JPC SYSTEMIC PATHOLOGY
URINARY SYSTEM
December 2023
U-M10 (NP)
SIGNALMENT (JPC #1901151): Beagle dog
HISTORY: Tissue from a 2-year-old female beagle dog used as a control in an inhalation toxicity study, and the histopathological changes were an incidental finding
HISTOPATHOLOGIC DESCRIPTION: Kidney: Multifocally, approximately 20% of glomeruli are variably and segmentally distorted and glomerular capillary lumina are compressed, expanded or obliterated by large, densely packed foam cells within the mesangium which are up to 25 µm in diameter with cytoplasm containing fine, clear microvacuoles with variably sized eosinophilic globules and granules. Foam cell nuclei are often pyknotic, and peripherally compressed. Occasionally, foam cells contain fine golden-yellow granules (lipofuscin). In the cortex, tubules are rarely mildly dilated, lined by attenuated epithelium, and filled with a homogenous, eosinophilic, hyalinized material (proteinosis). Tubules within the medulla rarely contain small deeply basophilic granular material (mineral).
MORPHOLOGIC DIAGNOSIS: Kidney, glomeruli: Vacuolar change, lipid-type, segmental, multifocal, moderate, with mesangial foam cells, beagle, canine
ETIOLOGIC DIAGNOSIS: Glomerular lipidosis
GENERAL:
- Often thought to be incidental, but aneurysmal dilation of capillaries may be associated with mesangiolysis indicating a disease process; may be associated with proteinuria and experimentally induced vascular injury
PATHOGENESIS:
- Source of these cells unknown – possibly mesangial cells, endothelial cells, or macrophages
TYPICAL CLINICAL FINDINGS:
- May be associated with proteinuric renal disease
TYPICAL GROSS FINDINGS:
- None
TYPICAL LIGHT MICROSCOPIC FINDINGS:
- Glomerular mesangium contains foam cells, which are large, closely packed, finely vacuolated, and have distinct cell borders
ULTRASTRUCTURE:
- Osmiophilic lipid droplets within glomerular capillaries
ADDITIONAL DIAGNOSTIC TESTS:
- Droplets within foam cells are sudanophilic (Sudan black)
DIFFERENTIAL DIAGNOSIS:
- Lipid emboli – occasionally seen in dogs with diabetes mellitus, dyslipidemia, or following trauma; lipid is intravascular in renal arterioles and glomerular capillaries rather than in foam cells +/- cholesterol clefts
- Tubular lipidosis – intracellular lipid within convoluted tubules; may be difficult to evaluate in species who normally have abundant lipid in their tubules (e.g. pigs, dogs, cats)
COMPARATIVE PATHOLOGY:
- Cats - similar, but more extensive, glomerular lipidosis has been associated with inherited hyperlipoproteinemia, which results in hyperchylomicronemia, atherosclerosis, and xanthogranulomas in multiple organs (including kidney)
- Dogs – similar findings reported in hyperlipidemic miniature schnauzers and hypercholesterolemic Shetland sheepdogs
- Avians, especially Amazon parrots and cockatiels – renal lipidosis common secondary to a high-fat diet or chronic hepatic disease; intracellular lipid within tubular epithelial cells and macrophages within glomerular capillaries
References:
- Cianciolo RE, Mohr CF. Urinary system. In: Maxie MG, ed. Jubb, Kennedy and Palmer’s Pathology of Domestic Animals. 6th ed. Vol 2, Philadelphia, PA: Elsevier; 2016:418, 422.
- Schmidt R, Reavill DR, Phalen DN. Pathology of Pet and Aviary Birds. 2nd ed. Ames, IA: John Wiley & Sons, Inc.; 2015:139.
- Sula MM, Lane LV. The urinary system. In: Zachary JF, ed. Pathologic Basis of Veterinary Disease. 7th ed. St. Louis, MO: Elsevier; 2022:734.
