History
An 11-year-old male sexually intact mixed-breed dog was referred to the University of Illinois Veterinary Teaching Hospital for evaluation of a right-sided perineal swelling and a perianal mass. The dog was evaluated 1 week earlier by the referring veterinarian for straining and inability to defecate. On physical examination, there was a 1-cm-diameter firm nodule 3 cm ventral to the anus and a 5 × 4-cm mass in the right perineal region that had a palpable fluid wave. Rectal palpation revealed a fluid-filled mass compressing the rectum and an irregular, enlarged, nonpainful prostate. All other physical examination findings were unremarkable.
Serum biochemical analysis revealed a mildly decreased albumin concentration (1.9 g/dL [reference range, 2.2 to 3.9 g/dL]) and was otherwise unremarkable. Findings on CBC and urinalysis were within reference ranges. A large amount (515 mL) of red-tinged fluid was aspirated from the right perineal mass and submitted for aerobic bacterial culture and cytologic evaluation. The mass was much smaller after aspiration, no longer compressing the rectum, but had partially refilled by the next morning. Cytologic findings were consistent with a transudate. The fluid creatinine concentration was 0.7 mg/dL and similar to the serum creatinine concentration, which was measured concurrently.
A fluid-filled cystic structure was observed caudal to the bladder on abdominal ultrasonography. A computed tomography scan of the abdomen was performed (Figure 1).
Computed tomographic images (3-mm slice thickness) obtained at the level of the prostate (A), pelvis (B), and ischia (C) in an 11-year-old dog that had right-sided perineal swelling.
Citation: Journal of the American Veterinary Medical Association 234, 9; 10.2460/javma.234.9.1127
Determine whether additional imaging studies are required, or make your diagnosis from Figure 1—then turn the page→
Diagnostic Imaging Findings and Interpretation
On computed tomography, a heterogeneous, symmetrically enlarged (approx 5 cm in diameter) prostate is evident (Figure 2). Density within the prostatic parenchyma ranges from 20 to 130 Hounsfield units. Multiple thin-walled, fluid-filled structures extend from the prostatic parenchyma on the right side with smaller cystic lesions extending from the left lateral and ventral margin of the prostate. A thick-walled, fluid-attenuating mass is closely associated with the prostate. Density within the fluid ranges from −7 to 70 Hounsfield units. This mass communicates caudally with a thin-walled cystic mass that extends through the right pelvic canal and enlarges caudally to the ischium into the right perineal region (Figure 3). On contrast computed tomography, there is mottled enhancement of the soft tissue capsule surrounding the cystic masses within the perineal region as well as heterogeneous enhancement of the prostate gland (Figure 4). Perineal paraprostatic cyst with benign prostatic hypertrophy and multiple smaller paraprostatic cysts is the most likely diagnosis.
Same image as Figure 1A. Notice the heterogeneous and enlarged prostate (arrowhead) and its associated paraprostatic cyst (arrow).
Citation: Journal of the American Veterinary Medical Association 234, 9; 10.2460/javma.234.9.1127
A 3-dimensional computed tomographic reconstruction of the caudal portion of the abdomen and pelvis. On this oblique parasagittal section, notice the prostate gland (arrow) with associated paraprostatic cyst (arrowheads) extending from the prostate through the pelvic canal and into the perineum.
Citation: Journal of the American Veterinary Medical Association 234, 9; 10.2460/javma.234.9.1127
Contrast computed tomographic image at the same level as Figure 1A. The prostate (arrowhead) appears heterogeneous and enlarged. There is mottled enhancement of the soft tissue capsule of the paraprostatic cyst (arrow).
Citation: Journal of the American Veterinary Medical Association 234, 9; 10.2460/javma.234.9.1127
Comments
Discrete cysts originating from the prostate have been classified as prostatic retention or paraprostatic cysts.1 These cysts are thin-walled structures that are often attached to the dorsal prostatic midline but do not communicate with the parenchyma itself.2
Abdominal ultrasonography is useful for diagnosing prostatic disorders, allowing good visualization of the prostate, draining lymph nodes, surrounding tissues, and distant abdominal organs.1,3 Abdominal radiography is also helpful in the diagnosis of paraprostatic cysts; mineralized paraprostatic cysts are fairly characteristic on a standard radiographic view of the abdomen.2,4 In this dog, ultrasonography revealed the presence of a prostate with a heterogeneous appearance and paraprostatic cysts. Findings on cytologic evaluation of the prostate were consistent with benign prostatic hypertrophy. The definitive diagnosis was achieved by use of computed tomography, which allowed visualization of the paraprostatic cyst extending through the pelvic canal.
In this dog, paraprostatic cyst marsupialization, perianal mass excision, and castration were performed through a perineal approach. Drainage from the stoma stopped 10 days after the surgery. Diagnoses of prostatic cyst, perianal gland adenoma, sertoli cell tumor, and seminoma were made from tissues submitted for histologic evaluation.
- 1.↑
Freitag T, Jerram RM, Walker AM, et al. Surgical management of common canine prostatic conditions. Compend Contin Educ Pract Vet 2007;29:656–663.
- 2.↑
Head LL, Francis DA. Mineralized paraprostatic cyst as a potential contributing factor in the development of perineal hernias in a dog. J Am Vet Med Assoc 2002;221:533–535.
- 3.
Boland LE, Hardie RJ, Gregory SP, et al. Ultrasound-guided percutaneous drainage as the primary treatment for prostatic abscesses and cysts in dogs. J Am Anim Hosp Assoc 2003;39:151–159.
- 4.
Zekas LJ, Forrest LJ, Swainson S, et al. Radiographic diagnosis: mineralized paraprostatic cyst in a dog. Vet Radiol Ultrasound 2004;45:310–311.
