Page 430 - Feline diagnostic imaging

26.2 Contrast adiography 441

(b)

(a)

Figure 26.3 Poorly prepared abdomen. It is important to properly prepare the abdomen before performing an excretory urogram. (a)
In this lateral projection of a cat with chronic renal disease, one of the kidneys (arrow) is seen to be abnormally small and misshappen.
(b) In the ventrodorsal projection, neither of the kidneys can be evaluated because of a large amount of fecaloid material in the colon
superimposed over the kidneys.

The excretory urogram can be broken down into four (antegrade ureteropyelography) or into the ureter distal to
phases that occur in order but overlap (Figure 26.4) [4]. an obstruction (retrograde pyelography) [7].
The immediate phase is the vascular phase during which
time contrast medium can be found in the aorta, renal 26.2.3 Cystography
artery, and interlobar arteries. As the contrast medium
reaches proximal renal tubules, the nephrogram phase Cystography can be performed using positive contrast, neg-
becomes visible. The nephrogram should gradually fade ative contrast or a combination of both. In positive contrast
over the next hour. Contrast medium in the renal pelves, cystography, water‐soluble iodinated contrast medium is
diverticula, and ureters defines the pyelogram phase. The delivered through a catheter into the urinary bladder. The
cystogram phase begins as contrast medium enters the iodinated contrast can be either ionic or nonionic although
bladder. During initiation of this phase, the nephrogram if a ruptured bladder is suspected in a debilitated cat, non-
and pyelogram phases will still be visible. ionic contrast may be preferable. Positive contrast cystogra-
The excretory urogram is not without complications but phy is the best procedure to confirm rupture of the urinary
these will be fewer when a nonionic rather than an ionic bladder (Figure 26.5). On the other hand, because small
iodinated contrast medium is used. Vomiting is common in calculi are difficult to see within a large amount of positive
cats but is usually transient. Contrast‐induced renal failure contrast, this is not a good choice when calculi are sus-
is a more serious consequence that is signaled by persistence pected. Prior to the administration of contrast, 2–3 mL of
of the nephrogram phase [6]. Fluid therapy and diuretics lidocaine can be instilled to reduce straining during the
should be given to combat renal failure if it occurs [3]. procedure [3].
Anaphylaxis and pulmonary edema are other rare but Room air or carbon dioxide can be used for negative con-
serious consequences. Care should be taken to correct trast cystography [3,8,9]. Although the use of CO 2 lessens
dehydration prior to administration of intravenous the possibility of air embolism, the incidence of that com-
contrast media, particularly if ionic iodinated contrast plication is so rare that room air is most commonly used.
medium is used. The likelihood of air embolism can also be decreased by
keeping the cat in left lateral recumbency. This position
will result in any air being more likely to be on the right
26.2.2 Ureteropyelography
side of the heart, where it will be pumped into the lungs
Instead of iodinated contrast being injected intravenously, rather than into the systemic circulation. Nevertheless,
it can also be injected directly into the renal pelvis pneumocystography should be avoided if the bladder