The relative incidence of detrusor instability and bacterial cystitis detected on the urodynamic-test day

Objective To determine whether patients with detrusor instability (DI) were more likely to have bacterial cystitis or significant bacteriuria on the u rodynamic-test day than were women with a stable bladder. Patients and methods A catheter specimen of urine was cultured (overnight i n air) from 862 consecutive women at the time of urodynamic testing. The up per urinary tract was imaged, with cystoscopy when indicated, to exclude up per tract lesions or malignancy. The percentage of patients with pure idiop athic DI and those with mixed DI/genuine stress incontinence (GSI), in whom the urine culture was positive, was compared with the percentage who had a stable bladder (pure GSI or urodynamically normal) and a positive urine cu lture, both for the entire dataset and for women aged > or < 65 years. Data were also analysed to detect the converse relationship; in those women fou nd to have bacterial cystitis, the relative risk of being found urodynamica lly unstable or stable was determined. Results The likelihood of bacterial cystitis occurring in patients with idi opathic DI (5.6%) was significantly greater than that in patients with GSI (1.1%; P = 0.009, Fisher's exact test). The proportion of patients with DI and significant bacteriuria (15.4%) was significantly greater than that in patients with GSI (7.9%; P = 0.02). In patients with combined pure and mixe d DI, bacterial cystitis was significantly more likely to occur (6.3%) than in GSI (P < 0.001), but bacteriuria was no more likely (12.5%, P = 0.09). Conversely, of those women found to have bacterial cystitis, the relative r isk of having an unstable bladder was increased (+1.56), but for those with bacteriuria the relative risk of detrusor instability was not increased. Conclusion There was a significant association between idiopathic DI and ba cterial cystitis, and we suggest that in some women with an unstable bladde r, urinary infection may enhance detrusor contractility. Nevertheless, larg e-scale studies are needed of the temporal relationship between the onset o f bacterial cystitis and the onset of DI.