An adult male presented with symptoms of lower abdominal pain & vomiting since four days and one episode of melena after a binge of alcohol. There was no history of fever, weight loss or surgery. Severe tenderness was present in the lower abdomen during examination. Laboratory investigations revealed mild leukocytosis. His C-reactive protein was mildly elevated and arterial lactate was 1.6 mmol/L (normal < 2mmol/L).
CT topogram revealed pneumatosis of proximal sigmoid colon with no features of pneumoperitoneum. Small bowel loops seemed mildly dilated with no transition point, likely due to paralytic ileus. Extensive intramural air foci were seen in distal third of descending colon and proximal sigmoid colon with loss of normal haustral pattern. Circumferential wall thickening (~11 - 12mm) was seen in the descending colon. There was surrounding mesenteric fat stranding extending to the left psoas muscle & anterolaterally up to the left abdominal wall muscles with fasciitis. There was no significant lymphadenopathy and no ascites. There was no portal venous gas or intra-peritoneal collection. Arterial phase showed partial filling defect in distal descending aorta which was extending into the inferior mesenteric artery and its branches, suggestive of partial thrombosis. Due to features of ischemic colitis & necrosis on CT and worsening signs & symptoms, the patient was operated. Gangrene of the mentioned distal left colon was present intraoperatively, thus necessitating resection of the involved segment.
‘Pneumatosis intestinalis’ was first described in 1946 by Lerner and Gazin. It now encompasses all cases of intramural bowel gas which include necrotizing enterocolitis, ischemic bowel necrosis and neutropenic typhlitis.  It is an imaging sign and not a diagnosis. It may be asymptomatic or patients can present with abdominal pain, vomiting and abdominal distension. There are two categories of causes of Pneumatosis- i) benign (due to systemic diseases like asthma & scleroderma, intestinal inflammation) and ii) life-threatening conditions (ischemia, gastrointestinal obstruction, trauma, drugs). Additionally, Pneumatosis must be differentiated from Pseudo Pneumatosis to prevent errors. Gas trapped within faecal matter or against mucosal surface with a normal intestinal wall, favours the latter. It is more commonly seen in the caecum and ascending colon. The gas does not extend beyond the intraluminal free gas-fluid level. Porto mesenteric venous gas and vascular thrombus favour true Pneumatosis.  The other differentials include Pseudomembranous colitis, which is characterized by marked bowel wall thickening, usually in an older patient and is associated with broad-spectrum antibiotic treatment. Neutropenic colitis demonstrates right-sided colonic and ileal involvement, while ischaemic colitis, such as in this case, is characterised by typical vascular distribution.  Inflammation surrounding colonic diverticula will be seen in diverticulitis. Radiation colitis and inflammatory bowel diseases like Crohn's & ulcerative colitis have typical imaging patterns and longer history.
Plain radiographs and contrast computed tomography with oral & rectal contrast are the main investigations. Neutral oral contrast material with intravenous contrast agents allow visualisation of bowel wall hypo- or hyperenhancement since bright intraluminal positive contrast might interfere with enhancement of the bowel wall. CT is the best modality to show intramural disease and pericolonic structures with disease complications.  Findings of Pneumatosis need to be communicated to the referring clinician or surgeon urgently as it can have serious consequences like bowel gangrene and rupture.  Complications include pneumoperitoneum, bowel obstruction, volvulus and haemorrhage.  Thus the role of a radiologist is extremely important in providing a timely diagnosis and initiating a multidisciplinary approach for patient management. 
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