JPC SYSTEMIC PATHOLOGY
URINARY SYSTEM
November 2023
U-M04 (NP)
Signalment (JPC 1419010): A dog.
HISTORY: Tissue from a diabetic dog.
HISTOPATHOLOGIC DESCRIPTION: Urinary bladder: The urinary bladder wall is expanded to 1 cm. Diffusely expanding the submucosa and multifocally widely separating and compressing the connective tissue and muscle fibers of the tunica muscularis are round to polygonal clear spaces that lack an epithelial lining (pseudocysts) and are up to 1mm in diameter (emphysema). Multifocally, the submucosa is moderately expanded by fibrous connective tissue, and myocytes of the tunica muscularis often contain small intrasarcoplasmic clear vacuoles (degeneration). The urothelium is hyperplastic and piled up to 20 cell layers deep, and epithelial cells multifocally have vacuolated cytoplasm (hydropic degeneration) and pyknotic nuclei. The superficial submucosa is multifocally expanded by aggregates of few lymphocytes, plasma cells, macrophages, fewer neutrophils, mild hemorrhage and few hemosiderin-laden macrophages. Lymphatics in the superficial submucosa are often ectatic and surrounded by clear space (edema).
MORPHOLOGIC DIAGNOSIS: Urinary bladder, submucosa and tunica muscularis: Emphysema, diffuse, moderate, with multifocal mild lymphoplasmacytic cystitis, transmural edema, and moderate urothelial hyperplasia, breed unspecified, canine.
ETIOLOGIC DIAGNOSIS: Bacterial emphysematous cystitis
CAUSE: Glucose-fermenting bacteria or yeast
CONDITION: Emphysematous cystitis
GENERAL DISCUSSION:
- Uncommon condition resulting from fermentation of glucose by bacteria or yeast
- Most cases are associated with glucosuria due to diabetes mellitus
PATHOGENESIS:
- +/- Glucosuria due to:
- Diabetes mellitus (most common cause of glucosuria)
- Acromegaly
- Catecholamine release
- Primary renal glucosuria (as may occur in Fanconi syndrome)
- Glucose-fermenting bacteria (e.g., Escherichia coli, Klebsiella, Citrobacter, Clostridium perfringens, Staphylococcus, Streptococcus, Nocardia, Proteus, and Enterobacter) or yeast (e.g., Candida sp.) infect urinary bladder > aerobic fermentation of glucose by bacteria causes formation of CO2, which dissects through urinary bladder wall and is absorbed by lymphatic vessels > thin-walled, gas-filled pseudocysts easily rupture and release gas into the urinary bladder lumen
TYPICAL CLINICAL FINDINGS:
- Stranguria, pollakiuria, +/- hematuria, +/- pneumaturia
- Diagnosis is most frequently made radiographically; evidence of air in the bladder wall or lumen is pathognomonic
- Ultrasonography often reveals gas shadowing with reverberation artifact
TYPICAL GROSS FINDINGS:
- Bladder lumen diminished by variably-sized gray-white, gas-filled cystic spaces
- Spongy consistency, with marked crepitus on palpation
- Honeycomb appearance on cut section
TYPICAL LIGHT MICROSCOPIC FINDINGS:
- Gas pockets dissect the urinary bladder wall layers and form pseudocysts
- Submucosal fibroplasia with congestion and lymphocytic infiltration
- Edema and congestion of the subserosa
- Multifocal epithelial hyperplasia
- Cystitis
DIFFERENTIAL DIAGNOSIS:
- Unique syndrome, with distinctive histologic lesions
- Clinical differentials include other causes of gas in the urinary bladder: catheterization of the urogenital tract and fistulous connection between the bladder and colon or bladder and vagina
COMPARATIVE PATHOLOGY:
- Dogs and cats most frequently reported
- Cattle: Reported following intravenous injection of dextrose or other glucose-liberating compounds (e.g., calcium borogluconate)
- Humans: Rare; reported bacterial isolates include the same isolates listed above
REFERENCES:
- Cianciolo RE, Mohr FC.. Urinary system. In: Maxie MG, ed. Jubb, Kennedy, and Palmer's Pathology of Domestic Animals. 6th ed. Vol 2. Philadelphia, PA: Elsevier Saunders;2016:459-460.
- Sula MM, Lane LV. The urinary system. In: Zachary JF, ed. Pathologic Basis of Veterinary Disease. 7th ed. St. Louis, MO: Elsevier;2022:753-754.
