Kidney stones are solid pieces of material that form in the kidneys when certain minerals crystallize in the urine. While they can cause intense pain as they move through the urinary tract, many kidney stones ultimately pass from the body on their own. The exact time it takes for a kidney stone to pass varies significantly.
Key Factors Affecting Passage Time
Several factors influence how quickly a kidney stone navigates the urinary system. The size of the stone is a primary determinant; smaller stones pass more readily and with less discomfort. A stone’s location within the urinary tract also plays a significant role, as stones closer to the bladder tend to pass with greater ease and speed than those higher up in the kidney or ureter.
Individual anatomical variations, such as ureter width, can impact the passage process. Adequate hydration is important, as sufficient fluid intake helps increase urine flow, facilitating stone movement. Medical management can also influence passage time. Certain medications, like alpha-blockers such as tamsulosin, are sometimes prescribed to relax ureter muscles, potentially making it easier for larger stones to pass.
Typical Passing Durations
The duration a kidney stone takes to pass is largely dependent on its dimensions. Small stones, typically less than 5 millimeters (mm), have a high likelihood of passing spontaneously. Around 80% to 90% of stones smaller than 4 mm may pass on their own, often within 31 days, or sometimes within a few days to a few weeks.
Medium-sized stones, ranging from 5 mm to 10 mm, present a more varied outcome. These stones may take longer to pass, often several weeks to a few months, and have a lower spontaneous passage rate compared to smaller stones. About 50% to 60% of stones in the 5-10 mm range might pass spontaneously, typically requiring around 45 days. Stones larger than 10 mm are considerably less likely to pass without medical intervention. If a large stone does pass naturally, it can potentially take up to a year.
Recognizing Complications and When to Get Help
While many kidney stones pass without surgical intervention, certain symptoms indicate a need for prompt medical evaluation. Severe or worsening pain that does not respond to pain medication warrants immediate attention. The presence of fever and chills is a serious sign, as it can indicate an infection in the kidney or urinary tract.
Persistent nausea and vomiting can lead to dehydration or signal a blockage within the urinary system. Although blood in the urine is common with kidney stones, excessive amounts or its occurrence alongside other concerning symptoms should prompt medical consultation. An inability to urinate or a significant decrease in urine output is a medical emergency, suggesting a complete blockage. If a stone has not passed after several weeks, or if symptoms persist without relief, seeking medical advice is recommended.