Comparison of flowrates and voided volumes during non-instrumented uroflowmetry and pressure-flow studies in women with stress incontinence

Abstract

Aims The Blaivas-Groutz nomogram defines voiding obstruction in women using Qmax from the NIF and the maximum detrusor pressure (Pdetmax) from the PFS. The aim of this study was to understand the relationship between NIF and PFS maximum flow rates in women with stress incontinence. Methods We analyzed the UDS of 597 women with stress-dominant urinary incontinence. Each subject underwent a NIF and then a PFS. Mixed model was used to test the hypothesis that the relationship between flow rates and voided volume were similar for NIF and PFS. Results There were 452 subjects with both NIF and PFS studies that met the inclusion criteria and had max flow rate (Qmax) for both NIF and PFS. The mean age was 53. Overall, higher voided volumes were observed during PFS compared to NIF and subjects had higher Qmax with NIF compared to PFS. The relationship between Qmax and VV was significantly different between NIF and PFS (p < 0.004). At 200 mL, NIF Qmax was 14% higher than PFS Qmax and this difference increased to 30% at 700mL. Conclusion The difference between PFS Qmax and NIF Qmax increases as voided volumes increase. As a result, values from PFS and NIF cannot be used interchangeably as has been suggested in the Blaivas-Groutz nomogram for obstruction in women.

Relationship between maximum voided volume obtained by bladder diary compared to contemporaneous uroflowmetry in men and women

“…It is well documented that, to a large degree, uroflow is dependent on bladder volume -the larger bladder volume, the greater the flow (15,16). For this reason, patients are usually instructed to wait until the bladder is full before obtaining a uroflow.…”

Objective comparison of subtotal vs. total abdominal hysterectomy regarding pelvic organ prolapse and urinary incontinence: a randomized controlled trial with 14-year follow-up

“…The relationship between Qmax and voided volume is well known [29] and described in the Liverpool nomogram [22]. The women were asked to present with a comfortably full bladder and this result could mean that the SAH group have a larger bladder capacity.…”

Can we say that detrusor contractility did not change in: “Evaluation of the effect of 100 U of Onabotulinum toxin A on detrusor contractility in women with idiopathic OAB: A multicentre prospective study. De Rienzo G, Minafra P, Iliano E et al. Neurourol Urodyn. 2021 Oct 19. doi: 10.1002/nau.24820”

“…However, this estimate must be interpreted with caution because the Liverpool nomogram was constructed with free flow rates from asymptomatic and younger women (with a median age of 32 years), 3 and because, for example, in women with stress urinary incontinence (with a mean age of 52.9 years) it has been shown that as voided volume increases, the difference between free and invasive Q max also increase, and that regression equations that model Q max versus voided volume of invasive flow rates have smaller slopes than those of free flow rates (indicating lower increases in Q max with rising voided volumes). 5 Second, it would have been very interesting to have the information of how abdominal pressure changed from baseline to Q max before and after BTX-A injection, to know if there was any modification of the voiding pattern of the patients with this treatment. The article by Sahai et al 6 that studied the effect of 200 U BTX-A injections in patients with refractory idiopathic detrusor overactivity did not give this information either.…”