Shell-shaped stone in a urethral diverticulum diagnosed by 3D-CT

A 66-year-old man presented with urinary retention and scrotal hard mass. Computed tomography (CT) scan showed acute prostatitis with prostatic stones and a urethral diverticulum with stone formation. Retrograde urethrography showed little information to place the location of stones in urethra and diverticulum. We report a case of a shell-shaped stone in a urethral diverticulum, which was successfully imaged by three dimensional-CT (3D-CT) filled with air.

Male urethral diverticula are rare and can be congenital or acquired [1, 2]. Some diverticula can be complicated by infection or stone formation [2]. We report a case of an acquired diverticulum with stones, accompanied by urethral stricture. We show our three dimensional-computed tomography (3D-CT) image technique, with air filling of urethra, to identify the position of diverticulum and stones.Case Report

 A 66-year-old man was referred to our hospital complaining of urinary retention and scrotal hard mass. In his past history, he received urethral injury around 40 years old. A scrotal mass was found intra-scrotally as a hard and cylindrical shape with smooth surface on physical examination. The mass was palpable around urethra and clearly delineated from the testis and epididymis, while the left testis was atrophic. Transillumination was negative. Urine analysis revealed microscopic haematuria (RBC>100/HPF) and urinary inflammation(WBC10-19/HPF). Urine culture showed Streptococcus agalactiae (5X105). Physical examination and laboratory tests suggested acute prostatitis. A plain X-ray demonstrated several high-density nodules in the pelvic cavity. The patient underwent plain CT, which showed prostatitis with prostatic stones and suspected urethral diverticulum with stone formation (Figure 1).

Retrograde urethrography showed little information to place the precise location of stones in urethra and diverticulum; urethral stricture was suspected in the anterior urethra. To evaluate the exact position of diverticulum and urethral stones, a 3D-CT technique employing air-filling of the urethra was performed. We observed two shell-shaped stones and several stones in a urethral diverticulum, prostatic stones, and small urethral and bladder stones (Figure 2).

After treatment with antibiotic medicine to recover the acute prostatitis, he initially received cutaneous vesicostomy, endoscopic transurethral incision and cystolithotripsy. We extracted some stones endoscopically and observed the opening of diverticulum, however we could not evacuate the diverticular stones. He subsequently underwent open diverticulectomy and stone removal two months later. Two shell-shaped stones with several small stones were removed. The infrared spectroscopic analysis revealed that the stones were composed of calcium phosphate. One month after this operation, the catheter was removed and he was able to void.

Computed tomographic colonography is a minimally invasive technique for imaging the entire colon. In this technique, the patient’s colon is cleansed and transiently inflated with air. Subsequently, a 3D image volume is acquired of the abdomen by CT. Finally, the bowel surface images are extracted and visualized, after which the physician can examine the colonic surface virtually for abnormalities [3]. For CT urethrography or virtual urethroscopy, diluted water-soluble iodine contrast medium is usually introduced to bladder by Foley catheter [4, 5]. However, in our case, we used an air technique to diagnose provisionally urethral stones and urethral diverticulum, because the patient had urethral stricture with multiple urethral stones. There are many factors affecting the successful performance of CT uretherography. Adequate air distention, the optimal CT technique and interpretation with using the newest software by a trained reader will help ensure high accuracy for lesion detection. Air distension in the urethra for 3D-CT may improve the diagnostic accuracy and allow for low cost intervention. With continued research and development, the use of such 3D-CT imaging techniques may become appropriate for future clinical diagnostic applications to evaluate the lower urinary tract.

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[2] Ho CH, Yu HJ, Huang KH. Scrotal mass with bladder outlet obstruction. Urology. 2008 Jul: 72:66-7

[3] Achiam MP, Bulow S, Rosenberg J. CT- and MR colonography. Scand J Surg. 2002: 91:322-7

[4] Chou CP, Huang JS, Yu CC, Pan HB, Huang FD. Urethral diverticulum: diagnosis with virtual CT urethroscopy. AJR Am J Roentgenol. 2005 Jun: 184:1889-90

[5] Chou CP, Huang JS, Wu MT, et al. CT voiding urethrography and virtual urethroscopy: preliminary study with 16-MDCT. AJR Am J Roentgenol. 2005 Jun: 184:1882-8