Hello and welcome to HCM, A rise in level of ammonia occurs in cases of hepatic failure or liver failure. Lactulose is prescribed in cases of hepatic encephalopathy. Hepatic encephalopathy is the liver failure affecting the brain. Ammonia is metabolised by liver. In cases of liver failure, the liver is unable to metabolise ammonia. Thus, accumulation of ammonia is toxic to cells of the brain and thus encephalopathy. Urinary tract infection has to be managed with antibiotics. The two conditions have separate pathogenesis and thus should be treated separately. Thanks and take care Dr Shailja P Wahal