In a postpartum woman with multifocal renal abscesses who has had a ureteral stent placed for pelvicalyceal drainage, completed a full course of meropenem, and continues to have fever spikes, and repeat contrast‑enhanced computed tomography shows a 3‑cm collection in the upper pole and two 3‑cc collections in the interpolar region, what is the next step in management?

Percutaneous Drainage of the 3-cm Upper Pole Collection

In this postpartum patient with persistent fever despite completed meropenem therapy and a 3-cm upper pole renal abscess, percutaneous catheter drainage (PCD) of the dominant collection is the next step in management 1.

Rationale for Intervention

The ACR Appropriateness Criteria (2020) provide clear guidance: collections >3 cm that persist despite appropriate antibiotics require drainage 1. Your patient has:

• A 3-cm (29 cc) upper pole collection—at the threshold requiring intervention
• Persistent fever spikes despite completing a full course of meropenem
• Already has a stent in place for drainage, yet the abscess persists
• Two additional small (3 cc) collections that are below the intervention threshold

This clinical scenario mirrors the guideline's Variant 2: a patient with persistent fever and unchanged abscess size despite antibiotics and drainage attempts 1.

Why the Stent Alone Is Insufficient

The ureteral stent addresses pelviureteral junction obstruction and provides pelvicalyceal drainage, but it does not drain parenchymal or perinephric abscesses 2. The persistent fever indicates the dominant upper pole collection requires direct drainage. The stent may have prevented worsening hydronephrosis but cannot evacuate the walled-off abscess cavity.

Management Algorithm

Immediate Next Steps:

1. Percutaneous catheter drainage of the 3-cm upper pole collection 1

   • Image-guided (CT or ultrasound) placement
   • Send aspirate for culture and sensitivity to guide antibiotic adjustment
   • Leave drainage catheter in place until output decreases and fever resolves

2. Reassess antibiotic coverage 3

   • While awaiting culture results from the abscess, consider that meropenem failure suggests:
     • Resistant organism (though meropenem has broad coverage) 4
     • Inadequate source control (most likely—hence need for drainage)
     • Fungal infection (consider in postpartum patient with prior antibiotics) 2
   • Obtain blood cultures if not recently done

3. Monitor the smaller 3-cc collections conservatively 1

   • Collections <3 cm typically respond to antibiotics alone once source control is achieved 1
   • These will likely resolve once the dominant abscess is drained and appropriate antibiotics are continued

If PCD Fails or Is Technically Difficult:

Consider these options in sequence 1:

• Catheter upsizing or manipulation if initial drainage is inadequate 1
• Intracavitary thrombolytic therapy (tissue plasminogen activator) if the collection is complex/septated and not draining well—this has shown 72% clinical success in refractory abdominal abscesses 1
• Surgical drainage or nephrectomy only as last resort 1—reserved for cases where PCD fails and the patient remains septic

Critical Pitfalls to Avoid

1. Do not simply continue or change antibiotics without drainage—the 3-cm collection requires source control 1, 3. Antibiotics alone have limited efficacy for abscesses >3 cm, with success rates of only 14-32% for complex renal collections 1.

2. Do not assume the stent provides adequate drainage—stents drain the collecting system, not parenchymal abscesses 2.

3. Do not delay drainage waiting for antibiotics to work—persistent fever after completing meropenem indicates treatment failure requiring procedural intervention 1.

4. Do not drain the small 3-cc collections—these are below the threshold and will likely resolve with appropriate management of the dominant abscess 1.

5. Consider fungal infection—postpartum patients with prior broad-spectrum antibiotics and instrumentation are at risk for Candida or Aspergillus 2. If cultures from the abscess grow fungal organisms, antifungal therapy (not just antibiotics) will be needed.

Expected Outcomes

With appropriate PCD and targeted antibiotics based on culture results, success rates exceed 75% without need for surgery 1. The smaller collections should resolve spontaneously once source control is achieved. Monitor with repeat imaging in 1-2 weeks to confirm resolution.

Special Considerations in Postpartum Patients

• Postpartum patients may have altered anatomy and increased risk of stent-associated infections 5, 6
• The combination of recent instrumentation (stent placement), pregnancy-related immune changes, and prior antibiotics creates risk for resistant or atypical organisms 7, 6
• Ensure adequate imaging follow-up as postpartum patients may have delayed healing