Urinary Neurotrophin Levels Increase in Women With Stress Urinary Incontinence After a Midurethral Sling Procedure

Abstract

To investigate the association between urinary neurotrophin levels, maximum flow rate (Qmax) variation, and the appearance of urgency in women with stress urinary incontinence (SUI) after a midurethral sling (MUS) procedure. Thirty-one women with SUI were treated with a MUS. One year later, the outcome of surgery and the onset of urgency were assessed. At baseline and 1-year follow-up, urine was collected to measure nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF) concentration, and Qmax variation was calculated. Urine samples from healthy women (n = 20) without lower urinary tract symptoms and overactive bladder (OAB) wet patients (n = 32) were used as controls. Urinary neurotrophin levels were measured by enzyme-linked immunosorbent assay and normalized to creatinine concentration. At baseline, urinary levels of NGF and BDNF were similar between SUI and healthy women (NGF: 2.10 ± 0.68 vs 1.99 ± 1.05; BDNF: 1.99 ± 0.71 vs 1.81 ± 0.90), and significantly inferior to OAB wet patients (NGF: 2.10 ± 0.68 vs 2.50 ± 0.54, P < .05; BDNF: 1.99 ± 0.71 vs 2.71 ± 0.45, P < .05). After surgery, there was a significant increase of both neurotrophins (vs baseline, P < .05) to the values of OAB wet patients. Moreover, there was a significantly higher percentage increase of NGF in women with de novo urgency than in those without lower urinary tract symptoms (P = .019). A trend for a higher mean Qmax reduction in women with de novo urgency was also found (P = .085). These findings suggest that increased bladder outlet resistance after a MUS may play a key role in the rise of urinary neurotrophins, promoting sensitization of bladder primary afferents and causing de novo urgency in susceptible patients.