A New Technique for Computed-Tomography Urethrography in Males: The Clamp Method

Round 1

Reviewer 1 Report

Authors present a study regarding an innovative technique (clamp method) to be used for CT-RUG in patients with urethral anomalies. A statistical approach has been used to evaluate the results of the clamp method, compared to the conventional radiographic techniques. The study demonstrate that CT-RUG has an accuracy similar or grater with respect to common RUG, resulting less annoying for the patients

The study is clear and well written, however some minor revisions should be applied to improve the quality of the paper. Authors should give more details (voltage, currents, distance...) on the X-ray parameters used for all the methods they compared, together with a comparision on the effective dose.

Moreover, the work will be more clear for the readers introducing the "Conclusion" paragraph, separated from "discussion".

Overall, the paper can be considered for publication after minor revisions.

Author Response

Authors present a study regarding an innovative technique (clamp method) to be used for CT-RUG in patients with urethral anomalies. A statistical approach has been used to evaluate the results of the clamp method, compared to the conventional radiographic techniques. The study demonstrate that CT-RUG has an accuracy similar or grater with respect to common RUG, resulting less annoying for the patients

The study is clear and well written, however some minor revisions should be applied to improve the quality of the paper. Authors should give more details (voltage, currents, distance...) on the X-ray parameters used for all the methods they compared, together with a comparision on the effective dose.

Overall, the paper can be considered for publication after minor revisions.

We have added X-ray parameters and a comparision on the effective dose in accordance with your indications:

" The studies were conducted by a nurse with approximately 7 years’ experience in the clamp method for urethrography using a fluoroscopy machine (Luminos Fusion, Siemens Healthcare, Erlangen, Germany); the parameters were as follows: 60-90 kV, 20-80 mAs and 150 cm of focus object distance."

"Patients with periurethral fistulas had location and measurements recorded only by urethrography and CT-RUG, as RSUG was not performed (a limitation for detecting filling of the fistula with anechoic serum); this was also the case for patients with an intraurethral stent (limitation of ultrasound to penetrate the metal). We also recorded fluoroscopy time and dose-area product [DAP: µGy.m2] in the urethrography"

"The urethrography showed a mean fluoroscopy time of 5.9 ± 1.1 (SD) min (range, 3.5-6.8 min) and a DAP of 3335,46 µGy.m2, with an effective dose of 0.67 mSv."

"Moreover the effective mean dose obtained on urethrography was 0.67 mSv, which shows a significantly greater irradiation than with fluoroscopy. This is why CT is not recommended in males of a childbearing age and why 9 cases with reproductive plans were excluded from the study (because of the risk of gonadal irradiation); it is also why the study patients were aged over 50 years."

Moreover, the work will be more clear for the readers introducing the "Conclusion" paragraph, separated from "discussion".

Thank you. Done.

Reviewer 2 Report

This is a novel study looking at the feasibility and sensitivity of CT retrograde urethrography compared to RSUG and RUG. The clamp method and protocol are relatively novel and may provide clinical utility in future urethral imaging. Overall excellent case study. Several suggestions to improve manuscript quality.

1. While the clamp method will be useful for mid penile and proximal anterior urethral strictures. Do the authors have a suggestion to CT image the distal urethra where strictures would otherwise be obscured with the current clamping device?
2. Did all patients that underwent CT imaging for anterior urethral stricture also undergo RUG and RSUG? If so this should be clarified. Furthermore a table analyzing imaging variables and characteristics between the 3 imaging modalities could provide useful.
3. Fluoroscopic evaluation of the urethra is dynamic and done in real time. One could argue that this could prove advantageous in characterizing fistula/abnormalities of the anterior urethra that may otherwise be missed with static CT imaging
4. Indeed floor scopic imaging can underestimate the length of strictures if the patient is not in oblique positioning. For instance figure 3a, the patient is positioned almost completely AP and it is not surprising that the stricture length is underestimated relative to the sagittal nature in image figure 3 C. The authors need to make a comment about this in the discussion, and while this is a limitation of fluoroscopic imaging, it can be modified
5. Indeed there is significantly more radiation with CT imaging. This is particularly problematic in many men who are of childbearing age. In fact most idiopathic strictures occur in men in their 40s and 50s. Further clarification on this point the discussion is warranted.
6. Lastly, 1 of the most important characteristics of urethral stricture disease is the surrounding spongiofibrosis. One could argue that ultrasound and furthermore MR would be better for this. When performing urethral reconstruction knowing the extent of scar formation in the underlying spongiosal tissue is critical. Did the authors look at differences in ability to characterize scarring in the spongiosal tissue relative to ultrasound?

Author Response

Please see the attachment

Author Response File: Author Response.docx