Cytomegalovirus Enteritis

Cytomegalovirus enteritis is infection of the small bowel by cytomegalovirus, causing ulceration, haemorrhage and perforation. It occurs almost only in immunocompromised patients and is less common than cytomegalovirus colitis.

Over 50% of adults are seropositive. Disease occurs in organ and stem cell transplant recipients, advanced HIV infection (CD4 count under 50 cells/microlitre), patients on high dose corticosteroids, anti-tumour necrosis factor agents, thiopurines or chemotherapy, and critical illness.

Pathophysiology.

Virus reactivation in endothelial and mesenchymal cells causes vasculitis, mucosal ischaemia and punched out ulcers. Perforation risk is high in the ileum.

Watery or bloody diarrhoea, abdominal pain, nausea, vomiting, fever, weight loss, gastrointestinal bleeding, perforation and protein losing enteropathy.

Red flags.

• Peritonitis or perforation.
• Massive bleeding.
• Obstruction.
• Concurrent retinitis or pneumonitis.

Tissue is needed: endoscopy (gastroscopy, ileocolonoscopy or enteroscopy) shows ulcers, erosions and haemorrhage. Biopsy with haematoxylin eosin ("owl's eye" inclusions) and cytomegalovirus immunohistochemistry (more sensitive). Blood quantitative PCR supports but may be negative in localised disease. CT shows wall thickening, ulceration and complications. Check CD4 count, full blood count and other pathogens in stool.

Differential diagnosis.

• Other infections (Clostridioides difficile, Cryptosporidium, Mycobacterium avium complex, microsporidia).
• Graft-versus-host disease.
• Crohn disease.
• Lymphoma.
• Drug enteropathy (mycophenolate).
• Ischaemia.

Start antiviral therapy and reduce immunosuppression where possible.

• Ganciclovir: 5 mg/kg IV every 12 hours for 2 to 3 weeks, extended to 6 weeks if response is slow; maximum 10 mg/kg daily; monitor full blood count twice weekly and renal function; adjust by creatinine clearance: 50 to 69 mL/min 2.5 mg/kg every 12 hours; 25 to 49 mL/min 2.5 mg/kg every 24 hours; 10 to 24 mL/min 1.25 mg/kg every 24 hours; under 10 mL/min 1.25 mg/kg three times weekly after dialysis; withhold when neutrophils are under 0.5 x 10^9/L or platelets under 25 x 10^9/L.
• Valganciclovir (stepdown when oral absorption is reliable and disease is mild to moderate): 900 mg orally twice daily with food, to complete the course; maximum 1,800 mg daily; monitor counts and creatinine; reduce to 450 mg twice daily for creatinine clearance 40 to 59 mL/min, 450 mg once daily for 25 to 39 mL/min and 450 mg every 2 days for 10 to 24 mL/min.
• Foscarnet (ganciclovir resistance or marrow suppression): 90 mg/kg IV every 12 hours for 2 to 3 weeks with saline loading; maximum 180 mg/kg daily; monitor creatinine, calcium, magnesium, potassium and phosphate; reduce stepwise by creatinine clearance.

Start or optimise antiretroviral therapy in HIV. Surgery is needed for perforation, obstruction or uncontrolled bleeding.

Monitoring. Blood viral load weekly, full blood count twice weekly, renal function, electrolytes and symptom review. Repeat endoscopy if there is no response in 1 to 2 weeks.

Referral and escalation. Infectious diseases or transplant medicine and gastroenterology; surgery for complications.