ISHEN Consensus Standardizes Ammonia Testing in Cirrhosis : J Hepatol | May 2026

Introduction

Hepatic Encephalopathy is a major complication of Cirrhosis and is closely linked to ammonia metabolism. Despite ammonia’s central pathogenic role, the clinical value of blood ammonia measurement has remained controversial because of inconsistent sampling methods, laboratory variability and uncertainty regarding interpretation in routine practice.

Problem Statement

Lack of standardized guidance regarding ammonia measurement has resulted in major variability in clinical practice, limiting its reliable use in diagnosis, prognostication, therapeutic monitoring and research in cirrhosis and hepatic encephalopathy.

Summary

This International Society for Hepatic Encephalopathy and Nitrogen Metabolism (ISHEN) consensus represents the first structured international effort to standardize the role of ammonia measurement in cirrhosis care using a formal evidence-based Delphi methodology.

The recommendations were developed through a rigorous multinational multidisciplinary consensus process involving expert hepatologists and researchers with specific expertise in hepatic encephalopathy and ammonia metabolism. The panel addressed 25 clinically relevant PICO questions spanning diagnostic utility, prognostication, therapeutic monitoring and technical aspects of ammonia measurement.

A major contribution of the document is its emphasis on preanalytical standardization. The consensus highlights that ammonia measurements are highly susceptible to methodological error, including delays in processing, improper sample handling and variability in collection techniques. Standardized acquisition and processing protocols are therefore essential for clinically interpretable results.

The panel supports the clinical relevance of ammonia measurement in selected settings rather than indiscriminate routine use. Elevated ammonia levels were recognized as useful in supporting the diagnosis of overt hepatic encephalopathy, particularly when diagnostic uncertainty exists, while acknowledging that ammonia alone cannot definitively establish or exclude the diagnosis.

Importantly, the consensus also emphasizes ammonia’s prognostic role. Elevated levels may help identify patients at higher risk of developing overt hepatic encephalopathy and other liver-related complications, supporting incorporation into risk stratification frameworks for both inpatient and outpatient management.

The recommendations additionally address therapeutic monitoring. Serial ammonia assessment may provide supportive information regarding response to ammonia-lowering therapies, although clinical evaluation remains the cornerstone of management decisions.

A particularly valuable aspect of the document is its balanced interpretation of ammonia biology. The panel acknowledges that hepatic encephalopathy is multifactorial and not solely ammonia-dependent, explaining why some patients with elevated ammonia remain clinically asymptomatic while others develop encephalopathy despite lower concentrations.

The consensus also identifies several important research priorities. These include development of reliable point-of-care ammonia testing, validation of ammonia-based predictive models and improved understanding of non-hyperammonemic encephalopathy phenotypes.

Clinically, the document may substantially improve harmonization of practice across centers and trials. Standardized ammonia measurement protocols are especially important for multicenter hepatic encephalopathy studies, biomarker development and emerging therapeutic trials targeting ammonia metabolism.

The work additionally reinforces the growing movement toward precision phenotyping in cirrhosis. Rather than viewing ammonia as a binary diagnostic marker, the consensus frames ammonia as a dynamic biologic variable integrated within broader clinical, inflammatory and metabolic contexts.

From a translational perspective, the document is also highly relevant for drug development. Reliable ammonia measurement frameworks will likely become increasingly important as novel therapies targeting nitrogen metabolism, microbiome modulation and skeletal muscle ammonia handling continue to emerge.

Overall, this ISHEN Delphi consensus establishes the first evidence-based international framework for ammonia measurement in cirrhosis. The recommendations provide practical guidance for clinicians, standardize best practices for sampling and interpretation, and reinforce ammonia’s evolving role in diagnosis, risk stratification and management of hepatic encephalopathy.