Helicobacter species and liver diseases: association or causation?

The discovery of Helicobacter hepaticus as a causal agent of hepatitis and hepatocarcinoma in mice has stimulated interest in looking for Helicobacter spp in human liver samples. These bacteria could be a risk factor for the progression of liver disease to cirrhosis and hepatocellular carcinoma, especially among patients chronically infected with hepatitis C virus. We reviewed the studies done on this topic, and, with the exception of one, all studies reported an association between the presence of Helicobacter spp and liver disease. However, these data are weakened by the fact that Helicobacter spp DNA was detected but no bacteria could be grown, and by the difficulties in identifying the Helicobacter spp involved. More studies are therefore needed to confirm whether a causal association exits between the presence of Helicobacter spp in the liver and the development of cirrhosis and hepatocellular carcinoma.