History

A 4-year-old sexually intact male Yorkshire Terrier was examined because of intermittent dysuria of approximately 1 month's duration. Two days previously the dog had a consistently poor urine stream. There was no evidence of blood in the urine; however, blood was observed in the feces. Stranguria had been observed 2 days previously. The result of a recent heartworm test was negative, and immunizations were current.

Physical examination revealed a firm, moderately distended urinary bladder and bilateral grade II of IV medial patellar luxation. Bilaterally symmetric prostatomegaly was detected during per rectal examination. Results of a CBC were within reference ranges. A mildly high BUN concentration (32 mg/dL; reference range, 7.0 to 27.0 mg/dL) was identified on serum biochemical analysis. Urine was collected by cystocentesis. Urine specific gravity was 1.025. Urinalysis by use of a commercially available reagent test strip revealed proteinuria (1+) and blood (3+). Urine contained 11 to 20 WBCs/hpf and 21 to 50 RBCs/hpf. Urine was not submitted for bacteriologic culture. Radiographs of the abdomen were obtained (Figure 1).

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Lateral (A) and ventrodorsal (B) radiographic views of the abdomen of a 4-year-old sexually intact male Yorkshire Terrier with a history of intermittent dysuria of approximately 1 month's duration.

Citation: Journal of the American Veterinary Medical Association 234, 2; 10.2460/javma.234.2.201

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Determine whether additional imaging studies are required, or make your diagnosis from Figure 1—then turn the page →

Radiographic Imaging Findings and Interpretation

A moderately distended urinary bladder, prostatomegaly and a fracture of the os penis are evident. Rounded edges of the fractured os penis indicate a chronic, nonunion fracture.

A urethral filling defect is evident in the region of the fracture on serial lateral radiographic views following positive-contrast urethrography (Figure 2). The filling defect appears to originate in the ventral wall of the penile urethra. This pattern is most consistent with a fibrous urethral stricture; however, proliferative urethritis cannot be ruled out. Variably sized, smooth bordered radiolucencies are evident in die urethra as it bends around the ischial arch. Change in size and number of these radiolucencies between serial positive-contrast urethrograms is most consistent with air bubbles.

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Serial radiographic views of the abdomen following positive-contrast urethrography of the same dog as in Figure 1. An intralumina filling defect originating in the ventral wall of the penile urethra in the region of the fracture of the os penis is evident. Contrast medium is present in the urethra and bladder. Notice the smooth border and change in number and size of the radiolucencies in the area of the ischial arch on serial urethrograms.

Citation: Journal of the American Veterinary Medical Association 234, 2; 10.2460/javma.234.2.201

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Comments

Differential diagnoses for dysuria in sexually intact male dogs include obstructive uroliths, urethral or bladder neoplasia, perineal or body wall hernia with bladder entrapment, prostatic disease, penile trauma, urethritis, and urethral stricture.¹ A fibrous urethral stricture from previous urethral trauma is the suspected cause of dysuria in the dog reported here. Urethral trauma most likely occurred at the same time as fracture of the os penis. The fracture was evident on survey radiographs (Figure 1); however, positive-contrast urethrography was required to diagnose urethral obstruction (Figure 2).

Positive-contrast urethrography is a simple and valuable tool in the diagnostic workup of dysuria. In the dog of this report, findings on urethrography revealed an intra-luminal filling defect in the urethra. It is important to note that orthogonal views of the abdomen should be obtained during urethrography, as these views often provide additional information regarding the cause and extent of the urethral obstruction. The presence and location of extramural urethral compression, urethral tears, mural and mucosal lesions, and radiolucent urethral calculi can also be detected with positive-contrast urethrography².

The urethral stricture in the dog of this report prevented passage of a 5-F red rubber feeding tube for urinary catheterization at the time of urethrography; however, contrast medium was able to flow past the stricture site, indicating a partial urethral obstruction. Because the filling defect appeared to originate in the ventral wall of the penile urethra, it was unlikely that the fractured os penis was causing extramural compression to the urethra.

Radiolucencies in the area of the ischial arch on serial urethrograms were presumed to be air bubbles but could be confused with radiolucent calculi. Air bubbles can be avoided by removing air from the urinary catheter and the syringe prior to injection of contrast media. Applying digital pressure to the prepuce will help maintain a tight seal at the end of the penile urethra. In addition, agitating the area of air bubble accumulation during acquisition of serial images may also be helpful. Serial images should also be acquired during urethrography to help distinguish air bubbles from radiolucent calculi.

Fracture of the os penis in dogs is rare. Fractures may be transverse and minimally displaced or comminuted.¹ Minimally displaced fractures of the os penis can be managed conservatively¹. In a report³ of a dog with a fracture of die os penis, urethral compression from callus and fibrous tissue proliferation occurred 2 years after the fracture. In the dog of the current report, the temporal relationship between fracture of the os penis and urethral trauma to the development of a partial urethral obstruction was unclear because die owners of the dog did not recall any traumatic episode. The presence of an os penis in dogs may help to protect the urethra during initial injury to the penis. If a fracture of the os penis occurs, fracture segments may remain unstable, leading to nonunion, exuberant callus formation, and fibrous tissue formation. Serial monitoring of the fracture with plain radiography or positive-contrast urethrography may be required to evaluate progression of callus formation.

In the dog of this report, scrotal urethrostomy following castration and scrotal ablation was performed to bypass the region of urethral compression. Following surgery, adequate urine flow was observed with moderate bleeding from the urethrostomy site. Bleeding gradually resolved over the next 7 days. At the 14-day follow-up examination, the urethrostomy site was patent and sutures were removed.