2009 Radiology Exam - Spec Proced/NM Case 2

CASE 2: This case was presented electronically. Candidates were given a collage of 4 still images selected from a fluoroscopic study.

• 8 yr, male, Labrador retriever
• Disappeared for 1 day and upon return was only able to dribble a small amount of urine when trying to urinate. 2 days later was unable to urinate.
• There is a large swelling palpable along the os penis.

See images below. Click to enlarge.

OBSERVATIONS:

• The first image is a survey image and shows a vertical radiolucent gap with moderately irregular borders in the mid-section of the os penis.
• The 2nd through 4th images are images of a retrograde positive contrast urethrogram with the tip of the catheter placed just distal to the os penis fracture.
• The contrast simultaneously outlines 2 tubular structures – one dorsal and one ventral to the os penis – being the dorsal vein of the penis and the urethra respectively.
• The urethra is distinguished by its position ventral to the os penis. In the sequence of contrast images the urethra can be followed in its normal location into and through the pelvic cavity. There is “jetting” of the urethral contrast into the urinary bladder most evident in the last image.
• The dorsal vein of the penis is positioned dorsal to the os penis. In the first contrast image there is a region of lacy or small tubular pattern of contrast uptake at the tip of the catheter that is then continuous with the contrast filled tube dorsal to the os penis. The lacy pattern is contrast in the corpus cavernosum urethrae. From the cavernous tissue the contrast is immediately drained by the dorsal vein of the penis. At the level of the ischiatic tuberosity there is a dorsally directed vascular connection from the dorsal vein of the penis to a vessel located dorsal to the rectum. This is the internal pudendal vein that then drains into the vena cava, best seen in the final image. Also in the final image there is some retrograde flow into the femoral vein to the level of the first venous valve.

SYNTHESIS:

Os penis fracture with concurrent urethral laceration forming a urethral-cavernous fistula.

MANAGEMENT:

This is a diagnostic study with no further imaging needed. Surgical treatment would be the next step in management.

FOLLOW-UP:

The patient was treated by penile amputation, scrotal urethrostomy and castration.

CANDIDATE PERFORMANCE:

Candidates varied greatly in their assessment of this case. Those that did poorly failed to identify that a urethral-vascular communication had developed. Misdiagnoses of abnormal ureteral connections, prostatic contrast extravasation, and bizarre congenital urethral anomalies were made.