Impact of different sized catheters on pressure-flow studies in women with lower urinary tract symptoms

Aims: This study assessed the impact of two catheters on urinary £ow in women undergoing a pressure/flow (P/F) study for lower urinary tract symptoms (LUTS). Materials and Methods: Women who agreed to undergo urodynamic testing were assigned prospectively to a 7 or 9 Fr catheter in P/F study according to a balanced randomized block design. Exclusion criteria: urinary tract infection, bladder stone or tumor, neuropathy, complete urinary retention, inability to void with catheter in place, free £owmetry volume below 150 ml, and urine volume varying by more than 20% on both free and P/F studies.We compared free £owmetry and P/F £owmetry with a 9 Fr catheter in 126/ 239 patients (Group A) and with a 7 Fr catheter in 113/239 (Group B).We determined the differences in the P/F results in terms of pre-voided bladder volume, clinical and urodynamic categories, and age groups in the two groups.We compared the diagnosis of obstruction based on Qmax during the P/F study and on Qmax in free uro£owmetry. Results: In Groups A and B, the Qmax rate was significantly less (P < 0.001) in P/F studies. Catheter size did not impact signi¢cantly. In patients with cystocele, post-void residue or obstruction £ow was reduced more than in the other categories.Qmax diminished with age, by about 15% in women aged 50^ 60 and by 21% in women over 70 years old. Conclusions: Qmax in P/F studies is always reduced independently of catheter size, volume of urine, age, and clinical or urodynamic category. This may have clinical implications when interpreting P/F results and in accurately diagnosing obstruction.