The prevailing understanding of the pathophysiology of female stress urinary incontinence (SUI) indicates a gradual deterioration of urethral and paraurethral structures. Although urodynamic studies (UDS) represent the most precise method for diagnosing SUI, this invasive procedure is associated with potential risks such as infections and discomfort for patients. As a result, current guidelines advise against routine UDS for cases of uncomplicated SUI. Nevertheless, to improve surgical results and mitigate risks, conducting a thorough preoperative assessment of the lower urinary tract is crucial. In this study, transrectal sonography, a familiar instrument among urologists, provides a dynamic evaluation that accurately measures changes in the pelvic floor during rest, coughing, and Valsalva maneuvers. This feature renders it an effective and straightforward approach for categorizing the severity of female SUI, thereby facilitating more informed surgical planning.

This prospective study, carried out from January to October 2023, involved 70 consecutive female patients who sought treatment for SUI at outpatient clinics. Beyond the standard physical and pelvic examinations, these patients underwent routine uroflowmetry and dynamic transrectal sonography[1], the latter administered by a single urologist and including assessments during rest, coughing, and Valsalva maneuvers, for a comprehensive evaluation of urinary incontinence. Initial screenings that identified cases of uncomplicated SUI promptly led to the initiation of conservative treatment and pelvic floor muscle training (PFMT), overseen by a physiotherapist. 
When clinical symptoms and preliminary tests indicated mixed-type incontinence, coexisted with pelvic organ prolapse or other symptoms of lower urinary tract dysfunction, a videourodynamic study (VUDS) was conducted. Subsequent treatments were customized based on VUDS findings. Patients whose uncomplicated SUI did not improve with conservative treatment and PFMT, as well as those diagnosed with stress-predominant urinary incontinence through VUDS, a total of 10 patients received sling-only surgery. The selection of sling type is based on findings from dynamic transrectal sonography.

In this study, 70 female patients were preliminarily included, with 33 being diagnosed with uncomplicated SUI upon initial assessment. Out of these, 30 showed significant improvement following PFMT, vaginal estrogen therapy, and vaginal Er-YAG laser treatment. The other 37 patients, classified with complicated SUI, included eight with stage 2 or higher pelvic organ prolapse (POP) who underwent concomitant prolapse and anti-incontinence surgery. Twenty-two patients with urge-predominant incontinence experienced improvement after overactive bladder treatment. Furthermore, seven patients with stress-predominant incontinence and three with moderate to severe uncomplicated SUI were treated with sling-only surgery. For a detailed overview of the patient management process, please see Figure 1.
The median age of patients undergoing sling-only surgery was 49 years (interquartile range [IQR] 44-69.7 years). Preoperative uroflowmetry revealed a median maximum flow rate of 28 ml/s (IQR 21.1-37.0 ml/s) and a median voiding efficiency of 95.7% (IQR 93.6-98.3%). Dynamic transrectal sonography showed that five patients (50%) had intrinsic sphincter deficiency (ISD), with a median bladder neck hypermobility displacement of 1 cm (IQR 0.5-1.35 cm) and a median urethral angle change of 30 degrees (IQR 12.5-37.5 degrees). 
Sling selection was based on the severity of SUI, with four patients receiving retropubic slings, two trans-obturator slings, and four single-incision slings. The post-surgery continence rate was 100%. 
Notably, a 2 cm paraurethral cyst was incidentally found in one patient through transrectal sonography, which was removed during the sling procedure. Pathological examination confirmed it as a Gartner’s cyst.

Dynamic transrectal sonography can act as a primary screening tool for SUI, categorizing its pathophysiology into two principal types: ISD and pelvic floor hypermobility. ISD severity is measured by the width of urethral incompetence, while changes in the bladder neck's position and the urethral angle quantify the pelvic floor hypermobility. This classification enables the prediction of which patients with uncomplicated SUI might not benefit from PFMT and conservative treatments, potentially necessitating anti-incontinence surgery. For complicated SUI, performing a VUDS is advised to secure an accurate diagnosis and customize treatment. 
Findings from dynamic transrectal sonography that show severe ISD with wider urethral incompetence (longer than 0.5cm), bladder neck displacement exceeding 2 cm, or a changed urethral angle greater than 40 degrees during stress tests suggest that choosing a retropubic sling over a trans-obturator approach could enhance the continence outcomes.
Although current guidelines do not mandate the imaging examination before the sling surgery for uncomplicated SUI, our research underscores the importance of transrectal sonography for ruling out paraurethral lesions such as Gartner’s cyst, thus preventing postoperative complications.

For female patients with SUI, dynamic transrectal sonography, beyond basic assessments, offers three notable benefits. Firstly, it distinguishes between uncomplicated and complicated SUI, informing the decision on the need for a urodynamic study. Secondly, it allows for the quantification of SUI severity, aiding in the selection of the most suitable sling procedure. Thirdly, it plays a crucial role in identifying paraurethral lesions, significantly minimizing the risk of surgical complications.

Eur Urol. 2000 Feb;37(2):149-55.