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Collins Knife

The Collins knife is a hook-shaped or right-angled electrosurgical incising electrode used with a compatible resectoscope system. It makes a directed linear incision under endoscopic vision, whereas a wire loop scoops and shaves tissue. The name is also commonly spelled "Collings knife." Monopolar and bipolar knives are not interchangeable. The electrode, working element, sheath, generator and irrigant must be matched according to their instructions.[15][16] Described uses include TUIP, transurethral incision of bladder-neck contracture (BNC) and vesicourethral anastomotic stenosis (VUAS), external sphincterotomy, and transurethral bladder-cuff excision at nephroureterectomy.[1][2]

Design​

  • Thin hook-shaped wire protruding from the resectoscope sheath in place of the standard loop.
  • Generator mode and power are device- and procedure-specific; there is no shared 20 W cut and 20 W coag prescription. For example, Nealon's 2022 BNC series used a 30–50 W cutting current with its Collins-knife and resectoscope setup. This describes that protocol and is not a setting for another electrode or generator.[2][15]
  • Single-plane scalpel-like cut. This is the operative distinction from a loop, which removes tissue in chips and does not incise in a controlled line.

Reconstructive-Urology and Functional-Urology Uses​

TUIP — transurethral incision of the prostate​

  • Indication: bladder-outlet obstruction from BPH with prostate ≤ 30 g.
  • Technique: deep incisions at 5 and 7 o'clock (or single 6 o'clock) from the interureteric ridge through the bladder neck and prostatic urethra to the verumontanum, cutting down to the prostatic capsule.[4][5]
  • Outcome versus TURP. In the Yang 2001 meta-analysis of 9 RCTs, symptom improvement was equivalent at 12 months, but TURP produced a greater improvement in maximum flow rate. TUIP had fewer complications, fewer transfusions, less retrograde ejaculation and shorter operative time and hospital stay (retrograde ejaculation 15% versus 66%, transfusion 1% versus 6%, incontinence 1% versus 6%). Comparative evidence beyond 12 months is limited.[6]

See the TUIP procedure page for full technique and outcomes.

TUIBNC and TUIVUAS — bladder-neck contracture / VUAS incision​

  • Endoscopic incision is an established option for selected post-prostatectomy, post-radiation and post-TURP BNC and VUAS. Prior procedures, sphincter function, radiation and recurrence affect the choice.
  • Lateral incisions at 3 and 9 o'clock are typical and avoid the rectum at 6 o'clock.[2][3]
  • Nealon 2022 (retrospective, n = 123, treated over 2008–2020). Collins-knife TUIBNC after balloon dilation to 24 Fr yielded 82.1% patency after one procedure and 94.3% after two at the reported 12-month follow-up; the 12 years describe the treatment period, not each patient's follow-up.[2]
  • AUA 2023 urethral-stricture guideline. Bladder-neck incision and resection have comparable outcomes; repeat endoscopic treatment is sometimes necessary.[7]

See Transurethral Incision of BNC for the full procedure page.

External sphincterotomy for detrusor-sphincter dyssynergia (DSD)​

  • External sphincterotomy is performed in spinal-cord-injury and selected neurogenic-bladder patients to reduce urethral resistance.
  • Linker and Tanagho anatomic experiment: in 18 male cadavers, the authors found that an incision 2 cm long from the verumontanum and 6 mm deep divided the external-sphincter fibers completely. This is a cadaver result and not a universal patient incision depth or safety margin.[1]

Bladder-cuff excision at radical nephroureterectomy​

  • The Collins knife circumscribes the ureteric orifice with a bladder cuff, detaching the intramural ureter from the bladder wall, as the transurethral step of laparoscopic or robotic nephroureterectomy for UTUC.[8][9][10]
  • Allard 2013 (retrospective, n = 110). This three-technique comparison detected no association between cuff-excision method and recurrence or metastasis after a median 22-month follow-up; it was not an equivalence trial.[11]

Endoscopic transvesical ureterotomy​

  • Gardiner described the technique in two cases of lower ureteral stricture: after dilation and ureteral catheterization, the Collins knife made a full-thickness incision at 12 o'clock through the strictured segment, cutting down onto the catheter. Both obstructions were relieved, and reflux was present on voiding studies.[12]

En-bloc resection of small bladder tumors​

  • Saito 2001 described a circumferential incision approximately 10 mm from the tumor edge to the superficial muscle, followed by a level incision beneath the tumor, with the lesion retrieved as a single specimen. A holmium laser was used for bladder-neck tumors and a knife electrode for bladder-wall tumors. In 35 patients and 50 lesions, sections through the tumor center determined invasion depth (pTa to pT2) and there were no serious complications.[13]

Percutaneous nephrostomy tract creation — niche use​

  • In difficult percutaneous access (scarification, failed wire passage), the Collins knife can create a nephrostomy tract. Davis 1991 (17 patients, 19 renal units) established the tract in all 19 procedures in an average of 12 minutes; two major complications required transfusion and open operation.[14]

Advantages​

  • Directed incision. The knife incises tissue where a loop removes chips; depth still depends on vision, anatomy and technique.
  • System-specific versatility. Mono- and bipolar options exist, but fitment, insulation, electrical rating and irrigant must match the exact platform.[15][16]
  • Product-dependent use life. Disposable and reusable electrodes exist; follow the specific label and do not assume one processing or cost profile.

Limitations​

  • Thermal injury to adjacent structures. The rectum at 6 o'clock is at risk during bladder-neck or prostatic incision. Lateral cuts (3 and 9 or 5 and 7 o'clock) are preferred.
  • Fluid management. Monopolar systems using nonconductive irrigant carry the classic hyponatremic TUR-syndrome risk. Compatible bipolar saline systems markedly reduce that risk, but saline absorption, volume overload and acid–base disturbance remain possible.[17][18]
  • Not for bulk resection. For tissue removal use the resectoscope loop; for stone fragmentation use a laser fiber or pneumatic lithotripsy.

See also: Resectoscope, Sachse Urethrotome (DVIU), Otis Urethrotome, Balloon Dilator, Electrosurgical Pencil, TUIP, Transurethral Incision of BNC.

References​

1. Linker DG, Tanagho EA. "Complete external sphincterotomy: correlation between endoscopic observation and the anatomic sphincter." J Urol. 1975;113(3):348–52. doi:10.1016/s0022-5347(17)59478-1

2. Nealon SW, Bhanvadia RR, Badkhshan S, et al. "Transurethral incisions for bladder neck contracture: comparable results without intralesional injections." J Clin Med. 2022;11(15):4355. doi:10.3390/jcm11154355

3. Quarta L, Bandini M, Corsini C, et al. "Assessing predictors of failure after bladder neck incision in patients who developed bladder neck stenosis following transurethral surgery for benign prostatic enlargement." Prostate. 2025;85(15):1424–31. doi:10.1002/pros.70027

4. Tkocz M, Prajsner A. "Comparison of long-term results of transurethral incision of the prostate with transurethral resection of the prostate, in patients with benign prostatic hypertrophy." Neurourol Urodyn. 2002;21(2):112–6. doi:10.1002/nau.10013

5. Oesterling JE. "Benign prostatic hyperplasia — medical and minimally invasive treatment options." N Engl J Med. 1995;332(2):99–109. doi:10.1056/NEJM199501123320207

6. Yang Q, Peters TJ, Donovan JL, Wilt TJ, Abrams P. "Transurethral incision compared with transurethral resection of the prostate for bladder outlet obstruction: a systematic review and meta-analysis of randomized controlled trials." J Urol. 2001;165(5):1526–32.

7. Wessells H, Morey A, Souter L, Rahimi L, Vanni A. "Urethral stricture disease guideline amendment (2023)." J Urol. 2023;210(1):64–71. doi:10.1097/JU.0000000000003482

8. Agarwal DK, Khaira HS, Clarke D, Tong R. "Modified transurethral technique for the management of distal ureter during laparoscopic-assisted nephroureterectomy." Urology. 2008;71(4):740–3. doi:10.1016/j.urology.2007.11.048

9. Gill IS, Soble JJ, Miller SD, Sung GT. "A novel technique for management of the en bloc bladder cuff and distal ureter during laparoscopic nephroureterectomy." J Urol. 1999;161(2):430–4.

10. Wong C, Leveillee RJ. "Hand-assisted laparoscopic nephroureterectomy with cystoscopic en bloc excision of the distal ureter and bladder cuff." J Endourol. 2002;16(6):329–32. doi:10.1089/089277902760261329

11. Allard CB, Alamri A, Dason S, et al. "The method of bladder cuff excision during laparoscopic radical nephroureterectomy does not affect oncologic outcomes in upper tract urothelial carcinoma." World J Urol. 2013;31(1):175–81. doi:10.1007/s00345-012-0915-0

12. Gardiner RA. "Endoscopic transvesical ureterotomy." J Urol. 1985;134(4):729–32. doi:10.1016/s0022-5347(17)47411-8

13. Saito S. "Transurethral en bloc resection of bladder tumors." J Urol. 2001;166(6):2148–50.

14. Davis BE, Noble MJ, Mebust WK. "Use of the Collings knife electrode for percutaneous access in difficult endourology cases." J Urol. 1991;145(2):257–61. doi:10.1016/s0022-5347(17)38308-8

15. Cook Medical. Cook Single-Use RF Electrode instructions for use, T_CRFE_REV1, English pp. 3–4. Manufacturer IFU. This is a monopolar product; its ratings and nonconductive-irrigant instruction are not bipolar-system settings.

16. Olympus America. Resection in Saline Electrodes, product family and system compatibility information. Product page, not a complete electrode IFU.

17. Alexander CE, et al. Bipolar versus monopolar TURP for LUTS secondary to BPO. Cochrane Database Syst Rev. 2019;CD009629. Detailed public review summary and abstract.

18. You AH, Lee JY, Choi JH, Kim MK. Hyperchloremic metabolic acidosis during bipolar transurethral resection of the prostate: a report of two cases. J Int Med Res. 2021;49:3000605211024480. doi:10.1177/03000605211024480.