We determine the prevalence and clinical presentation  of underactive bladder  among patients diagnosed with overactive bladder.

Retrospectively, we included all consecutive patients with LUTS who presented with urgency and increased voiding frequency or nocturia with or without urgency urinary incontinence who underwent invasive urodynamic testing (January 2022 – December 2022). We defined underactive bladder with BCI (Pdet at Qmax + 5Qmax, within the range of 100 and 150 is classified as normal contractility) for male patients and with PIP1 (PIP1 = Pdet@Qmax + Qmax, between 30 and 75 cmH2O is considered normal detrusor contractility) for female patients.
They were divided into coexisting overactive underactive bladder, group A, and only overactive bladder with or without detrusor overactivity, group B. Sex, age, body mass index, comorbidities, previous surgeries, bladder pain syndrome, urinary frequency, first desire to urinating, maximum bladder capacity, post-void residual volume and Pdet at Qmax were compared in two groups.

Out of records of 76 patients included in this study, 33 (43.42%) patients were diagnosed with underactivity bladder based on bladder contractility index or PIP1 in overactive bladder patients.
The overall incidence of detrusor underactivity was 48.65%  ( 18 patients) and 38.46 % (15 pacientes)  in male and female OAB patients, respectively (p=0.37). The mean age in coexisting overactive-underacive bladder was  44.03 ± 14.09 and in overactive bladder without underactive bladder was 46.72 ± 15.26 (p=0.43). In coexisting overactive-underacive bladder showed a increased presence of constipation but it is has not significant differences (p=0.12).

In both group we found almost similar prevalence of hypersensitivity bladder (72.73% in coexisting overactive-underactive bladder patients in comparison to 77.44%, p=0.84). the coexisting overactive-underactive bladder patients showed 60.61 % of abnormal uroflowmetry and overactive bladder patients showed 67.44% (p=0.1). 
Coexisting  overactive-underacive bladder were significantly correlated with absence of detrusor overactivity (24.24 % in coexisting overatvive- underactive patients and 46,51 in overactive patients, p=0.46)

The bladder contractility becomes impaired with age, but in our data we can’t found a statistical difference. Even we found the presence of this condition in young patients.
the absence of detrusor overactivity could be a predictor of development of underactive bladder .However, further studies are lacking
Several limitations were found in this study, for example, the sample size prevalent in the bladder contractility index was small

Coexisting overactive-underacive bladder is a complex syndrome because the clinical characteristics the urodynamic characteristics have not been demonstrated and lack a gold standard diagnostic criterion

Yu YD, Jeong SJ. Epidemiology of underactive bladder: common but underresearched. Investig Clin Urol.
Osman NI, Esperto F, Chapple CR. Detrusor underactivity and the underactive bladder: A systematic review of preclinical and clinical studies. Eur Urol. 2018
Eleonora Rosato, Livia Mollo, Vincenza Laurendi, Luca Orecchia, Pietro Bachetti, Enrico Finazzi Agrò, May coexisting overactive-underactive bladder (COUB) be due to muscle fatigue? Data from a single-centre urodynamic database,