Managing Stone Disease Effective approaches to kidney careKidney stone disease is common in the United States, affecting one in 10 people and accounting for seven to 10 of every 1,000 hospital admissions. The incidence of stone disease is highest in patients between 30 and 45 years of age, while the condition declines in patients over 50. Treatment selection for stone disease depends on many factors, including the size and type of stone and the existence of underlying medical conditions.
Kidney stones are hard deposits of minerals that do not dissolve completely in the urine and grow slowly in the kidneys. Factors contributing to kidney stone formation include high levels of urine calcium, oxalate, or uric acid. Dehydration or low levels of urine magnesium, pyrophosphate, and citrate, in particular, also favor stone formation.
Approximately 85% of kidney stones are caused by urine hypercalciuria and mainly consist of calcium deposits, especially calcium oxalate. Calcium phosphate stones occur in patients with hormonal or metabolic disease, such as renal tubular acidosis or hyperparathyroidism.
Risk factors for developing kidney stones include inadequate fluid intake, dehydration, reduced urinary flow and volume, and increased levels of calcium, oxalate, uric acid, or other urinary chemicals. Other risk factors are low levels of urinary citrate and conditions that block or reduce urine flow. Medical conditions that increase risk include hyperparathyroidism, gout, hypertension, colitis, renal tubular acidosis, Crohn’s disease, and medullary sponge kidney. Poor diet may also increase the risk.
Performing a Diagnosis
Diagnosis of stone disease is based on medical history, physical examination, and imaging tests. Urine should be tested for hematuria or bacteriuria. Blood tests indicated include creatinine for kidney function, blood urea nitrogen and electrolyte for dehydration, calcium levels for hyperparathyroidism, and a complete blood count for infection.
The noncontrast computed tomography (CT) scan is the most frequently used imaging technique for diagnosing a kidney stone attack. Although a CT scan may miss small kidney stones, it can detect medical conditions with symptoms similar to stone disease. If detected, stones can be imaged with an abdominal x-ray to assess their size, shape, and orientation.
Ultrasound is preferred for patients who are pregnant, but it may not detect small stones. Most kidney stones can be located using intravenous pyelogram (IVP), which requires injection of a contrast agent followed by a series of x-rays. Only patients with normal kidney function can undergo IVP, and there is a small risk for allergic reaction to the dye. The IVP procedure can be lengthy if kidney blockage is severe.
Retrograde pyelogram is the most reliable means of imaging kidney stones but may require anesthesia. This technique is used when other imaging methods are unsuccessful.
Prevention and Treatment
Prevention strategies depend on individual risk factors and the type of stone present. Recommendations may include lifestyle modifications, such as increased fluid intake and dietary changes, as well as treatment of underlying medical conditions. Some patients should limit intake of meat, salt, and foods with high levels of oxalate.
Approximately 85% of kidney stones are small enough to pass during urination, usually within 72 hours of symptom onset. Most stones measure 4 mm or less in diameter, and about half of those measuring 5 mm to 7 mm will pass on their own. The best treatment for these stones is to drink up to two or three quarts of water per day, stay physically active, and wait. Walking is useful for helping stones to pass. Painkillers help with the pain associated with passing a stone.
Urinating through a strainer may be recommended so the stone can be recovered and analyzed. The mineral composition of the kidney stone will dictate treatment and future preventive measures. Medications, such as diuretics, and dietary restrictions, such as reduced calcium, are not generally required but may be prescribed. Stones that are not treatable with more conservative measures may require removal using the minimally invasive surgical procedures offered at Urology Associates of North Texas.
Minimally Invasive Surgical Procedures
Extracorporeal shock wave lithotripsy (ESWL) is the usual way to remove stones measuring up to 1.5 cm, which are located in any part of the urinary system. The patient is partially submerged in a tub of water or placed on a cushion during the procedure. The shock waves are moderately painful, so the procedure is performed with sedatives or anesthesia. The physician uses x-rays to monitor the location and status of the stone as shock waves pound the stone for about one hour. Each shock wave produces a loud noise, so patients must wear earplugs.
In many cases, the stone will begin to crumble after 200 to 400 shock waves. The sand-like particles that remain after treatment are easily passed in the urine. Side effects of ESWL include blood in the urine for a short time after the procedure, minor bruising on the back or abdomen, and discomfort with the passing of the stone fragments. Repeated ESWL treatments may be needed to completely break up some stones. This procedure should not be used to treat pregnant women or to remove struvite stones.
Percutaneous nephrolithotomy is recommended when ESWL is not effective or when the stone is very large. The surgeon inserts a nephroscope through a small incision in the patient’s back and into the back of the kidney. An ultrasonic probe or laser, fed through the nephroscope, is used to break up the stones for extraction. Percutaneous nephrolithotomy is performed under general anesthesia, and patients usually stay in the hospital for one to two days, with an additional recovery time of one to two weeks. Because all stones and fragments are removed through the nephroscope during the procedure, this surgery is recommended for people whose jobs or health conditions require that they be stone free.
Ureteroscopic stone removal is used to break up or remove stones lodged in the lower third of the ureter and is usually performed on an outpatient basis under general or local anesthesia. The surgeon passes a small ureteroscope through the bladder into the ureter to snare the stone. In some cases, the surgeon will shatter the stone using ultrasound, laser, or a technique called electrohydraulic lithotripsy. To relieve swelling and help with healing, the surgeon may place a small stent in the ureter for two to three days.
Parathyroid surgery is indicated when the stone is caused by overactive parathyroid glands. Usually a small benign growth in one of these glands causes it to be overactive, increasing the body’s calcium level. Removing the growth on the parathyroid gland cures the kidney stone problem in these patients.