Akyva First In Human

List of Eligibility Criteria apply to both Non-neurogenic and Neurogenic underactive bladder study participants unless otherwise noted. Inclusion Criteria: * Are male or female, as assigned at birth, aged ≥ 22 years of age. * Presents lower urinary tract (LUT) symptoms that have been ongoing for at least the past 90 days prior to consent. * Is currently performing clean intermittent catheterization (CIC) for urinary retention at a rate of ≥3 catheterizations per day, as reflected in a 3-day self-catheterization record taken within 180 days prior to consent or a 7-day self-catheterization record collected between day of consent and before the implant procedure. * Have a post-void residual (PVR) volume ≥ 300 mL as evaluated at least twice within 180 days prior to screening or during screening. NOTE: Individuals unable to void any volume without catheter assistance, i.e. complete retention, are considered to have a PVR equivalent to pre-catheterization volume. * Have prior history of recurrent urinary tract infection (UTI) with at least two episodes of infection in the past 180 days or currently managing recurrent UTIs with antibiotic medication (e.g. Hiprex). * Urodynamic measurements consistent with detrusor underactivity. NOTE: Urodynamics performed within the last 365 days prior to consent are acceptable. (1) Bladder contractility index (BCI) \< 100 (in Males) (2) Qmax \< 15 mL/s and PdetQmax \< 20 cmH2O (in Males or Females). * Are medically fit to withstand abdominal-pel…