Kidney stones are hard deposits of minerals and salts that form inside the kidneys. While both men and women can develop them, their incidence in women has been increasing. This article explores factors unique to females, general causes, symptoms, and treatment options.
Prevalence in Females
While kidney stones have historically been more prevalent in men, their incidence among women has been increasing. Recent data indicates that the overall prevalence in U.S. adults has remained stable, but cases have notably risen among women, particularly those under 60. For instance, prevalence in women increased from 6.5% (2007-2008) to 9.1% (2017-2020). Some studies suggest the lifetime risk is about 1 in 10 for men and 1 in 12 for women.
Improved diagnostic techniques, which can detect even small, asymptomatic stones, partly explain this narrowing gap. Changes in diet, lifestyle, and an increase in chronic conditions like obesity and diabetes also contribute to rising rates. Women tend to have a higher frequency of infected stones, often linked to recurrent urinary tract infections.
Factors Unique to Females
Several factors unique to females influence kidney stone formation. Hormonal fluctuations play a role; some research suggests estrogen levels can impact calcium absorption and stone development. While natural estrogen was once thought to protect against stones, postmenopausal estrogen therapy may increase risk. A study of over 24,000 postmenopausal women found those receiving estrogen therapy were 1.21 times more likely to develop kidney stones over five years.
Pregnancy also predisposes women to kidney stones. Physiological changes during pregnancy, including increased pressure on the urinary system and hormonal shifts, can create an environment conducive to stone crystallization. Urinary tract infections (UTIs) are more common in women and can lead to struvite stones.
General Causes and Prevention
Kidney stones form when urine contains a high concentration of crystal-forming substances (e.g., calcium, oxalate, uric acid) and lacks enough fluid to dilute them. Inadequate fluid intake is a primary cause, as concentrated urine allows minerals to form stones. Dietary factors also play a significant role; diets high in sodium, animal protein, and sugar can increase stone formation risk. High sodium intake causes kidneys to excrete more calcium, increasing stone risk. High animal protein consumption can lead to increased uric acid and calcium excretion.
Prevention often involves lifestyle and dietary adjustments. Drinking plenty of water daily is effective for prevention, as it dilutes urine and reduces mineral concentration. Clear or nearly clear urine indicates adequate hydration. Limiting sodium intake to about 2,300 milligrams daily can help reduce calcium excretion.
While calcium is a component of common kidney stones, adequate dietary calcium is important, as low-calcium diets can paradoxically increase stone risk. Calcium supplements should be taken with caution and ideally with meals, as they may increase risk. Reducing intake of high-oxalate foods (e.g., spinach, rhubarb, beets, chocolate) may be advised for individuals prone to calcium oxalate stones.
Recognizing Symptoms
Small kidney stones may not always cause immediate symptoms, especially if they remain in the kidney. Symptoms typically emerge when a stone moves within the kidney or passes into the ureter, the tube connecting the kidney to the bladder. This movement can block urine flow and cause severe pain, often described as renal colic. This pain is usually sharp and cramping, located in the lower back, side, or belly, and can radiate to the groin. Pain often comes in waves, varying in intensity.
Other common symptoms include nausea, vomiting, blood in the urine (red, pink, or brown), painful urination, and a frequent urge to urinate. Cloudy or foul-smelling urine, fever, and chills can also occur, sometimes indicating infection. Seek medical attention if severe pain, persistent nausea or vomiting, fever, chills, or visible blood in the urine are present. Immediate medical care is needed for difficulty urinating or unbearable pain.
Treatment Approaches
Treatment for kidney stones varies by stone size, location, and composition. For smaller stones, conservative management is often sufficient. This approach typically involves pain medication (e.g., ibuprofen, naproxen sodium) and increased fluid intake to help the stone pass naturally. Alpha-blockers may also be prescribed to relax ureter muscles, facilitating stone passage. Most small stones (under 6 mm) often pass on their own within a few weeks.
For larger stones, or those causing blockages, severe pain, or infection, more involved procedures may be necessary. Shockwave lithotripsy (SWL) uses high-energy sound waves to break stones into smaller fragments that can be passed in urine. Ureteroscopy involves inserting a thin, lighted tube with a camera through the urethra and bladder into the ureter or kidney to remove or break up stones. Percutaneous nephrolithotomy (PCNL) is typically used for very large stones, involving a small incision in the back to access the kidney and remove the stone. These treatments aim to facilitate stone passage, remove the stone, or manage pain and prevent complications.