Equine Hepatic Disease and Biliary Disorders – NAVLE Study Guide

Overview and Clinical Importance

Hepatic disease in horses represents a significant diagnostic and therapeutic challenge in equine practice. The liver comprises approximately 1.5% of body weight and possesses remarkable regenerative capacity, which paradoxically means clinical signs often do not manifest until 70-80% of hepatic function is compromised. This delayed presentation makes early detection challenging and emphasizes the importance of understanding subtle clinical and laboratory indicators.

A unique anatomical feature of equine hepatobiliary anatomy is the absence of a gallbladder. Bile flows continuously from the liver directly into the duodenum via the common bile duct. This anatomical distinction affects the pathophysiology and clinical presentation of biliary disorders in horses compared to other species.

Hepatic Anatomy and Physiology

Functional Anatomy

The equine liver is positioned in the cranial abdomen, primarily on the right side, and can be imaged ultrasonographically from the 9th to 15th intercostal spaces on the right side. The liver receives dual blood supply: approximately 75% from the portal vein (nutrient-rich blood from GI tract) and 25% from the hepatic artery (oxygenated blood).