Botox Bladder Injections and Urinary Retention

Risk of Urinary Retention

Urinary retention is one of the most common adverse events following intradetrusor onabotulinumtoxinA injections, with retention rates ranging from 2.6% to 54% in treatment groups versus 1.9% to 5.0% in placebo groups, particularly in neurogenic lower urinary tract dysfunction (NLUTD) patients 1, 2
Meta-analysis data shows an overall retention rate of 20.49% for onabotulinumtoxinA versus 3.67% for placebo (p<0.00000) 2, 3
There is an increasing dose-dependent relationship between higher doses (200 U vs 300 U) and risk of retention requiring CIC 1, 4

Clinicians must discuss the specific risks of urinary retention and the potential need for intermittent catheterization prior to selecting botulinum toxin therapy, applying to all patients who spontaneously void 1, 2
Pre-treatment PVR measurement is mandatory, with caution exercised when performing injections in patients with PVR >100-200 mL, as RCTs used this as exclusion criteria 5, 6

The standard treatment for urinary retention after Botox injection is clean intermittent catheterization (CIC) 1, 2
Symptomatic incomplete emptying is an initiation criterion for CIC 5, 6
If patients do not improve symptomatically after Botox injection, obtaining PVR, urinalysis, and urine culture is crucial, as UTI or incomplete emptying may be the cause rather than treatment failure 5, 6