In a stable adult without fever, urinary infection, obstruction, or impaired renal function, what size renal calculi can be managed outpatient without hospital admission?

Kidney Stone Size Criteria for Outpatient Management

In stable adults without fever, infection, obstruction, or renal impairment, stones ≤10 mm can be managed outpatient with observation and medical expulsive therapy if pain is controlled with oral analgesics. 1, 2

Outpatient Management Criteria

Stone Size Thresholds

• Stones <5 mm: Expected to pass spontaneously without intervention and can be managed outpatient 3
• Stones 5-10 mm: May be managed outpatient initially, though up to 50% may ultimately require urological intervention 3
• Stones >10 mm: Should be discussed with urology as they are unlikely to pass spontaneously and typically require admission or urgent intervention 1, 3

Mandatory Requirements for Outpatient Management

All of the following must be present to safely discharge a patient with a ureteral stone <10 mm 1, 2, 4:

• Pain control: Symptoms adequately controlled with oral analgesics (combination of NSAIDs, acetaminophen, and/or codeine)
• No infection: Absence of fever, pyuria, or clinical sepsis
• No obstruction with infection: This combination mandates urgent drainage 1, 2
• Adequate renal function: Normal contralateral kidney function and no acute kidney injury 1
• Patient reliability: Ability to follow up with periodic imaging 4

Absolute Indications for Admission

The following scenarios require hospital admission regardless of stone size 1, 4:

• Obstructing stone with suspected infection: Requires urgent collecting system drainage with nephrostomy tube or ureteral stent before any stone treatment 1, 2
• Intractable pain: Failure to control pain with oral analgesics 4
• Solitary kidney or bilateral obstruction: Risk of acute renal failure 1
• High-grade hydronephrosis with large stones (>10 mm): Particularly if associated with elevated creatinine 5

Common Pitfalls to Avoid

Do not confuse small stone size with low symptom risk - even stones <5 mm can cause severe renal colic if they cause complete ureteral obstruction 4. The size determines likelihood of spontaneous passage, not symptom severity.

Do not delay drainage in obstructed, infected patients - this combination can rapidly progress to urosepsis and requires immediate intervention before definitive stone treatment 1, 5. Percutaneous nephrostomy is preferred for severe pyonephrosis or high-grade hydronephrosis, while retrograde ureteral stenting may be suitable for small stones (≤10 mm) with low-grade hydronephrosis 5.

Follow-up Protocol for Outpatient Management

Patients discharged with stones <10 mm require 1, 4:

• Maximum observation period: 4-6 weeks from initial presentation
• Periodic imaging: To monitor stone position and evaluate for hydronephrosis
• Return precautions: Fever, worsening pain, inability to urinate, or vomiting

Predictors of eventual intervention in discharged patients include larger stone size within the <10 mm range, longer pain duration at presentation, and history of prior stone procedures 6.