If you’ve ever been told you have a kidney stone, you probably asked the same question everyone asks: “Will it pass on its own?” The honest answer is that it depends. Most people know stone size matters, but fewer realize that kidney stone location can be just as important. Where a stone sits plays a major role in whether it passes naturally or requires treatment.
Kidney stones form inside the kidney and often do not cause symptoms until they begin to move. Doctors usually describe stones by their location within the kidney, using the terms upper, mid, and lower pole.
What “Upper Pole” and “Lower Pole” Actually Mean
The word “pole” simply refers to position within the kidney. The kidney is bean-shaped, so doctors describe it by its top and bottom ends, much as we talk about the North and South Poles. The upper pole is the top of the kidney near the ribs. The lower pole is the bottom of the kidney near the pelvis. The mid pole sits between the two. When a doctor says “lower pole kidney stone,” they are referring to the location of the stone within the kidney, not the tube (ureter) that drains urine. It can be confusing; that is why I’m bringing it up with you.
Why Location Affects Your Stone’s Journey
This distinction matters because each pole drains urine at a different angle. Urine from the upper and mid pole drains more directly toward the kidney’s main exit, making it easier for stones to move out. Urine from the lower pole must move upward before it can leave the kidney, making stone passage more difficult.
The Ureter: The Toughest Part of the Trip
To exit the body, a stone must travel from the kidney into the ureter, which is the narrow tube that connects the kidney to the bladder. The ureter is the most difficult part of the journey. It is long, tight, and muscular, with natural narrow points where stones often get stuck.
Upper and Mid-Pole Stones: Better Odds of Passing
Upper-pole kidney stones pass on their own in about 20 percent of cases. Mid-pole stones pass more often, with estimates around 40 to 50 percent, because they are better positioned to enter the ureter.
Lower-Pole Stones: Fighting Gravity
Lower-pole kidney stones behave differently. Because they sit at the bottom of the kidney and must move upward against gravity, they have the lowest chance of passing naturally. Estimated passage rates range from about 10 to 35 percent. Even small lower-pole stones often remain stuck and may never move. Lower pole stones can stay the same size for years, especially when someone follows a kidney stone prevention plan that includes good hydration (think the Kidney Stone Diet®). Drinking enough fluid will not make an existing stone shrink, but it does help prevent that stone from growing and lowers the chance that new stones will form.
Once It Reaches the Ureter, Your Odds Improve
Once a stone leaves the kidney and enters the ureter, the chance of passing improves significantly. Stones are more likely to pass as they approach the bladder. Stones near the bladder have the highest chance of passing naturally, and once a stone reaches the bladder, it almost always passes without intervention.
Size Still Matters (But Not Alone)
Stone size still matters. Small stones, especially those measuring less than 5 millimeters, often pass through the ureter. Medium-sized stones are unpredictable but tend to pass more often when lower in the urinary tract. Larger stones, especially those over ten millimeters, rarely pass on their own and usually require a procedure. This is why doctors always consider stone size and location together.
How Long Should You Wait?
Many people also wonder how long the passage takes. If pain is controlled and there is no infection or kidney damage, doctors often allow four to six weeks for a stone to pass naturally. If the stone does not move or symptoms worsen, treatment is usually recommended.
When Waiting Becomes Dangerous
Waiting is not always safe. Fever, chills, vomiting, difficulty urinating, or severe pain that does not improve can signal infection or blockage and should be evaluated immediately.
Understanding Location Reduces Anxiety
Understanding the location of kidney stones can reduce anxiety. Knowing a stone has already entered the ureter can be reassuring, even if symptoms are uncomfortable. Location does not predict future stones, which is why prevention matters. Staying well hydrated, lowering sodium intake, and following an individualized prevention plan can reduce the risk of recurrence.
The Bottom Line
If you’ve had kidney stones before, understanding how they move through the body can help you feel more informed, prepared, and less overwhelmed the next time one shows up.
Are you typically able to pass your kidney stones?
Your friend,
Nurse Jill
P.S. There are always exceptions to the rules. Each of you is different, and each of you tells me stories every day that sometimes go against the statistics. I have had patients pass a lower pole stone, and I have had patients pass a 9mm stone.
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