Hepatic encephalopathy and Helicobacter pylori: a critical reappraisal

Hepatic encephalopathy (HE) is a frequent complication of liver cirrhosis, and plasma ammonia plays a pivotal role in its pathogenesis. Ammonia disposal in cirrhotics depend on intricately balanced enzyme and transport systems, involving liver, large and small bowel, muscle, and kidney. Recently, it has been suggested that Helicobacter pylori could contribute to hyperammonemia in cirrhotics, but conflicting data are available in the literature. This is a systematic review of experimental (animals and humans), epidemiological, case-control, and prospective studies, to evaluate the arguments in favor and against the role of H. pylori in HE pathogenesis. Although H. pylori produces ammonia in the stomach, several studies have shown that both basal ammonia levels and HE prevalence did not significantly differ between cirrhotics with and without infection. Moreover, some prospective studies have documented that both blood ammonia levels and mental status in HE cirrhotics are not significantly affected by H. pylori eradication. Even if a small sub-group of cirrhotics with both a high bacterial density and more severe hepatic impairment seems to benefit by bacterial eradication, data indicate that ammonia production in the stomach by H. pylori urease appears to be inadequate to clinically affect ammonia disposal in the majority of cirrhotic patients. Further studies are warranted in this field.