What is the true catheterization rate after intravesical onabotulinumtoxinA injection?

A known side effect of intravesical onabotulinumtoxinA (Botox®) injection for overactive bladder (OAB) is urinary retention requiring clean intermittent catheterization (CIC), the fear of which deters patients from choosing this therapy. In clinical practice, patients with an elevated postvoid residual (PVR) are often managed by observation only, providing they do not have subjective complaints or contraindications. We sought to determine the true rate of urinary retention requiring CIC in clinical practice. A retrospective review was performed over a 3-year period of patients who received 100 units of intravesical onabotulinumtoxinA for the treatment of OAB. Patients were seen 2 weeks after the procedure to measure PVR. CIC was initiated in patients with a PVR ≥350 ml and in those with subjective voiding difficulty or acute retention. A total of 187 injections were performed on 99 female patients. CIC was required following three injections (1.6%): for acute retention in two patients and subjective voiding difficulty in one patient with a PVR of 353 ml. Following 12 injections, the patient had a PVR of ≥350 ml, and following 29 injections, the patient had a PVR of >200 but