Am. Grooters et al., RENOMEGALY IN DOGS AND CATS .2. DIAGNOSTIC-APPROACH, The Compendium on continuing education for the practicing veterinarian, 19(11), 1997, pp. 1213
Renomegaly is an important clinical finding in small animal patients,
not only because it provides a fairly narrow list of differential diag
noses but also because it is easily investigated using minimally invas
ive imaging techniques and fine-needle aspiration. Kidney enlargement
may result from various pathophysiologic processes, such as infiltrati
on of the renal parenchyma by inflammatory or neoplastic cells, altera
tion of renal structure by developmental disorders or renal insult, an
d distortion of the collection system secondary to urinary tract obstr
uction. For ease of discussion, causes of renomegaly can be grouped in
to several categories - diffuse parenchymal disorders, such as acute r
enal failure, amyloidosis, renal lymphoma, pyogranulomatous nephritis
secondary to FIP, and renal hypertrophy; focal or multifocal parenchym
al disorders, such as polycystic kidney disease and primary or metasta
tic renal neoplasia; subcapsular and perirenal disorders, such as peri
nephritic pseudocysts and subcapsular hematomas; and collecting system
disorders, such as hydronephrosis and bacterial pyelonephritis. The d
iagnostic approach to renomegaly is straightforward. When enlargement
of one or both kidneys is identified during physical or radiographic e
xamination, a list of differential diagnosis is formulated based on si
gnalment, clinical signs, laboratory abnormalities, and survey radiogr
aphic findings. This is followed by specific evaluation of the kidneys
using contrast radiography or ultrasonography, which provides a more
complete assessment of the renal parenchyma and collecting system. In
some patients, ultrasonography or contrast radiography may provide a d
efinitive diagnosis. In others, fine-needle aspiration or needle core
biopsy of the kidney is required to obtain a definitive diagnosis.