From the Guidelines
The likelihood of passing a kidney stone varies significantly based on its location, with stones in the distal ureter having the highest chance of spontaneous passage at approximately 74%. The location of the kidney stone plays a crucial role in determining the likelihood of its passage.
- Stones located in the distal ureter have a high chance of spontaneous passage, with a stone-free rate of 74% 1.
- Stones in the mid ureter have a lower chance of passing without intervention, with a stone-free rate of 73% 1.
- Stones in the proximal ureter have a stone-free rate of 82% 1. The size of the stone also impacts these percentages significantly, with stones smaller than 10 mm having a higher chance of passing regardless of location.
- For example, stones in the distal ureter that are less than 10 mm have a stone-free rate of 86% 1.
- In contrast, stones in the distal ureter that are greater than 10 mm have a lower stone-free rate of 74% 1. During the waiting period for stone passage, pain management and adequate hydration are essential to help flush the stone. If a stone doesn't pass within 4-6 weeks, or if complications develop, urological intervention becomes necessary.
From the Research
Kidney Stone Passage Likelihood Based on Location
The likelihood of passing a kidney stone is influenced by its location, size, and other factors.
- Studies have shown that the location of the stone in the ureter affects the likelihood of spontaneous passage 2, 3.
- Stones located in the distal ureter (closer to the bladder) are more likely to pass spontaneously than those in the proximal ureter (closer to the kidney) 3.
- The size of the stone is also a significant factor, with smaller stones being more likely to pass spontaneously 2, 3.
Percent Likelihood of Passing a Kidney Stone Based on Size and Location
- For stones 0-2 mm in size, the spontaneous passage rate is around 98% 2.
- For stones 3 mm in size, the spontaneous passage rate is around 98% 2.
- For stones 4 mm in size, the spontaneous passage rate is around 81% 2.
- For stones 5 mm in size, the spontaneous passage rate is around 65% 2.
- For stones 6 mm in size, the spontaneous passage rate is around 33% 2.
- For stones ≥6.5 mm in size, the spontaneous passage rate is around 9% 2.
- A study found that 95% of stones 2 mm or less pass spontaneously within 31 days, while stones 2-4 mm take around 40 days, and stones 4-6 mm take around 39 days 3.
Factors Affecting Kidney Stone Passage
- Stone size and location are the most important predictors of spontaneous passage 2.
- The side of the stone (left or right) and the grade of hydronephrosis (swelling of the kidney) can also affect stone passage, but only in specific subgroups 2.
- The use of alpha-blockers such as tamsulosin may facilitate stone clearance, particularly for larger stones 4, 5.