Pneumatosis intestinalis - A challenging biopsy diagnosis

Background: Pneumatosis intestinalis is characterized by the accumulation of gas in the gastrointestinal wall. The histopathologic diagnosis is easily made on resection specimens in which the presence of submucosal or subserosal empty spaces lined by histiocytes and giant cells presents little diagnostic dilemma. In biopsy material, though, the diagnosis is more challenging, as giant cells and histiocytes can be interpreted as granulomatous inflammation indicative of other conditions such as infection or Crohn disease. Design: Nine gastrointestinal biopsies diagnosed as pneumatosis intestinalis from 7 patients were reviewed. Clinical history, radiologic features, and endoscopic findings were obtained from patient records. Results: Five patients presented with blood in the stool (one also with diarrhea) and 2 patients were diagnosed after screening colonoscopies. The endoscopist frequently described polyps or raised mucosal folds (6 cases). In all biopsies submucosal cystic spaces lined by giant cells could be observed. The cysts were intact (2 biopsies), partially intact (5 biopsies), or collapsed (5 biopsies), with 3 biopsies showing 2 cyst architectural conformations. The arrangement of the giant cells lining a rounded or clefilike space was the most helpful feature in distinguishing pneumatosis intestinalis from granulomatous colitis. Additional useful features included the recognition of "pseudolipomatosis" (n = 4) and the presence of round empty spaces in the submucosa resembling fat (n = 3). Nonspecific findings included variable inflammation, eosinophilia, mild gland disarray, vascular ectasia and edema, and mild melanosis coli. Two cases were initially given a diagnosis of granulomatous inflammation. One patient with acquired immunodeficiency syndrome and positive cytomegalovirus antigenemia assay had ischemic colitis on the biopsy and another had a subsequent resection with ischemic colitis. A third patient was treated for cytomegalovirus colitis. None had a history of or developed Crohn disease. Conclusions: Pneumatosis intestinalis remains a challenging diagnosis on biopsy material, particularly because endoscopy usually does not suggest that diagnosis. The presence of giant cells in the submucosa, variable inflammation, and crypt disarray can be easily confused with Crohn disease. Attention to the arrangement of the giant cells lining intact, partial, or collapsed cysts is crucial to making the correct diagnosis. Although nonspecific by itself. pseudolipomatosis may also indicate the presence of gas within the tissue and suggest the diagnosis.