Urethral features in women with primary urethral pain syndrome according to transvaginal ultrasound

BACKGROUND: Primary urethral pain syndrome is conventionally defined by the absence of structural abnormalities of the urethra. Transvaginal ultrasound is a simple and accessible diagnostic modality that provides comprehensive information on the lower urinary tract. However, the urethra is often underexamined, as primary urethral pain syndrome / chronic primary pelvic pain syndrome is usually associated with the absence of structural changes in the pelvic organs. AIM: This study aimed to assess structural changes of the urethra and its blood flow in women with primary urethral pain syndrome using transvaginal ultrasound with Doppler and elastography. METHODS: A total of 69 women were examined using transvaginal ultrasound: 45 with primary urethral pain syndrome and 24 controls. Philips EPIQ5 with a high-sensitivity transvaginal probe (6.5–7 MHz) was used for the examinations. The urethral lumen diameter and shape, wall thickness, vascular resistance index, diameter of periurethral veins, peak systolic velocity, and stiffness of urethral wall tissues were measured. RESULTS: In the control group, the urethral lumen was closed in 21% of patients, whereas in 79% the urethra appeared as a tubular structure with a uniform lumen diameter (4.0 ± 1.6 mm); the wall thickness was 2.7 ± 0.4 mm. In all patients with primary urethral pain syndrome, changes in urethral lumen shape and/or diameter and wall thickness were detected. The urethra retained a straight tubular shape in only 60% of cases, with dilation of the lumen to 6.6 ± 0.8 mm. In the remaining 40% of cases, the urethra exhibited either a funnel-shaped or bulbous configuration. Mean urethral wall thickness in primary urethral pain syndrome was 3.3 ± 1.2 mm compared with 2.7 ± 0.4 mm in controls (p = 0.111). Doppler ultrasound demonstrated a significant increase in the resistance index of periurethral vessels in primary urethral pain syndrome compared with controls (0.83 ± 0.06 vs 0.68 ± 0.04; p 0.0001). Compression elastography revealed greater stiffness of urethral wall tissues in patients with primary urethral pain syndrome. CONCLUSION: Transvaginal ultrasound was used to assess the urethra in women with primary urethral pain syndrome. In all patients with primary urethral pain syndrome, an increase in the diameter of the urethral lumen, as well as changes in its shape and urethral wall thickness, were identified. Doppler ultrasound revealed a substantial increase in the resistance index of vessels surrounding the urethra, as well as changes in venous diameter, indicating the presence of impaired blood flow in the urethral region in patients with primary urethral pain syndrome. Ultrasound elastography confirmed increased stiffness of urethral wall tissues in the presence of primary urethral pain syndrome compared with the control group.