Equine Cholelithiasis and Secondary Hepatic
Encephalopathy
NECROPSY REQUEST
CLINICAL DIAGNOSIS:
Cholestatic liver disease.
HISTORY:
Mild episode of colic and fever one month prior to euthanasia.
Referring DVM ran bloodwork and noted elevated GGT, bilirubin, and AST.
Treated with IV fluids and Baytril for two days. Sent home on
trimethoprim-sulfa for two weeks. GGT continued to elevate so case was
referred. Mare was depressed but stable on arrival. GGT, Alk Phos,
total and direct bilirubin, and globulins continued to increase.
Ammonia was 222 ug/dL on arrival and increased daily. Bile acids also
elevated at 114. Liver ultrasound showed diffuse hepatomegaly,
increased hyperechogenicity, and distended bile ducts. Biopsy still
pending.
Mare became profoundly hepatoencephalopathic prempting euthanasia.
CLINICAL QUESTIONS:
Especially focus on liver - any choleliths?
NECROPSY GROSS REPORT
ANIMAL
IDENTIFICATION:
A 500kg, 13-year-old, palomino, Quarter Horse mare with a star is presented
for necropsy in good body condition.
INTEGUMENTARY AND SPECIAL SENSES: Shaved areas include: a 150 x 86cm
on the ventral and right and left lateral abdominal walls, and a 7 x 6cm area
on the right lateral aspect of the jugular furrow.
LIVER AND PANCREAS (Liver weight: 15.56kg): The liver is
diffusely and markedly enlarged, gray-green, firm, with rounded edges, an
irregular surface, and an enhanced green and tan reticular pattern on cut
surface. Multiple, intra-hepatic bile ducts contain firm to crumbly,
tan-green material and two, up to 3cm diameter, firm, round concretions (choleliths).
Additionally, many fibrous tags are multifocally and strongly adhered to the
diaphragmatic surface (capsular fibrosis).
RESPIRATORY, CARDIOVASCULAR (Heart weight: 4.26kg. The right
ventricular free wall is 2cm in width. The left ventricular free wall is 5cm
in width.), HEMIC AND LYMPHATIC (Spleen weight: 2.24kg), URINARY
(Right kidney weight: 1.54kg; Left kidney weight: 1.44kg), GENITAL,
DIGESTIVE, ENDOCRINE, MUSCULOSKELETAL, NERVOUS (Brain
weight: 0.71kg): No significant lesions observed.
POSTMORTEM ANALYSIS AND DIAGNOSIS:
The cause of death is euthanasia. The gross findings are consistent with
cholelithiasis. Histopathology of selected tissues is pending.
TENTATIVE DIAGNOSIS:
Cholelithiasis.
(Fig. 1 The liver is enlarged, diffusely firm, pale, and has an irregular surface.)
(Fig. 2 The liver after removal from the body. Note the radiating pale bands of fibrosis evident on the capsular surface.)
(Fig. 3 Close-up of the opened bile duct, showing orange-brown choleliths.)
NECROPSY HISTOPATHOLOGY REPORT
MICROSCOPIC LESIONS:
Liver: Diffuse, severe, chronic, bridging periportal fibrosis, with marked
biliary hyperplasia, cholestasis, and hepatocellular vacuolar change.
Cerebrum: Diffuse moderate astrocytosis and astrogliosis (Alzheimer type II
astrocytes).
Kidney: 1) Multifocal, mild, acute, intratubular birefringent crystals; 2)
Minimal lymphoplasmacytic interstitial nephritis.
Cerebellum, Gastrointestinal tract, Heart, Lung: Unremarkable histologic
changes.
DIAGNOSIS: Cholelithiasis; Hepatic encephalopathy.
(Fig. 4 Histologically, hepatic lobules are separated by prominent bands of fibrous connective tissue (black arrows), accompanied by hyperplastic biliary ducts (white arrow).)
(Fig. 5 At higher magnification, cholestasis is evident, with accumulations of bile present both intra- and extracellularly (arrows).)
INTERPRETIVE SUMMARY/COMMENTS:
The histologic
changes are consistent with cholelithiasis and secondary hepatic
encephalopathy. The pattern of liver lesions in cholelithiasis is unusual.
Most chronic liver diseases with bridging fibrosis are due to toxicity and
result in small, firm livers from hepatocellular necrosis and replacement
fibrosis. Because there is little hepatocyte loss with cholelithiasis, the
disease can result in a diffusely enlarged and firm liver.
