Frequency, poor flow and nycturia are mostly observed by the patient himself, residual urine and/or high voiding pressures are findings for the urologist to indicate intervention. Particularly if detrusor underactivity starts to take place, patients may show little symptoms, however, further waiting to correct the obstruction may put the detrusor at risk even driving the patient into retention. Therefore, the appropriate moment for deobstruction may be clinically challenging to define when symptoms are still insignificant, but medical parameters seem to deteriorate.
 
Urodynamic Pressure Flow Studies (PFS) are considered the gold standard to assess micturition situation in pts with BPH/BPO. However, even before scheduling deobstructive interventions, PFS is rarely applied because of invasively and/or lack of capacity. Therefore, often decision making for deobstructive surgery is based upon anamnesis, PVR, uroflowmetry and IPSS alone. 
We set out to investigate, if a simplified PFS based on Pves during micturition and uroflowmetry alone is an indicator for assessment of BPH/BPO patients.

The urodynamic parameters of 50 men with obstructive symptoms from 2 centers of expertise were retrospectively analyzed. Qmax, PVR, Pdet@Qmax and Pves@Qmax were assessed. The BOOI was calculated both with pDet and pVes (modified BOOI – "BOOIm") as described by Jang et al.

All patients were suffering from obstructive LUTS, 4 patients being in retention were excluded from the study. Median Qmax was 7,05ml/sec (SD 5,33) and PVR 140ml (SD 163,13). Median PdetQmax of all cases was 65cmH2o, (SD 34,83), PvesQmax 93cmH2o (SD 43,34).
In the assessment of obstruction by BOOI no obstruction (0-20) was found in 4 cases, 12 were equivocal (20-40) and 31 obstructed (>40). The results for BOOI and BOOIm classifying into grade of obstruction (unobstructed/intermediate/obstructed) were identical in 39/46 cases (group I). In all remaining 7 cases (group II) the BOOIm grade was higher than BOOI (5x intermediate => obstructed, 1x unobstructed => obstructed, 1x unobstructed=>intermediate). The median PdetQmax in group II was 48cmH2o (SD 9,4) and the BCI 76 (SD 36,5) as compared to 96 cmH2o (SD 44,2) and BCI 125 (SD 139,7), respectively in group I. Median PVR was 177ml (SD 100,3) in groupII and 82ml (SD 175,8) in group I.

this simplified PFS based on Pves during micturition and uroflowmetry alone can be an indicator for assessment of BPH/BPO patients.

For the question of indicating a deobstructive procedure for BPH/BPO patients a PFS based upon Pves/Qmax using the modified BOOIm seems appropriate. A false negative assessment of obstruction due to DU can be avoided, however, diagnosis of DU for preoperative patient consent may be missed. For this reason, patients with high PVR should always receive a full UD. Clearly, these considerations need to be confirmed in future studies.

Han JH, Yu HS, Lee JY, Kim J, Kang DH, Kwon JK, Choi YD, Cho KS. Simple Modification of the Bladder Outlet Obstruction Index for Better Prediction of Endoscopically-Proven Prostatic Obstruction: A Preliminary Study. PLoS One. 2015 Oct 27;10(10):e0141745. doi: 10.1371/journal.pone.0141745. PMID: 26505196; PMCID: PMC4624432.