Is a Lasix (furosemide) renogram necessary before undergoing a stent procedure in the operating room (OR)?

Lasix Renogram Before Ureteral Stent Placement

A Lasix renogram is not routinely necessary before ureteral stent placement in the operating room. The decision to proceed directly to stent placement can be made based on clinical presentation and standard imaging findings without requiring this additional functional study.

Diagnostic Approach for Ureteral Obstruction

Primary Imaging

• Non-contrast CT scan is the preferred initial imaging modality for suspected ureteral obstruction
  • Provides anatomical details of obstruction location and severity
  • Identifies stone size, location, and density if present
  • Low-dose CT protocols should be used when possible, especially in pediatric patients 1

Role of Lasix Renogram

Lasix renograms are primarily indicated for:

• Differentiating between true mechanical obstruction and non-obstructive dilation of the collecting system 2
• Evaluating the functional significance of anatomical abnormalities 2
• Assessing relative function of each kidney before intervention in certain cases 1

However, they are not routinely indicated before stent placement when the diagnosis of obstruction is already established by other imaging modalities.

Evidence-Based Approach to Stent Placement

Direct Intervention Pathway

• For patients with clear evidence of obstruction on CT or ultrasound, proceeding directly to stent placement is appropriate
• The European Association of Urology (EAU) guidelines support direct intervention with stent placement when indicated, without requiring additional functional studies 1

Specific Clinical Scenarios

1. Ureteral stones requiring intervention:

   • URS (ureteroscopy) with stent placement can be performed without prior Lasix renogram 1
   • The AUA/Endourological Society guidelines strongly recommend URS as first-line therapy for mid or distal ureteral stones requiring intervention 1

2. Upper urinary tract tumors:

   • Stent placement may be needed for drainage before definitive management
   • No recommendation for Lasix renogram prior to stenting 1

3. Post-stent assessment:

   • Lasix renogram may be more valuable after stent placement to assess patency rather than before placement 3
   • Diuretic renography has been shown to be the most sensitive test for detecting stented ureteral patency (89% sensitivity) 3

Important Considerations

Stent-Related Decisions

• Routine pre-stenting before ureteroscopy is not recommended by multiple guidelines 1
• Post-URS stenting decisions should be based on procedural findings rather than pre-procedure functional studies 1

Potential Risks of Delay

• Delaying stent placement to perform a Lasix renogram could potentially lead to irreversible kidney injury if obstruction is prolonged
• Conservative therapy for obstruction should not exceed six weeks from initial presentation 1

Special Populations

Pediatric Patients

• Low-dose CT is recommended prior to intervention 1
• Stent placement decisions follow similar principles as in adults
• Routine pre-stenting is not recommended 1

Pregnant Patients

• Coordinate all interventions with the obstetrician 1
• Observation is first-line for well-controlled symptoms
• When intervention is needed, direct stent placement without Lasix renogram is appropriate

Conclusion

While Lasix renograms provide valuable functional information in certain clinical scenarios, they add little value when the decision to place a ureteral stent has already been made based on clinical and standard imaging findings. Proceeding directly to the operating room for stent placement is appropriate in most cases of established ureteral obstruction.