Case 32: Herniation of the ascending colon into the lesser sac.
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Biomedical subjects
Publications and source records attributed to B L Pear.
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This review illustrates the changing paradigms in the understanding of the pathogenesis of pneumatosis intestinalis. Although many theories have been evoked, pragmatically there appear to be four major clinical and diagnostic imaging considerations. The most common and most emergent life-threatening cause of intramural bowel gas is the result of bowel necrosis due to bowel ischemia, infarction, necrotizing enterocolitis, neutropenic colitis, volvulus, and sepsis. In the stomach, intramural gas can be caused by emphysematous gastritis or ingestion of caustic agents. These situations represent surgical emergencies. Pneumatosis is found secondary to mucosal disruption presumably due to over-distention from peptic ulcer, pyloric stenosis, annular pancreas, and even to more distal obstruction. Disruption can also be caused by ulceration, erosions, or trauma, including the trauma of child abuse. Disruption can also be iatrogenic from intracatheter jejunal feeding tubes, stent perforation, sclerotherapy, or surgical or endoscopic trauma. In these cases, the gas may be focal or linear. Treatment depends on the extent of the disruption and the underlying cause. A more subtle form of mucosal disruption may occur due to mucosal erosions and also to defects in intestinal crypts secondary to acute and subclinical enteritides that allow intraluminal bacterial gas under pressure to percolate into the bowel wall layers, particularly the submucosa (29). Pneumatosis, often linear or cystic in appearance, is seen with increased frequency in patients who are immunocompromised because of steroids, chemotherapy, radiation therapy, or AIDS. In these cases, the pneumatosis may result from intraluminal bacterial gas entering the bowel wall due to increased mucosal permeability caused by defects in bowel wall lymphoid tissue. Clinical and imaging findings are important in the differentiation of this transient pneumatosis from fulminant life-threatening causes in this subset of patients. A pulmonary cause must still be considered in cases of chronic obstructive pulmonary disease, asthma, and cystic fibrosis. It can occur with barotrauma and after chest tube placement. It may relate to increased intrathoracic pressure associated with retching and vomiting. The possibility remains that occasionally the origin of pneumatosis intestinalis will remain cryptogenic--caused but unexplained.
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We have described a case of osteomyelitis of the ischium with extension into the adjacent soft tissues and abscess formation. Diagnosis and treatment were initially delayed due to the assumption that edema in the thigh muscles seen on initial MRI represented polymyositis. Subsequent radiographs demonstrated a destructive lesion containing a sequestrum within the ischium, indicative of osteomyelitis. It was, however, the MRI imaging that dramatically demonstrated the full extent of the complicating abscess which extended downward to mid-thigh and upward under the gluteal muscles almost to the top of the iliac crest. This proved to be an invaluable guide for the surgeon.
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Extrahepatic manifestations due to an immunologic response to a surface antigen of hepatitis B virus have been identified. These include a serum sicknesslike syndrome and a necrotizing vasculitis. The latter is far more important and in indistinguishable histologically from nonhepatitis related polyarteritis. At least 90 cases have been reported in the decade since 1970, and five are added here. The necrotizing vasculitis syndrome results from fibrinoid necrosis and inflammation of small and medium-sized arterial walls recognizable angiographically by arterial microaneurysms and often by visceral infarction and hemorrhage. Renal failure is common and often associated with pulmonary edema. Gastrointestinal symptoms are a prominent feature due to bowel ischemia. Infarction and perforation are significant causes of morbidity and mortality. Necrotizing vasculitis is also one cause of pancreatitis and of cholecystitis. Plain films, contrast studies, computed tomography, and sonography have been shown to be useful in the recognition of these complications.
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