Small Animal Radiology and Ultrasound: A Diagnostic Atlas and Text

396 Small Animal Radiolo g y and Ultrasono graphy
Fig. 3-183 An 8-month-old female
Poodle with urinary incontinence
since the owner adopted the dog (4
months). Survey radiographs were
normal. The excretory urogram
revealed the right ureter bypassed
the normal site of entry into the
bladder and extended to enter into
the vagina (black arrow). Diagnosis:
Ectopic right ureter.
Fig. 3-184 A 4-month-old female
German Shepherd dog with urinary
incontinence. A positive-contrast
cystogram and vaginogram (black v)
have been performed. The excretory
urogram revealed that the left ureter
penetrates the serosa of the bladder,
burrows through the submucosa,
and then exits and extends to enter
into the urethra distal to the urinary
sphincter (black arrows). Diagnosis:
Ectopic left ureter.
An uncommon finding is a ureterocele. 417,526,533 This is a ureteral dilation that occurs
between the serosa and mucosa of the bladder wall. It will appear as a small focal dilation
of the ureter, and there may be apparent narrowing of the ureter as it empties into the bladder.
The ureterocele will produce a round contrast-containing structure at the trigone and
may produce a focal bladder wall mass or filling defect as the bladder fills with contrast. If
ectopic ureter or ureterocele is considered likely, such as in a case of a young, incontinent
female dog, it is helpful to distend the bladder with air and take multiple oblique views of
the pelvic area in addition to the routine views. In some cases, the ureter will penetrate the
bladder serosa, travel in the submucosa, and continue to some distant site of termination
without spilling urine into the bladder (Fig. 3-185). Ectopic ureter may be unilateral or
bilateral. The presence of contrast within the urinary bladder does not rule out bilateral
ectopic ureters, because the bladder may fill with contrast retrograde from the urethra.
Repair of ectopic ureters usually requires surgical transplantation. Shortly after ureteral
transplantation into the bladder there will be ureteral dilation. This is probably due to
postsurgical inflammation, which creates a temporary partial ureteral stenosis. This change
usually will revert to normal condition over several months as the swelling subsides.
The accumulation of contrast medium in the retroperitoneal space identifies ureteral
rupture. The greatest concentration of contrast medium is noted at the level of rupture
(Fig. 3-186). Ureteral dilation may accompany ureteral rupture. Contrast also may accumulate
in the peritoneal cavity as a result of direct leakage or diffusion through the
peritoneum.