Renal biopsy should only be considered when the information obtained is likely to alter patient management.
Examples include differentiating between protein-losing glomerulopathies, differentiating between acute and chronic kidney disease, determining the status of tubular basement membranes in acute renal failure, monitoring the progression of a previously diagnosed renal disease.
Extensive evaluation of the renal disease and clinical evaluation of the patient should be completed prior to biopsy.
A coagulation profile is essential prior to biopsy due to the considerable risk of haemorrhage.
A needle, or Tru-cut biopsy usually provides sufficient tissue to obtain an accurate diagnosis. The sample can either be taken during an exploratory laparotomy, or percutaneously using ultrasound guidance.
The cortex is usually sampled several times.
For animals with glomerular disease, one sample should be placed in formalin for light microscopy, one sample placed in a fixative, and one sample frozen for immunofluorescence microscopy.
A wedge biopsy obtained at surgery provides superior quality samples.
To control haemorrhage during the biopsy, the renal artery and vein should be occluded and the surgeon should wait 60 seconds for the kidney to soften.
The renal capsule must be apposed after biopsy whilst the artery is still occluded. Occlusion should be limited to a maximum of 20 minutes.
Digital pressure can be applied for 5 to 10 minutes if bleeding occurs, or the omentum can be sutured over the area with interrupted sutures.
After renal biopsy, patients should be diuresed for several hours to decrease the risk of blood clot formation and obstruction of the renal pelvis or urethra.
Activity should be restricted for 72 hours.
Complications include perirenal haemorrhage and haematuria but these are usually limited to the post-biopsy period.
Cats and miniature-breed dogs are more prone to haemorrhage.
Haematuria is rare and usually resolves without treatment.
Monitoring for haemorrhage should include: immediate post-biopsy scan of the kidney and bladder for signs of haemorrhage, serial PCV measurements at 30 minutes intervals, and close observation of vital signs.
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Ettinger, S. (2001) Pocket companion to textbook of veterinary internal medicine Elsevier Health Sciences
Nyland, T. (2002) Small animal diagnostic ultrasound Elsevier Health Sciences
Tobias, K. (2009) Manual of small animal soft tissue surgery John Wiley and Sons
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