Retrograde urethrography, sonouretrography and magnetic resonance urethrography in evaluation of male urethral strictures. Should the novel methods become the new standard in radiological diagnosis of urethral stricture disease?

Abstract

Purpose: To verify which of the diagnostic modalities: Voiding cystouretrography (VCUG), Sonouretrography (SUG) or Magnetic resonance uretrography (MRU) is the most accurate in the assessment of urethral strictures in males and in what cases the application of novel imaging techniques benefits most.

Methods: 55 male patients with a diagnosis of urethral stricture, were enrolled in this prospective study. Initial diagnosis of urethral stricture was based on anamnesis, uroflowmetry and VCUG. Additional imaging procedures-SUG and MRU were performed before the surgery. Virtual models and 3D printed models of the urethra with the stricture were created based on the MRU data. Exact stricture length and location were evaluated by each radiological method and accuracy was verified intraoperatively. Agreement between SUG and MRU assessments of spongiofibrosis was evaluated. MRU images were independently interpreted by two radiologists (MRU 1, MRU 2) and rater reliability was calculated.

Results: MRU was the most accurate [(95% CI 0.786-0.882), p < 0.0005] with an average overestimation of 1.145 mm (MRU 1) and 0.727 mm (MRU 2) as compared with the operative measure. VCUG was less accurate [(95% CI 0.536-0.769), p < 0.0005] with an average underestimation of 1.509 mm as compared with operative measure. SUG was the least accurate method [(95% CI 0.510-0.776), p < 0.0005] with an average overestimation of 2.127 mm as compared with the operative measure. There was almost perfect agreement of MRU interpretations between the radiologists.

Conclusions: VCUG is still considered as a 'gold standard' in diagnosing urethral stricture disease despite its limitations. SUG and MRU provide extra guidance in preoperative planning and should be considered as supplemental for diagnosing urethral stricture. Combination of VCUG and SUG may be an optimal set of radiological tools for diagnosing patients with urethral strictures located in the penile urethra. MRU is the most accurate method and should particularly be considered in cases of post-traumatic or multiple strictures and strictures located in the posterior urethra.

Keywords: Conventional retrograde urethrography; Magnetic resonance imaging; Pelvic fracture; Sonouretrography; Urethral stricture.

Fig. 1

A MRU, sagittal T2-WI image of the urethra presenting a short stenosis of the penile part (arrow) with associated fibrosis (hipointense tissue modeling the lumen of the urethra at and around the level of stenosis). B VCUG, site of stenosis (arrow). C SUG, stenosis with associated fibrosis (arrow). D Surgery specimen, fibrotic tissue around the stricture (arrow). E Spongiofibrosis (arrow) surrounding the strictured urethra (curved arrow) segmented from the MRU Sagittal Contrast-enhanced T1-weighted sequence. F 3-D printout of the urethra based on raw data provided by MRU with visible site of stenosis (arrow), green color marks the extent of fibrotic changes

Fig. 2

The deviation between the radiological measures and the operative measure (axis “0”). Negative scores represent underestimation, whereas positive scores—overestimation. Dots represent significant outliers in the measurements

Fig. 3

MRU sagittal T2-WI image (A) and reformat through the lumen of the urethra (B) present two stenoses within the bulbar part and at the border of the bulbar and penile part with surrounding fibrosis (arrows). C VCUG. Stenosis in the bulbar part of the urethra is also visualized in urethrography. D MRU sagittal T2-weighted image presents a short stenosis (arrow) in the bulbar part of the urethra, impossible to demonstrate in SUG