Akyva First In Human

List of Eligibility Criteria apply to both Non-neurogenic and Spinal Cord Injury (SCI) Neurogenic underactive bladder study participants unless otherwise noted. Inclusion Criteria: * Are male or female, as assigned at birth, aged ≥ 22 years of age. (SCI Only: 22 to 70 years of age) * Able to initiate at least three (3) volitional voiding episodes over the 7-day period based on review of their 7-day bladder diary collected between day of consent and before the implant procedure. * Currently performing clean intermittent catheterization (CIC) for urinary retention at a rate of ≥7 catheterization episodes over the 7-day period, as reflected in a 7-day bladder diary collected between day of consent and before the implant procedure. * Are medically fit to withstand abdominal-pelvic surgery under general anesthesia, as evaluated by standard-of-care pre-operative surgical clearance. * Females of childbearing potential must agree to the use of contraception for the duration of the study * Are able to understand the risks associated with the study, are willing and able to provide written informed consent prior to any study-related activity, willing and capable of participating in all follow up assessments and willing to undergo all study assessments as described at an approved clinical investigator site. * No neurologic cause * SCI Only: Chronic spinal cord injury (\>= 6 months post-injury) with sacral/infrasacral (L1 or below) lesions, or mixed lesions associated with neurogenic lower urinary tract dysfunction (NLUTD). Exclusion Criteria: * Have or are scheduled for implant of any active implantable medical device (e.g., pacemaker or intrathecal or infusion pump). Individuals with implanted but inactive SNM may participate. Individuals with implanted and inactive SNM devices may participate. * Have metallic implants/fragments in the abdomen or pelvis (e.g., piercings or hip replacement). * Have a documented allergy to tissue contacting Akyva System materials: tecothane, titanium, silicone, epoxy, stainless steel, nickel/cobalt/chromium/molybdenum, polyether ether ketone (PEEK), platinum, iridium, polymethylpentene (TPX), polycarbonate, polyester. * In the opinion of the Investigator(s), participants who need or are likely to need magnetic resonance imaging (MRI) as part of their routine care for the duration of the study. If MRI is clinically indicated, during or after the study, explant of the Akyva System may be required * Have active infection requiring treatment with antibiotics at Screening, unless cleared before Akyva System Surgical Implant (Visit 2). * Previous or planned major surgical procedures, including, but not exclusive to: prior mesh implant, augmentation cystoplasty, urinary diversion, bladder reconstruction, sacrocolpopexy, and any other procedure that increases the risk of device implantation. * Active medical conditions that could increase the risk of surgery or device implantation, including, but not exclusive to: ascites, severe inflammatory diseases, bleeding or clotting disorders, severe cardiopulmonary disease, etc. * Have a significant clinical finding that would, in the opinion of the Surgical Co-Investigator, increase the risk associated with the implant procedure (e.g. ascites, severe inflammatory disease, bleeding or clotting disorder, other interfering devices etc.). * Have complete urinary retention. * An acontractile detrusor. * Any evidence of current bladder outlet obstruction from any cause, including, but not exclusive to, bladder neck stenosis, prostatic hypertrophy, or urethral stricture. Participants with prior surgical treatment of BPH with no clinical evidence of obstruction and do not require routine MRI may be included. * Type I or Type II diabetes, with an HbA1C ≥ 7.0% within the last 60 days from consent. * Have documented renal dysfunction, defined as an estimated glomerular filtration rate (eGFR) ≤ 50 mL/min/1.73 m² or * Evidence of moderate to severe hydronephrosis (grade 3 or 4 per Society for Fetal Urology \[SFU\] grading scale) on renal and bladder ultrasound within 60 days prior to implant. * Have any history of dialysis or kidney transplant. * Have a history of kidney or bladder stones within the last 5 years. * Have any history of bladder cancer. * Locally advanced or metastatic thoracic, abdominal, or pelvic malignancy other than bladder cancer unless disease-free for five (5) years or greater. * Have any history of radiation cystitis. * Have had botulinum toxin injection in the bladder or pelvic floor in the past 6 months measured from the day of consent. * Diagnosis of overactive bladder (OAB), with urge urinary incontinence (OAB-wet), whether treated or untreated. * In the opinion of the PI, an iatrogenic cause, e.g., prior pelvic surgery, multiple or complicated deliveries, and/or other potential events are the suspected cause of UAB symptoms. * Currently using an indwelling (e.g. Foley) catheter for bladder emptying, with an exception for nighttime-only use. * Currently using suprapubic catheters, unless the suprapubic catheter is removed at least 30 days prior to implant. * Participants who are unable to discontinue anticoagulant therapy for the implant procedure. * Females of childbearing potential who are pregnant, not using medical birth control or who are planning to become pregnant during the anticipated study period. * Predicted life expectancy of less than two years from the day of consent. * Any condition that, in the Investigator's opinion, would preclude participation in the study (e.g., have a medical condition that may interfere with interpretation of study results, inability to adhere to the visit schedule, poor cognitive abilities, poor compliance with treatment regimen, or poor dexterity to use the system etc.). * Previously (within 5.5x the terminal half-life (drug trial) or 8 weeks (device trial) of the screening visit) or currently enrolled in another investigational drug or device trial that targets lower urinary tract symptoms/function. * Vulnerable persons such as prisoners, mentally-disabled or cognitively impaired, homeless or economically disadvantaged, nursing home patients, or others requiring legally authorized representatives. * Participants that work in an environment with exposures to high levels of electromagnetic interference such as working with high powered electrical equipment.