Hepatic Schistosomiasis

Hepatic schistosomiasis is liver disease caused by eggs of Schistosoma mansoni, S. japonicum and S. mekongi trapped in the portal venules. It causes periportal (pipe stem) fibrosis and presinusoidal portal hypertension, with preserved hepatocellular function.

Over 200 million people are infected worldwide, mostly in sub-Saharan Africa, Brazil and Southeast Asia. Hepatosplenic disease develops in 4% to 8% of those infected with S. mansoni, and variceal bleeding is the main cause of death. Hepatitis B or C coinfection accelerates fibrosis.

Pathophysiology.

Eggs lodge in portal venules and cause granulomatous inflammation, collagen deposition and portal fibrosis. Portal vein obstruction before the sinusoids raises portal pressure and produces varices, splenomegaly and portosystemic shunting.

Often silent for years. Splenomegaly, haematemesis from oesophageal and gastric varices, abdominal discomfort, ascites (when coinfection or decompensation develops), growth impairment in children and pulmonary hypertension. Liver function stays normal in early disease.

Red flags.

• Variceal haemorrhage.
• Decompensation with ascites or jaundice (suspect coinfection).
• Pulmonary hypertension.
• Immune complex glomerulonephritis.

Stool or rectal biopsy for eggs, serology and antigen tests when eggs are not seen. Ultrasound shows periportal fibrosis (thick echogenic bands around portal branches, a pipe stem or network pattern), splenomegaly and collaterals. Liver tests are near normal. Endoscopy grades varices. Test for hepatitis B and C and HIV, and assess for pulmonary hypertension by echocardiography.

Differential diagnosis.

• Cirrhosis.
• Idiopathic non-cirrhotic portal hypertension.
• Chronic portal vein thrombosis.
• Hepatic fibrosis from other infections or toxins.
• Budd-Chiari syndrome.

Give praziquantel to kill the adult worms, although established fibrosis responds poorly. Treat variceal bleeding with endoscopic band ligation, and prevent rebleeding with band ligation and beta blockers. Splenectomy with devascularisation or shunt surgery is for refractory bleeding or symptomatic hypersplenism.

• Praziquantel (S. mansoni, S. haematobium): 40 mg/kg orally as a single dose, or in two divided doses 4 to 6 hours apart on the same day, with food; for S. japonicum and S. mekongi 60 mg/kg in 2 to 3 divided doses on the same day; repeat after 4 to 6 weeks if eggs persist; maximum 3 g in a single dose; monitor for dizziness, abdominal pain and allergic reactions; use caution in decompensated liver disease, and avoid giving with rifampicin, which lowers levels.
• Carvedilol (variceal prophylaxis): 6.25 mg orally daily for 3 days then 12.5 mg daily; maximum 12.5 mg daily (25 mg daily without ascites); monitor blood pressure and heart rate; hold when systolic pressure is under 90 mmHg.

Vaccinate against hepatitis A and B, and treat coinfection.

Monitoring. Endoscopy every 6 to 12 months until varices are eradicated; ultrasound and platelet count yearly; stool eggs 6 weeks after treatment.

Referral and escalation. Hepatology and infectious disease; surgery for refractory portal hypertension.

Special groups. Pregnancy: praziquantel may be given after the first trimester, or earlier if the benefit is greater. Children need weight based dosing.