DIAGNOSIS AND GRADING OF DETRUSOR INSTABILITY USING A COMPUTERIZED ALGORITHM

Purpose: Detrusor instability and hyperreflexia are characterized by i nvoluntary detrusor contractions in the filling phase of the voiding c ycle. The diagnosis is made when urodynamic evaluation reveals such co ntractions. To compare patients and evaluate treatment a method is nee ded to quantify the degree of instability. We developed an instability parameter based on the area under the curve of involuntary detrusor c ontractions on conventional filling cystometry. Materials and Methods: We developed an automatic method to calculate the area under the curv e of involuntary detrusor contractions in conventional filling cystome try. Logistic regression was used to construct decision rules to diffe rentiate stable from unstable bladders. These rules, derived from a gr oup of 100 children, were applied to a second group of 77 who were ind ependently assessed by 3 urodynamics experts. Results: Typically 88% o f the second group were correctly classified as stable or unstable by the automatic procedure. In the unstable subgroup there was poor corre lation between the calculated instability parameter and the instabilit y score assigned by the experts. Most likely this difference occurred because the experts based their opinion mainly on the amplitude of the highest unstable contraction and the percentage of filling time that instability was found. Conclusions: The proposed method of automatical ly grading detrusor instability based on the area under detrusor contr actions differs from the intuitive method used by experts. Since no st andard is available, it cannot be concluded which method is better. Ou r proposed method is objective and it results in a single physical val ue.