Intravesical botulinum toxin A (BTX-A) has been long established as treatment for overactive bladder and neurogenic bladder dysfunction. However adverse events such as intermittent self-catheterisation (ISC) play a large role in discontinuation of therapy. ISC rates have been reported between 6% and 45% and there is currently limited information regarding predictive factors to appropriately counsel patients particularly in men.

We retrospectively collected data on patients undergoing their first intravesical BTX-A therapy from January 2017 to July 2021 in a high volume, tertiary centre. Data included demographics, past medical and surgical history, and urodynamic parameters. Patients were excluded if they had a long-term catheter or ISC prior to initiation of therapy. Univariable logistic regression was used to identify suitable risk factors for ISC (p<0.05) which were then combined to generate a multivariable logistic regression model. Internal validity of the model was assessed with bootstrap sampling.

A total of 109 patients were included in the study (55 male, 54 female) with a median age of 64. There were 28 patients with neurogenic bladder dysfunction. Amongst the male cohort, 24 men had urge incontinence secondary to radical prostatectomy. Overall rates of ISC were 41.3% (Male: 41.8%, Female 40.7%). Predictors for ISC included a baseline post-void residual (PVR) ≥ 50 ml (OR 8.0, 95% CI 3.1 – 20.6, p <0.001), BTX-A dose > 100 units (OR 5.9, 95% CI 2.0 – 17.8, p=0.002), having a prostate in situ (OR 3.85, 95% CI 1.61 - 9.26, p=0.002) and bladder outflow obstruction on urodynamics (OR 3.5, 95% CI 1.2 – 10.1, p = 0.02). Stress urinary incontinence was protective against ISC (OR 0.31, 95% CI 0.13 – 0.76, p = 0.01). A multivariable logistic regression model with these factors yielded a C statistic of 0.83. Bootstrapped internal validation conferred an average optimism of 0.049 and an optimism adjusted C statistic of 0.78.

Amongst our cohort, high PVR, prostate in situ, high dose, lack of stress urinary incontinence and bladder outflow obstruction on urodynamics were all predictors of requiring ISC after BTX-A. These factors have been used to generate an internally validated model which has been incorporated into a risk calculator to predict ISC after BTX-A.

The factors identified in this study have been used to generate a predictive model which can be used to assist in counselling patients regarding individual risk for ISC. Validation of this model with other centres is required to increase external validity.