What is the best course of action for a 35-year-old female with a history of right renal (kidney) stone, who had a retained ureteral stent (indwelling catheter) that was removed, and now presents with severe right hydronephrosis (fluid accumulation in the kidney) and hydroureter (fluid accumulation in the ureter) without evidence of an obstructing stone on computed tomography (CT) scan?

Management of Severe Hydronephrosis After Ureteral Stent Removal

This patient requires urgent CT urography (CTU) with IV contrast or MR urography (MRU) to identify the cause of persistent severe hydronephrosis, followed by prompt urologic consultation for likely intervention, as severe hydronephrosis without an obstructing stone suggests ureteral stricture, injury, or other non-calculous obstruction that will not resolve spontaneously. 1

Immediate Diagnostic Approach

The American College of Radiology explicitly states that when CT has already excluded obstructing stones, ultrasound cannot reliably determine the etiology of hydronephrosis and should be skipped. 1 Your patient needs definitive anatomic and functional imaging:

First-Line Imaging Selection

• Proceed directly to CTU with IV contrast if renal function is normal, as this provides near-comprehensive morphological and functional evaluation of the entire genitourinary tract 2, 1
• Choose MRU without and with IV contrast if renal function is impaired due to contrast concerns 1
• Do not order repeat ultrasound—it will not change management or provide the etiologic information needed 1

Alternative Imaging Considerations

• MAG3 renal scintigraphy with diuretic renography is the gold standard for confirming true obstruction and can differentiate functional from anatomic obstruction 2
• Consider MAG3 scan if you need to determine whether the severe hydronephrosis represents true obstructive uropathy versus non-obstructive dilation 2

Critical Clinical Context

Why Severe Hydronephrosis Without Stone is Concerning

The American College of Radiology guidelines note that severe hydronephrosis is rare in simple stone disease and should prompt consideration of alternate causes. 2 In your patient's context:

• History of retained ureteral stent raises concern for ureteral stricture formation, which is a known complication 3
• Severe hydronephrosis after stent removal suggests either ureteral injury, stricture, or other structural pathology 4
• All cases with severe hydronephrosis in one study underwent urologic intervention, highlighting the clinical significance 2

Differential Diagnosis to Consider

The most likely etiologies given this clinical scenario include:

• Ureteral stricture from prolonged stent indwelling or instrumentation (most common in this context) 3
• Ureteral injury during stent placement or removal 5
• Radiolucent stone (rare but reported with certain medications like atazanavir) 3
• Extrinsic compression or ureteral kinking 5

Urgent Management Algorithm

Step 1: Assess for Infection and Renal Function

• Check for fever, leukocytosis, positive urinalysis—infected obstructed kidney is a urological emergency requiring immediate decompression 6
• Measure serum creatinine to assess renal function impact 6
• If septic or febrile with obstruction, proceed directly to emergency decompression before definitive imaging 7

Step 2: Obtain Definitive Imaging

• Order CTU with IV contrast (if Cr normal) or MRU (if Cr elevated) to identify the exact location and nature of obstruction 1
• CTU detected 100% of renal calculi in one study but is also excellent for identifying strictures and other non-calculous causes 2

Step 3: Urgent Urology Referral

Severe hydronephrosis with this clinical history mandates urgent urologic consultation, as intervention is highly likely needed 6, 4:

• Passage failure rates increase dramatically with severe hydronephrosis (43% in one study), and your patient has no stone to pass 4
• Delayed treatment risks progressive renal damage, infection, and potential loss of kidney function 6

Intervention Options Based on Etiology

If Ureteral Stricture is Identified

• Retrograde ureteral stent placement may be attempted first 8
• Balloon dilation or endoscopic incision for short strictures 5
• Surgical ureterolysis or ureteral reconstruction for complex strictures 5

If Immediate Decompression Needed

Two randomized trials showed no superiority between percutaneous nephrostomy (PCN) and retrograde stent for decompression, though:

• PCN had 100% success rate versus 80% for stents in one trial 8
• PCN required shorter indwelling time and less antibiotic administration 8
• In infected cases, both methods are equally effective at resolving sepsis 7

Critical Pitfalls to Avoid

• Do not assume the hydronephrosis will resolve spontaneously—severe hydronephrosis after stent removal suggests structural pathology requiring intervention 4
• Do not order additional ultrasound imaging—it adds no diagnostic value when CT has already excluded stones 1
• Do not delay urologic referral—severe hydronephrosis carries high risk of intervention need and renal damage 6, 4
• Do not miss occult infection—check for fever and urinalysis even if patient appears well, as infected obstruction requires emergency decompression 6, 7