Small Animal Radiology and Ultrasound: A Diagnostic Atlas and Text

440 Small Animal Radiolo g y and Ultrasono graphy
Fig. 3-251 An 8-year-old male
Miniature Poodle with a small
amount of blood dripping from the
penis for 3 days. The lateral radiograph
reveals a moderately
enlarged prostate that is clearly cranial
to the brim of the pelvis (black
arrow). Differential diagnoses
include benign hyperplasia, prostatitis,
or prostatic neoplasia. Diagnosis:
Prostatitis.
automatic indicator of enlargement. A system of measurement of the normal canine
prostate gland based on the distance between the sacral promontory and the anterior
edge of the pubic bond as viewed from the lateral radiographic perspective has been
described. 54 In some chondrodystrophic breeds (e.g., Scottish Terriers), the normal
prostate may be located cranial to the pelvic brim. In some animals, the prostate may be
normal to small in size but is displaced cranial to the pelvic brim due to urinary bladder
or colonic distention. The most common cause of prostatic enlargement is benign
prostatic hyperplasia. Other considerations for prostatomegaly are neoplasia, metaplasia,
intraprostatic cyst, paraprostatic cyst, some intersex anomalies, or inflammatory
disease. 847-873 Abrupt changes in prostatic outline suggest prostatic abnormalities
including cyst, abscess, or tumor. Density changes within the prostate are uncommon.
Punctate calcifications may be present with benign prostatic concretions or calculi, prostatic
abscess, or prostatic carcinoma, but it is most common with carcinoma and is an
indication for biopsy. 54 Prostatic neoplasia may be accompanied by enlarged sublumbar
lymph nodes and the formation of periosteal new bone on the ilial wings and ventral
aspects of the caudal lumbar vertebrae secondary to hematogenous metastases (Fig. 3-
252). 53,863 In some cases of prostatitis, inflammatory elements will penetrate the prostatic
capsule and there will be hazy, streaky tissue densities in the fat between the
bladder and the prostate (Fig. 3-253). In some male dogs, the persistence of müllerian
ducts will result in the development of paraprostatic cysts. These may be visible as
round, oval, or tubular soft tissue–dense structures in the caudal ventral abdomen.
These masses may be present between the colon and bladder, may be cranial or lateral
to the bladder, or may even be in perineal hernia sacs. They are always attached by a
stalk to the prostate gland, but this attachment may not be radiographically apparent
and may have a calcified wall (Figs. 3-254 and 3-255). 862
Urinary tract contrast studies offer little specific information regarding the etiology
of prostatic disease. When there is doubt as to the identity of a caudal abdominal mass,
radiographs with a radiopaque urinary catheter in the bladder, cystograms, or urethrograms
may be helpful. Although retrograde urethrography may identify a large cystic
prostatic structure that communicates with the urethra, the more common situation is