Gross findings: The subcutis of the cat was jaundiced and the liver was markedly enlarged and misshapen, and weighed 12.6% of the cat's total body weight. The capsular surface of the liver was irregular, mottled red to white, and had multiple white umbilicated depressions. The left lateral lobe of the liver had a cavernous cyst that contained 20-30 ml of serosanguinous fluid. On cut section, the lobe had a dark red lining with multifocal embedded white strands of fibrous tissue. The right medial liver lobe was expanded by a cyst that contained 10-15 ml of clear, viscous fluid. The lining of the cyst was dark tan to pale white. The remainder of the liver was mottled dark red to tan with multifocal white and green foci that extended into the parenchyma.
In addition, within the mid-jejunum, there was a dilation of the small intestine, approximately 5 cm in length, which contained a 1.4 cm vertical, transmural tear that was surrounded by a focal, dark purple to red discoloration of the adjacent serosa. Within the intestinal lumen in this area, there was a 1.2 cm in diameter foreign body that was black, jagged, fetid, and had an orange-brown core. Both kidneys were mildly shrunken and palpably firm with a pitted appearance to the capsule. The renal medullas were prominently bright white.
Histologic findings: The liver was characterized by multiple, variably sized, cystic compartments that were lined by flat, cuboidal epithelium that was suggestive of bile duct epithelium. These polycystic bile ducts were occasionally encapsulated by moderate amounts of fibrous stroma and contained proteinaceous material. Adjacent hepatic parenchyma was congested, compressed, and disorganized. Portal areas contained numerous proliferating bile ducts and increased fibrous connective tissue. Bile pigment was observed in sinusoids and numerous hepatocytes (bile stasis).
The capsular surface of both kidneys was irregular and thickened by fibrous connective tissue. Numerous tubules contained proteinaceous casts and the renal medulla was characterized by tubular mineralization.
The small intestinal tear was characterized by necrotic edges, fibrinous connective tissue, and large numbers of mononuclear inflammatory cells.
Discussion: Polycystic bile duct disease was the prominent lesion in this case and appeared to be chronic and responsible for generalized icterus and loss of condition in the patient. Polycystic bile duct disease, although not common, can be a primary or incidental finding, especially in cats. In the last 6 months, there have been two cases of this nature at the ADDL. Some intrahepatic bile duct cysts can be congenital and may go unrecognized until they are discovered incidentally at necropsy; however, in this case, it was causing pathological lesions.
The renal lesions were generalized, the likely cause of hematuria, and were suggestive of chronic renal failure. The intestinal tear, a surprising and incidental finding in this case, proved to be an acute lesion that was evidenced to be ante-mortem in nature. The core of the foreign body resembled cat or human food.
-by Angela Smith, ADDL Graduate Student
