Small Animal Radiology and Ultrasound: A Diagnostic Atlas and Text

370 Small Animal Radiolo g y and Ultrasono graphy
Fig. 3-140 A 4-year-old female Maltese with occasional seizures.
The ventrodorsal radiograph revealed a calcific density shaped like a
renal pelvis within the left renal pelvis (black arrow). This location
was confirmed on the lateral view. Diagnosis: Left renal calculus.
Excretory Urography. The EU, also known as intravenous pyelogram or intravenous urogram,
is the radiographic method for evaluating abnormalities of the kidneys and ureters
that are not apparent on the survey radiographs.* The study may be divided into two distinct
phases. 421,426,474 The first phase is the nephrogram stage—usually seen on the radiographs
exposed within the first few minutes after contrast injection (Figs. 3-141, A and
3-142, A). During this phase, contrast is distributed evenly throughout the renal intravascular
compartment and to some extent within the renal tubules. 426,474 Homogenous opacification,
or blush, of the kidneys occurs due to the relatively large fraction of total blood
volume that goes to the kidney. This is the ideal phase for evaluation of the renal size and
shape. In some studies, a difference in density between renal cortex and medulla will be
seen and a cortical medullary ratio may be determined. The second phase of the study is
the pyelogram (Figs. 3-141, B and 3-142, B). During this phase the collecting structures and
renal pelvis should be seen. This usually is visualized on the radiographs made at or beyond
5 minutes after contrast injection.
Although not usually considered a phase of the EU, the vascular anatomy sometimes
can be identified during an EU (vascular nephrogram phase) if the patient is positioned for
radiography before the contrast is injected, the contrast is injected rapidly, and the radiographic
exposure is made approximately 10 seconds after the injection is completed.
Often the renal artery and vein can be identified in this radiograph. The nephrogram phase
will follow this vascular phase very quickly. In patients with severe renal dysfunction, this
may be the only opportunity to see the kidneys.
In the dog, the normal kidney has a small, triangle-shaped pelvic sinus and evenly
spaced, regular pelvic recesses, or diverticula. The lobar renal arteries, the first branches
from the renal arteries, may be seen as linear radiolucencies lying between the paired pelvic
recesses. In many normal dogs, the diverticula may not be readily apparent on the EU. In
instances when it is necessary to visualize the diverticula, or when overall opacification of
the kidney is poor, it may be useful to apply a tight, constricting bandage circumferentially
*References 23, 26, 37, 415, 416, 419, 468-473.