Subcutaneous emphysema may result from pathological changes in the thorax or lung, as a result of localised infection with gas producing organisms, after abdominal procedures, or herald an intestinal perforation. The location and spread of extraperitoneal gas is determined by the anatomical barriers and fixed fascial layers surrounding the region of pathological change. The case highlights the extent of extraperitoneal gas after colonic perforation despite minimal clinical features and the importance of intra-abdominal causes of cervical subcutaneous emphysema.
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A 62 year old woman presented to the accident and emergency department with a three day history of progressive abdominal pain in the left iliac fossa. This followed several weeks of constipation. She had one episode of fresh red blood per rectum and nausea on the day she presented. She had a past history of diverticulitis. Clinically she looked well, afebrile with mild tenderness in her left iliac fossa. Subcutaneous emphysema was present in her neck. Blood tests revealed a neutrophilia of 24.6. Diverticulitis was suspected and abdominal radiographs requested. The supine film demonstrated retroperitoneal gas outlining psoas, the left kidney and adrenal (fig 1).
Contrast enhanced computed tomography confirmed retropneumoperitoneum, with gas extending between internal and external oblique abdominal musculature (fig 2). Gas also extended into the mediastinum outlining the aorta circumferentially and the oesophagus to its right.
Laparotomy was performed and a large cavity found behind the proximal sigmoid colon along the pelvic brim. It contained free faeces and pus. A Hartmann’s procedure was completed with oversewing of the rectosigmoid junction and fashioning of an end colostomy. A reversal is planned later.
Perforation of a colonic diverticulum from infection and inflammation typically causes faecal or purulent peritonitis. Usually the inflammatory process involves surrounding tissues such as mesentery, gut, and posterior abdominal wall. The localised abscess may rarely rupture into retroperitoneal tissues with gas tracking upwards, most often localising to the left side.1 The psoas muscle typically limits posterior pararenal retroperitoneal gas medially, laterally gas may extend into the flank, and superiorly gas may outline the suprarenal area, medial crus of the diaphragm, and posterior aspect of the liver and spleen. Extension above the diaphragm through diaphragmatic hiati can lead to the development of cervical and thoracic subcutaneous emphysema.1
Subcutaneous emphysema of the neck, chest wall, abdomen or thigh may be the first manifestation of an occult perforation, either from sigmoid diverticulitis of from other retroperitoneal processes.2 In particular, infradiaphragmatic causes of pneumomediastinum and subcutaneous gas in the neck and chest should always be considered.3
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