Imaging May Lessen Liver Biopsies to Diagnose Fibrosis

ROCHESTER, Minn., Oct. 3 -- Many liver biopsies to diagnose liver fibrosis and cirrhosis may soon be supplanted by non-invasive imaging techniques, researchers here said.

New methods of evaluating fibrosis are highly accurate, according to three papers in the October issue of Clinical Gastroenterology and Hepatology.

Two of the studies evaluated new diagnostic methods, while the third was a meta-analysis of research on ultrasound-based transient elastography, the method that has received the most research attention.

The method involves using an ultrasound generator to send a wave through the organ, wrote Jayant Talwalkar, M.D., of the Mayo Clinic College of Medicine, and colleagues.

The wave moves faster through stiffer tissue, allowing clinicians to gauge the extent of fibrosis, Dr. Talwalkar and colleagues said.

All told, the researchers found nine published studies comparing the results of ultrasound-based transient elastography to standard biopsies as a diagnostic tool for patients with stage IV fibrosis, or frank cirrhosis.

Seven of them also allowed comparison for patients with stages II, III, and IV fibrosis.

For the cirrhosis patients, the researchers said, the pooled sensitivity estimate for the nine studies was 87%, while the pooled specificity estimate was 91% -- results that qualified as "excellent."

The results were "consistent with values seen among tests considered to provide strong diagnostic evidence in clinical decision making," the researchers said.

The estimates were lower for patients with less advanced disease, with a pooled sensitivity estimate of 70% and a pooled specificity estimate 84%.

Although the studies used differing cutoff points, so that the analysis could not pin down true accuracy, "ultrasound-based transient elastography appears to be a clinically useful test for detecting cirrhosis," the researchers concluded.

A second Mayo team, led by Richard Ehman, M.D., Ph.D., investigated a variation on ultrasound-based transient elastography - this time using magnetic resonance to create mechanical shear waves in the liver.

The researchers studied the technique in 35 normal volunteers and 50 patients with chronic liver disease and found that the average liver stiffness (measured in kilopascals) was 2.2 for normal volunteers and 5.8 for those with liver disease.

The degree of stiffness was significantly correlated with the degree of fibrosis (P<0.001), Dr. Ehman and colleagues reported.

The technique had a sensitivity of 98% and a specificity of more than 99% for differentiating any stage of liver fibrosis from normal liver tissue, the researchers said.

The study also showed that hepatic steatosis had no effect on the diagnostic power of the technique, the researchers said.

Finally, another technique - this one analyzing blood flow in the liver - also proved useful in evaluating the extent of fibrosis and cirrhosis in patients with chronic hepatitis C, according to Chen-Hua Liu, M.D., of the National Taiwan University Hospital in Taipei, and colleagues.

The researchers prospectively evaluated consecutive hepatitis C patients between January, 2003 and December, 2006, and enrolled 503 of them. Duplex Doppler ultrasonography was used to assess splanchnic vascular hemodynamics before a liver biopsy.

In multivariate logistic regression analyses, two hemodynamic characteristics - the mean portal vein velocity and the splenic artery pulsatility index - significantly predicted (P<0.001) patients with hepatic fibrosis up to and including cirrhosis, Dr. Liu and colleagues found.

But the splenic artery pulsatility index was more accurate, the researchers said.

On the other hand, they added, because of variations among observers and equipment, obtaining reproducible results might be difficult. It's also not clear how well the technique will work in patients with other types of underlying disease, so more research is needed, they said.

The studies are the wave of the future, said journal editor C. Mel Wilcox, M.D., of the University of Alabama. "

Using Doppler ultrasound and MRI, these investigators found these modalities to be accurate and reproducible in detecting fibrosis and cirrhosis." he said in a statement.

"Look for more studies using these non-invasive imaging studies, and perhaps others in the future."

Dr. Liu's study was supported by the National Taiwan University Hospital, the National Science Council, and the Taiwan Department of Health. The authors reported no conflicts.

For the meta-analysis, Dr. Talwalkar and colleagues reported no conflicts.