JPC SYSTEMIC PATHOLOGY

Urinary System

November 2023

U-B05 (NP)

 

Signalment: (JPC #1376954): Unknown gender, young calf

 

HISTORY: Incidental finding at post mortem in a young calf.

 

HISTOPATHOLOGIC DESCRIPTION: Kidney: Multifocally and randomly expanding the subcapsular and peripheral cortical interstitium, occasionally extending to the corticomedullary junction, and surrounding, separating, infiltrating, and occasionally replacing glomeruli and renal tubules are up to 2mm diameter inflammatory foci composed of moderate numbers of lymphocytes with fewer plasma cells, macrophages, and neutrophils admixed with edema, fibrin, and variable numbers of reactive fibroblasts and collagen bundles. Renal tubular epithelium within these foci often exhibits one of the following changes: atrophy, degeneration (characterized by pale, swollen, vacuolated epithelial cells), necrosis (characterized by shrunken cells with hypereosinophilic cytoplasm and pyknotic nuclei), or regeneration (characterized by large epithelial cells with basophilic cytoplasm, prominent vesiculate nuclei, and increased numbers of mitotic figures). Affected tubules are occasionally ectatic, lined by attenuated epithelium, and contain intraluminal granular eosinophilic material, or occasionally are filled with degenerate neutrophils, sloughed epithelial cells, and eosinophilic cellular and karyorrhectic debris (necrosis). Multifocally throughout the section, lymphatic vessels are ectatic.

 

MORPHOLOGIC DIAGNOSIS: Kidney, cortex: Nephritis, interstitial, lymphoplasmacytic, neutrophilic, and histiocytic, chronic, multifocal, moderate, with tubular atrophy, degeneration, necrosis, regeneration, and interstitial fibrosis, breed unspecified, bovine.

 

CAUSE: Usually undetermined; Escherichia coli can occasionally be recovered from the lesions, but other suggested etiologies include Salmonella sp., Brucella sp., and Leptospira sp. 

 

CONDITION: White-spotted kidneys of calves

 

GENERAL DISCUSSION:

• Best-known form of multifocal nonsuppurative interstitial nephritis in calves
• Early lesions may be suppurative, but quickly become nonsuppurative
• Common, largely incidental finding in young calves
• Can progress to scar tissue with advancing age

• Lesions probably resolve as the animal ages; however a small number of animals may die of renal failure

 

 

PATHOGENESIS:

• Unknown; likely similar to pathogenesis of leptospirosis (hematogenous localization)  
• Exposure to the organism > bacteremia > organisms localize in renal interstitial capillaries > migrate through vascular endothelium > persist in interstitial spaces > incite inflammatory response  
• May occur as a component of septicemic colibacillosis
• Organisms also migrate through lateral intercellular junctions into tubular lumina > tubular epithelial cells undergo degeneration and necrosis due either to direct toxic effects of the bacteria or to accompanying interstitial inflammatory reaction
• Inflammation and subsequent scarring may cause tubular obstruction and/or atrophy

 

TYPICAL CLINICAL FINDINGS:

 

TYPICAL GROSS FINDINGS: 

• Multiple small, white, nodules up to 1cm diameter, distributed throughout the cortex
• Larger nodules may bulge from the capsular surface and adhere to the capsule (capsular adhesions)

 

TYPICAL LIGHT MICROSCOPIC FINDINGS:

• Microabscesses are present initially (rarely seen), and are soon replaced by numerous interstitial infiltrates of lymphocytes and few plasma cells and macrophages admixed with variable numbers of fibroblasts, variable fibrous connective tissue, and atrophic nephron components
• Progressive fibrosis results in scar formation with atrophy and loss of cortical tubules
• Glomeruli are usually spared

 

DIFFERENTIAL DIAGNOSIS:  

Multifocal interstitial nephritis in cattle:

• Malignant catarrhal fever (Gammaherpesvirus: alcelaphine herpesvirus-1); U-V02, S-V01
• Theileria parva (East Coast Fever); H-P05 A/B
• Lumpy skin disease (Capripoxvirus); P-V24
• Leptospirosis (L. interrogans serovars pomona and hardjo); U-B03 A/B
• Fatal autosomal recessive disorder in Japanese Black (Wagyu) cattle (null mutation in Claudin-16 gene, a tight junction protein expressed between tubular epithelial cells); affected cattle are azotemic, proteinuric, have increased urine magnesium but normal serum magnesium, and have marked interstitial inflammation and zonal fibrosis with cystically dilated tubules and Bowman’s capsules
• Vetch (Vicia spp.) ingestion: Multiple organs (i.e. kidney, heart, skin, etc.); multifocal eosinophilic and granulomatous inflammation; U-T16, I-T02

 

COMPARATIVE PATHOLOGY:

Interstitial nephritis in other species: 

• Sheep:  
  • Sheeppox (Capripoxvirus) 
  • Small Ruminant Lentivirus (formerly known as Maedi-Visna virus, can also cause membranoproliferative glomerulonephritis)
• Horses: 
  • Equine Infectious Anemia (Lentivirus; renal lesions do not contribute do disease progression but are diagnostically important)
  • Equine Viral Arteritis (Arterivirus)
• Pigs:
  • Leptospirosis (L. interrogans serovar pomona)
  • Porcine Reproductive and Respiratory Syndrome (Arterivirus)
• Dogs:
  • Leptospirosis (L. interrogans serovars canicola, icterohemorrhagiae, and others)
  • Infectious Canine Hepatitis, recovery phase (Canine Adenovirus 1)
  • Encephalitozoon cuniculi
  • Canine herpesvirus (severe necrotizing nephritis)
  • Leishmania spp
  • Borrelia burgdorferi
  • Hepatozoon canis

• Cats: 
  • Feline infectious peritonitis (mutated Feline Enteric Coronavirus; multifocal pyogranulomatous nephritis)

 

For embolic suppurative nephritis:

• Cats: Pasteurella multocida
• Dogs: Klebsiella pneumoniae
• Horses:  
  • Actinobacillus equuli
  • 2 reported cases of equine polyomavirus
• Pigs: Erysipelothrix rhusiopathiae
• Cattle: Truperella pyogenes
• Sheep and goats:  
  • Corynebacterium pseudotuberculosis 
  • Sheep adenovirus (characteristic large, basophilic, intranuclear inclusion bodies within endothelium and/or interstitial cells)

 

References: 

1. Cianciolo RE, Mohr FC. Urinary system. In: Maxie MG, ed. Jubb, Kennedy and Palmer’s Pathology of Domestic Animals. Vol 2. 6th ed. Philadelphia, PA: Elsevier Saunders; 2016:431-432, 436.
2. Sula MM, Lane LV. The urinary system. In: Zachary JF, ed. Pathological Basis of Veterinary Disease. 7th ed. Philadelphia, PA: Mosby Elsevier Inc.; 2022:747.
3. Uzal FA, Dobrenov B, Smythe L, et.al. A study of "white spotted kidneys" in cattle. Vet Microbiol. 2002;86:369-375.

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