What is the true catheterization rate after intravesical onabotulinumtoxinA injection: Beyond the Abstract

A known side effect of intravesical onabotulinumtoxinA (Botox®) injection for overactive bladder (OAB) is urinary retention requiring clean intermittent catheterization (CIC). Many providers require that their patients demonstrate an ability and willingness to undergo CIC if they elect this treatment option.

However, it must be considered that although many patients retain urine, they do not necessarily need to perform self-catheterization. The clinical consequences of asymptomatic, incomplete bladder emptying after intravesical onabotulinumtoxinA treatment have not been specifically described. It also remains unclear if and/or when CIC should be initiated in these patients. Nonetheless, the relatively high reported rate of CIC following intravesical onabotulinumtoxinA injection shown in clinical trials is a common reason for patients to decline this treatment. In our experience, asymptomatic patients with an elevated postvoid residual (PVR) can be safely managed by observation only, providing there are no subjective complaints or contraindications for observation. As such, we sought to determine the true clinical rate of the need for catheterization in a tertiary female pelvic medicine practice.

During the study period, 187 onabotulinumtoxinA injections were performed. All injections were performed in the office setting with topical anesthesia (2% viscous lidocaine). A total of 100 units of onabotulinumtoxinA was injected into the detrusor muscle, including the trigone. Patients were seen 2 weeks after the procedure and the PVR was checked using a bladder ultrasound scanner. The primary outcomes were post-procedure urinary retention, defined as inability to void requiring catheterization, and the presence of symptomatic incomplete bladder emptying, defined as the presence of symptoms indicative of poor emptying (i.e. straining, weak stream or the sensation of incomplete emptying) with an elevated PVR of ≥350 ml. Patients with a PVR of ≥350 ml were followed every 1 to 2 weeks until PVR was. 

Following injection, the median PVR was 117 ml (IQR 58–225 ml. Following 13 of 187 injections (6.9%), the patient had a PVR of ≥350 ml. Of these 13 patients, 12 were asymptomatic and CIC was not initiated. Of these 12 patients not started on CIC, none had subsequent acute urinary retention and PVR decreased to <350 ml in a median of 5.8 weeks (range 4–8 weeks). Following 29 injections (15.5%), the patient had a PVR between 200 and 350 ml. All of these patients were asymptomatic and CIC was not initiated. Following the remaining 143 injections, the patient had a PVR of <200 ml. Based on our criteria, only 3 patients (1.6%) required catheterization.

In our series of 187 intravesical injections of 100 units of onabotulinumtoxinA for the treatment of 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 it remains important to counsel patients on the risk of retention after intravesical onabotulinumtoxinA injection, patients can be reassured that the actual rate of urinary retention requiring catheterization is low. 

Read the Abstract

Written By: Devin N Patel 
Pelvic Health Weekly Newsletter