Imaging After RIRS Before DJ Stent Removal
Non-contrast CT scan is the recommended imaging modality after retrograde intrarenal surgery (RIRS) before removing the double-J stent, as it is the only reliable method to accurately assess residual stone burden and guide decisions about stent removal versus additional intervention.
Primary Imaging Recommendation
Non-contrast CT should be performed 2-3 months after RIRS to detect residual fragments before stent removal, as this is the gold standard for assessing stone-free status 1, 2.
CT is significantly superior to X-ray/ultrasound combinations for detecting clinically significant residual fragments (≥4 mm), identifying them in 43.1% of cases versus only 23.9% with plain imaging 1.
The timing of imaging should occur after stent placement but before removal to determine whether the stent can be safely removed or if additional intervention is needed 2, 3.
Why CT Over Other Modalities
Plain X-rays and ultrasound miss the majority of residual fragments, with CT detecting residual stones in 35.7% of patients compared to only 13.9% with conventional imaging 1.
Silent obstruction occurs in 2.9% of patients post-ureteroscopy and cannot be reliably excluded by symptoms alone, making functional imaging essential 3.
Relying on postoperative pain to determine imaging necessity places patients at risk for progressive renal failure from unrecognized obstruction, as 23.3% of obstructed patients remain asymptomatic 3.
Clinical Decision Algorithm
For stone burden <25 mm:
- Perform non-contrast CT at 2 months post-RIRS 2
- If stone-free or fragments <4 mm: proceed with stent removal 2
- Stone-free rates approach 100% in this group 2
For stone burden ≥25 mm:
- Mandatory CT imaging before stent removal 2
- Stone-free rates drop to 80%, requiring closer surveillance 2
- Higher likelihood of needing secondary intervention 1
For bilateral RIRS:
- At minimum, maintain unilateral stent until imaging confirms no obstruction 2
- CT or ultrasound required to prevent postrenal failure 2
Critical Pitfalls to Avoid
Never remove stents based solely on symptom resolution - 7 of 241 patients (2.9%) developed silent obstruction despite being asymptomatic, with one ultimately requiring chronic hemodialysis 3.
Do not rely on intraoperative assessment alone - residual fragments are common and require objective post-procedure imaging to detect 1.
Avoid planning reintervention based on ultrasound/X-ray - these modalities significantly underestimate residual stone burden and lead to inadequate treatment planning 1.
Alternative Imaging Considerations
Ultrasound may be used in pregnant patients or those with contrast allergies, but recognize its limitations in detecting small fragments 3.
MRI can substitute for CT in patients with radiation concerns, though this is not standard practice for routine post-RIRS assessment 4.
Excretory urography or delayed-phase CT should be added if urinary extravasation or collecting system injury is suspected 4.