Right hepatic lobe atrophy in horses: 17 cases (1983-1993).

This research studies the condition of right hepatic lobe atrophy in horses, examining 17 cases from over a decade. The findings reveal various complications in the horses, conjuncted with signs of colic or unrelated clinical issues. The study suggests that this type of atrophy may be caused by constant compression of the liver due to excessive distention of the right dorsal colon and cecum.

Case Review and Colic Symptoms

• The researchers reviewed the records of 17 horses with atrophy of the right hepatic lobe, a condition characterized by a reduction in size and possible deterioration of the affected part of the liver.
• Out of these horses, 15 showcased signs of colic, a term used to describe severe, often fluctuating pain in the abdomen that is usually associated with disturbances in the gastrointestinal tract.
• However, the remaining 2 horses had clinical problems that were not associated with any diseases of the gastrointestinal tract.

Variables Amongst the Cases

• The ages of the affected horses ranged from 5 to 30 years with no preference shown to a specific breed or gender.
• The size of the right hepatic lobe in the horses studied varied greatly. Normally, this lobe of the liver constitutes about half the total liver weight in healthy horses, but in this case, the right lobe’s weights ranged from 11.0 to 38.3% of the total liver weight.
• A microscopic examination of the hepatic tissue highlighted various abnormalities, with most horses having lost hepatocytes, the main cell type in the liver. Other observations included a denser hepatic stroma and thick, wrinkled hepatic capsules.

Additional Pathologies Found

• Other complications detected in the horses included a range of gastrointestinal and systemic issues, such as colon torsion, colon infarction, strangulated small intestine, and nephrosplenic entrapment.
• Contrary to what might be expected, the researchers found no morphological signs of vascular disease affecting the arterial or venous blood supply to the right hepatic lobe.
• Additionally, there were no signs of bile duct diseases in the studied liver section.

Proposed Causes

• The researchers speculate that right hepatic lobe atrophy might be due to prolonged, subtle compression of the right hepatic lobe caused by abnormal swelling of the right dorsal colon and base of the cecum.
• The feeding trend of offering horses high-concentrate, low-fiber diets could lead to a loss of muscular tone in the right dorsal colon. This can result in an expansive state that presses the right hepatic lobe against the rigid, visceral surface of the diaphragm, causing the deterioration of hepatocytes over time.