of food. Patients also frequently suffer from undesired weight loss. It is caused by severe arterial stenosis at or near its origins with inadequate collateral supply. Thus, when the patient eats, the fixed arterial supply is unable to meet the increased demand needed to facilitate digestion. If diagnosed early, this condition can be treated with mesenteric bypass grafting.
Occlusive mesenteric ischemia results from acute thrombosis or embolic occlusion of the mesenteric arterial supply. This is often superimposed on underlying stenosis. Patients typically present with acute central abdominal pain, shock and peritonitis. This condition carries a prognosis of approximately 90% mortality. Thrombectomy can be attempted but is usually unsuccessful. There are reports in the literature of attempts to use thrombolysis to dissolve the clot but these are limited. If thrombolysis is to be attempted, it should be noted that the patient’s condition represents a surgical emergency and that thrombolysis should not delay surgical intervention but possibly be used as an adjunct to surgical embolectomy.
Nonocclusive mesenteric ischemia usually results from a low flow state in the setting of stenosis from atherosclerotic disease. Hypoperfusion can result from many clinical conditions including shock, surgical intervention and multiple other procedures. The bowel is most likely to recover from nonocclusive ischemia, although stricture formation may result.
Angiography is the gold standard of diagnosis. Findings typically found in angiography include mesenteric occlusion with nonvisualization, vasoconstriction, vascular bleeding, and evidence of embolic disease. CT can give supportive evidence as well. Specific findings are seen on CT in 26% of the patients. These include: pneumatosis intestinalis, portal or mesenteric venous gas, and thumbprinting. Less specific CT findings include: focal/diffuse bowel dilatation, bowel wall thickening, SMA thrombosis, pneumoperitoneum and ascites.
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Myers MA, et al. Pneumatosis Intestinalis. Gastrointestinal Radiology. 1977;2:91-105.
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