From the Guidelines
The chances of spontaneously passing a ureteral stone are significantly influenced by its size, with stones ≤5 mm having a higher likelihood of passage, estimated at 68% 1. When considering the spontaneous passage of ureteral stones, several factors come into play, but size is the most critical determinant.
- Stones ≤5 mm have a relatively high chance of passing spontaneously, with an estimated 68% passage rate, as indicated by a meta-analysis of five patient groups 1.
- For stones between 5 mm and 10 mm, the spontaneous passage rate decreases, with an estimated 47% of stones passing spontaneously, based on an analysis of three patient groups 1.
- The location of the stone within the ureter also plays a role, with stones in the lower ureter having a better chance of spontaneous passage compared to those in the upper ureter.
- Pain management is crucial during this period and may include NSAIDs like ibuprofen or naproxen, and in some cases, alpha-blockers such as tamsulosin may be prescribed to facilitate stone passage 1.
- Adequate hydration, aiming for at least 2-3 liters of water daily, is essential to help flush the stone.
- If a stone hasn't passed within 4-6 weeks, or if complications arise, urological intervention such as ureteroscopy or extracorporeal shock wave lithotripsy may be necessary, with both SWL and URS being acceptable first-line treatments, though URS yields significantly greater stone-free rates for the majority of stone stratifications 1.
From the Research
Chances of Spontaneously Passing a Ureteral Stone Based on Size
- The chances of spontaneously passing a ureteral stone are significantly influenced by the size of the stone, with smaller stones having a higher likelihood of passing on their own 2, 3, 4.
- According to a study published in European Radiology, the spontaneous passage rates for stones of different sizes are:
- 0-2 mm: 98%
- 3 mm: 98%
- 4 mm: 81%
- 5 mm: 65%
- 6 mm: 33%
- ≥6.5 mm: 9% 2
- Another study published in AJR. American Journal of Roentgenology found similar results, with spontaneous passage rates of:
- 1 mm: 87%
- 2-4 mm: 76%
- 5-7 mm: 60%
- 7-9 mm: 48%
9 mm: 25% 3
- A study published in BJU International also reported that stone size is a significant predictor of spontaneous stone passage, with rates of:
- <5 mm: 89%
- 5-7 mm: 49%
7 mm: 29% 4
Factors Influencing Spontaneous Stone Passage
- In addition to stone size, other factors such as stone location, hydronephrosis, and medical expulsive therapy (MET) can influence the likelihood of spontaneous stone passage 2, 3, 4, 5.
- A study published in The Journal of Urology found that serum C-reactive protein and white blood count can also be used to predict spontaneous stone passage in patients with 4 to 10 mm distal ureteral stones 6.