Kidney stones are solid formations of minerals and salts that develop inside the kidneys when waste products in the urine become concentrated and crystallize. Asymptomatic kidney stones do not produce any discomfort or signs of their presence. These stones can reside in the kidneys or urinary tract for extended periods, often leading to their delayed discovery.
How Asymptomatic Stones Are Discovered
Asymptomatic kidney stones are typically found by chance during medical imaging tests conducted for other health concerns. These incidental discoveries often occur when individuals undergo scans such as computed tomography (CT) scans, ultrasounds, or X-rays for unrelated abdominal or retroperitoneal issues. For example, a patient might have an ultrasound for abdominal pain, and a kidney stone is unexpectedly identified.
Over half of patients with asymptomatic ureteral stones have been identified during routine health insurance examinations. Stones are also found during follow-up appointments for previously diagnosed conditions, including prior kidney stones or other diseases. This accidental detection explains why many people are unaware they have kidney stones until a medical scan reveals their presence.
Potential Risks and When to Act
Leaving asymptomatic kidney stones untreated carries potential risks, including the stone growing larger, becoming symptomatic, or causing complications such as infection or obstruction. Stones can obstruct the urinary tract, leading to swelling of the kidney (hydronephrosis), severe pain, or even kidney damage and reduced kidney function. An obstruction can also result in a kidney infection, which may progress to sepsis.
Factors influencing the decision to intervene or observe an asymptomatic stone include its size, location, composition, and growth rate. Stones smaller than 5 millimeters often pass naturally, but larger stones, particularly those 7 millimeters or more, are less likely to pass spontaneously. Stone location also plays a role; for example, stones in the renal pelvis may be more likely to progress than small upper pole stones. Patient preferences and overall health, including comorbidities that increase surgical risk, also factor into the decision.
Studies indicate that a significant percentage of asymptomatic stones do not remain silent. Data suggests that 26% of patients eventually require intervention, 48% experience pain, and 55% experience stone growth within four years of identification. This highlights the importance of careful consideration and discussion between patients and their healthcare providers regarding observation versus early intervention.
Management Approaches
Managing an identified asymptomatic kidney stone involves different strategies, ranging from close monitoring to active removal, depending on individual circumstances. Watchful waiting, also known as active surveillance, is a common approach for many asymptomatic stones. This involves regular monitoring with imaging tests, such as ultrasounds or low-dose CT scans, and ongoing clinical follow-up to track the stone’s size, location, and any development of symptoms or complications. The goal is to avoid unnecessary interventions while ensuring potential issues are identified promptly.
Active removal, or intervention, becomes an option when specific factors indicate a higher risk of future problems or when watchful waiting is not preferred.
Extracorporeal Shock Wave Lithotripsy (ESWL)
This non-invasive procedure uses high-energy shock waves to break kidney stones into smaller fragments that can pass through the urinary tract. ESWL is effective for small to medium-sized stones, particularly those less than 2 centimeters, and is often performed as an outpatient procedure.
Ureteroscopy (URS)
URS involves inserting a small, flexible telescope through the urethra and bladder into the ureter to locate and treat stones. If the stone is small, it can be removed with a basket device; larger stones are fragmented with a laser before removal. Ureteroscopy is effective for stones located anywhere in the ureter or kidney and is often preferred for pregnant women, obese individuals, or those on blood thinners.
Percutaneous Nephrolithotomy (PCNL)
PCNL is a minimally invasive surgical procedure for larger or more complex stones, often those greater than 2 centimeters. It involves making a small incision in the back to directly access the kidney and remove or break up the stone using specialized instruments. PCNL offers a higher stone-free rate for large stones compared to ESWL.
Medical management can also play a role, particularly in helping to pass existing stones or preventing their growth. Alpha-blockers, such as tamsulosin, can relax the muscles in the ureter, potentially aiding the passage of smaller stones. For certain stone types, like uric acid or cystine stones, medications such as potassium citrate can be prescribed to increase urine pH, making the urine less acidic and helping to dissolve existing stones or prevent their growth. However, these medications are not effective for dissolving calcium stones, which are the most common type.
Preventing Future Stones
Preventing new kidney stones or the growth of existing ones is a long-term strategy, especially for individuals identified as stone formers. Adequate hydration is a primary preventive measure; drinking enough fluids, aiming for at least 2.5 liters of urine output daily, helps dilute stone-forming substances in the urine. Water is the best choice, but citrus drinks like lemonade and orange juice can also be beneficial as they contain citrate, which helps prevent stone formation.
Dietary modifications are also important and often depend on the specific type of kidney stone. Limiting sodium intake to less than 2,300 milligrams per day can reduce calcium excretion in the urine, a factor in calcium stone formation. Reducing animal protein intake, such as beef, chicken, and pork, can help decrease uric acid levels in the urine, lowering the risk of uric acid stones. For individuals prone to calcium oxalate stones, being mindful of foods high in oxalate, like spinach, beets, nuts, and chocolate, is suggested. It is recommended to consume calcium-rich foods with oxalate-rich foods during meals, as this can help calcium and oxalate bind in the digestive tract before reaching the kidneys.
Medical therapies can also be used to prevent recurrence. Thiazide diuretics may be prescribed to reduce calcium levels in the urine for those with recurrent calcium stones and high urinary calcium. For uric acid and cystine stones, potassium citrate is commonly used to alkalinize the urine, which increases the solubility of these stone types. Regular follow-up with a healthcare provider, including metabolic evaluations and imaging, helps tailor prevention plans and monitor for new stone formation or growth.