Pneumatosis Intestinalis

Pneumatosis intestinalis is gas within the bowel wall, shown as linear or cystic collections in the submucosa or subserosa. It is a sign, not a disease, and ranges from a benign incidental finding to a marker of bowel necrosis.

Primary (idiopathic) cystoides forms are about 15% and secondary forms about 85%. It is seen in about 0.03% of the population on imaging and up to 3% of the critically ill.

Causes are ischaemia and necrosis, necrotising enterocolitis in neonates, infection (Clostridium), obstruction, immunosuppression (corticosteroids, chemotherapy, targeted agents, transplant), chronic obstructive pulmonary disease, connective tissue disease (scleroderma), inflammatory bowel disease, post-endoscopy or post-surgery barotrauma, medicines (alpha glucosidase inhibitors, lactulose) and graft-versus-host disease.

Pathophysiology.

Proposed mechanisms are mechanical (raised luminal pressure forcing gas through mucosal defects), bacterial (gas forming organisms invading the wall) and biochemical (fermentation gas) with pulmonary dissection along vessels in lung disease.

Often none. Possible features are abdominal pain, distension, diarrhoea, bloody stool, constipation, vomiting, tenesmus and mucus discharge. Peritonitis, shock and sepsis suggest necrosis.

Red flags.

• Peritonitis.
• Lactate over 2 mmol/L.
• Portal or mesenteric venous gas.
• Haemodynamic instability.

CT with intravenous contrast is the best test: shows linear or bubbly intramural gas, bowel wall thickening or thinning, reduced enhancement, mesenteric stranding, portal venous gas and free air. Radiograph shows gas patterns. Check lactate, blood count, C-reactive protein and amylase. Colonoscopy shows submucosal gas filled cysts in benign disease and is avoided with suspected ischaemia.

Differential diagnosis.

• Mesenteric ischaemia.
• Necrotising enterocolitis.
• Colonic polyps or lipomas.
• Bowel obstruction or perforation.
• Faecal material mimicking gas.
• Emphysematous infection.

Management depends on the cause and on the presence of ischaemia.

• Benign, asymptomatic: observation, treat the underlying cause (stop causative drugs, treat lung disease).
• Mild symptoms with a stable patient: bowel rest, intravenous fluids, and antibiotics for suspected infection.
• Metronidazole: 500 mg orally or IV every 8 hours; 7 to 14 days; maximum 1.5 g daily; monitor for neuropathy and liver function; reduce to 500 mg every 12 hours in severe hepatic impairment.
• Piperacillin-tazobactam (sepsis or ischaemia): 4.5 g IV every 6 hours for 5 to 7 days after source control; maximum 18 g daily; monitor renal function and counts; reduce for creatinine clearance under 40 mL/min.
• Oxygen therapy has been used for benign cases: high flow oxygen by mask at 70% to 80% for 2 to 5 days; limited evidence; monitor saturation and oxygen toxicity; avoid prolonged use in chronic carbon dioxide retention. Hyperbaric oxygen is another option in selected centres.

Emergency laparotomy or laparoscopy applies to peritonitis, perforation, lactate over 2 mmol/L with worsening signs or clinical deterioration.

Monitoring. Serial examination, lactate every 4 to 6 hours initially, and repeat imaging when symptoms persist.

Referral and escalation. General surgery urgently when symptomatic; critical care for sepsis.