**6. Clinical Outcomes of Intravesical Botulinum Toxin A Injection for Patients with DM-Associated OAB**

Although numerous laboratory and clinical findings support that BoNT-A inhibits overactivity and chronic inflammation of OAB by different pathways, very few clinical studies have investigated intravesical BoNT-A treatment of patients with DM-associated OAB. Wang et al. reported the first retrospective study to compare the efficacy and safety of intravesical 100 U onabotulinumtoxinA injection in 48 patients with refractory type 2 DM-associated OAB [45]. During the 6-month follow-up period, similar success rates were noted between the diabetic and non-diabetic OAB groups (DM, 56% versus non-DM, 61%, *p* = 0.128). The disappearance rate of detrusor overactivity proved by videourodynamic studies was also similar in both groups (DM, 56.3%, versus non-DM, 47.8%, *p* = 0.41). However, the patients with DM more commonly had adverse events such as large postvoid residual urine volumes and general weakness than the non-DM group.

One hypothesis is that early phase DM causes compensated bladder function, and late-phase DM causes decompensated bladder function [46,47]. Thus, DHIC, a paradoxical condition involving both the storage and voiding phases of bladder function, could happen during the transition from OAB to underactive bladder in DM patients. An interesting study comparing the efficacy and safety of intravesical onabotulinumtoxinA injection in patients with DHIC or OAB showed that the OAB symptoms in both groups significantly improved during the 3-month follow-up period [48]. However, the mean duration of therapeutic efficacy in patients with DHIC was significantly shorter than that of patients with OAB (4.9 ± 4.8 months versus 7.2 ± 3.3 months, *p* = 0.03). Additionally, the incidences of adverse events including acute urinary retention, large postvoid residual urine volume, urinary tract infection, gross hematuria, and general weakness were comparable in both groups.

Furthermore, Kuo et al. analyzed the adverse events after intravesical BoNT-A injection in 217 patients with idiopathic detrusor overactivity [49]. The results showed that male sex, large baseline postvoid residual urine, comorbidities, and higher doses of BoNT-A (>100 U) were risk factors for adverse events after BoNT-A injection for OAB. However, the occurrence of adverse events did not affect treatment outcome. As a result, intravesical BoNT-A injection is still recommended in patients with DM-associated OAB who develop DHIC. Patients should be informed of the possibility of shorter therapeutic duration and adverse events before injection.
