A comparison of ambulatory and conventional urodynamic studies in men withborderline outlet obstruction

Objective To compare detrusor function and outlet behaviour on ambulatory u rodynamic monitoring (AUM) with conventional cystometrography in symptomati c men with borderline evidence of bladder outlet obstruction (BOO), as dete rmined by conventional cystometrography, and to assess the usefulness of AU M in reclassifying this population of patients into obstructed and unobstru cted groups. Patients and methods Sixty-nine consecutive men (mean age 59.6 years) with lower urinary tract symptoms (mean International Prostate Symptom Score 19. 1) and borderline BOO on a medium-fill conventional urodynamic study (CUS) were examined prospectively with AUM. Detrusor contractility, obstruction g rade, maximal voiding detrusor pressure (pdet(max)) detrusor pressure at pe ak now (pdet Q(max)) and peak flow rate (Q(max)) determined by both methods were compared. The incidence of detrusor instability (DI) detected by both modalities was also evaluated. Results There was considerable disagreement between the investigations duri ng the voiding phase. Detrusor contractility was higher on AUM than on CUS (P= 0.003) and obstruction grade was significantly lower on AUM (P=0.018), There was no difference in pdet(max) nor pdet Q(max), The mean (95% confide nce interval) Q(max) was higher on AUM, at 12.9 (1.3) mL/s, than on CUS, at 8.9 (0.8)mL/s. On the Abrams-Griffiths nomogram the most significant chang es were sis men (10%) from equivocal to obstructed, seven (11%) from equivo cal to unobstructed and two (3%) from obstructed to unobstructed on CUS and on AUM respectively, Thus, in 24% of patients there was a potentially clin ically significant change resulting from the information generated by,AUM. DI was identified on CUS in 26 (41%) men and on AUM in 25 (40%); 35 men (56 %) had evidence of DI on either AUM or CUS. Conclusion The significant disagreement between the findings on CUS and AUM suggests that the conditions under which pressure-flow investigations are carried out significantly affect findings in borderline cases. The reclassi fication of patients by AUM into obstructed and unobstructed groups occurs in 24% and may be clinically relevant. AUM appears to be complementary to C US in the assessment of men who are borderline for obstruction on conventio nal testing, but the clinical implications of this have yet to be determine d.