Ammonia-to-Urea Ratio: A Noninvasive First-Line Tool for Detecting Clinically Significant Portal Hypertension

Area of Science:

• Hepatology
• Gastroenterology
• Biochemical Diagnostics

Background:

• Cirrhosis progression involves compensated and decompensated phases, frequently complicated by portal hypertension.
• Portal hypertension leads to serious complications such as ascites, variceal hemorrhage, and hepatic encephalopathy.
• The ammonia-to-urea (A-to-U) ratio may offer a more accurate assessment of urea cycle efficiency than plasma ammonia alone.

Purpose of the Study:

• To compare the diagnostic accuracy of the A-to-U ratio versus plasma ammonia levels in identifying portal hypertension.
• To evaluate the A-to-U ratio's effectiveness in detecting clinically significant portal hypertension (CSPH) and related complications.

Main Methods:

• A two-phase study (derivation and validation) involving patients with chronic liver disease.
• Outcomes included imaging findings of portal hypertension, CSPH (Baveno VII criteria), gastroesophageal varices, and portal hypertensive gastropathy.
• Statistical analysis focused on diagnostic odds ratios (dOR) for the A-to-U ratio and plasma ammonia.

Main Results:

• The A-to-U ratio (> 1.53 mg/g) demonstrated high diagnostic accuracy for portal hypertension and CSPH in the derivation cohort (dORs 4.04 and 5.71, respectively).
• This accuracy was validated in a separate cohort (dOR 9.42 for CSPH).
• The A-to-U ratio showed independent associations with esophageal varices and portal hypertensive gastropathy, outperforming BAVENO VII criteria.

Conclusions:

• An A-to-U ratio exceeding 1.53 mg/g is a potentially valuable noninvasive tool for identifying CSPH in chronic liver disease patients.
• This ratio may aid in diagnosing gastroesophageal varices and portal hypertensive gastropathy.
• The A-to-U ratio offers a promising alternative to traditional diagnostic methods for portal hypertension complications.