Voiding with Bilateral Nephrostomy Tubes
Patients with bilateral nephrostomy tubes typically experience significantly reduced or absent normal voiding through the urethra, as urine is diverted externally through the nephrostomy catheters before reaching the bladder.
Mechanism of Urinary Diversion
When bilateral nephrostomy tubes are placed, the drainage catheters are inserted directly into each renal collecting system 1. These catheters permit external urinary decompression, meaning urine flows from the kidneys directly out through the tubes into external collection bags, bypassing the normal urinary pathway (ureters → bladder → urethra).
Key Physiological Points:
- Urine follows the path of least resistance: Once nephrostomy tubes are functioning, the majority or all urine drains externally rather than continuing down the ureters to the bladder
- Bladder filling is minimal to absent: With effective bilateral drainage, little to no urine reaches the bladder, resulting in minimal or no urge to void
- Normal voiding mechanism is interrupted: The bladder does not fill adequately to trigger the normal micturition reflex
Clinical Evidence
The evidence supports that bilateral nephrostomy creates effective urinary diversion. One study specifically demonstrated that bilateral percutaneous nephrostomy tube drainage successfully diverted urine away from the bladder in patients with hemorrhagic cystitis, with the mechanism involving "diverting endogenous urokinase as well as avoiding overdistention of the bladder" 2. After tube removal at 6 months, these patients resumed "voiding spontaneously," confirming that normal voiding was absent during the period of bilateral nephrostomy drainage.
Important Caveats:
- Partial vs. complete obstruction: If nephrostomy tubes are placed for incomplete bilateral obstruction, some residual urine flow to the bladder may occur, allowing minimal voiding
- Tube malfunction: If one or both tubes become occluded or malpositioned, urine may resume flowing to the bladder
- Internal/external catheters: Percutaneous nephroureteral catheters (PCNU) allow internal drainage through the ureter and bladder, which would permit more normal voiding patterns 1
Bottom line: Counsel patients that they should expect little to no normal urination while bilateral nephrostomy tubes are functioning properly, with urine output occurring entirely through the external drainage system.