What is a kidney stone?
Urine normally contains many dissolved substances. Occasionally, some materials may become concentrated in the urine and form solid crystals. These crystals can lead to the development of stones when materials continue to build up around them. Most common stones contain calcium with oxalate and/or phosphate. A less common type of stone is caused by an infection in the urinary tract.
Caucasians are more prone to develop kidney stones than African Americans. Although stones occur more frequently in men, the number of cases in women has been increasing over the past 10 years. Kidney stones most typically strike between the ages of 20 and 40 and can sometimes recur.
What are the symptoms of a kidney stone?
The most common symptom of a kidney stone is extreme pain that has been described as being comparable to "labor pains." Pain often begins suddenly as the stone moves in the urinary tract, causing irritation and blockage. Typically, a patient feels a sharp, cramping pain in the low back and side or in the lower abdomen, which may spread to the groin. A patient may also complain of blood in the urine, nausea, and/or vomiting.
Stones sometimes do not produce any symptoms at all. However, even if a stone is not large enough to prompt major symptoms, it can still trigger a dull ache that is often confused with muscle or intestinal pain.
If a stone is too large to pass easily, pain continues as the muscles in the wall of the tiny ureter try to squeeze the stone along into the bladder. The patient may feel the need to urinate more often or feel a burning sensation during urination. For men, pain may move down to the tip of the penis. If the stone is close to the lower end of the ureter at the opening into the bladder, a person will frequently feel like they have not fully completed urination.
If fever or chills accompany any of the above symptoms, then there may also be an infection present.
How are kidney stones diagnosed?
When a urinary stone is suspected, an immediate evaluation is required. Blood is tested to determine overall kidney function as well as to exclude signs of infection throughout the body. Urine is sent for a urinalysis and culture. An X-ray of the abdomen is sometimes enough to locate a calcification in the area of the kidneys or ureters.
If the X-ray does not provide enough information to make a diagnosis, an intravenous pyelogram (IVP) or abdominal/pelvic CT scan may be performed. The IVP is an imaging technique that uses radiopaque injections of dye followed, during kidney excretion, by abdominal X-rays. An abdominal/pelvic CT scan is an extremely accurate diagnostic tool that can detect almost all types of kidney stones painlessly.
How are kidney stones treated?
Treating kidney stone disease depends largely on the size, position and number of stones. The majority of small stones (0.2 inch or 5 mm in diameter) that are not causing infection, blockage or symptoms can be flushed from the body by drinking plenty of fluids (2 to 3 quarts per day). Once a stone has passed, no other treatment is typically necessary. The doctor may have the patient save the passed stone(s) for testing using a strainer. Pain related to passing kidney stones is commonly treated with bed rest and analgesics or painkillers.
Shock wave lithotripsy (SWL) is the most frequently used procedure for eliminating larger kidney stones. It works by directing ultrasonic or shock waves to break the stones down into sand-like particles, which are easily passed through the urinary tract.
Ureteroscopy (URS) may be needed for mid- and lower-ureteral stones. Ureteroscopy involves the use of small fiber-optic "telescopes" that can be inserted up the urethra, through the bladder and into the ureter without an incision. These instruments have small working channels through which various devices can be passed to remove or fragment the stone.
Percutaneous nephrolithotomy (PNL) is a surgical treatment for large stones located within the kidney that will not be effectively treated with either SWL or URS. General anesthesia is required to perform a PNL. The urologist places a guide wire through a small incision. The wire is then inserted into the kidney under fluoroscopic guidance and directed down the ureter. A passage is created around the wire using dilators to provide access into the kidney. A nephroscope is then passed into the kidney to visualize and remove the stone. For larger stones, a type of energy probe (ultrasonic, electrohydraulic or hydraulic) may be needed to break the stone into small pieces.