What is a nephrostogram, how is it performed, when is it indicated, what are the normal and abnormal imaging findings, possible complications, and subsequent management?

Nephrostogram: Definition, Technique, Indications, and Management

What is a Nephrostogram?

A nephrostogram is a fluoroscopic imaging procedure where water-soluble contrast material is injected directly through an existing nephrostomy tube to evaluate the renal collecting system, assess tube position, identify obstruction, and confirm ureteral patency. 1

How the Procedure is Performed

Technical Steps

• Water-soluble contrast material (never barium) is injected through the nephrostomy tube under fluoroscopic guidance to provide real-time visualization of the collecting system, tube position, and drainage pathway 1, 2
• The contrast injection should be performed via a catheter placed over a wire to confirm intracollecting system location 2
• Exchange transfusion technique should be used for opacification rather than overdistention, which can increase risk of sepsis or retroperitoneal contamination 2
• Fluoroscopy allows immediate assessment of tube patency, position within the collecting system, integrity of the drainage pathway, and visualization of contrast extravasation around the tube, malposition, dislodgement, or collecting system injury 1

Alternative Emerging Technique

• Contrast-enhanced ultrasound nephrostograms using microbubble contrast agents (perflutren protein-type A microspheres) have shown perfect concordance with fluoroscopic findings in evaluating ureteral patency after percutaneous nephrolithotomy, offering a radiation-free alternative 3, 4
• This technique demonstrated 79.3% concordance with fluoroscopy in a larger study, with most discordance attributable to higher sensitivity of ultrasound for detecting patency 4

Clinical Indications

Primary Indications

• Evaluating ureteral patency before nephrostomy tube removal, particularly after percutaneous nephrolithotomy 3, 4, 5
• Identifying the exact location and mechanism of nephrostomy tube leakage, including tube malposition, dislodgement, or collecting system injury 1
• Assessing for distal ureteral obstruction without evidence of residual stone fragments 5
• Diagnostic evaluation when complications are suspected (fever, sepsis, persistent hematuria, or signs of infection) 1

Timing Considerations

• Typically performed on postoperative day 2 (range day 2-8) after percutaneous nephrostomy placement 5
• Immediate imaging is mandated when fever, sepsis, or signs of infection are present, as sepsis is the most serious and potentially fatal complication 1

Normal and Abnormal Imaging Findings

Normal Findings

• Unobstructed antegrade ureteral flow demonstrated by presence of contrast material in the bladder 3
• Proper tube position within the renal collecting system 1
• No extravasation of contrast material around the tube 1
• Patent drainage pathway without filling defects or obstruction 1

Abnormal Findings

Obstruction-Related:

• Distal ureteral obstruction without antegrade flow to bladder 3, 5
• Contrast extravasation indicating collecting system injury or tube malposition 1
• Hydronephrosis or delayed drainage 5

Tube-Related:

• Complete tube dislodgement from collecting system 1
• Tube malposition outside the collecting system 1

Vascular Complications:

• Persistent or recurrent gross hematuria after initial post-placement period suggests vascular injury (pseudoaneurysm, arteriovenous fistula) requiring CT angiography or conventional angiography 1
• Active contrast extravasation indicating arterial injury 1

Complications and Their Management

Immediate Complications During Nephrostogram

• Sepsis risk from overdistention: Use exchange transfusion technique rather than excessive contrast injection 2
• Contrast extravasation into retroperitoneum: Use water-soluble contrast to avoid peritoneal contamination 1, 2

Post-Procedure Complications

Prolonged Urinary Drainage:

• Distal ureteral obstruction on nephrostogram predicts prolonged urinary leak (>24 hours) in 36% vs 8% without obstruction 5
• However, obstruction may not necessitate ureteral stent placement as blood clot or ureterovesical junction edema typically resolve spontaneously with expectant management 5
• In 27% of patients with distal obstruction, nephrostomy tubes were safely removed the same day as nephrostography 5

Vascular Injuries:

• If imaging shows vascular injury, angiography with selective embolization is the treatment of choice for pseudoaneurysms, arteriovenous fistulas, or active extravasation 1
• Excessive bleeding can usually be stopped with tract tamponade using a balloon catheter or appropriate-sized nephrostomy tube 2
• Almost all renal artery injuries can be treated with selective embolization of the involved branch artery, preserving functioning renal parenchyma 2

Adjacent Organ Injury:

• Transcolonic nephrostomy tracts can generally be treated nonsurgically by ensuring adequate urinary drainage (ureteral stent and bladder catheter) before catheter removal 2
• Withdraw catheter into colon for use as percutaneous colostomy drain, allow tract to mature for several days, and administer appropriate antibiotics 2
• Transthoracic entry causing pneumothorax or pleural effusions should be treated only if large or symptomatic 2

Subsequent Management Algorithm

When Tube Cannot Be Accessed for Contrast Injection

• If the tube is completely dislodged and cannot be accessed, proceed directly to CT with IV contrast and delayed excretory phase imaging to assess the collecting system 1

Based on Nephrostogram Findings

Patent System Without Obstruction:

• Safe to remove nephrostomy tube, typically on same day as study 5
• Monitor for urinary leakage (expected <24 hours in most cases) 5

Distal Ureteral Obstruction:

• Expectant management is appropriate as most obstruction from blood clot or edema resolves spontaneously 5
• Consider ureteral stent only if prolonged drainage persists beyond expectant management period 5
• Readmission with stent placement may be needed in rare cases of persistent leakage (occurring around postoperative day 7) 5

Tube Malposition or Dislodgement:

• Urgent tube replacement is required, preferably under ultrasound and fluoroscopic guidance 1

Vascular Injury Identified:

• Proceed to angiography with selective embolization 1
• Monitor hematocrit sequentially to quantify bleeding 2

Adjunctive Imaging When Needed

• Bedside ultrasound can rapidly assess for hydronephrosis, perirenal fluid collections, or hematoma formation but cannot definitively evaluate tube position or drainage pathway 1
• Doppler ultrasound may identify vascular complications if persistent hematuria accompanies the leak 1

Critical Safety Points

• Always use water-soluble contrast (never barium) to avoid peritoneal contamination if significant extravasation exists 1, 2
• Fever, sepsis, or signs of infection mandate immediate imaging, preferably CT with IV contrast, as sepsis is the most serious complication and can be fatal 1
• Avoid unnecessary prolonged procedures in infected, obstructed systems 2