What Are Kidney Stones?
Kidney stones, or renal calculi, are solid masses made of crystals. Kidney stones originate in your kidneys, but can be found at any point in your urinary tract. The urinary tract includes the kidneys, ureters, bladder, and urethra.
Kidney stones are known to be one of the most painful medical conditions. The causes of kidney stones vary according to the type of stone. National Institute of Diabetes and Kidney Disease reports that about 1 million people in the United States are treated for kidney stones each year (NIDKD).
Types of Kidney Stones
Not all kidney stones are made up of the same crystals. The different types of kidney stones include:
Calcium stones are the most common. They can be made of calcium oxalate (most common), phosphate, or maleate. Vitamin C and spinach contain oxalate. Calcium-based kidney stones are most commonly seen in young men between the ages of 20 and 30.
This type of kidney stone is more common in men than in women. They can occur in people with gout or those going through chemotherapy.
This type of stone is found mostly in women with urinary tract infection. These stones can be quite large and cause urinary obstruction.
Cystine stones are rare. They occur in both men and women who have the genetic disorder cystinuria.
Medications like triamterene and acyclovir also can cause stones.
Risk Factors for Kidney Stones
The greatest risk factor for developing kidney stones is making less than one liter of urine per day. This why they are frequently seen in premature infants, who tend to have kidney problems. However, kidney stones are most likely to occur between the ages of 20 and 40. Other risk factors include:
- ethnicity (Caucasians are more likely to have kidney stones than African-Americans)
- sex (although kidney stones are most often seen in men, the incidence in women is increasing)
- past history of kidney stones (once someone has kidney stones, the likelihood of having another episode increases)
- family history of kidney stones
- dehydration (dehydration causes decreased urine flow, which increases risk significantly)
- high-protein, salt, or glucose diet
- gastric bypass surgery
- inflammatory bowel diseases (which can cause increase calcium absorption)
- other medical conditions (hyperparathyroidism can cause increase absorption of calcium and phosphorus; renal tubular acidosis can also be a risk factor for kidney stones)
Recognizing the Symptoms and Signs of a Kidney Stone
Kidney stones are known to cause severe pain. Symptoms of kidney stones may not occur until the stone begins to move down the ureters. The severe pain is called renal colic. Pain may be located on one side of your back or abdomen. In men, pain may radiate to the groin area. The pain of renal colic comes and goes, but is quite intense. People with renal colic tend to be restless. Other symptoms that can be present are:
- blood in the urine
- discolored or foul-smelling urine
Why Kidney Stones Can Be a Problem
Stones don’t always stay in the kidney. Sometimes, they pass from the kidney into the ureters. Ureters are small and delicate, and the stones may be too large to pass smoothly down the ureter to the bladder. Passage of stones down the ureter can cause spasms and irritation of the ureters as they pass, which causes blood to appear in the urine.
Sometimes stones block the flow of urine. This is called a urinary obstruction. Urinary obstructions can lead to kidney infection (pyelonephritis) and kidney damage.
Testing for and Diagnosing Kidney Stones
Diagnosis of kidney stones requires a complete health history assessment and a physical exam. Other tests include:
- blood tests for calcium, phosphorus, uric acid and electrolytes
- blood urea nitrogen (BUN) and creatinine to assess kidney functioning
- urinalysis to check for crystals, bacteria, blood, and white cells
- examination of passed stones to determine type
The following tests can rule out obstruction:
- abdominal X-rays
- intravenous pyelogram (IVP)
- retrograde pyelogram
- ultrasound of the kidney
- MRI of the abdomen and kidneys
- abdominal CT scan
How Kidney Stones Are Treated
Treatment is tailored according to the type of stone. Urine can be strained and stones can be collected for evaluation. Drinking six to eight glasses of water a day increases urine flow. People who are dehydrated or have severe nausea and vomiting may need intravenous fluids. Other treatment options include:
Pain relief may require narcotic medications. The presence of infection requires treatment with antibiotics. Other medications include:
- allopurinol for uric acid stones
- sodium bicarbonate or sodium citrate
- phosphorus solutions
Extracorporeal shock wave lithotripsy uses sound waves to break up large stones so they can more easily pass down the ureters into your bladder. This procedure can be uncomfortable and may require light anesthesia. It can cause bruising on the abdomen and back and bleeding around the kidney and nearby organs.
Tunnel Surgery (Percutaneous Nephrolithotomy)
Stones are removed through a small incision in your back and may be needed when:
- the stone causes obstruction and infection or is damaging the kidneys
- the stone has grown too large to pass
- pain cannot be controlled
When a stone is stuck in the ureter or bladder, your doctor may use an instrument called a ureteroscope to remove it. A small wire with a camera attached is inserted into the urethra and passed into the bladder. A small cage is used to snag the stone and remove it. The stone is then sent to the laboratory for analysis.
Hydration to Prevent Kidney Stones
Proper hydration is a key preventive measure. Johns Hopkins Medicine recommends drinking six to eight glasses of water daily (Johns Hopkins). You can substitute some glasses with ginger ale, lemon-lime soda, and fruit juice. Your doctor also may prescribe medications to help prevent the formation of calcium and uric acid stones.