Is it possible to pass a 6 mm proximal ureter stone?

Spontaneous Passage of a 6 mm Proximal Ureteral Stone

Yes, it is possible to pass a 6 mm proximal ureteral stone spontaneously, but the chances are relatively low at approximately 33-47% without intervention.

Spontaneous Passage Rates by Stone Size and Location

The likelihood of spontaneous passage depends primarily on two factors: stone size and location.

• Stone size:

  • Stones ≤5 mm: 68% pass spontaneously (95% CI: 46-85%) 1
  • Stones >5 mm and ≤10 mm: 47% pass spontaneously (95% CI: 36-59%) 1
  • Specifically for 6 mm stones: 33% pass spontaneously 2

• Stone location impact:

  • Proximal ureteral stones have lower passage rates compared to mid or distal stones
  • Time to 50% expulsion for proximal stones: 28.8 days vs 15.6 days for mid/distal stones 3

Medical Expulsive Therapy (MET)

Adding medical therapy can improve passage rates:

• Alpha blockers:

  • Increase stone passage rates by 29% (95% CI: 20-37%) compared to control 1
  • Passage rate of 81% (95% CI: 72-88%) in studies examining alpha blockers 1
  • Superior to calcium channel blockers like nifedipine 1

• Calcium channel blockers (nifedipine):

  • Increase stone passage rates by 9% (95% CI: 7-25%) compared to control 1
  • Passage rate of 75% (95% CI: 63-84%) in studies examining nifedipine 1

Time to Stone Passage

For a 6 mm stone:

• Mean time to passage: approximately 21.8 days 4
• Cumulative passage rates over time:
  • 55.3% in 7 days
  • 73.7% in 14 days
  • 88.5% in 28 days
  • 97.7% in 60 days (for stones that will pass) 4

When to Consider Intervention

If the stone doesn't pass spontaneously, intervention may be necessary:

• For proximal ureteral stones >6 mm:
  • Both SWL and URS have similar stone-free rates:
    • SWL: 68% (95% CI: 55-79%) 1
    • URS: 79% (95% CI: 71-87%) 1

Important Caveats

1. Stent placement impact: Even with a stent in place, passage rates for 5-6.9 mm stones are only about 10% 5

2. Observation period: If choosing observation, most stones that will pass do so within 30 days 3

3. Complications risk: Prolonged observation increases risk of complications including obstruction, infection, and renal damage

4. Individual factors: Patient's pain tolerance, comorbidities, and preference should be considered alongside stone characteristics

5. Imaging follow-up: CT without contrast is the gold standard (97% sensitivity) for monitoring stone position and detecting complications 1

In summary, while spontaneous passage of a 6 mm proximal ureteral stone is possible, the probability is relatively low. Medical expulsive therapy with alpha blockers may improve the chances, but patients should be counseled about the likelihood of eventually needing intervention if the stone doesn't pass within 4-6 weeks.