Can You Pass a 6mm Kidney Stone on Your Own?
A 6mm kidney stone has approximately a 33% chance of passing spontaneously, making it borderline for conservative management, but observation with medical expulsive therapy is a reasonable initial approach for patients with controlled symptoms, no infection, and adequate kidney function. 1
Spontaneous Passage Rates by Stone Size
The likelihood of spontaneous passage decreases significantly as stone size increases:
- Stones ≤5mm: Approximately 68% spontaneous passage rate (95% CI: 46-85%) 2
- Stones >5mm but ≤10mm: Approximately 47% spontaneous passage rate (95% CI: 36-59%) 2
- 6mm stones specifically: Only 33% spontaneous passage rate 1
- Stones >10mm: Unlikely to pass spontaneously and typically require surgical intervention 2, 3
Initial Management Approach for 6mm Stones
Observation with medical expulsive therapy (MET) using alpha-blockers is appropriate as first-line management for stones ≤10mm in patients meeting specific criteria: 2, 3
Patient Selection Criteria for Conservative Management
You can attempt spontaneous passage if you have: 2
- Well-controlled pain with oral medications
- No clinical evidence of sepsis or infection
- Adequate renal functional reserve (normal contralateral kidney function)
- No anatomic abnormalities preventing passage
Medical Expulsive Therapy
Alpha-blockers increase stone passage rates by approximately 29% (95% CI: 20-37%) compared to observation alone, making them a valuable adjunct. 2 This is an off-label use that should be discussed with your physician. 2
Timeline and Monitoring Requirements
Conservative management should be limited to a maximum of 6 weeks from initial presentation to avoid irreversible kidney injury. 2, 3
Expected passage times for stones that do pass spontaneously: 4
- Average time to passage for 4-6mm stones: 22-39 days
- 95% of stones that will pass do so within 39-40 days
Required Monitoring During Observation
Periodic imaging studies are mandatory to monitor stone position and assess for hydronephrosis. 2, 3 This typically involves:
- Follow-up imaging every 1-2 weeks
- Assessment for development of obstruction or infection
- Monitoring of kidney function
When Surgical Intervention Becomes Necessary
Approximately 50% of stones in the 5-10mm range ultimately require intervention. 5 Indications for proceeding to surgery include: 2, 6
- Failure to pass after 6 weeks of conservative management
- Uncontrolled pain despite adequate analgesia
- Development of infection or sepsis
- Progressive hydronephrosis
- Deteriorating kidney function
- Patient preference for definitive treatment
Surgical Options
If the stone fails to pass, treatment options include: 2
- Ureteroscopy (URS): 93-94% stone-free rate for distal ureteral stones 2
- Shock wave lithotripsy (SWL): 74% stone-free rate for distal ureteral stones 2
Critical Factors Affecting Passage
Stone location significantly impacts passage probability, with distal ureteral stones having higher passage rates than proximal stones. 3, 1 A 6mm stone in the distal ureter has a better chance of passing than one in the proximal ureter or kidney.
Common Pitfalls to Avoid
- Do not exceed 6 weeks of conservative management without reassessment, as prolonged obstruction can cause permanent kidney damage 2, 3
- Do not ignore signs of infection (fever, elevated white blood cell count), which requires immediate intervention 2
- Do not rely solely on symptom improvement as a marker of stone passage; imaging confirmation is essential 3
- Do not assume the stone will pass simply because it is under 10mm; at 6mm, the odds are actually against spontaneous passage 1