Small Animal Radiology and Ultrasound: A Diagnostic Atlas and Text

374 Small Animal Radiolo g y and Ultrasono graphy
Fig. 3-146 A 9-year-old neutered male domestic short-haired cat
with palpably enlarged kidneys but no clinical signs. Survey radiographs
revealed bilaterally enlarged, regularly shaped kidneys. The
excretory urogram revealed bilaterally small, regular kidneys (the left
is superimposed over the spine, open black arrows) with large accumulations
of fluid between the kidneys and the renal capsules.
Diagnosis: Perirenal cysts.
PYELONEPHRITIS. Acute bilateral pyelonephritis appears as a normal to slightly diminished
homogenous density during the nephrogram phase. Mild to moderate dilation of the
renal pelvis and proximal ureters as well as shortening and blunting of the pseudopapillae
and pelvic recesses may be seen in the pyelographic phase (Figs. 3-148 and 3-149). 469 The
changes are usually irreversible and persist despite resolution of the infection.
ACUTE INTERSTITIAL AND GLOMERULAR NEPHRITIS. The EU may be normal or may have
slightly diminished homogenous density during the prolonged nephrogram phase. The
pyelogram image may be faint with a normal renal pelvis and normal pelvic recesses visible.
Acute swelling of the kidney may cause compression of the renal pelvic recesses. This
will persist despite properly applied abdominal compression. The EU is not recommended
as a diagnostic technique if this diagnosis is anticipated.
POLYCYSTIC KIDNEYS. The density during the nephrogram phase will generally be irregular
due to obliteration of normal renal tissue by the cysts. Classically, there is a fine rim of
normally dense renal tissue surrounding the nonopacified cyst. The pyelogram may
show distortion of the collecting structures if the cysts produce pressure upon them (Fig.
3-150). 475
AMYLOIDOSIS. The nephrogram image is usually less opaque than normal. Frequently
the pyelogram image is difficult to see, but the collecting structures are usually normal in
shape and size. 473
ETHYLENE GLYCOL TOXICITY. The nephrogram will reveal a smoothly marginated, mild
to moderate enlargement of both kidneys. The nephrogram density may remain the same
or increase in density throughout the study; the pyelogram image either will not be visible
or will be poorly seen. 426,471
LIPIDOSIS. Although there is no documentation in the veterinary literature that animals
with diabetes mellitus are more likely to experience contrast media–induced renal failure,
as is the case for humans, this possibility should be strongly considered in determining the
need for the EU in suspected cases of renal lipidosis secondary to diabetes. If performed,
the EU will appear normal except for the overall renal size. 470