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 <350 ml without symptoms. CIC was not initiated in these 41 patients. None of these patients experienced subsequent retention, and all showed resolution of their elevated PVR within 8 weeks.

In our series of 187 intravesical injections for OAB, the rate of postprocedure urinary retention requiring catheterization was only 1.6%. This low rate can be attributed to less rigorous criteria for CIC initiation than those applied in previous studies. While important to counsel patients on the risk of retention, patients can be reassured that the actual rate of CIC is low.