kidney stones

(redirected from Magnesium Ammonium Phosphate)
Also found in: Acronyms.

Kidney Stones



Kidney stones are solid accumulations of material that form in the tubal system of the kidney. Kidney stones cause problems when they block the flow of urine through or out of the kidney. When the stones move along the ureter, they cause severe pain.


Urine is formed by the kidneys. Blood flows into the kidneys, and specialized tubes (nephrons) within the kidneys allow a certain amount of fluid from the blood, and certain substances dissolved in that fluid, to flow out of the body as urine. Sometimes, a problem causes the dissolved substances to become solid again. Tiny crystals may form in the urine, meet, and cling together to create a larger solid mass called a kidney stone.
Many people do not ever find out that they have stones in their kidneys. These stones are small enough to allow the kidney to continue functioning normally, never causing any pain. These are called "silent stones." Kidney stones cause problems when they interfere with the normal flow of urine. They can block (obstruct) the flow down the tube (the ureter) that carries urine from the kidney to the bladder. The kidney is not accustomed to experiencing any pressure. When pressure builds from backed-up urine, the kidney may swell (hydronephrosis). If the kidney is subjected to this pressure for some time, it may cause damage to the delicate kidney structures. When the kidney stone is lodged further down the ureter, the backed-up urine may also cause the ureter to swell (hydroureter). Because the ureters are muscular tubes, the presence of a stone will make these muscular tubes spasm, causing severe pain.
About 10% of all people will have a kidney stone in his or her lifetime. Kidney stones are most common among:
  • Caucasians
  • Males
  • People over the age of 30
  • People who have had kidney stones previously
  • Relatives of kidney stone patients

Causes and symptoms

Kidney stones can be composed of a variety of substances. The most common types of kidney stones include:
  • Calcium stones. About 80% of all kidney stones fall into this category. These stones are composed of either calcium and phosphate, or calcium and oxalate. People with calcium stones may have other diseases that cause them to have increased blood levels of calcium. These diseases include primary parathyroidism, sarcoidosis, hyperthyroidism, renal tubular acidosis, multiple myeloma, hyperoxaluria, and some types of cancer. A diet heavy in meat, fish, and poultry can cause calcium oxalate stones.
  • Struvite stones. About 10% of all kidney stones fall into this category. This type of stone is composed of magnesium ammonium phosphate. These stones occur most often when patients have had repeated urinary tract infections with certain types of bacteria. These bacteria produce a substance called urease, which increases the urine pH and makes the urine more alkaline and less acidic. This chemical environment allows struvite to settle out of the urine, forming stones.
  • Uric acid stones. About 5% of all kidney stones fall into this category. Uric acid stones occur when increased amounts of uric acid circulate in the bloodstream. When the uric acid content becomes very high, it can no longer remain dissolved and solid bits of uric acid settle out of the urine. A kidney stone is formed when these bits of uric acid begin to cling to each other within the kidney, slowly growing into a solid mass. About half of all patients with this type of stone also have deposits of uric acid elsewhere in their body, commonly in the joint of the big toe. This painful disorder is called gout. Other causes of uric acid stones include chemotherapy for cancer, certain bone marrow disorders where blood cells are over-produced, and an inherited disorder called Lesch-Nyhan syndrome.
  • Cystine stones. About 2% of all kidney stones fall into this category. Cystine is a type of amino acid, and people with this type of kidney stone have an abnormality in the way their bodies process amino acids in the diet.
Patients who have kidney stones usually do not have symptoms until the stones pass into the ureter. Prior to this, some people may notice blood in their urine. Once the stone is in the ureter, however, most people will experience bouts of very severe pain. The pain is crampy and spasmodic, and is referred to as "colic." The pain usually begins in the flank region, the area between the lower ribs and the hip bone. As the stone moves closer to the bladder, a patient will often feel the pain radiating along the inner thigh. In women, the pain may be felt in the vulva. In men, the pain may be felt in the testicles. Nausea, vomiting, extremely frequent and painful urination, and obvious blood in the urine are common. Fever and chills usually means that the ureter has become obstructed, allowing bacteria to become trapped in the kidney causing a kidney infection (pyelonephritis).


Diagnosing kidney stones is based on the patient's history of the very severe, distinctive pain associated with the stones. Diagnosis includes laboratory examination of a urine sample and an x-ray examination. During the passage of a stone, examination of the urine almost always reveals blood. A number of x-ray tests are used to diagnose kidney stones. A plain x ray of the kidneys, ureters, and bladder may or may not reveal the stone. A series of x rays taken after injecting iodine dye into a vein is usually a more reliable way of seeing a stone. This procedure is called an intravenous pyelogram (IVP). The dye "lights up" the urinary system as it travels. In the case of an obstruction, the dye will be stopped by the stone or will only be able to get past the stone at a slow trickle.
When a patient is passing a kidney stone, it is important that all of his or her urine is strained through a special sieve. This is to make sure that the stone is caught. The stone can then be sent to a special laboratory for analysis so that the chemical composition of the stone can be determined. After the kidney stone has been passed, other tests will be required in order to understand the underlying condition that may have caused the stone to form. Collecting urine for 24 hours, followed by careful analysis of its chemical makeup, can often determine a number of reasons for stone formation.


A patient with a kidney stone will say that the most important aspect of treatment is adequate pain relief. Because the pain of passing a kidney stone is so severe, narcotic pain medications (like morphine) are usually required. It is believed that stones may pass more quickly if the patient is encouraged to drink large amounts of water (2-3 quarts per day). If the patient is vomiting or unable to drink because of the pain, it may be necessary to provide fluids through a vein. If symptoms and urine tests indicate the presence of infection, antibiotics will be required.
Although most kidney stones will pass on their own, some will not. Surgical removal of a stone may become necessary when a stone appears too large to pass. Surgery may also be required if the stone is causing serious obstructions, pain that cannot be treated, heavy bleeding, or infection. Several alternatives exist for removing stones. One method involves inserting a tube into the bladder and up into the ureter. A tiny basket is then passed through the tube, and an attempt is made to snare the stone and pull it out. Open surgery to remove an obstructing kidney stone was relatively common in the past, but current methods allow the stone to be crushed with shock waves (called lithotripsy). These shock waves may be aimed at the stone from outside of the body by passing the necessary equipment through the bladder and into the ureter. The shock waves may be aimed at the stone from inside the body by placing the instrument through a tiny incision located near the stone. The stone fragments may then pass on their own or may be removed through the incision. All of these methods
Kidney stones can occur in the ureter near the bladder or kidney.
Kidney stones can occur in the ureter near the bladder or kidney.
(Illustration by Argosy Inc.)
reduce the patient's recovery time considerably when compared to the traditional open operation.

Alternative treatment

Alternative treatments for kidney stones include the use of herbal medicine, homeopathy, acupuncture, acupressure, hypnosis, or guided imagery to relieve pain. Starfruit (Averrhoa carambola) is recommended to increase the amount of urine a patient passes and to relieve pain. Dietary changes can be made to reduce the risk of future stone formation and to facilitate the resorption of existing stones. Supplementation with magnesium, a smooth muscle relaxant, can help reduce pain and facilitate stone passing. Homeopathy and herbal medicine, both western and Chinese, recommend a number of remedies that may help prevent kidney stones.


A patient's prognosis depends on the underlying disorder causing the development of kidney stones. In most cases, patients with uncomplicated calcium stones will recover very well. About 60% of these patients, however, will have other kidney stones. Struvite stones are particularly dangerous because they may grow extremely large, filling the tubes within the kidney. These are called staghorn stones and will not pass out in the urine. They will require surgical removal. Uric acid stones may also become staghorn stones.


Prevention of kidney stones depends on the type of stone and the presence of an underlying disease. In almost all cases, increasing fluid intake so that a person consistently drinks several quarts of water a day is an important preventative measure. Patients with calcium stones may benefit from taking a medication called a diuretic, which has the effect of decreasing the amount of calcium passed in the urine. Eating less meat, fish, and chicken may be helpful for patients with calcium oxalate stones. Other items in the diet that may encourage calcium oxalate stone formation include beer, black pepper, berries, broccoli, chocolate, spinach, and tea. Uric acid stones may require treatment with a medication called allopurinol. Struvite stones will require removal and the patient should receive an antibiotic. When a disease is identified as the cause of stone formation, treatment specific to that disease may lessen the likelihood of repeated stones.



American Foundation for Urologic Disease. 300 West Pratt St., Baltimore, MD 21201-2463. (800) 242-2383.
National Kidney Foundation. 30 East 33rd St., New York, NY 10016. (800) 622-9010.

kidney stones

Renal calculus, nephrolithiasis, kidney stone disease Urology Small irregular solid structures, often composed of calcium, uric acid, phosphate, found in the urine or ureters, which are a major cause of morbidity; up to 12% of those in developed nations have KS Clinical Renal colic–the worst pain ever experienced, hematuria, ureteral or renal pelvic obstruction, which may lead to hydronephrosis or facilitate infection Risk factors Familial tendency, prematurity, bowel disease, ileal bypass for obesity, renal tubule acidosis and nephrocalcinosis. See Gout, Oxaluriasis.
Kidney stone types
Calcium 75-85% of stones; more common in men, composed of calcium oxalate, carbonate or phosphate, controlled by altering diet
Uric acid More common in ♂; ± 50% of Pts with UA stones also have gout
Cystic acid Formed in Pts with cystinuria
Magnesium ammonium phosphate Struvite stones More common in ♀, due to bacterial–eg Proteus—spp which produce specific enzymes UTIs; MAP stones can be very large, fill renal pelvis, develop a staghorn appearance, obstruct urinary tract, and cause kidney damage

kidney stones

Crystallization out of various substances dissolved in the urine, especially during DEHYDRATION when the urine is most concentrated. Stone formation is promoted by infection or by any increase in the amount or character of substances dissolved in the urine. Some drugs can form stones, others can protentiate the formation of stones. Stones may occur in inherited disorders in which abnormal amounts of substances such as cystine and xanthine are excreted, but most kidney stones contain various combinations of calcium, magnesium, phosphorus, and oxalate. Uric acid stones tend to develop when the blood levels of this substance are abnormally high, as in gout.

kidney stones,

n precipitates of calcium salts, uric acid, or struvite that develop within the upper urinary tract or bladder. The presence of these materials within the body may not initially produce symptoms, but the progression of the condition may result in severe, sporadic pain that radiates from the kidney or flank region.


either of the two organs in the lumbar region that filter the blood, excreting the end-products of body metabolism in the form of urine, and regulating the concentrations of hydrogen, sodium, potassium, phosphate and other ions in the extracellular fluid. Bean-shaped in the dog, cat, sheep and laboratory animals, lobed in the ox and some fetal animals such as the horse; irregularly lobed in birds. See also renal.
Enlarge picture
Dog kidney. By permission from Sack W, Wensing CJG, Dyce KM, Textbook of Veterinary Anatomy, Saunders, 2002

artificial kidney
an extracorporeal device used as a substitute for nonfunctioning kidneys to remove endogenous metabolites from the blood, or as an emergency measure to remove exogenous poisons such as barbiturates. Called also hemodialyzer.
balloon kidney
meat hygiene term for cystic kidney.
basal lamina kidney
part of the filtration barrier of the kidney; is much thicker than most basal laminae.
cake kidney
a solid, irregularly lobed organ of bizarre shape, formed by fusion of the two renal anlagen. Called also lump kidney.
cicatricial kidney
a shriveled, irregular and scarred kidney due to suppurative pyelonephritis.
contracted kidney
an atrophic kidney that may be scarred and granular.
duplicate kidney
occurs in most species, without apparent increase in total renal mass.
enlarged kidney
may be due to polycystic kidney disease, hydronephrosis, pyelonephritis or congenital absence of one kidney resulting in hypertrophy of the other.
fatty kidney
one affected with fatty degeneration.
floating kidney
one that is freely movable, especially a human kidney (normally more firmly fixed than those in quadrupeds); called also hypermobile kidney. See also nephroptosis.
Enlarge picture
Bovine kidney. By permission from Sack W, Wensing CJG, Dyce KM, Textbook of Veterinary Anatomy, Saunders, 2002
fused kidney
a single anomalous organ developed as a result of fusion of the renal anlagen.
giant kidney worm
Goldblatt kidney
one with obstruction of its blood flow, resulting in renal hypertension. Produced experimentally in dogs.
horseshoe kidney
an anomalous organ resulting from fusion of the corresponding poles of the renal anlagen.
hypermobile kidney
one that is freely movable; called also floating kidney. See also nephroptosis.
lump kidney
cake kidney.
kidney meridian points
acupuncture points on the kidney meridian.
pelvic kidney
a kidney which has failed to ascend from its primordial site to the roof of the abdomen.
polycystic kidney disease
the most common congenital renal defect but most cases are sporadic and do not cause clinical illness because there is still sufficient renal mass to avoid uremia. In some cases the enlarged kidney is detected incidentally during a clinical examination. Rarely both kidneys are badly involved and the animal is dead at birth or dies soon afterwards. In some cases, there are signs of progressive renal failure, perhaps not until later in life. The defect is inherited in Persian cats, Cairn terriers and pigs. In Cairn terriers, cysts may also occur in the liver. See also feline perirenal cysts.
pulpy kidney disease
see Clostridium perfringensenterotoxemia.
kidney scan
radioimaging of a kidney by the use of a rectilinear scanner after the intravenous administration of a radiopaque material.
kidney stones
supernumerary kidney
additional kidneys which develop as a consequence of two ureteric buds arising from one mesonephric duct so that two kidneys develop on the one side.
kidney transplant
commonly and successfully performed in experimental dogs. Increasingly used as a therapeutic procedure in clinical veterinary medicine for renal failure in cats and dogs.
turkey egg kidney
a speckled pattern caused by hemorrhagic glomeruli in diseases such as porcine erysipelas.
wandering kidney
floating or hypermobile kidney. See also nephroptosis.
waxy kidney
amyloid kidney.
white-spotted kidney
focal nonsuppurative interstitial nephritis, seen most commonly in calves.

Patient discussion about kidney stones

Q. Why do i get kidney stones? I am 38 and have had three stones pass so far. Is it the coffee, the meat, the stress, or the damned DNA?! My uncle is in his 50s and has passed over 30 stones!

A. Kidney stones are very common and even without the genetic or familial background people tend to get them. Of course, the more family predisposition you have, the higher are your chances of developing them, which is probably why you did. Also, a diet rich with dairy and calcium can cause your body to store excess calcium, that tends to calcify and create stones. Not drinking enough fluid is also one of the reasons.

Q. Would kidney stones affect a PSA reading? Would drinking lots of grapefruit juice affect a PSA reading? My husband's PSA reading jumped from a 4.2 to a 17 in @ 2 years' time. How can that be? This man takes all sorts of supplements and really watches his diet. He also takes good care of his body, and does NOT look or act 68.

A. You should get your parathyroid gland checked out. Your calcium level might be causing the kidney stones.

Q. How can i overcome kidney ache? in the morning it appears.after wake up.

A. First of all, it is important to distinguish kidney ache from lower back ache. If you have ever suffered from kidney problems or infections, it might be advisable to see a doctor, and rule out an infection. However, if you are otherwise healthy, and have been experiencing back pain after you wake up, it is very much possible your pain is not from the kidneys, but from the muscles of your back. In this case, some exercise on a daily basis to help strengthen your lower back can very much ease the pain you're experiencing.

More discussions about kidney stones
References in periodicals archive ?
Struvite uroliths belong to the magnesium ammonium phosphate (MAP) category.
The Penticton trial showcased how a magnesium ammonium phosphate fluidized bed crystallizer could prevent this outcome.
Among the organizers of the event was Don Mavinic, the UBC civil engineer who spearheaded the early work on magnesium ammonium phosphate crystallization.
Most calculi contain magnesium ammonium phosphate, while others contain calcium phosphate, cosine, oxalate, orate and silica.
1] + Urea equivalent to nitrogen of MAP; MAP = Magnesium ammonium phosphate.