Most patients with obesity, and especially morbid obesity accumulate fat in the liver, which can be associated with liver inflammation and injury. Routine blood tests measuring elevations of liver enzymes are usually done in these patients to detect possible liver inflammation and injury.

In this retrospective study, 147 patients with morbid obesity were screened for elevations of liver enzymes and then underwent gastric bypass surgery. A liver biopsy done at surgery showed that fat accumulation was present in 134 patients (91%) and NASH was found in 20 patients (13%). NASH is known to progress to significant liver scarring and even cirrhosis.

Routine screening tests measuring liver enzymes and liver function, however, were entirely normal in 15 of those 20 patients (75%) who were found to have NASH, including one of the two patients with cirrhosis.

According to Dr. Patricia Latham, "Unfortunately, routine blood tests that screen for liver disease may not detect significant injury and scarring in the majority of these persons. More investigative studies are needed to determine the extent of liver injury in persons with lesser degrees of obesity, and additional noninvasive diagnostic tests are needed to evaluate liver injury and scar formation in these cases. These issues will become more pressing as future research helps us to understand the mechanism of the injury and the means to prevent it."