Kidney stones are solid masses formed from minerals and salts that can develop inside your kidneys. When these stones move out of the kidney, they travel through a narrow tube called the ureter, which connects the kidney to the bladder.
Factors Affecting Passage Time
The time it takes for a kidney stone to pass through the ureter depends on several contributing factors, with stone size being a primary determinant. Smaller stones, generally those under 4 millimeters (mm), have a high likelihood of passing spontaneously, with approximately 80% doing so within an average of 31 days. Stones ranging from 4 to 6 mm may also pass naturally in about 45 days, though they often require some form of medical intervention. Stones larger than 6 mm are less likely to pass on their own (only about 20%), and this process can take up to a year.
The stone’s location within the ureter also influences passage time. Stones situated closer to the bladder, in the lower ureter, tend to pass more quickly than those located higher up, near the kidney. Research indicates that around 79% of stones in the distal (bladder-adjacent) end of the ureter pass spontaneously, compared to approximately 48% of stones in the proximal (kidney-adjacent) end. The ureters also have natural constrictions, such as where they meet the renal pelvis and the bladder, which can be common sites for a stone to become lodged.
Ureter anatomy also plays a role; narrower ureters or pre-existing strictures can impede stone movement. Adequate hydration is another significant factor that can facilitate stone passage. High fluid intake increases urine flow, which can encourage the stone to move through the urinary tract. Dehydration is a recognized risk factor for kidney stone formation and can hinder their passage.
Signs and Symptoms of Stone Passage
When a kidney stone moves through the ureter, it can cause noticeable symptoms. The most characteristic symptom is severe, fluctuating pain, often referred to as renal colic. This pain typically originates in the back or side, just below the ribs, and can radiate to the lower abdomen, groin, and even the genital area. The pain often comes in waves, intensifying and subsiding as the ureter contracts to push the stone along.
Urinary symptoms are also common during stone passage. Individuals may experience an increased and sudden urge to urinate, painful urination (dysuria), and frequently pass only small amounts of urine. Blood in the urine (hematuria) is another common sign, appearing as red, pink, or brown discoloration, caused by the stone irritating the urinary tract lining. Nausea and vomiting frequently accompany the severe pain, as the intensity of the discomfort can trigger these responses.
Strategies to Aid Stone Passage
Several strategies can help facilitate kidney stone passage at home. Drinking plenty of water is a primary recommendation, as increased fluid intake boosts urine production and flushes the stone through the urinary system. Aiming for enough water to produce about 2 liters of urine daily is often suggested to help prevent new stones and aid passage. Adding fresh lemon juice to water can also be beneficial, as lemons contain citrate, which may help prevent calcium stones from forming and potentially break up small stones.
Pain management is also an important aspect of self-care. Over-the-counter pain relievers such as nonsteroidal anti-inflammatory drugs (NSAIDs) like ibuprofen can help reduce discomfort. Applying heat to the lower back or abdomen with a heating pad or warm bath can relax muscles and alleviate pain. While strenuous exercise should be avoided, light activity, such as walking, might help encourage the stone to move. It is advisable to strain urine through a filter or gauze to catch the stone once it passes, which can then be given to a doctor for analysis.
When to Seek Medical Help
While many kidney stones pass without surgical intervention, certain signs indicate the need for prompt medical attention. Unmanageable pain, too severe to control with medication, is a clear indication to seek emergency care. Fever (higher than 101.5°F), chills, or persistent vomiting alongside kidney stone symptoms can signal a serious infection, requiring immediate medical evaluation.
An inability to urinate or a significant decrease in urine output (anuria) suggests a possible blockage of the urinary tract, which can lead to kidney damage. Individuals with pre-existing conditions like diabetes or decreased kidney function should also seek medical help more readily, as these conditions can make stone passage more complicated. If a stone has not passed after several weeks, or if symptoms worsen, it is prudent to consult a healthcare provider for further guidance and potential intervention.