Glomerular Lesions in Proteinuric Miniature Schnauzer Dogs

Abstract

Miniature Schnauzer dogs are predisposed to idiopathic hypertriglyerceridemia, which increases risk for diseases such as pancreatitis and gallbladder mucocele. Recently, elevated triglyceride concentrations have been associated with proteinuria in this breed, although it is difficult to determine which abnormality is primary. Retrospective review of renal tissue from 27 proteinuric Miniature Schnauzers revealed that 20 dogs had ultrastructural evidence of osmophilic globules consistent with lipid in glomerular tufts. Seven of these dogs had lipid thromboemboli in glomerular capillary loops that distorted their shape and compressed circulating erythrocytes. Triglyceride concentrations were reported in 6 of these 7 dogs, and all were hypertriglyceridemic. In addition, glomerular lipidosis (defined as accumulation of foam cells within peripheral capillary loops) was identified in a single dog. The remaining 12 dogs had smaller amounts of lipid that could only be identified ultrastructurally. Neither signalment data nor clinicopathologic parameters (serum albumin, serum creatinine, urine protein-to-creatinine ratio, and blood pressure) differed among the various types of lipid lesions. During the time course of this study, all dogs diagnosed with glomerular lipid thromboemboli were Miniature Schnauzers, underscoring the importance of recognizing these clear spaces within capillary loops as lipid.

Keywords: dogs; glomerulonephropathy; hyperlipidemia; hypertriglyceridemia; proteinuria.

Figures 1–3

Lipid thromboembolus, kidney glomerulus, dog. Figure 1. Glomerulus with an intracapillary nonstaining circular structure, which is a lipid thromboembolus. (a) Hematoxylin and eosin. (b) Periodic acid–Schiff. (c) Masson’s trichrome. (d) Jones’s methenamine silver. Figure 2. Lipid droplets inside glomerular capillary lumens. Oil red O. Figure 3. Glomerular capillary loop with an intraluminal osmophilic structure, consistent with lipid. Bar = 5 μm. Transmission electron microscopy.

Figure 4

Glomerular lipidosis, dog. Approximately two-thirds of the glomerular tuft is effaced by the presence of numerous foam cells containing small clear vacuoles consistent with lipid. The remaining portion of the glomerulus is compressed against Bowman’s capsule but is neither hypercellular nor sclerotic. (a) Hematoxylin and eosin. (b) Periodic acid–Schiff. (c) Masson’s trichrome. (d) Jones’s methenamine silver.