What is the difference between a nephrostomy tube and a nephrolithotomy in a patient with elevated Blood Urea Nitrogen (BUN) levels and normal kidney function?

Nephrostomy Tube vs. Nephrolithotomy: Key Distinctions

A nephrostomy tube is a drainage catheter placed through the skin into the kidney to relieve obstruction, while nephrolithotomy is a surgical procedure to remove kidney stones—these are fundamentally different interventions serving distinct purposes in urological care.

Nephrostomy Tube: A Drainage Device

A nephrostomy tube is a catheter inserted percutaneously into the renal collecting system to provide urinary drainage 1, 2. This is a temporizing measure rather than definitive treatment.

Primary Indications:

• Urgent decompression in obstructing stones with infection or sepsis 1, 2
• Failed retrograde ureteral stenting 1
• Bilateral obstruction or solitary kidney with obstruction 3
• Bridge to definitive stone treatment 1, 4

Technical Characteristics:

• Placed under imaging guidance (ultrasound or fluoroscopy) 1
• Sizes range from small pigtail catheters (8.5-10F) to large-bore tubes (20-28F) 5, 6
• Technical success rate approaches 100% 1
• Can remain in place for days to weeks as needed 5

Clinical Context with Elevated BUN:

In patients with elevated BUN and normal kidney function (suggesting prerenal azotemia or early obstruction), a nephrostomy tube serves to relieve obstruction and prevent further renal injury 1, 3. The tube allows monitoring of urine output and can serve as access for subsequent stone removal 1, 4.

Nephrolithotomy: A Stone Removal Procedure

Nephrolithotomy refers to surgical stone removal, most commonly percutaneous nephrolithotomy (PCNL), which is both a diagnostic and therapeutic intervention 1, 4.

Primary Indications:

• First-line therapy for stones >20mm 2
• Staghorn calculi 1
• Lower calyceal stones >10mm 4
• Failed less invasive approaches (SWL, ureteroscopy) 1

Technical Characteristics:

• Requires percutaneous tract creation (24-30F dilation) 4
• Active stone fragmentation using ultrasonic, pneumatic, or laser lithotripsy 1, 4
• Stone-free rates of 70.5-80.5% with primary procedure 4
• May require nephrostomy tube placement afterward (though tubeless approaches exist) 5, 7, 8

Definitive vs. Temporizing:

Unlike nephrostomy tube placement, PCNL is definitive treatment aimed at rendering the patient stone-free 1, 4. The procedure addresses the underlying pathology rather than just relieving obstruction 1, 4.

Critical Algorithmic Distinction

When Obstruction + Infection Present:

1. Immediate nephrostomy tube or ureteral stent for decompression 1, 2
2. Delay definitive nephrolithotomy until sepsis resolves 2
3. Proceed with PCNL once infection controlled 1, 2

When Obstruction Without Infection:

• Small stones (<20mm): Consider ureteroscopy or SWL; nephrostomy tube only if these fail 2
• Large stones (>20mm): PCNL as first-line definitive treatment 2, 4

Common Pitfall to Avoid

Never attempt nephrolithotomy (stone fragmentation) in the presence of active infection—this can precipitate sepsis 4. If purulent urine is encountered during PCNL, abort the procedure immediately and establish drainage only 4. The nephrostomy tube serves as the bridge intervention in this scenario 1, 2.

Relationship Between the Two:

A nephrostomy tube may be placed after nephrolithotomy for postoperative drainage 5, 6, though tubeless approaches (with or without ureteral stent) are increasingly common in uncomplicated cases 7, 8, 9. Conversely, a nephrostomy tube placed initially for obstruction can later serve as the access tract for percutaneous nephrolithotomy 1, 4.

Summary Algorithm

For elevated BUN with obstructing stone:

• If infection/sepsis present: Nephrostomy tube → antibiotics → delayed PCNL 1, 2
• If no infection, stone >20mm: Direct PCNL (may place nephrostomy after) 2, 4
• If no infection, stone <20mm: Ureteroscopy or SWL; nephrostomy only if these fail 2

The key distinction remains: nephrostomy tube = drainage device; nephrolithotomy = stone removal surgery 1, 4.