Small Animal Radiology and Ultrasound: A Diagnostic Atlas and Text

Chapter Three The Abd omen 407
Fig. 3-200 A 7-year-old female
Yorkshire Terrier with hematuria for
1 month. The survey radiographs
were normal. A double-contrast cystogram
revealed an ulcer crater that
retained contrast medium when it
was on the nondependent surface
(black arrows). Differential diagnoses
include cystitis or neoplasia with a
mucosal ulcer. Diagnosis: Cystitis
with a mucosal ulcer.
differentiation from cystitis difficult; however, tumor is more common at other sites, particularly
the trigone (Fig. 3-201). Another tumor that may be identified radiographically is
the botryoid rhabdomyosarcoma. This tumor usually is seen in young dogs, those 1 to 4
years of age, and most commonly is located on the dorsal surface of the trigone of the bladder.
It consists typically of cauliflower-shaped fingers of tissue protruding into the bladder
lumen (Fig. 3-202). 699 Other types of neoplasia (e.g., leiomyoma, leiomyosarcoma, polyp)
may cause a smooth thickening of the wall, but there usually is some degree of mucosal
irregularity and, more commonly, a mass protruding into the bladder lumen (Fig. 3-203).
Polypoid cystitis produces a generalized thickening of the bladder mucosa. Multiple
smooth polypoid masses are evident throughout the entire bladder (see Fig. 3-199). 700 Usually
the entire bladder wall is involved, which helps to differentiate this condition from tumors.
It usually is easy to differentiate bladder tumor from chronic cystitis based on the location
and appearance of the bladder wall irregularity. However, because pyogranulomatous
cystitis and urethritis may resemble an infiltrative tumor, a final diagnosis requires definitive
cytologic analysis or biopsy (Fig. 3-204). Lesions that are close to the area of the trigone
should be evaluated by means of an EU in addition to the cystogram in order to determine
the site of ureteral opening into the bladder. A common complication of trigonal lesions,
particularly tumors, is ureteral infiltration and secondary obstruction. This is especially
important if surgical removal of the bladder tumor is anticipated.
Another type of bladder wall change is a rupture or tear. 701 This is usually due to
trauma but occasionally is seen with other diseases. The tear will frequently develop a fibrin
seal over the rent, which allows partial bladder filling. Eventually, bladder distention
stretches the bladder wall and this exceeds the strength of the fibrin seal. A sequence of partial
sealing and subsequent rupture develops, releasing urine into the abdominal cavity. To
assess bladder rupture by cystography, one must produce adequate distention to test for a
partial bladder seal. Positive-contrast cystography or excretory urography should be used
instead of pneumocystography if rupture of the urinary bladder is suspected. Detection of
air leakage in the presence of moderate or significant hydroperitoneum is difficult. The leak
will be detected readily when a positive-contrast medium is used, because there will clearly
be positive contrast distributed throughout the abdomen (Fig. 3-205). Bladder rupture
may be retroperitoneal or into the pelvic cavity. In those cases, the positive contrast will be
contained within the pelvic cavity or retroperitoneal space and may not diffuse into the
peritoneal cavity.