What's known on the subject? and What does the study add? This article provides a current update on the risk factors, clinical features, and diagnosis on obstruction after female stress incontinence surgery using the mid-urethral synthetic sling. Particular attention has been paid to identify the patient at risk for developing voiding difficulty post-sling surgery, as well as the utility of urodynamics and various imaging modalities, especially translabial ultrasound, in the diagnostic process. Urethral obstruction is not an uncommon complication after sling surgery for female stress urinary incontinence (SUI). This paper focuses on this complication in the context of the mid-urethral synthetic sling, which is now the predominate surgical option used by many surgeons in the treatment of female SUI. The epidemiology and risk factors predisposing to sling obstruction is reviewed, followed by a description of clinical features used in supporting the diagnosis. The use of urodynamics in conjunction with translabial ultrasound as a novel approach to assess the position of the sling and its relation to the urethra is explained. This is particularly important in the understanding of why the sling obstructs from an anatomical standpoint. The paper concludes with a brief overview on treatment options.