Durasphere — Carbon-Coated Beads
Durasphere EXP is a permanent particulate urethral bulking implant indicated in the United States for adult women with stress urinary incontinence due to intrinsic sphincter deficiency (ISD). Current EXP labeling must be distinguished from the original zirconium-oxide formulation studied before the product's first FDA approval in September 1999.[1][2]
For clinical treatment selection and operative context, see Urethral Bulking Agents.
Material and Imaging: Identify the Formulation
| Feature | Original pivotal-trial material | Current US EXP instructions |
|---|---|---|
| Beads | Pyrolytic carbon-coated zirconium oxide, 212–500 μm | Pyrolytic carbon-coated graphite, 90–212 μm |
| Carrier | Water-based gel containing beta-glucan | Water-based gel containing beta-glucan |
| Imaging | Zirconium-containing deposits can be radiopaque | The label states graphite-containing EXP is not visible on X-ray and identifies MRI for visualization |
The current DFU explicitly describes the original material in its clinical-trial section.[1]
The beads provide bulk and improve coaptation after submucosal injection.
Current US Safety Restrictions
Do not inject in the presence of acute cystitis, urethritis or another acute genitourinary infection. Correct bladder-neck or urethral strictures before use. Intravascular injection can cause vascular occlusion, infarction or embolic injury.[1]
Pregnancy safety and effects on later pregnancy and delivery are unknown. Assess reproductive plans when counseling. Use viable mucosa, maintain sterility and do not resterilize or reuse the product.[1]
The March 2026 DFU restricts use to CMT 890-XXX injection needles. For transurethral injection it specifies a 17 to 24 Fr cystoscope with at least a 5 Fr working channel; the needle enters the submucosa about 1 to 1.5 cm distal to the bladder neck and is advanced 0.5 to 1 cm under the mucosa with the bevel toward the urethral lumen, and blebs are raised at successive sites until the bladder neck closes, typically with 4 to 6 mL. The periurethral route starts about 1 cm lateral to the meatus, with cystoscopic confirmation of the needle tip. Avoid forcing injection against resistance: intramuscular placement can prevent bead flow while carrier gel is forced into tissue, causing clogging and inappropriate deposition.[1]
Use the label's anatomy and coaptation endpoint, then assess emptying. Patients should remain under observation until they can void; retention may require catheterization.[1] The label prohibits retreatment within seven days.[1]
Delivery-system update. FDA cleared the InjecSURE Injection System on March 31, 2026 as a cystoscopic accessory for delivering injectable material into urethral tissues. This accessory clearance does not broaden the implant's indication.[4]
Published Injection Technique
Madjar and colleagues described a modified technique for the original large-bead formulation, which was difficult to inject. The steps were a single needle stick at the 4 o'clock position, hydrodissection of the submucosa with 1.5 mL of 1% lidocaine, gradual withdrawal, advancement or rotation of the needle tip when resistance is met, and holding the needle in place for 10 seconds after coaptation to limit leakage of beads from the puncture site. In their retrospective series, injections were given in 1–3 sessions (mean 1.52) 1–3 months apart, at a mean 3.2 mL (range 2–6 mL) per session, and coaptation was rated excellent or good in 92% of injections. This is one group's technique and preceded the current EXP formulation; the current DFU governs needle, syringe and approach.[13]
In that series, 46 of 70 patients responded when full contact information was available (mean age 69.4 years; 15/46 [32.6%] with a failed prior anti-incontinence procedure). At a mean follow-up of 9.4 months, 6 (13%) considered themselves cured, 24 (52.2%) improved and 16 (34.7%) failed. Among 36 who completed a 24-hour pad test, 18 (50%) lost 8 g or less.[13]
Evidence: Keep Timepoint and Denominator Visible
Original Randomized Trial
The multicenter double-blind trial treated 355 women, 178 with Durasphere and 177 with collagen. The published cohort used an abdominal leak-point pressure below 90 cmH₂O as its study eligibility criterion.[2][1]
| Analysis | Result | What it means |
|---|---|---|
| DFU, 12-month follow-up | 76/115 (66%) improved at least one continence grade; 36/115 (31%) dry[1] | Available follow-up from 178 treated women. |
| Published analysis, one year after last treatment | 49/61 (80.3%) improved versus 47/68 (69.1%) with collagen, p = 0.162[2] | A smaller denominator and different treatment-anchored timepoint; not 80% cure among all 355 women. |
| Injection burden | DFU reports mean initial volume 4.8 mL, total volume 7.6 mL, and mean 1.7 treatments[1] | — |
These data did not establish superior clinical efficacy over collagen. The absence of a significant difference is insufficient to rank Durasphere against contemporary agents that were studied with different endpoints and follow-up.[2][1]
Longer Follow-up
The label's post-approval study invited only the 76 initial 12-month responders; 70 enrolled. At an average 5.2 years after initial treatment, 65 of the 70 enrolled responders were located; 38/70 (54.3%) had the same or a better continence grade than at the start of the post-approval study, and six of those 38 were dry. This is selected-responder durability, not a 54% five-year cure rate among all patients initially treated.[1]
In a separate institutional comparison, 43 of 56 Durasphere-treated women were available for extended telephone follow-up. Nine of those 43 reported continuing effectiveness at a median 51 months. Outcomes declined with both Durasphere and collagen, with no significant adjusted difference in time to failure. This cohort supports retreatment counseling but offers no comparison with modern agents.[5]
The AUA/SUFU 2023 guideline finds inadequate comparative data to recommend one injectable over another.[6] The 2017 Cochrane review likewise found insufficient evidence for clear agent superiority; its trial search ended in November 2010.[6][7]
Complications and Follow-up
Interpret Label Frequencies Correctly
The original 178-patient trial table includes both treatment-related and unrelated events. Any urinary urgency was reported in 44/178 (24.7%), whereas investigator-attributed treatment-related urgency occurred in 23/178 (13%). Similarly, all reported UTIs (53/178) differ from treatment-related UTIs (16/178).[1]
Retention can be transient or prolonged. The label separately records treatment-related retention lasting up to seven days in 29/178 and longer than seven days in 10/178. Persistent obstruction, pain, irritative symptoms or recurrent infection warrants evaluation.[1]
Migration and Delayed Local Complications
A small early series of 13 women and seven men (mean follow-up 10 months) documented carbon-coated bead migration to lymph nodes and urethral mucosa at six months. Among women, 76.9% improved at six months and the reported success rate was 33% at 12 months; among men, the reported success rates were 66% at six months and 33% at 12 months.[8]
A retrospective series identified four periurethral masses among 135 treated women, presenting 12–18 months after injection. Cases required drainage or excision; the authors explicitly considered the true incidence uncertain. Chronic outlet obstruction requiring endoscopic evacuation has also been reported a year after injection.[3][9]
Document the product generation and prior injections. Explain that improvement can diminish despite retained material and that uncommon delayed complications may need intervention.
Male and Fecal Incontinence
Male incontinence and anal injection are outside the current US Durasphere indication. For incontinence after prostate treatment, AUA/GURS/SUFU 2024 recommends counseling that efficacy is low and cure is rare with urethral bulking agents ; choose among the male-incontinence pathways based on the patient's condition.[1][10]
In a prospective multicenter series of 33 patients (mean 8.8 mL injected), the median Cleveland Clinic continence score fell from 12 to 8 at a median 20.8 months and anal pressures rose, but fecal incontinence quality of life did not change; two patients had distal migration of the beads.[14] A pilot of ultrasound-guided intersphincteric injection in 23 patients reported sustained score improvements at 12 months, and six of 21 followed patients reported no improvement.[15] The 2013 Cochrane review found limited, methodologically weak evidence, and reported that a silicone biomaterial (PTQ) was safer than Durasphere in the short term. ASCRS 2023 states that injection of biocompatible bulking agents into the anal canal is not routinely recommended for FI .[12] See Fecal Incontinence.[11][12]
See also: Bulkamid, Macroplastique, Coaptite.
References
1. Carbon Medical Technologies. Durasphere EXP Directions for Use. 51013(1), March 2026. Current US instructions.
2. Lightner D, Calvosa C, Andersen R, et al. A New Injectable Bulking Agent for Treatment of Stress Urinary Incontinence: Results of a Multicenter, Randomized, Controlled, Double-Blind Study of Durasphere. Urology. 2001;58(1):12-15. doi:10.1016/s0090-4295(01)01148-7
3. Madjar S, Sharma AK, Waltzer WC, Frischer Z, Secrest CL. Periurethral Mass Formations Following Bulking Agent Injection for the Treatment of Urinary Incontinence. The Journal of Urology. 2006;175(4):1408-1410. doi:10.1016/S0022-5347(05)00679-8
4. US Food and Drug Administration. InjecSURE Injection System, K253598. Cleared March 31, 2026. FDA record; 510(k) summary.
5. Chrouser KL, Fick F, Goel A, et al. Carbon Coated Zirconium Beads in Beta-Glucan Gel and Bovine Glutaraldehyde Cross-Linked Collagen Injections for Intrinsic Sphincter Deficiency: Continence and Satisfaction After Extended Followup. The Journal of Urology. 2004;171(3):1152-1155. doi:10.1097/01.ju.0000103688.83606.06
6. Kobashi KC, Vasavada S, Bloschichak A, et al. Updates to Surgical Treatment of Female Stress Urinary Incontinence (SUI): AUA/SUFU Guideline (2023). The Journal of Urology. 2023;209(6):1091-1098. doi:10.1097/JU.0000000000003435
7. Kirchin V, Page T, Keegan PE, et al. Urethral Injection Therapy for Urinary Incontinence in Women. Cochrane Database of Systematic Reviews. 2017;7:CD003881. doi:10.1002/14651858.CD003881.pub4
8. Pannek J, Brands FH, Senge T. Particle Migration After Transurethral Injection of Carbon Coated Beads for Stress Urinary Incontinence. The Journal of Urology. 2001;166(4):1350-1353. PubMed. doi:10.1016/s0022-5347(05)65767-9
9. Hartanto VH, Lightner DJ, Nitti VW. Endoscopic Evacuation of Durasphere. Urology. 2003;62(1):135-137. doi:10.1016/s0090-4295(03)00249-8
10. Breyer BN, Kim SK, Kirkby E, et al. Updates to Incontinence After Prostate Treatment: AUA/GURS/SUFU Guideline (2024). The Journal of Urology. 2024;212(4):531-538. doi:10.1097/JU.0000000000004088
11. Maeda Y, Laurberg S, Norton C. Perianal Injectable Bulking Agents as Treatment for Faecal Incontinence in Adults. Cochrane Database of Systematic Reviews. 2013;(2):CD007959. doi:10.1002/14651858.CD007959.pub3
12. Bordeianou LG, Thorsen AJ, Keller DS, et al. The American Society of Colon and Rectal Surgeons Clinical Practice Guidelines for the Management of Fecal Incontinence. Diseases of the Colon and Rectum. 2023;66(5):647-661. doi:10.1097/DCR.0000000000002776
13. Madjar S, Covington-Nichols C, Secrest CL. New Periurethral Bulking Agent for Stress Urinary Incontinence: Modified Technique and Early Results. The Journal of Urology. 2003;170(6 Pt 1):2327-2329. doi:10.1097/01.ju.0000090968.85279.84
14. Altomare DF, La Torre F, Rinaldi M, Binda GA, Pescatori M. Carbon-Coated Microbeads Anal Injection in Outpatient Treatment of Minor Fecal Incontinence. Diseases of the Colon and Rectum. 2008;51(4):432-435. doi:10.1007/s10350-007-9170-7
15. Beggs AD, Irukulla S, Sultan AH, Ness W, Abulafi AM. A Pilot Study of Ultrasound Guided Durasphere Injection in the Treatment of Faecal Incontinence. Colorectal Disease. 2010;12(9):935-940. doi:10.1111/j.1463-1318.2009.01927.x