What is a retrograde nephrostogram, how is it performed, and what are its indications, normal findings, complications, and alternative imaging options?

Retrograde Nephrostogram: Definition, Technique, and Clinical Applications

What is a Retrograde Nephrostogram?

A retrograde nephrostogram (also called retrograde pyelogram or RPG) is a fluoroscopic imaging procedure where water-soluble contrast is injected in a retrograde fashion through the ureter into the renal collecting system to visualize the upper urinary tract anatomy. 1

How the Procedure is Performed

The technique involves the following steps:

• Cystoscopic placement of a ureteral catheter (typically 9-10 French) into the ureter and advanced to the desired level under fluoroscopic guidance 2
• Contrast injection through the catheter while obtaining fluoroscopic images to visualize the collecting system, ureter, and any abnormalities 1
• The procedure is performed in an operative setting, typically under anesthesia 1
• Direct visualization of contrast filling the renal pelvis and calyces allows for real-time assessment of anatomy and pathology 1

Primary Clinical Indications

Retrograde pyelography is indicated when detailed collecting system visualization is imperative but cross-sectional imaging with contrast is contraindicated. 3

Specific indications include:

• Iatrogenic ureteral injuries - to identify location and extent of injury 1
• Ureteral obstruction - when CT or MRI cannot be performed 3
• Stone or tumor identification - particularly when other imaging is inadequate 1
• Assistance for stent placement or ureteroscopy - to guide therapeutic interventions 1
• Trauma evaluation - in patients who cannot undergo CT urography 1
• Patients with renal insufficiency, contrast allergy, or pregnancy - where multi-phase CT is contraindicated 3

Special Populations

For pregnant patients or those with contraindications to both CT and MRI (such as pacemakers), combining non-contrast CT or renal ultrasound with retrograde pyelograms provides adequate upper tract evaluation. 3

Normal Findings

Normal retrograde pyelography demonstrates:

• Smooth, symmetric filling of the renal pelvis and calyces 1
• Patent ureter without filling defects or strictures 1
• No extravasation of contrast outside the collecting system 1
• Normal calyceal anatomy without clubbing or irregularity 3

Abnormal Findings and Complications

Diagnostic Findings

Retrograde pyelography can identify:

• Filling defects suggesting stones or tumors 3
• Ureteral strictures or obstructions 1
• Contrast extravasation indicating ureteral perforation or injury 1
• Anatomic abnormalities of the collecting system 1

Procedural Complications

Retrograde pyelography is generally safe but carries risks inherent to any invasive urologic procedure:

• Infection risk - introduction of bacteria into the upper urinary tract 3
• Ureteral perforation - from catheter manipulation 1
• Contrast reactions - though rare with modern contrast agents 3
• Transient hematuria - from instrumentation 1

Alternative Imaging Options

The choice of imaging depends on clinical context and patient factors:

First-Line Alternatives

• Multi-phase CT urography (CTU) - the gold standard for comprehensive upper tract evaluation when not contraindicated 3, 4
• MR urography (MRU) - acceptable alternative for patients with renal insufficiency or contrast allergy, though sensitivity for collecting system detail is lower than CT 3

Combined Approaches

• MRI with retrograde pyelograms - provides comprehensive evaluation when CT is contraindicated but collecting system detail is imperative 3
• Non-contrast CT or ultrasound with retrograde pyelograms - for patients with contraindications to both contrast CT and MRI 3

Limited Role Options

• Intravenous urography (IVU) - largely replaced by CT and has no role in modern acute evaluation 3
• Plain radiography (KUB) - very limited utility except for following known large stones 3
• Ultrasound alone - inadequate for detailed collecting system evaluation 3

Important Clinical Caveats

The Panel does not advocate routine use of retrograde pyelograms, but in special circumstances where cross-sectional imaging is contraindicated and collecting system detail is deemed imperative, their use is appropriate. 3

• Retrograde pyelography is invasive and requires cystoscopy, making it less desirable than non-invasive imaging when alternatives are available 3
• The procedure allows confirmation of radiologic diagnosis while simultaneously confirming the need for ureteroscopy or upper tract sampling 3
• Decisions regarding imaging strategy in high-risk patients are best made by the treating clinician with detailed knowledge of the patient's history and available imaging resources 3