JPC SYSTEMIC PATHOLOGY

URINARY SYSTEM

January 2024

U-T14

 

Signalment (JPC# 2026206): 4‑month‑old female Hereford calf.

 

HISTORY: This herd lost fifteen 300-pound beef calves in two days.

 

MICROSCOPIC DESCRIPTION: Kidney: Affecting over 90% of the cortex and 50% of the medulla, small groups of tubular epithelium are characterized by one or more of the following changes: shrunken with pyknotic to karyolytic nucleus and sloughing into the lumen (necrosis); cytoplasmic vacuolation and swelling (degeneration); attenuation with tubular ectasia; or small size with high N:C ratio, mild basophilia, and crowding (regeneration). Ectatic tubular lumina often contain one or more of the following: hemorrhage; pale to intensely eosinophilic globular to homogenous material (proteinosis); sloughed tubular epithelial cells admixed with necrotic debris and/or degenerate leukocytes (granular casts); or mineral. Multifocally, vessels are lined by hypertrophied endothelium and arteries are occasionally surrounded by moderate perivascular hemorrhage, fibrin, and edema. Multifocally, the cortical interstitium is expanded by small aggregates of lymphocytes, plasma cells, fewer macrophages, mild interstitial fibrosis, and increased clear space with ectatic lymphatics (edema).Glomeruli often have parietal epithelium adhered to the visceral epithelium of Bowmans capsule (synechia) or eosinophilic fluid within the uriniferous space. 

 

MORPHOLOGIC DIAGNOSIS: Kidney, renal tubules: Necrosis, degeneration, and regeneration, diffuse, moderate, with intratubular hemorrhage, proteinosis, granular casts, and mineralization and mild lymphoplasmacytic interstitial nephritis and fibrosis, Hereford, bovine. 

 

ETIOLOGIC DIAGNOSIS: Oak bud nephrosis

 

CAUSE: Oak bud toxicity (Quercus spp.)

 

CONDITION: Oak bud, acorn, or gallotannin poisoning

 

GENERAL: 

• Blossoms, buds, leaves, stems, and acorns of oak shrubs and trees (Quercus spp.) can cause acute tubular injury due to containing toxic gallotannins and their metabolites (tannic acid, gallic acid, and pyrogallol)
• Cattle and sheep are the most susceptible, but can affect any species
• All oak species are potentially toxic, but not all are palatable

 

PATHOGENESIS:

• Gallotannins are hydrolyzed to tannic acid, gallic acid, and pyrogallol
• Toxins bind to endothelium resulting in endothelial damage and vascular leakage 
• GI tract: Toxins form peptide bonds à protein precipitation à ulceration

• DIC also à gastrointestinal ulcers

• The mechanism of tubular damage is unknown 
• Toxicity is dose-dependent

 

TYPICAL CLINICAL FINDINGS:

 

TYPICAL GROSS FINDINGS:

• Acute: Marked perirenal edema +/- hemorrhage, swollen pale kidneys with 2-3mm diameter petechial cortical hemorrhages (cattle), hydrothorax, ascites
• Variable: GI hemorrhage, liver damage
• Chronic (interstitial nephritis): Fibrosis, atrophy, thinned cortex, finely pitted surface

 

TYPICAL LIGHT MICROSCOPIC FINDINGS:  

• Acute: Proximal tubular necrosis with casts and intratubular hemorrhage; glomerular ischemia with dilation of Bowman’s capsule; extent of injury may vary considerably between groups of tubules in less severe toxicosis
  • “Necrosis in groups of tubules with intratubular hemorrhage distinguishes the nephrotoxicity of acute oak poisoning from that of most other causes.” (JKP 2016)
• Chronic: Renal parenchymal scarring, chronic interstitial nephritis

 

ADDITIONAL DIAGNOSTIC TESTS:

 

DIFFERENTIAL DIAGNOSIS:

 

COMPARATIVE PATHOLOGY:

• Horses: Oak bud toxicosis occurs occasionally; typically presents as colic with hemorrhagic and ulcerative enterotyphlocolitis with diarrhea
• Pigweed (Amaranthus spp.) contains phenolic compounds which are similar to oak gallotannins and is associated with acute renal failure in cattle, pigs, horses; causes perirenal edema, cavitary effusions, acute tubular injury
• Ochratoxin A (mycotoxin from Aspergillus, Penicillum) produces similar gross and histologic changes in monogastric animals, especially pigs
• Yellow-wood tree (Terminalia oblongata, Australia) produces punicalagin (hepatotoxin tannin) and termalin (nephrotoxic tannin); toxic to cattle and sheep; centrilobular hepatocellular necrosis is more severe than renal injury; chronic cases have renal fibrosis/atrophy
• Isotropis toxic to cattle and sheep, with gastrointestinal inflammation, perirenal edema, cavitary effusions
• Tannins in grapes may be an underlying cause for grape toxicity in dogs

 

REFERENCES:

1. Cianciolo RE, Mohr FC. Urinary system. In:  Maxie MG, ed.  Jubb, Kennedy and Palmer’s Pathology of Domestic Animals. Vol 2. 6^th ed. St. Louis, MO: Elsevier; 2016:386, 427-428.
2. Sula MM, Lane LV. The Urinary System. In: Zachary JF, ed. Pathologic Basis of Veterinary Disease. 7th ed. St. Louis, MO: Elsevier; 2022: 736, 746, 749.

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