Orthotopic neobladders have become an important solution for continent urinary diversion with excellent results for selected patients undergoining cystectomy. Consequently, bladder perception such as the feeling of bladder fullness, is expected to be altered after this surgical procedure. Moreover, depending on ureteric implantation technique and the physical properties of the reconstructed urinary diversion system (storage- and emptying phase parameters), uretero-renal reflux (URR) may evolve, leading to an increase in prevalence of urinary tract infections and long-term sequela of the upper urinary tract. 
In particular, neobladder emptying may be related to an individual type of bladder fullness sensation or may be based on a determined time-schedule/fixed emptying interval. However, neobladder sensation is assumed to be highly heterogeneous, commonly differing from standard sensation parameters as defined by the International Continence Society (ICS).
Regarding physical properties, functional assessment using video-urodynamics (VU) can be used to detect unfavourable functional parameters in patients with neurogenic and idiopathic bladder dysfunction.
The aim of this study was to assess video-urodynamic parameters, such as standard sensations during storage phase, maximum cystometric neobladder capacity and the occurrence of URR. Subgroups of patients with neobladders, with and without URR were compared.

This observational cohort study involved 20 patients (18 men, 2 women) having had robot-assisted radical cystectomy (RARC) with orthotopic neobladder (adapted Studer neobladder) between 2015 and 2022. Patients were asked to keep a bladder diary for 3 days. Prior to urodynamics, bladder-voiding habits including sensory qualities were assessed in an interview and compared with the bladder diary parameters. The ICS standard terminology for sensation was adapted to reflect individual sensory qualities and recorded during filling cystometry. 
Video-urodynamics were performed according to ICS standard recommendations. The occurrence of URR was documented and mean neobladder compliance (CPL; mL/cmH2O), mean cystometric maximum neobladder capacity (Vmax; mL), mean residual volume (PVR; mL), mean intravesical pressure (PUUR; cmH2O) and mean filling volume (VURR; mL) at the first detection of URR were compared. Medical records were reviewed for postoperative follow-up, recurrent urinary tract infections (rUTIs), and pre- and postoperative creatinine levels. All parameters are referred to as means with ranges between minimum and maximum values in brackets due to the small subgroups.

Bladder diaries of 19 out of 20 patients (95%) were analysed. Three patients (one without and two with URR) were missing post-operative data on rUTIs due to external treatment.
During the interview, 19 out of 20 patients (95%) reported initiating bladder emptying based on an individual feeling, while the remaining 5% (1/20) emptied the bladder according to a specific schedule. All patients reported a difference in bladder sensation during the storage phase after surgery. Regarding individual feeling, the following sensations were reported as triggers for bladder emptying: urge 84% (16/19), pressure in the lower abdomen 73% (14/19), tension 10% (2/19), pain 5% (1/19), undefinable abdominal discomfort 16% (3/19), genital discomfort 16% (3/19) and taste changes 5% (1/19). 
Uretero-renal reflux of any degree was found in 75% (15/20) of all patients: bilateral in 73% (11/15) and unilateral in 27% (4/15). In 80% (12/15) of these patients, a specific sensation was observed when the URR occurred.
In patients with URR, CPL, Vmax, PVR, PURR and VUUR were 166 (20-400) mL/cmH2O, 456 (160-780) mL, 230 (0-660) mL, 9.9 (2-20) cmH2O and 267 mL (100-445), respectively. Mean creatinine levels before and after surgery were 117 μmol/L (66-505) and 130 μmol/L (60-565), respectively. In 15% (2/13), rUTIs were reported during follow-up, all of whom voided spontaneously. In the URR subgroup without rUTI, 18% (2/11) of patients emptied the neobladder using aseptic intermittent self-catheterization (ISC), whereas 82% (9/11) emptied spontaneously. 
Among the remaining 25% (5/20) of patients without URR, the CPL, Vmax and PVR were 276 (30-750) mL/cmH2O, 656 (440-1000) mL and 420 (30-890) mL, respectively. Additionally, the mean creatinine levels before and after surgery were 86 μmol/L (73-111) and 93 μmol/L (65-129), respectively. In this group, rUTIs were reported in 75% (3/4) of patients, one of whom underwent ISC for bladder emptying.

The study findings allow an insight into post-operative bladder function in this cohort of patients. 
•	The data reveals that during the interview, 95% of patients reported emptying their bladder based on individual sensation, while only 5% followed a fixed schedule.  
•	All patients reported that bladder sensations during the storage phase after surgery differed from those before surgery. Most common triggers for bladder emptying were urge (84%) and pressure in the lower abdomen (73%).
•	75% of patients had URR, either bilateral (73%) or unilateral (27%). In most patients with URR, a specific sensation was observed during the onset of URR.
•	In patients with URR, video-urodynamics revealed a CPL of 166 mL/cmH2O, a Vmax of 456 mL, a PVR of 230 mL, a PURR of 9.3 cmH2O, and a VUUR of 267 mL. There were no significant differences in creatinine levels before and after surgery.
•	Recurrent urinary tract infections occurred in 15% of patients with URR voiding spontaneously. In the URR subgroup without rUTIs, 18% of patients were using ISC for bladder emptying.
•	In patients without URR, accounting for 25% of the cohort, CPL, Vmax and PVR measurements were higher. However, 75% of patients in this group experienced rUTIs.

Patients with neobladders having had RARC may have most likely different sensory triggers to initiate bladder emptying. Therefore, ICS criteria for bladder sensation during VU may not be appropriate in neobladders. We emphasize the need for standardized recommendations for the conduction of urodynamic studies in neobladders, which may help to improve the quality of research and patient care quality.

In addition, in our patient cohort, we observed that patients without URR had a higher bladder capacity and higher residual volumes. Furthermore, rUTIs were more frequent in this group. The presence of UUR appears to be a favourable factor for urinary tract infections. Outflow obstructions, such as those that can occur at the uretero-ileal implantation site, may be more problematic regarding development of rUTIs.
Therefore, functional patterns of neobladders may play a crucial role in long-term urinary tract morbidity and quality of life in these patients. Functional assessment with video-urodynamics may help to understand and distinguish favourable from unfavourable physical properties, but further research is required.

Continence 12S (2024) 101451
DOI: 10.1016/j.cont.2024.101451