Occurrence, management and outcome of immune-complex glomerulonephritis in dogs with suspected glomerulopathy in the UK

OBJECTIVES

To determine the proportion of dogs diagnosed with immune-complex glomerulonephritis in a large cohort of UK dogs with clinical suspicion of glomerular disease in which renal histopathology, including routine light microscopy, transmission electron microscopy and immunofluorescence, had been performed. The second objective was to describe treatment and long-term clinical outcome of dogs diagnosed with immune-complex glomerulonephritis.

MATERIALS AND METHODS

Sixty-two UK dogs that underwent renal biopsies for investigation of suspected glomerulopathy (urine protein-to-creatinine ratio persistently >0.5) were included in this retrospective multicentre study. Signalment, clinico-pathological abnormalities, histopathological diagnosis, treatment following diagnosis and survival were recorded.

RESULTS

Seventeen (27%) of the dogs with suspected glomerular disease were diagnosed with immune-complex glomerulonephritis and nine (53%) of these were still alive at the study end point, with a median follow-up of 366 days (range 52 to 1299). Six dogs diagnosed with immune-complex glomerulonephritis were treated with mycophenolate. Four received mycophenolate alone for immunosuppression and two received mycophenolate and chlorambucil; all these six dogs were alive at data collection [median follow-up time 712.5 days (range 73 to 1299)]. Seven dogs diagnosed with immune-complex glomerulonephritis did not receive immunosuppressive treatment; only one of these dogs was alive at study end point [median survival time 302 days (range 52 to 723)].

CLINICAL SIGNIFICANCE

Immune-complex glomerulonephritis may be less common in the UK than previously reported in North America and mainland Europe, reducing the likelihood of treatment modification following renal biopsy. Mycophenolate was the most commonly used immunosuppressant for cases of immune-complex glomerulonephritis.

Cardiovascular images: vascular hamartoma of the mitral valve in a horse

An 8-month-old Hanoverian gelding was presented with a history of cardiac murmurs that were not apparent as a foal nor reported at the time of castration. Major echocardiographic findings included mitral valvular thickening, functional stenosis, and mitral regurgitation of sufficient severity to cause diastolic and systolic cardiac murmurs, left-sided volume overload, and pulmonary hypertension. Due to the hemodynamic severity of the lesion and poor prognosis for future performance and longevity, euthanasia was elected. On gross postmortem examination, there was focal fibrous epicarditis affecting the heart base, and the left atrium was moderately dilated. The mitral valve surface was irregular and contained several nodules along the atrial face of the cusp. Histologically, this lesion was diagnosed as a vascular hamartoma, which is rarely reported in veterinary species and has not been described in heart valves. This benign proliferative lesion, and concurrent valvular dysfunction, was associated with an unusual manifestation of clinically evident disease and should be differentiated from common incidental valvular lesions such as hematocysts.

European Veterinary Renal Pathology Service: A Survey Over a 7-Year Period (2008-2015)

Background

The European Veterinary Renal Pathology Service (EVRPS) is the first Web‐based registry for canine renal biopsy specimens in Europe.

Hypothesis/Objectives

The aim was to verify whether differences exist between the clinical and laboratory presentation of dogs with nephropathy according to renal pathological findings, as defined by light and electron microscopy of renal biopsy specimens submitted to EVRPS.

Animals

Renal biopsy specimens of dogs were collected from the archive of the service (n = 254). Cases were included if both light and electron microscopy were available (n = 162).

Methods

Renal biopsy specimens were classified based on the morphological diagnoses. Thereafter, they were grouped into 3 disease categories, including immune‐complex‐mediated glomerulonephritis (ICGN), non‐immune‐complex‐mediated GN (non‐ICGN), and renal lesions not otherwise specified (RL‐NOS). Differences among morphological diagnoses and among disease categories were investigated for clinical and laboratory variables.

Results

Serum albumin concentration was lower in dogs with ICGN than in those with non‐ICGN (P = 0.006) or RL‐NOS (P = 0.000), and the urine protein‐to‐creatinine ratio (UPC) was significantly higher in ICGN than in the other 2 disease categories. Regarding morphological diagnoses, albumin was significantly lower in amyloidosis (AMY) and membranous (MGN), membranoproliferative (MPGN) or mixed glomerulonephritis (MixGN) than in minimal change disease, primary (FSGS I) or secondary (FSGS II) focal and segmental glomerulosclerosis and juvenile nephropathies (JN). The UPC was higher in MPGN than in FSGS I and FSGS II.

Conclusions and clinical importance

Dogs with ICGN, in particular MPGN, had higher protein loss than those with non‐ICGN or RL‐NOS, leading to more severe hypoalbuminemia. Clinical and laboratory differentiation among dogs with the different morphological diagnoses and among dogs with different disease categories was difficult due to overlapping results.

Glomerular Lesions in Proteinuric Miniature Schnauzer Dogs

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.

Correlation of Urine and Serum Biomarkers with Renal Damage and Survival in Dogs with Naturally Occurring Proteinuric Chronic Kidney Disease

Background

Urine protein loss is common in dogs with chronic kidney disease (CKD).

Hypothesis/Objectives

To evaluate new biomarkers of glomerular and tubulointerstitial (TI) damage compared with histology and as survival indicators in dogs with naturally occurring, proteinuric CKD.

Animals

One hunderd and eighty dogs with naturally occurring kidney disease.

Methods

Retrospective study using urine, serum, and renal biopsies from dogs with kidney disease, 91% of which had proteinuric CKD. Biomarkers were evaluated and correlated with pathologic renal damage, and significant associations, sensitivities, and specificities of biomarkers for renal disease type were determined.

Results

Fractional excretions of immunogloblin M (IgM_FE) and immunoglobulin G (IgG_FE) correlated most strongly with glomerular damage based on light microscopy (r = 0.58 and 0.56, respectively; P < .01). Serum creatinine (SCr) correlated most strongly with TI damage (r = 0.70, P < .01). Urine IgM/creatinine and urine NAG/creatinine had the highest sensitivity (75%) and specificity (78%) for detection of immune complex‐mediated glomerulonephritis. Although individually most biomarkers were significantly associated with decreased survival time (P < .05), in a multivariate analysis, SCr, IgM_FE, and glomerular damage based on transmission electron microscopy (TEM) were the only biomarkers significantly associated with survival time (SCr: P = .001; IgM_FE: P = .008; TEM: P = .017).

Conclusions and Clinical Importance

Novel urine biomarkers and FEs are useful for detection of glomerular and TI damage in dogs with proteinuric CKD and might predict specific disease types and survival.

Aging in the Canine Kidney

Given the irreversible nature of nephron loss, aging of the kidney is of special interest to diagnostic and toxicologic pathologists. There are many similarities among histologic lesions in aged human and canine kidneys, including increased frequency of glomerulosclerosis, interstitial fibrosis, and tubular atrophy. Unfortunately, there are few studies in which renal tissue from aged healthy dogs was adequately examined with advanced diagnostics—namely, transmission electron microscopy and immunofluorescence—so age-associated changes in canine podocytes and glomerular basement membranes are poorly characterized. An age-associated decrease in the glomerular filtration rate in humans and dogs (specifically small breed dogs) has been documented. Although lesions in aged rats and mice differ somewhat from those of aged dogs and humans, the knowledge gained from rodent models is still vital to elucidating the pathogenesis of age-associated renal disease. Many novel molecules implicated in renal aging have been identified through genetically modified rodent models and transcriptomic and proteomic analysis of human kidneys. These molecules represent intriguing therapeutic targets and diagnostic biomarkers. Likewise, influencing critical pathways of cellular aging, such as telomere shortening, cellular senescence, and autophagy, could improve renal function in the elderly.

World Small Animal Veterinary Association Renal Pathology Initiative: Classification of Glomerular Diseases in Dogs

Evaluation of canine renal biopsy tissue has generally relied on light microscopic (LM) evaluation of hematoxylin and eosin-stained sections ranging in thickness from 3 to 5 µm. Advanced modalities, such as transmission electron microscopy (TEM) and immunofluorescence (IF), have been used sporadically or retrospectively. Diagnostic algorithms of glomerular diseases have been extrapolated from the World Health Organization classification scheme for human glomerular disease. With the recent establishment of 2 veterinary nephropathology services that evaluate 3-µm sections with a panel of histochemical stains and routinely perform TEM and IF, a standardized objective species-specific approach for the diagnosis of canine glomerular disease was needed. Eight veterinary pathologists evaluated 114 parameters (lesions) in renal biopsy specimens from 89 dogs. Hierarchical cluster analysis of the data revealed 2 large categories of glomerular disease based on the presence or absence of immune complex deposition: The immune complex-mediated glomerulonephritis (ICGN) category included cases with histologic lesions of membranoproliferative or membranous patterns. The second category included control dogs and dogs with non-ICGN (glomerular amyloidosis or focal segmental glomerulosclerosis). Cluster analysis performed on only the LM parameters led to misdiagnosis of 22 of the 89 cases-that is, ICGN cases moved to the non-ICGN branch of the dendrogram or vice versa, thereby emphasizing the importance of advanced diagnostic modalities in the evaluation of canine glomerular disease. Salient LM, TEM, and IF features for each pattern of disease were identified, and a preliminary investigation of related clinicopathologic data was performed.

A comparison of biochemical and histopathologic staging in cats with chronic kidney disease

Chronic kidney disease (CKD) is prevalent in elderly cats. Frequently, a diagnosis is made in later stages of disease, by which time many renal lesions are irreversible. As such, little headway has been made in identifying an etiology and preventing this common disease. The aim of this study was to evaluate the presence and severity of both reversible and irreversible histopathologic changes in the kidneys of cats at each stage of CKD and, in addition, to determine if lesion prevalence and character were different between stages. A total of 46 cats with CKD were classified according to the International Renal Interest Society (IRIS) as stage I (3 cats), stage II (16 cats), stage III (14 cats), and stage IV (13 cats). Eleven young, nonazotemic and 10 geriatric, nonazotemic cats were included as controls. The severity of tubular degeneration, interstitial inflammation, fibrosis, and glomerulosclerosis was significantly greater in later stages of CKD compared with early stages of disease. Proteinuria was associated with increased severity of tubular degeneration, inflammation, fibrosis, tubular epithelial single-cell necrosis, and decreased normal parenchyma. Presence of hyperplastic arteriolosclerosis, fibrointimal hyperplasia, or other vascular lesions were not found to be significantly different between hypertensive and normotensive cats. The greater prevalence and severity of irreversible lesions in stage III and IV CKD implies that therapeutic interventions should be targeted at earlier stages of disease.

Polyomavirus-associated nephritis in 2 horses

Polyomaviruses produce latent and asymptomatic infections in many species, but productive and lytic infections are rare. In immunocompromised humans, polyomaviruses can cause tubulointerstitial nephritis, demyelination, or meningoencephalitis in the central nervous system and interstitial pneumonia. This report describes 2 Standardbred horses with tubular necrosis and tubulointerstitial nephritis associated with productive equine polyomavirus infection that resembles BK polyomavirus nephropathy in immunocompromised humans.