Radiographic testing after urethroplasty provides excellent detail of the reconstructed urethra.6
It can also provide peace of mind for the surgeon and the patient since it vividly shows a widely patent urethra after successful repair. However, in the era of cost conscious, minimally invasive medicine is routine RUG/VCUG really necessary? With a success rate of greater than 90% most of these men proceed to unnecessary testing that exposes them to radiation as well as to other complications, such as urinary tract infection.
To answer that question we looked at urethroplasties done at our institution in a 10-year period. We compared findings from our routine 3 and 12-month postoperative RUG/VCUG studies to those of the concomitant UF and evaluated whether noninvasive UF could supplant radiographic testing. Findings show that UF alone is not a sufficient study to screen for recurrence, especially when we used the maximum flow rate. While specificity of the maximum flow rate improved as the rate was decreased to 10 ml per second, this was at the expense of unacceptably low sensitivity (54%), which is undesirable for any screening test. Using voiding curve data was more helpful with 93% sensitivity and 84% specificity. However, interpretation of the voiding curve is admittedly subjective, is usually done by a nonblinded investigator and would be difficult to recommend as a stand-alone screening tool.
UF has been used to evaluate urinary obstruction in other urological disease processes, most commonly in men suspected of having benign prostatic hyperplasia. In this group a flow rate of less than 10 ml per second has greater than 90% specificity and PPV to diagnose obstruction. However, to achieve such a high PPV, which is desirable for benign prostatic hyperplasia since it provides information on who could potentially benefit from surgical intervention, sensitivity is again low with most groups reporting only 40%.5
Pediatric urologists have also popularized UF in children after hypospadias repair. In this population a noninvasive way to test for obstruction is ideal since it is generally difficult to perform any manipulative procedure in children without anesthesia. What small studies have shown is that children with a flow rate of 2 SD below the mean or those with a flat voiding curve have a high likelihood of post-repair urethral stricture.7,8
Children suspected of having postoperative pathology by UF parameters can then undergo urethral examination with a high likelihood of finding recurrence and of successfully managing recurrent obstruction at the same operative/anesthetic setting.
The adult urethroplasty population is a more complex group to analyze noninvasively. Although multiple studies show significant improvements in UF after successful urethroplasty, they generally mention only mean improvements in the flow rate in the entire group and not individual improvement.4,9
A problem with UF in adults is the wide variability among older patients, which is particularly problematic in the post-urethroplasty population.10
Since many of these men have had long-standing urethral obstruction, the bladder is often relatively decompensated and the flow rate can be relatively low even without obstruction.11
For example, in our series almost 16% of men without recurrence had a maximum flow rate of less than 15 ml per second, which has been used in some studies as a threshold for urethral imaging.4,9
Conversely almost 30% of men with recurrence had a flow rate of greater than 15 ml per second. Also, since the median age of repair in this study was 42 years (range 19 to 85), a large percent of the men had a component of benign prostatic hyperplasia, which further complicates UF data interpretation. These confounding variables make setting a maximum flow rate cutoff at which all men would be evaluated for recurrent recurrence problematic when using UF as a screening measure.
Instead, the most effective way to use UF may be to perform UF preoperatively in all men and then post-urethroplasty UF at 3 months after verifying a patent urethra on RUG/VCUG done the same day. These UF values would effectively represent the patient baseline UF. At subsequent followup visits UF could then be repeated and any deviation from baseline in maximum flow or voiding curve shape would represent possible recurrence and could be evaluated by RUG/VCUG.
Also, monitoring patient voiding symptoms should be an integral part of any followup protocol screening for recurrence. Of study patients 85% were symptomatic when recurrence was found and only 12% had symptoms without recurrence. Although we did not and do not routinely use validated questionnaires to monitor symptoms, the American Urological Association symptom index questionnaire was previously studied for use in the urethral stricture population and showed some promise in its ability to monitor urethral status after changes in symptom scores.4,12
Adding a questionnaire that generates a voiding score would make monitoring symptoms more objective. Similar to our proposed UF method one could obtain preoperative and postoperative symptom scores, and perform radiographic testing if the score significantly worsens. A combined UF/symptom score protocol was previously evaluated in men who underwent prior direct visual internal urethrotomy with 93% sensitivity to predict recurrence vs urethral calibration alone. It is likely that if a similar protocol were evaluated prospectively in patients after urethral reconstruction, similar sensitivity would be achieved.
Our study has limitations. Although we used prospectively recorded data, hypothesis generation was retrospective and, thus, any conclusions generated by the study must be evaluated in a dedicated prospective study. Also, 55 men (14%) were excluded from analysis due to inadequate UF. This happened partly because we did not look at UF prospectively but it may also highlight some inherent difficulties that a urologist may often encounter when trying to use UF in clinical practice. It is often difficult in a busy clinic to obtain accurate readings in all patients, which must be considered when attempting to use UF effectively to predict recurrence. Still, our study findings are important, in that they show that UF alone is not likely sufficient to find all recurrences. However, when combined with symptom evaluation, it may decrease the number of RUG/VCUG studies done when looking for recurrence. Further studies are needed to evaluate the safety and cost-effectiveness of such an approach.