Causes, incidence, and risk factors
Kidney stones can form when urine contains too much of certain substances. These substances can create small crystals that become stones.
The biggest risk factor for kidney stones is dehydration.
Kidney stones may not produce symptoms until they begin to move down the tubes (ureters) through which urine empties into the bladder. When this happens, the stones can block the flow of urine out of the kidneys. This causes swelling of the kidney or kidneys, causing pain. The pain is usually severe.
Kidney stones are common. A person who has had kidney stones often gets them again in the future. Kidney stones often occur in premature infants.
Some types of stones tend to run in families. Certain kinds of stones can occur with bowel disease, ileal bypass for obesity, or renaltubule defects.

types of stones
There are different types of kidney stones. The exact cause depends on the type of stone.
• Calcium stones are most common. They occur more often in men than in women, and usually appear between ages 20 - 30. They are likely to come back. Calcium can combine with other substances, such as oxalate (the most common substance), phosphate, or carbonate to form the stone. Oxalate is present in certain foods. Diseases of the small intestine increase the risk of forming calcium oxalate stones.
• Cystine stones can form in people who have cystinuria. This disorder runs in families and affects both men and women.
• Struvite stones are mostly found in women who have a urinary tract infection. These stones can grow very large and can block the kidney, ureter, or bladder.
• Uric acid stones are more common in men than in women. They can occur with gout or chemotherapy.
Other substances also can form stones.

Symptoms
The main symptom is severe pain that starts suddenly and may go away suddenly:
• Pain may be felt in the belly area or side of the back
• Pain may move to groin area (groin pain) or testicles (testicle pain)
Other symptoms can include:
• Abnormal urine color
• Blood in the urine
• Chills
• Fever
• Nausea
• Vomiting

Nephrolithiasis Diagnosis
Clinical presentation is highly specific for kidney stones, especially in patients with a history of the condition.

Noncontrast abdominal CT scan is the preferred test to detect stones and urinary tract obstructions. Abdominal x–ray (kidney–ureter–bladder film) will identify many radiopaque stones, but will not detect small or radiolucent stones or urinary tract obstructions.

The intravenous pyelogram has largely been replaced by abdominal CT scan. While the intravenous pyelogram has high sensitivity and specificity for detecting stones, its use is restricted by the risk of contrast reactions and by the fact that evaluation time is very limited when obstruction is present.

Ultrasound is used in patients who should avoid radiation, including pregnant women.

Urinalysis will usually reveal hematuria.

If a stone is passed, it should be sent to the laboratory for analysis.

Treatment
Immediate urologic attention is necessary for patients who present with fever, renal failure, intractable pain, persistent nausea, or urinary tract infections.

Small (<5 mm) stones will often pass spontaneously, and increased fluid intake will facilitate stone passage. In some cases, tamsulosin (Flomax) or an alpha blocker (eg, terazosin) can also facilitate stone passage. Nonsteroidal anti–inflammatory drugs (NSAIDs) or narcotics may be administered for pain. However, urologists may prefer not to use NSAIDs because of the increased risk of bleeding in the event that the patient should need urteroscopy or shock wave lithotripsy.

About 10% to 20% of stones require surgical removal. Minimally invasive surgical techniques include shock wave lithotripsy, percutaneous nephrostolithotomy, and ureteroscopy. Open renal and ureteral surgery is necessary for stone removal in about 1% of cases