After the introduction of the transvaginal midurethral synthetic sling  in 1996 by Ulmstem, and the description of the transobturator route by Delorme in 2001, the surgical correction of stress urinary incontinence was simplified allowing a minimally invasive approach, being nowadays considered the gold standard for the primary treatment of uncomplicated stress urinary incontinence (UI) without pelvic organ prolapse. The minimally invasive nature of the surgery allows patients to rapidly recover their previous functional status.
The aim of the study was to investigate possible risk factors influencing a delayed functional recovery in patients with stress urinary incontinence (SUI) treated with midurethral slings.

Multicentre, retrospective and observational study in a sample of 1000 women undergoing transobturator midurethral sling placement between April 2003 and March 2016. All the patients received the same type of sling (KimTM, Neomedic Int©, Terrasa, Spain).
Three groups were differentiated according to the anaesthetic risk:
•	Group A (GA, n=485): patients included in American Society of Anesthesiologists (ASA) score I;
•	 Group B (GB, n=373): ASA score II;
•	Group C (GC, n=142): ASA score III.
Variables: age, BMI, SUI time prior to surgery, follow-up time after surgery, medical and surgical background (including gynaeco-obstetric history), concomitant drug treatment, complications influencing functional recovery after surgery (bleeding, pain and infection). An specific analysis was performed regarding patients achieving urinary continence, without sling-related complications but with complications influencing functional recovery.
Statistics:  descriptive statistics, Student's t-test, Chi2, Fisher's exact test, ANOVA (with Scheffe's test for normal samples), Pearson and Spearman's correlation studies. p<0,05 was accepted as statistically significant.

Median age was 60 years (SD 13.38, range 20-87), without statistical differences between the 3 groups (p=0,485214). Median BMI was 25.80 kg/m2 (SD 4.51, range 17.96-50.78), lower in GA (p=0,001888). Median SUI time prior to surgery was 3285 days (SD 676.74, range 2190-5110), shorter in G3 (p=0,050358). Median follow-up was 2555 days (SD 831.35, range 1460-5475), shorter in GA (p=0,0000001). The most prevalent comorbidities in the sample are high blood pressure, diabetes mellitus, mixed anxiety–depressive disorder and other endocrine and digestive disorders.
Bleeding was recorded in 0.61% of patients in GA, 0.8% of patients in GB and 3.52% of patients in GC (p<0.005). Pain was recorded in 18.35% of patients in GA, 19.3% of patients in GB and 11.97% of patients in GC (p>0.005). Infection was recorded in 7.83% of patients in GA, 18.49% of patients in GB (p<0.005) and 6.33% of patients in GC.
Median time before functional recovery in those patients without complications was 5 days (SD 2.7, range 3-20), without differences between groups (p=0.6022). When bleeding occurred, median recovery time was shorter in groups A and B than in GC (p=0,049). When pain was present, median recover time was longer in GB (p=0,01468). No statistical differences were found in the recovery time after infection between groups (p=0,01468).

Age has been identified in multiple studies as a risk factor for sling failure after anti-incontinence surgery. Obesity has also been linked to sling failure (1), although several case studies did not find different outcomes between patients with high and low BMI (2). Other identified risk factors for persistent or recurrent urinary incontinence are nocturia, urgency incontinence and previous incontinence surgery (3). Post-surgical bleeding may influence a longer recovery in patients with a higher ASA score (in other words, patients with substantive functional limitations even before surgery). On the other hand, pain and infection would similarly affect the recovery in the three groups.

When post-surgical complications appear, median time before patient's functional recovery depends on the ASA score and the type of complication. In ASA I and II score patients, pain or infection lead to a longer recovery time than bleeding.

Curr Urol Rep. 2018 Feb 22;19(1):10. doi: 10.1007/s11934-018-0762-7.
BJU Int. 2018 Sep 29. doi: 10.1111/bju.14569.
Int J Gynaecol Obstet. 2010 Jul;110(1):18-22. doi: 10.1016/j.ijgo.2010.02.016.