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Kidney Stones

Description

An in-depth report on the causes, diagnosis, treatment, and prevention of kidney stones.

Alternative Names

Calcium Stones; Extracoporeal Shock Wave Lithotripsy; Lithotripsy; Nephrolithiasis; Oxalates; Uric Acid

Other Treatments

Surgery is usually needed if the stone is too large to pass on its own, if there are indications that it is growing, or if it is blocking the urine flow and causing urinary tract infection or damaging the kidney. Until recently, the procedure to remove a stone was a very painful, major surgery that required a four- to six-week recovery period. Today, treatments for stones are much less invasive and major surgery is performed in less than 2% of patients.

The primary methods of stone removal are the following:

  • Extracorporeal shock wave lithotripsy (ESWL). In general, ESWL is the first choice for small stones (less than one centimeter) in the upper ureter. (One 2000 trial attempted to determine whether ESWL offered any advantage for treating very small stones that caused no symptoms; no benefit was detected.)
  • Percutaneous nephrolithotomy (PNL). PNL can be used for very large stones in the upper tract, when ESWL fails, for kidney transplant patients, or when there are structural abnormalities in the kidney or surrounding area. It is the preferred procedure for drug-resistant cystine stones, which are usually resistant to shock wave therapy. For small staghorn calculi in normal or near normal kidneys, either ESWL or PNL is usually effective. For complicated conditions involving staghorn calculi, however, experts usually recommend PNL followed by ESWL (called a sandwich procedure) or a repeat PNL procedure.
  • Ureteroscopy. For stones in the lower tract, ureteroscopy is generally the best procedure, although lithotripsy is also usually feasible and patients ordinarily prefer it.
  • Standard open surgery (nephrolithotomy) may be required if any of these procedures fail or are not appropriate, or in special cases, such as when the patient is very obese.

Most procedures are more effective for calcium and uric acid stones and less effective for struvite and cystine stones, although new techniques may be improving their effects on all stones.

Extracorporeal Shock Wave Lithotripsy

Extracorporeal shock wave lithotripsy (ESWL) is the most frequently used procedure for destroying and removing simple stones located in the kidney or upper urinary tract, including struvite stones. ESWL is not used for cystine stones. It is generally not successful for stones larger than three centimeters in diameter (which is slightly over an inch).

All ESWL procedures deliver shock waves from outside the body to break the stones. ("Extracorporeal" means "outside the body" and "lithotripsy" means stone-breaking.) There are several variations. The following is a typical procedure:

  • Most ESWL procedures use some anesthesia, although they are often done on an outpatient basis.
  • The patient is positioned in a water bath. (In some procedures the patient lies on a soft cushion.)
  • The procedure uses ultrasound to generate shock waves that travel through the skin and body tissues until they hit the dense stones. (X-rays or ultrasound are used to help the surgeon pinpoint the stone during treatment.)
  • The stones are crushed into tiny sand-like pieces that usually pass easily through the urinary tract.
  • The shattered stone fragments may cause discomfort as they pass through the urinary tract. In such cases, the doctor may insert a small tube called a stent through the bladder into the ureter to help the fragments pass. This practice, however, has not proved to speed up passage of the stones in most cases and is not used routinely.
Lithotripsy procedure
Extracorporeal shock wave lithotripsy (ESWL) is a procedure used to shatter simple stones in the kidney or upper urinary tract. Ultrasonic waves are passed through the body until they strike the dense stones. Pulses of sonic waves pulverize the stones, which are then more easily passed through the ureter and out of the body in the urine.

Success rates range from 50% to 90% depending on the location of the stone and the surgeon's technique and level of experience. Recovery time is short, and most people can resume normal activities in a few days.

Complications. Complications may include the following:

  • The most common complication is blood in the urine, which lasts for a few days after treatment. To reduce the chances of bleeding, doctors usually tell patients to avoid taking aspirin and other NSAIDs, which can promote bleeding, for seven to 10 days before the treatment.
  • Bruising and minor discomfort due to the shock waves are common in the back or abdomen.
  • Sometimes the stone is not completely fragmented with one treatment, and additional treatments then may be required. Inability to pass stone fragments may also be a particular problem in patients who have cysts or other kidney abnormalities.
  • Its safety for small or abnormal kidneys is not fully known. For example, ESWL appears to be safe for children, although a 2001 study reported temporary damage in the kidney tubules after treatment. It is not known if this complication has any long-term consequences. Experts recommend minimizing as much as possible the impact and number of shocks in young people. If more than one treatment is needed, there should be a waiting period of at least 15 days.

Percutaneous Nephrolithotomy

Percutaneous nephrolithotomy may be used when ESWL is not available or effective (e.g., if the stone is very large, in an inaccessible location, or is a cystine stone). It is also preferred over ESWL for stones that have remained in the ureter for more than four weeks.

It is more effective that ESWL for patients with severe obesity and appears to be safe for the very elderly and the very young. Success rates have been reported to be about 98% for kidney stones and 88% for ureteral stones. They may vary according to the technique and patient group. For example, success rates are slightly lower in children, although the procedure can be done safely in young patients. Long-term effects are unknown.

A typical procedure is as follows:

  • The surgeon makes a tiny incision in the back and creates a tunnel directly into the kidney.
  • The surgeon then inserts an instrument called a nephroscope through the tunnel.
  • The stone is located and removed. If it is large it is destroyed using ultrasound, lasers, or other devices and the fragments are then removed. (An advantage of percutaneous nephrolithotomy over ESWL is that the surgeon is able to remove the stone fragments directly instead of relying on their natural passage from the kidney.)
  • Generally, patients stay in the hospital for five or six days and may need a small device called a nephrostomy tube left in the kidney during the healing process.

Devices Used to Destroy Stones. For large stones, some type of energy device may be needed to break the stone into small pieces. They are referred to as intracorporeal lithotripsy devices (meaning stone breakers within the body). The energy source may be one of the following:

  • Ultrasound is employed through a rigid nephroscope and results in a stone-free rate of 94%. It is currently the preferred method.
  • A more recent device uses a combination pneumatic drill and ultrasound with stone-free rates of 80% to 89%. It may be prove to be superior to ultrasound alone and to be effective against stones of all types.
  • The holmium laser literally melts the stones and destroys up 100% of stones of any composition. It uses a flexible nephroscopy and has an excellent safety record. It should be used sparingly, however, and particularly cautiously with large uric acid stones until more is understood about this effect. Another device, the erbium:YAG laser, is showing promise in lithotripsy but is not currently practical.

Complications. Complication rates are about 3%, with major complications occurring in about 1% of cases. Some scarring occurs, but studies indicate that it does not impair kidney function, even if the patient requires repeat surgery. The procedure also poses a risk for blood loss during and after the procedure, which, in some cases, can be significant. Because large volumes of fluid are used during the procedure, fluid overload is a potential problem, particularly in children or patients with heart disease. In some cases infection may result. Other complications encountered are collapsed lung and injuries to areas outside the kidney but within the operative area, such as the abdomen or chest.

Ureteroscopic Stone Removal

Ureteroscopy may be used for mid- and lower ureter stones. With the advent of smaller instruments, it is also now being done successfully in children as well. The procedure involves the following:

  • No incision is made in this procedure, but a general anesthetic is still required.
  • The surgeon passes a small fiberoptic instrument called a ureteroscope through the urethra and bladder into the ureter.
  • The surgeon then locates the stone or stones.
  • Smaller ones are grasped and removed with tiny forceps. Large ones are shattered with lasers or pneumatic drill-like devices.
  • A small tube, or stent, may be left in the ureter for a few days after treatment to help the lining of the ureter heal.

Complication rates range from 10% to 20%, with major problems occurring in between 0% and 6% of patients. In some cases, large stones are not broken up into small enough pieces that can be passed, resulting in obstruction of the urinary tract and possible kidney damage. Imaging tests such as ultrasound or spiral CT are useful within three months to check for residual stones, and a second procedure may be required. The risk of complications is highest when the procedure is performed by less experienced surgeons and if stones are found in the kidney. The risk for perforation of the ureter is higher the longer the operative time.

Open Surgery (Nephrolithotomy)

Open surgery involves incisions through the patient's flank and into the kidney. The kidneys are cooled down using ice. X-rays are used during the procedure to locate specific areas and the stone. The arteries in the kidney are identified and isolated away from the surgical region. The surgeon locates the collecting system and retrieves the stone. If the surgeon finds any blockage, this is corrected. The surgery is very invasive and is now restricted to the following candidates:

  • Patients with very large or complex stones that cannot be removed using less invasive measures.
  • Very obese patients. Some centers report success with lithotripsy, however, in this patient group, so even these patients should discuss other options with their surgeon.

The procedure is not appropriate for the following patients:

  • Those with bleeding or clotting disorders.
  • Those with untreated widespread infection.
  • Those with severe and chronic kidney insufficiency (unless removing the stone will improve kidney function).
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