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An Urban Experience
S. Vaden1
1North Carolina State University, Department of Clinical Sciences, Raleigh, USA
Clinical Evaluation of Dogs with Protein Losing Nephropathy
Shelly L. Vaden
North Carolina State University CVM, Raleigh, NC
The prevalence of chronic kidney disease (CKD) in
dogs may be as high as 1.5% of dogs presenting
to general practice. Glomerular disease may be the cause of renal injury in 50% or more of dogs with CKD. Because glomerular diseases are common in dogs
and the outcomes are not always favorable, there has been an enhanced effort to improve early recognition, diagnosis and treatment of all renal diseases in dogs, with particular emphasis on proteinuria renal diseases. In support of this effort, the WSAVA Renal Standardization Project developed a classification system for glomerular pathologic findings in dogs. At the same time, the International Renal Interest Society (IRIS) developed clinical guidelines for the management of dogs with glomerular disease. The latter initiative used a formal consensus method for developing several sets of recommendations, including one set about the clinical evaluation of dogs with protein losing nephropathy.
The purpose of this presentation is to discuss those recommendations, while bringing in additional information about monitoring proteinuria and performing renal biopsy.
Diagnostic Recommendations
When proteinuria is detected, there are three key elements that need to be assessed: localization, persistence, and magnitude. Although proteinuria is
the hallmark of glomerular disease, it can also occur secondary to pre-renal, post-renal or renal tubular causes. The magnitude of proteinuria is generally assessed via the urine protein: creatinine ratio (UPC). Persistent renal proteinuria that is of high magnitude (i.e., UPC >2) is most likely of glomerular origin; however, there is no range of numbers that is diagnostic for any one renal disease and the overlap in expected ranges
is too broad to be clinically reliable. In fact, glomerular lesions have been seen in dogs without proteinuria. Urine albumin can also be used to assess proteinuria. Microalbuminuria may develop before the UPC is increased. A dog with persistent microalbuminuria of increasing magnitude should be assessed as having an injurious process to the glomerular filtration barrier and
may eventually develop overt proteinuria.
Clinicopathologic findings in dogs with various forms of glomerular disease are diverse and with findings being widely variable between individual dogs. Likewise, secondary complications of glomerular disease are variably present in individual dogs. Because of this,
the consensus recommendations are to separate
dogs with glomerular disease into different tiers based
on their clinical manifestations. The tiers group dogs based on major clinical manifestations of disease and help direct the diagnostic recommendations. Each test
or procedure should serve one of three purposes: 1) Identify an underlying disorder that might be causing the glomerular injury; 2) Assess the presence and severity
of the different possible sequella of glomerular disease (e.g., azotemia, hypertension, hypercoagulability);
and, 3) Characterize the pathologic changes in
the kidney to better understand the diagnosis (and pathophysiololgic development of that diagnosis), prognosis and therapeutic options. The specific tests and procedures should be assigned a priority based
on severity of disease, resources, expertise, and client willingness and finances. Tests that are considered essential (i.e., the minimum diagnostic assessment)
for all dogs with glomerular disease include a history, physical examination, complete blood count, biochemical profile, urinalysis (including culture if indicated), UPC and regional infections disease testing. In most situations blood pressure measurement should also be considered essential. Additional testing may be classified as essential, recommended (i.e., what should always be done if resources permit) or potentially helpful (i.e., those that might be performed in specific circumstances or
for a complete evaluation) dependent upon the tier
the dog is in. These additional tests include abdominal ultrasound, chest radiographs, renal biopsy, antithrombin, thromboelastography, and SDS-PAGE.
Renal Biopsy
Renal biopsy provides a definitive diagnosis of glomerular disease, but may not be needed if treatment of a potential underlying disease leads to resolution of the proteinuria or end-stage renal disease is already present. Renal biopsy is generally not indicated in patients with CKD (stage IV and possibly late stage III). Results are unlikely to alter the prognosis, therapy or outcome in these patients. When evaluated appropriately, renal biopsy specimens can provide important clinical information about the type and severity of lesions in dogs and cats with glomerular disease. In fact obtaining an accurate histologic diagnosis may be one of the more important factors in successful management of the
dog or cat with glomerular disease. Clinical decisions regarding the diagnosis, treatment, and prognosis can be

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