Diagnosis
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The most appropriate investigations to assess the presence of a stricture of the urethra are the retrograde urethrogram (RGU) and/or voiding cystourethrogram (VCUG) combined with the urethroscopy.
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Urethrogram
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The RGU/VCUG are radiologic investigations that allow a comprehensive examination of the urethral lumen and the bladder. The procedure for RGU and VCUG are carried as follow:
1) RGU: A small amount of radiocontrast mixed with saline solution is injected through the external urethral meatus. A film is obtained. This first part of the study allows the visualization of the entire anterior urethra up to the sphincter in male and up to the bladder neck in female. To inject the radiocontrast, physicians and technicians usually rely on the Foley technique which consists on placing a Foley catheter tip in the first tract of urethra and gently inflate the balloon with sterile water until a seal is formed.
However, this procedure is frequently associated with patient’s discomfort and a non-negligible risk of urethral injury. For retrograde urethrogram we avoid the Foley technique. Instead, we place the tip of a metallic adaptor into the external urethral orifice with attached a contrast loaded syringe for injection.
2) VCUG: Using a small catheter (usually 10Ch) or filling tube (6-8Ch) that is passed through the urethra, the bladder is filled with a mix of radiocontrast and saline solution until the patient feels the need to urinate. At this point, the patient is asked to pass urine in standing position, and a film is captured. This second part of the study allows the assessment of the bladder neck opening and enhances the proximal part of male and female urethra.
3) Combined RGU/VCUG: In patients with pelvic fracture urethral injury (PFUI) involving the membranous urethra, a combined RGU/VCUG can help to visualize the gap between the two urethral ends. Here, the bladder is filled using a suprapubic catheter with radiocontrast and saline solution. When the bladder is full, we ask the patient to pass urine to enhance the proximal urethra. At the same time, we inject radiocontrast from the external meatus that allows the enhancement of the distal urethra. A film is captured.
To achieve good-quality results, RGU/VCUG should be performed by experts on this field regardless whether they are urologists or radiologists. Patient’s position during RGU/VCUG is crucial, as well as the X-ray device settings and the filling pressure. For the RGU, the patient should be placed in oblique position with the right leg folded and the pelvis slightly rotated on the right side, as well. The urethra should be stretched and distended while injecting the dye. Poor-quality radiograms may compromise the identification of a stricture or alter its features.
How to perform the urethrography
Urethroscopy
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The urethroscopy is a procedure that can be performed in the outpatient clinic under local anesthesia. Patients are usually adviced to take an antibiotic prophylaxis the morning of the exam. Lubricant gel, that contains an anesthetic, is gently instilled into the external meatus. A small (17 Ch) flexible cystoscope is gently placed into the urethra and advanced until it reaches the stricture. This procedure allows a direct visualization of the stricture and allows also to assess the severity of the stricture in term of residual lumen. When the residual urethral lumen is very narrow, the urethroscopy can be performed with a smaller rigid ureteroscope (caliber: 6.5/7Ch or 4.5/6.5Ch) that allows to go across the stricture and to examine the subsequent segments of the urethra and the bladder.
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Urethral calibration
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To assess the exact caliber of the strictured urethra, a bougie calibration can be required. Accordingly, the urologist can insert through the external urethral meatus an instrument called bougie-a-boules or simply dilator. This procedure offers two advantages: i) first, it allows a correct estimation of the urethral caliber; ii) second, it can enlarge the stenotic segment of the urtehra improving the urine flow and the symptoms of the patient, at least for a limited period of time. In female patients, an urethral stricture should be suspected when a 16Ch dilator cannot be accommodated into the urethral lumen to reach the bladder.
