Percutaneous Nephroureteral Catheter (PCNU)
A PCNU connects the renal collecting system to the bladder or urinary diversion through the ureter, while retaining a catheter segment and hub outside the flank. The external port can be connected to a bag or capped for internal drainage. Capping removes the bag requirement in selected patients; it does not remove the external catheter.[1][2]
Distinguish the Devices
| Device | Course and access | Meaning of capping |
|---|---|---|
| PCN | Flank to renal collecting system; does not itself bridge the ureter | A planned trial may assess drainage through the native ureter or a separate internal stent. |
| PCNU | Flank to collecting system and through the ureter to bladder/conduit | Urine can drain internally through the catheter; the external hub remains. |
| Double-J stent | Fully internal ureteral drainage | No external drainage hub to cap; removal method depends on the device. |
| Retrograde transileal catheter | From a conduit stoma retrograde to the kidney | External access/drainage is at the stoma, not the flank. |
Catheter length, side-hole locations and retention loops differ by product. In a ureteral leak, side holes must not direct urine into the injured segment or extraluminal space.[1][2]
When PCNU Is Useful
Consider PCNU when the ureter can be crossed and ongoing external access is valuable: obstruction, selected leaks or fistulas, transplant ureteral complications, planned antegrade interventions, or a trial before conversion to an internal stent. It is an option rather than the preferred device for every ureteral injury.[1][2]
Evaluate the receiving bladder or conduit. A poorly emptying or high-pressure bladder may compromise internal drainage and requires its own management. “Neurogenic bladder” alone does not describe storage pressure or establish an absolute contraindication to every internal stent.[1]
For an infected obstructed system, prompt decompression is the priority. An initial PCN with later crossing/internalization may be appropriate when sepsis, bleeding, severe obstruction or tortuosity makes prolonged manipulation undesirable. Selected patients can undergo a single-session procedure; there is no universal mandatory 1–2-week staging interval.[1][3]
Placement and Exchange Principles
Plan access with imaging and the intended future intervention in mind. Establish and confirm intraluminal wire passage across the lesion and into the receiving bladder/conduit before advancing the catheter. Hydrophilic wires and stiff support wires have different roles; neither should be forced through an uncertain path. Confirm the drainage side holes and retention portions are correctly positioned, and secure the external segment.[1][2]
Studies comparing single-stage versus staged antegrade Double-J placement do not prove that one PCNU technique has fewer complications. Patient selection and the reason for initial nephrostomy matter.[4]
Capping Trials: What They Can and Cannot Show
A trial should have an explicit purpose, monitoring plan and response to symptoms. Confirm that internal drainage is appropriate, then monitor pain, fever, pericatheter leakage, voiding/output and renal function as indicated. If symptoms occur, reconnect to drainage as instructed and contact the treating team; persistent symptoms need urgent reassessment.[1][2]
A capped PCNU still bypasses the ureteral lesion. Tolerance may support conversion to an internal stent, but does not by itself show that the native ureter can drain without a catheter. Removal requires a separate assessment of the underlying obstruction or leak. The capped port is also not an automatic pressure-release valve; it must be deliberately reopened when external drainage is needed.[1][2]
Capping trials are not unique to PCNU: a PCN may also be capped when native or separately stented internal drainage is being assessed. Duration and testing depend on the clinical situation rather than a universal 24–48-hour removal rule.[1][2]
Maintenance and Problems
Arrange image-guided exchange according to the device and local service, shortening the interval for blockage, encrustation or infection. The historical PCNU technique review describes starting at 6–8 weeks, with extension toward 12 weeks in patients without encrustation. This is practice guidance, not a trial-established optimum.[2]
Leakage, falling output, flank pain or rising creatinine can indicate blockage, migration or malposition. Fever or systemic illness requires infection assessment and attention to drainage. Persistent or substantial bleeding needs investigation. External securement and patient education remain important even while capped.[1][5]
Bacteriuria alone is not synonymous with UTI. Follow the infection treatment and procedural prophylaxis companions; pregnancy and mucosa-traumatizing endourologic procedures require specific assessment.[6]
Selected Scenarios and Evidence Limits
Ileal conduit: a retrograde transileal catheter can provide accessible drainage into the ostomy appliance and avoid a flank tube. Internal Double-J drainage is also used. Access anatomy, mucus, patency, symptoms and maintenance burden guide choice; neither route is universally superior.[2]
Refractory gross hematuria: a six-patient series reported cessation of transfusion requirements over 30 days after PCNU placement. This is limited salvage evidence. It does not establish that PCNU is clot-proof, that one catheter always drains both kidneys, or that a catheter entering the bladder guarantees complete diversion away from it.[7]
Malignant obstruction: assess drainage feasibility, prognosis, treatment goals and patient preference. PCN-versus-retrograde-stent meta-analysis results should not be presented as PCNU-specific outcomes.[8]
See also Metal & Long-Term Stents and Renal Anatomy.
References
1. Ryan AG, Irvine I, Bardgett H, et al. CIRSE Standards of Practice on Nephrostomy and Ureteric Stent Placement and Exchange. Cardiovasc Intervent Radiol. 2026;49:464–479. doi:10.1007/s00270-025-04328-9
2. Makramalla A, Zuckerman DA. Nephroureteral Stents: Principles and Techniques. Semin Intervent Radiol. 2011;28:367–379. doi:10.1055/s-0031-1296079
3. European Association of Urology. EAU Guidelines on Urolithiasis, 2026. Sections on sepsis, ureteroscopy, stenting and pregnancy.
4. 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
5. 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
6. Nicolle LE, Gupta K, Bradley SF, et al. Clinical Practice Guideline for the Management of Asymptomatic Bacteriuria: 2019 Update by IDSA. Clin Infect Dis. 2019;68:e83–e110. doi:10.1093/cid/ciy1121
7. 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
8. 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