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Percutaneous Nephroureteral Catheter (PCNU)

A percutaneous nephroureteral catheter (PCNU) — also called an internal/external nephroureteral tube — is a drainage catheter that extends from the renal collecting system, through the ureter, and into the bladder, with an external component exiting through the flank. Unlike a standard PCN (drains only externally) or a fully internalized double-J stent, the PCNU provides dual drainage — internally (antegrade through the ureter to the bladder) and externally (through the skin to a collection bag) — and uniquely allows a capping trial to assess obstruction resolution before tube removal.[1]

Design​

CatheterTipDrainageExternal component
Standard PCNRenal pelvisExternal onlyAlways
PCNUBladder (via ureter)Internal + externalWhen uncapped
Double-J stentRenal pelvis and bladder coilsInternal onlyNever

The PCNU is a long catheter (often > 60 cm) with sideports along the shaft, a retention pigtail in the bladder, and an external hub at the flank that can be capped or connected to a drainage bag.

Indications​

PCNU shares many indications with PCN, but is specifically preferred when:[1][2]

  1. Ureteral obstruction with planned capping trial to assess resolution before definitive tube removal.
  2. Ureteral leaks and fistulas — diverts urine away from the injury while splinting the ureter. Surgical ureteral repair failure rates are 13% with PCN / PCNU vs 87% without.[1]
  3. Renal transplant ureteral complications — leaks, fistulas, strictures, obstructions.[1]
  4. Intractable hemorrhagic cystitis — Spradling case series (n = 6): PCNU diversion produced stable hematocrit, no further transfusions within 30 days, and no clot obstruction of the tube in all patients.[2]
  5. Bridge to internalization — PCNU followed by conversion to a fully internalized DJ stent or transileal retrograde nephroureteral catheter (e.g., in ileal-conduit patients).[1]
  6. Access for endourologic procedures — antegrade stenting, balloon dilation, stone treatment.[1][3]

Advantages Over Standard PCN​

  • Internal drainage when capped — patient can void normally; enables a capping trial.[1]
  • Dual-drainage safety — if the internal pathway becomes obstructed (tumor progression, edema), the external limb is a safety valve.
  • Ureteral splinting — the indwelling segment maintains ureteral patency across strictures, anastomoses, or sites of injury.
  • Bridge to fully internalized stenting — existing access used for guidewire exchange.

Disadvantages​

  • Patient discomfort — often not well tolerated long-term due to skin irritation and external-component burden; fully internalized DJ stents are preferred when feasible.[1]
  • Dislodgement risk higher than simple PCN due to longer catheter.[1][4]
  • Bladder irritation — distal-tip irritative LUTS similar to a DJ stent.[5]
  • External bag when uncapped limits mobility; PCN / PCNU patients report more self-care difficulties than those with internalized stents.[6]

Placement Technique​

Fluoroscopic guidance; two-stage is most common.[3][7]

Two-Stage (Standard)​

  1. Stage 1 — standard PCN access via ultrasound + fluoroscopy / Seldinger technique.
  2. Stage 2 (1–2 weeks later) — through the existing tract, a guidewire is advanced antegrade across the renal pelvis, down the ureter, across the obstruction / injury, and into the bladder. The tract is dilated, and the PCNU is advanced over the wire until the distal pigtail coils in the bladder and the proximal end exits the flank.

Single-Stage ("First-Hand")​

Arslan 2024 comparison: first-hand single-session approach had equivalent technical success (93.1%) with shorter fluoroscopy time (6.8 vs 8.2 min) and a 3-fold lower complication rate vs the nephrostomy-route approach.[7]

Technical Considerations​

  • Stiff guidewire (e.g., Amplatz super-stiff) to navigate the ureter and provide support.[8]
  • Torque-control catheters and hydrophilic wires help with ureteral tortuosity or kinking.
  • Adult catheter size typically 8–12 Fr.[3]
  • Confirmation of distal-tip position in the bladder via contrast injection.

Capping Trial — Unique to PCNU​

A signature use case:[1]

  1. External port is capped, forcing all urine to drain internally through the ureter.
  2. Patient monitored 24–48 h for flank pain, fever, ↓ urine output, or peri-site leakage.
  3. Tolerated → obstruction considered resolved; catheter can be removed.
  4. Symptomatic → uncap to restore external drainage; reassess.

Complications​

ComplicationNote
Catheter dislodgement / migrationMost common long-term issue; higher than PCN due to length; 3–17% range[1][4]
Encrustation / blockageRisk rises with dwell; significant after 45–90 days; biofilm[9][10]
UTI / bacteriuria4–17%; asymptomatic bacteriuria is universal and should not be treated[1][5]
Bladder irritationFrequency / urgency / dysuria from the distal tip in the bladder[6]
Skin site infection / irritation~2–3%; a major source of long-term intolerance[1][6]
HemorrhageTransient hematuria nearly universal; transfusion-requiring ~4%[2]
Urine leak around catheter2–10%[1]
Sepsis~4% overall; up to 10% in pyonephrosis[6]

Maintenance & Exchange​

  • Recommended exchange interval ~3 months to limit encrustation, biofilm, and infection.[4][11][12]
  • Real-world data (Moon 2024 MarketScan analysis): 41% of exchanges occur within 29 days, 67% within 59 days — many patients require earlier exchange than the 90-day standard.[12]
  • Exchange performed under fluoroscopy; existing catheter removed over a wire and replaced.
  • Monitor catheter function (output), creatinine, and US for hydronephrosis.[13]

Special Clinical Scenarios​

Ileal Conduit Patients​

Fully internalized DJ stents tend to occlude rapidly from mucus production. The preferred approach is PCNU placement followed by fluoroscopically guided conversion to a transileal retrograde nephroureteral catheter — technical success 91.8%, clinical success 89.8% of renal units.[1] Chronic retrograde transileal ureteric stents need shorter routine maintenance intervals (median 8.5 wk) than conventional PCN (12.9 wk) but have lower rates of non-routine interventions due to fewer dislodgements (Dawson 2026).[14]

Hemorrhagic Cystitis​

PCNU is particularly useful because the catheter traverses the entire ureter, ensuring complete urinary diversion from the bladder while draining both kidneys. Unlike PCN, it is not susceptible to clot obstruction in this setting (Spradling).[2]

Malignant Ureteral Obstruction​

PCNU can serve as a bridge to antegrade DJ stent placement — antegrade technical success 98.4% vs 47.4% for retrograde in MUO.[7][15] Long-term PCNU is often poorly tolerated, so conversion to a fully internalized stent is preferred when possible.[1]

PCNU vs Standard PCN vs DJ Stent​

FeaturePCNPCNUDJ Stent
Drainage routeExternal onlyInternal + externalInternal only
Capping trialNoYesN/A
External bag requiredAlwaysOnly when uncappedNo
Patient comfortModerateLower (skin + bladder symptoms)Higher
Dislodgement riskModerateHigher (longer catheter)Lower
Ureteral splintingNoYesYes
Exchange accessPercutaneousPercutaneousCystoscopic
Ideal for ureteral leak / fistulaPartial (diverts but doesn't splint)Optimal (diverts + splints)Good if retrograde access possible

See also: Double-J Stent, Nephrostomy Tube (PCN), Metal / Long-Term Ureteral Stents, The Kidneys.

References​

1. Scheidt MJ, Hohenwalter EJ, Pinchot JW, et al. ACR Appropriateness Criteria® Radiologic Management of Urinary Tract Obstruction. Journal of the American College of Radiology. 2020;17(5S):S281-S292. doi:10.1016/j.jacr.2020.01.039

2. Spradling K, Elliott CS, Vo H, Reese J. Percutaneous Nephroureteral Tube: A Useful Tool for Management of Intractable Hematuria. Urology. 2019;126:232-235. doi:10.1016/j.urology.2019.01.003

3. Dyer RB, Regan JD, Kavanagh PV, et al. Percutaneous Nephrostomy With Extensions of the Technique: Step by Step. RadioGraphics. 2002;22(3):503-525. doi:10.1148/radiographics.22.3.g02ma19503

4. Cahill AM, Annam A, Baskin KM, et al. Society of Interventional Radiology Quality Improvement Standards for Percutaneous Nephrostomy in the Pediatric Population. Journal of Vascular and Interventional Radiology. 2021;32(1):146-149. doi:10.1016/j.jvir.2020.07.029

5. Lange D, Bidnur S, Hoag N, Chew BH. Ureteral Stent-Associated Complications — Where We Are and Where We Are Going. Nature Reviews Urology. 2015;12(1):17-25. doi:10.1038/nrurol.2014.340

6. Zhang KP, Zhang Y, Chao M. Which Is the Best Way for Patients With Ureteral Obstruction? Percutaneous Nephrostomy Versus Double J Stenting. Medicine. 2022;101(45):e31194. doi:10.1097/MD.0000000000031194

7. Arslan M, Aslan HS, Alver KH, Demirci M. Comparison of Percutaneous Antegrade Double-J Ureteral Stent Placement: First-Hand vs. Nephrostomy Route Approaches. British Journal of Radiology. 2024;97(1162):1683-1689. doi:10.1093/bjr/tqae143

8. Elyaderani MK, Belis JA, Kandzari SJ, Gabriele OF. Facilitation of Difficult Percutaneous Ureteral Stent Insertion. The Journal of Urology. 1982;128(6):1173-1176. doi:10.1016/s0022-5347(17)53408-4

9. Kaskarelis IS, Papadaki MG, Malliaraki NE, et al. Complications of Percutaneous Nephrostomy, Percutaneous Insertion of Ureteral Endoprosthesis, and Replacement Procedures. Cardiovascular and Interventional Radiology. 2001;24(4):224-228. doi:10.1007/s00270-001-0004-z

10. Tomer N, Garden E, Small A, Palese M. Ureteral Stent Encrustation: Epidemiology, Pathophysiology, Management and Current Technology. The Journal of Urology. 2021;205(1):68-77. doi:10.1097/JU.0000000000001343

11. Iyer D, Konstantinidis M, Li H, Bercu Z, Moon J. Impact of Drainage Catheter Material, Size, and Anti-Dislodgement Mechanism on Percutaneous Nephrostomy Exchange Intervals: A Systematic Review Protocol. F1000Research. 2023;12:1417. doi:10.12688/f1000research.135431.1

12. Moon JT, Nguyen J, Ricci J, et al. Analysis of Percutaneous Nephrostomy Exchange Intervals: Insights From a Retrospective Merative MarketScan Analysis Between 2009–2021. World Journal of Urology. 2024;42(1):424. doi:10.1007/s00345-024-05132-9

13. Yoo MJ, Bridwell RE, Inman BL, Henderson JD, Long B. Approach to Nephrostomy Tubes in the Emergency Department. The American Journal of Emergency Medicine. 2021;50:592-596. doi:10.1016/j.ajem.2021.09.034

14. Dawson C, Brar L, Rey C, Huynh MJ, Cool DW. Outcomes of Retrograde Transileal Ureteric Stents for Chronic Urinary Drainage: Comparison With Chronic Nephrostomy Tube Drainage. Journal of Vascular and Interventional Radiology. 2026;37(7):108785. doi:10.1016/j.jvir.2026.108785

15. Ahmad MU, Siddiqui S, Ashraf FA, et al. Retrograde Ureteral Stents Versus Percutaneous Nephrostomy in the Management of Malignant Ureteral Obstruction: A Systematic Review and Meta-Analysis. Urology. 2024;192:158-167. doi:10.1016/j.urology.2024.05.042