Renal disease is often categorized as acute renal failure, chronic renal failure, and glomerular disease. Although history, physical examination, and clinical laboratory data may allow for differentiation, renal biopsy is often required for a definitive diagnosis. Practitioners are often reluctant to pursue renal biopsy on the basis of several concerns, including potential complications and costs. Studies show that the frequency of severe complications is relatively low if proper technique is used; ultrasound guidance has become the method of choice for dogs larger than 5 kg and for cats. Biopsy can also be done using laparoscopy. Isotonic solutions should be given for several hours afterward to reduce the likelihood that clots will form in the renal pelvis or ureter. If possible, 2 samples should be obtained-one should be placed in formalin and the other divided into 2 pieces, each with glomeruli. One piece should be put into fixative for electron microscopy, the other frozen for immunofluorescence. This article is a good review of the techniques for proper specimen collection.

COMMENTARY: Renal biopsies are most frequently performed in dogs and cats with acute renal failure or proteinuric renal disease. Information gained from histologic examination can help confirm the clinical diagnosis and prognosis, and in some cases, guide treatment regimens. Currently, there are few prospective, controlled clinical trials evaluating the efficacy of various treatments in dogs and cats with histologically defined renal disease; as a result, it is difficult to make firm treatment recommendations based on biopsy findings. However, a definitive diagnosis and the prognostic information gained from renal biopsy can be quite helpful. For example, histologic evidence of tubular regeneration in a patient with acute renal failure is a positive prognostic indicator. Conversely, glomerular amyloidosis or glomerulosclerosis is less likely to respond to treatment than immune-complex glomerulonephritis. As Dr. Vaden states in this article, "Accurate assessment of response to therapy requires knowledge of both the type and severity of the disease being treated."

Renal biopsy of dogs and cats. Vaden S. CLIN TECH SMALL ANIM PRACT 20:11-22, 2005.