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Friday, March 26, 2010

Kidney Stones



[Extracted from the website of www.emedicinehealth.com]

The kidney acts as a filter for blood, making urine and removing waste products from the body. It also helps regulate electrolyte levels that are important for body function. Urine drains from the kidney into the bladder through a narrow tube called the ureter. When the bladder fills and there is an urge to urinate, the bladder empties through the urethra, a much wider tube than the ureter.

In some people, chemicals crystallize in the urine and form the beginning, or nidus, of a kidney stone. These stones are very tiny when they form, smaller than a grain of sand, but gradually can grow over time to a 1/10 of an inch or larger. Urolithiasis is the term that refers to the presence of stones in the urinary tract, while nephrolithiasis refers to kidney stones. The size of the stone doesn't matter as much as where it is located.

When the stone sits in the kidney, it rarely causes problems, but when it falls into the ureter, it acts like a dam. As the kidney continues to function and make urine, pressure builds up behind the stone and causes the kidney to swell. This pressure is what causes the pain of a kidney stone, but it also helps push the stone along the course of the ureter. When the stone enters the bladder, the obstruction in the ureter is relieved and the symptoms of a kidney stone are resolved.

Causes

There is no consensus as to why kidney stones form.

* Heredity : Some people are more susceptible to forming kidney stones, and heredity may play a role. The majority of kidney stones are made of calcium, and hypercalciuria (high levels of calcium in the urine) is a risk factor. The predisposition to high levels of calcium in the urine may be passed on from generation to generation. Some rare hereditary diseases also predispose some people to form kidney stones. Examples include people with renal tubular acidosis and people with problems metabolizing a variety of chemicals including cystine (an amino acid), oxalate, (a type of salt), and uric acid (as in gout).

* Geographical location : There may be a geographic predisposition to form kidney stones. There are regional "stone belts," with people living in the southern United States, having an increased risk of stone formation. The hot climate and poor fluid intake may cause people to be relatively dehydrated, with their urine becoming more concentrated and allowing chemicals to come in closer contact to form the nidus, or beginning, of a stone.

* Diet : Diet may or may not be an issue. If a person is susceptible to forming stones, then foods high in calcium may increase the risk; however, if a person isn't susceptible to forming stones, diet will not change that risk.

* Medications : People taking diuretics (or "water pills") and those who consume excess calcium-containing antacids can increase the amount of calcium in their urine and potentially increase their risk of forming stones. Taking excess amounts of vitamins A and D are also associated with higher levels of calcium in the urine. Patients with HIV who take the medication indinavir (Crixivan) can form indinavir stones. Other commonly prescribed medications associated with stone formation include dilantin and antibiotics like ceftriaxone (Rocephin) and ciprofloxacin (Cipro).

* Underlying illnesses : Some chronic illnesses are associated with kidney stone formation, including cystic fibrosis, renal tubular acidosis, and inflammatory bowel disease.

Symptoms and Signs

When a tubular structure is blocked in the body, pain is generated in waves as the body tries to unblock the obstruction. These waves of pain are called colic. This is opposed to non-colicky type pain, like appendicitis or pancreatitis, in which movement causes increased pain and affected people hold very still.

* Renal colic (renal is the medical term for things related to the kidney) has a classic presentation when a kidney stone is being passed.

o The pain is intense and comes on suddenly. It may wax and wane, but there is usually a significant underlying ache between the acute spasms of pain.

o It is usually located in the flank or the side of the mid back and radiates to the groin.

o Those affected cannot find a comfortable position, and many writhe in pain.

* Sweating, nausea, and vomiting are common.

* Blood may be visible in the urine because the stone has irritated the ureter. Blood in the urine (hematuria), however, does not always mean a person has a kidney stone. There may be other reasons for the blood, including kidney and bladder infections, trauma, or tumors. Urinalysis with a microscope may detect blood even if it is not appreciated by the naked eye. Sometimes, if the stone causes complete obstruction, no blood may be found in the urine because it cannot get past the stone.

Exams and Tests

The classic presentation of renal colic associated with blood in the urine suggests the diagnosis of kidney stone. Many other conditions can mimic this disease, and the physician or health-care provider may need to order tests to confirm the diagnosis. One example is that pain radiating to the back, may cause the health-care provider to be concerned about the possibility of a leaking abdominal aortic aneurysm.

Physical examination is often not helpful in patients with kidney stones, aside from the finding of flank (side of the body between the ribs and hips) tenderness. The examination is often directed to ensuring that other potentially dangerous conditions are not present. As examples, when examining the abdomen, the physician may look for a palpable mass that pulsates, which may be a sign of an aortic aneurysm. Tenderness under the right rib cage margin may signal gallbladder disease. Tenderness in the lower quadrants may be associated with appendicitis, diverticulitis, or ovarian disease.

Symptom control is very important, and medication for pain and nausea may be provided before the confirmation of the diagnosis occurs.

A urinalysis may detect blood in the urine. It is also done to look for evidence of infection, a complication of kidney stone disease.

Blood tests are usually not indicated, unless the health-care provider has concerns about the diagnosis or is worried about kidney stone complications.

Computerized tomography (CT) scanning of the abdomen without oral or intravenous contrast dye is the most commonly used diagnostic test. The scan will demonstrate the anatomy of the kidneys, ureter, and bladder and can detect a stone, its location, its size, and whether it is causing dilation of the ureter and inflammation of the kidney. The CT can also evaluate many other organs in the abdomen, including the appendix, gallbladder, liver, pancreas, aorta, and bowel. However, since no contrast material is used, there are some limitations to the detail that can be observed in the images of the scan.

Ultrasound is another way of looking for kidney stones and obstruction and may be useful when the radiation risk of a CT scan is unwanted (for example, if a woman is pregnant). Ultrasound requires a specially trained person to obtain the images, and therefore, it may not always be available.

In those patients who already have the diagnosis of a kidney stone, plain abdominal X-rays may be used to track its movement down the ureter toward the bladder.

Medical Treatment

* In the emergency department, intravenous fluids may be provided to help with hydration and to allow the administration of medications to control pain and nausea. Ketorolac (Toradol), an injectable antiinflammatory drug, and narcotics may be used for pain control, with the goal being to relieve suffering and not necessarily to make the patient pain free. Nausea and/or vomiting may be treated with antiemetic medications like ondansetron (Zofran), promethazine (Phenergan), or droperidol (Inapsine).

* The decision to send a patient home will depend upon the response to medication. If the pain is intractable (hard to control) or if vomiting persists, then admission to the hospital is necessary. Also, if an infection is associated with the stone, then admission to the hospital will be considered.

* Pain control at home follows the lead of the hospital treatment. Over-the-counter (OTC) ibuprofen is used as an antiinflammatory medication, and narcotic pain pills may be provided. Anti-nausea medication may be prescribed either by mouth or by suppository. Tamsulosin (Flomax, a drug used to facilitate urination in men with enlargement of the prostate) may be used to help facilitate the passage of stones into the bladder.

* Because of their size or location, some stones may not be able to be passed without help. If the stone is high up in the ureter, near the kidney, and is large, then a urologist may need to consider using lithotripsy, or shock wave therapy (EWSL), to break the stone up into fragments to allow the smaller pieces to pass into the bladder. Shock waves work by vibrating the urine surrounding the stone and causing the stone to break up. Stones that are lodged nearer the bladder do not have surrounding urine to allow this procedure to work successfully.

* If the stone is not located in a place where lithotripsy can work or if there is a need to relieve the obstruction emergently (an example would include the presence of an infection), the urologist may perform ureteroscopy, in which instruments are threaded into the ureter and can allow the physician to place a stent (a thin hollow tube) through the urethra, past the bladder, and into the ureter to bypass the obstructing stone. This stent may be left in place for a longer period of time. Occasionally, the urologist may be able to use instruments to grab the stone and remove it.

Complications

* Since most patients have two kidneys, a temporary obstruction of one is not of great significance. For those patients with only one kidney, an obstructing stone can be a true emergency, and the need to relieve the obstruction becomes greater. A kidney that remains completely obstructed for a prolonged period of time may stop working.

* Infection associated with an obstructing stone is another emergent situation. When urine is infected and cannot drain, it acts like an abscess and can spread the infection throughout the body (sepsis). Fever is a major sign of this complication, but urinalysis may show an infection and cause the urologist to decide to place a stent or remove the stone.

Follow-up

* For the first-time kidney stone patient, there should be an attempt to catch the stone by straining the urine, so that it can be sent for analysis. The stone may be so tiny that it may not be recognized. While most stones are made of calcium oxalate, stones can also consist of other chemicals. It may be possible to prevent future stone formation by taking medications. For those whose stone disease is recurrent and the kind of stone is known, this instruction is often omitted.

* Drinking plenty of water will help push the stone down the ureter to the bladder and hasten its elimination.

* A follow-up visit with a urologist may be arranged one to two weeks after the initial visit, allowing the stone to pass on its own.

* Patients should call their physician or return to the emergency department if the pain medication is not working to control the pain, if there is persistent vomiting, or if a fever occurs.

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