This is a First in Human study to assess the feasibility, safety and effectiveness of the Zenflow Spring System in relieving the symptoms of obstructive Benign Prostatic Hyperplasia (BPH).

The purpose of the Zenflow Study is to evaluate the feasibility and safety of a novel prostatic urethral implant for the treatment of Lower Urinary Tract Symptoms (LUTS) that arise due to bladder outlet obstruction (BOO), secondary to the presence of Benign Prostatic Hypertrophy (BPH). Effectiveness will also be measured. It is intended that the features of the Zenflow Spring will provide an effective office-based treatment and management therapy for BPH with little or no side effects.

Inclusion Criteria:

1. 50 to 80 years of age
2. Baseline IPSS score > 13, and a baseline Quality of Life (Qol) question score > 3
3. Prostate volume 25 - 80 cc by Trans Rectal Ultrasound (TRUS), measured within past 90 days
4. Anterior prostatic urethral length 2.5 - 4.0 cm by cystoscopy, as measured from bladder neck to verumontanum. TRUS will be accepted as a primary screening measure.
5. Failed or intolerant to medication regimen for the treatment of LUTS.

Exclusion Criteria:

New Zealand only: A maximum of 5 participants in acute or chronic urinary retention may be included in the study provided they meet other entry criteria. Exclusion exemptions for these patients are described in 4a, 5a and they are exempt from #6.

Participants will be excluded from participating in this trial if they meet any of the following criteria:

1. Obstructive median prostatic lobe or high bladder neck
2. Urethral stricture, meatal stenosis, or bladder neck obstruction - either current, or recurrent requiring 2 or more dilatations
3. Elevated Prostate Specific Antigen (PSA) (age 50-70 PSA ≥4; age 70+ PSA ≥6.5) unless negative biopsy within last 3 months, or a positive biopsy
4. Post-void residual volume (PVR) > 250 ml, if not in acute retention 4a. No maximum post void residual volume required if patient in acute or chronic urinary retention. (New Zealand Only, up to 5 patients)
5. Peak urinary flow rate > 12 ml/second, with ≥ 125 ml voided volume at baseline. 5a. No maximum urinary flow or minimum voided volume required if participant in acute or chronic urinary retention. (New Zealand Only, up to 5 patients)
6. History of chronic urinary retention. (New Zealand Only, up to 5 patients)
7. History of neurogenic bladder
8. Compromised renal function (e.g., serum creatinine > 1.8 mg/dl)
9. Concomitant Urinary Tract Infection (UTI)
10. Concomitant bladder stones
11. Confirmed or suspected prostate/bladder cancer
12. Previous pelvic irradiation or radical pelvic surgery
13. Previous prostate surgery, stent implantations, laser prostatectomy, hyperthermia or another invasive treatment to the prostate
14. Chronic prostatitis, or recurring prostatitis within the past 12 months
15. Serious concurrent medical conditions such as uncontrolled diabetes
16. Known allergy to nickel
17. Life expectancy less than 12 months
18. Use of concomitant medications (e.g., anticholinergics, antispasmodics or antidepressants) affecting bladder function
19. Anti-coagulant, anti-platelet, or thrombolytic medication other than Acetylsalicylic Acid (ASA) or Clopidogrel. ASA and Clopidogrel must be ceased 7 days prior to the procedure.
20. 5--reductase inhibitors within 6 months of pre-treatment evaluation unless evidence of same drug dose for at least 6 months with a stable voiding pattern (the drug dose should not be altered or discontinued for entrance into or throughout the study).
21. -blockers within 2 weeks of pre-treatment evaluation unless evidence of same drug dose for at least 6 months with a stable voiding pattern (the drug dose should not be altered or discontinued for entrance into or throughout the study).
22. Future fertility concerns
23. Any severe illness that might prevent study completion or would confound study results