Renal Stones (Kidney Stones, Renal Calculi)

The kidneys are bean-shaped organs, each about the size of a clenched fist. They are located in the middle of the back, just below the rib cage, one on each side of the spine. The kidneys are sophisticated filtration machines. Every day, a person's kidneys process about 200 quarts of blood to sift out about 2 quarts of waste products and extra water. The wastes and extra water become urine, which flows to the urinary bladder through tubes called ureters. The bladder stores urine until it releases it when a person urinates. The kidneys are primarily responsible for filtering metabolites and minerals from the blood circulation.

There are many potential causes of kidney stone formation. In general, they are the result of a superconcentration of chemicals in the urine which form crystals and finally stones / calculi.

A disorder in metabolism, dietary habit, dehydration, recurrent urinary tract infection and / or blockage of the urinary tract could alter your urine concentration :

• A positive family history (genetic tendency) also makes a person prone to kidney stone formation. Hereditary factors also play a strong role. Hypercalciuria (where there is excess of calcium excreted in urine) is also a genetically acquired factor which leads to frequent development of kidney stones.
• Metabolism : Metabolic disorders are one of the main causes of kidney or renal stones. The body is not able to assimilate the minerals and salts such as calcium, uric acid or other salts in the blood. Metabolism is commonly impaired in endocrine disorders such as hyperparathyroidism, certain diseases like ulcerative colitis and regional enteritis. In gouty arthritis, the high level of uric acid in the urine can act as a breeding ground for calcium oxalate stones. On the whole, the formation of kidney or renal stones is a complex process.
• Dietary habits : Diet contributes a part in the formation of renal or kidney stones and is considered a major maintaining cause. Clinically, it is observed that too much of a particular food promotes kidney or renal stones. A pregnant woman was advised to take plenty of 'greens' to raise iron in the blood, and she developed renal or kidney stones which came into light because of an acute renal colic (pain). Similarly, a patient who had an abnormal craving for 'tomatoes' is now on treatment for renal calculi or kidney stones. Habits like 'betel chewing' with lime, should also be considered as probable causes.
  Certain foods that increase the risk for kidney or renal stones in susceptible individuals include spinach, strawberries, tomatoes, grapefruit juice, apple juice, soda, and all types of teas and berries.
  An imbalance of vitamins and minerals can increase the amount of calcium oxalate in the urine; when the levels become too high, the calcium oxalate does not dissolve and crystals may begin to form.
• Inadequate intake of fluids : Some people do not take sufficient water and fluids. In some people, living in areas with a high temperature causes sweating and loss of fluids. The above may lead to long-term dehydration, resulting in concentration of urine, which further leads to over concentration of metabolic byproducts in the urine.
• Infection : Chronic urinary tract infection (UTI) may predispose a person to stone formation. The slough and the crusts which result following an infection, would combine with high levels of minerals and salts to form stones. This is considerably noted in the formation of vesical calculus after chronic cystitis.
• Urinary obstruction : Urinary bloackage as in prostate enlargement, stricture urethra and limited activity for several weeks will predispose a person to stone formation through sedimentation. Prostatic enlargement invariably causes stones in many patients.
• Patients with inflammatory bowel disease or who have had an intestinal bypass or ostomy surgery are also more likely to develop kidney stones.
• Some medications also raise the risk of kidney stones which include diuretics, calcium containing antacids and crixivan - a drug used to treat HIV infection.

• Calcium oxalate stones : These kidney stones are very common and are found in many patients. Most of these patients have inheritated metabolic disorders, which cause increased presense of calcium in the urine.
  Consumption of low calcium diets is actually associated with a higher risk for the development of kidney stones. This is perhaps related to the role of calcium in binding ingested oxalate in the gastrointestinal tract.
• Uric acid stones : These stones are not visible on X-rays. Patients with gout often develp uric acid stones.
• Cystine stones : These type of renal stones develop due to excessive amounts of amino acid cystine in the urine. Cystinuria is an inherited condition and is uncommon.
• Silicate, struvite and xanthine stones are rare.

A stone may quietly grow for years together and may remain silent for many years. Often, it is an incidental finding in a routine screening for other illness/es. A kidney stone can cause problems in 2 ways :

• when it moves or
• when it grows so large that it begins to disupt kidney function and cause damage

After keeping silent for sometime, the stone may start to move downwards, drawn by the urine and gravity. When the stone makes its run for freedom, it hurts the patient with severe abdominal pain with or without nausea and vomiting causing :

• Colicky pain : The pain is 'loin to groin'. The pain may be felt over the back or on one side, radiates to the groin, scrotum in men and the labia in women. It is often described as 'the worst pain' ever experienced, even more painful than gunshot, surgery, fractured bones and so on.
• Haematuria : Blood in the urine which may look pink or orange.
• Pyuria : Pus in the urine. Cloudy or foul-smelling urine.
• Dysuria : Buring pain on urination; more typical with associated infection.
• Oliguria : Reduced urinary volume caused by obstruction of the bladder or urethra by a stone.
• Frequent urge to urinate.
• Abdominal distension.
• Nausea or vomiting.
• Fever and chills.
• Profuse sweating.

• An X-ray of the kidneys, ureter and bladder (KUB) or an ultrasonography (USG) of the kidneys, ureter and bladder (KUB) can reveal the presense of most stones.
• Intravenous pyelograms.
• Blood tests, 24 hour urine samples, provocative calcium loading tests and stone analysis to determine the type of stone, its underlying cause and proper course of treatment.

• Drink at least 3 litres of water every day and even more in hot weather.
• Avoid or eat sparingly, food containing calcium oxalate (spinach, strawberries, tomatoes, grapefruit juice, apple juice, chocolate, celery, bell peppers, beans, asparagus, beets, soda, and all types of teas and berries).
• Reduce uric acid by eating a low-protein diet.
• Reduce salt; higher amounts may raise the level of calcium oxalate in your urine.
• Avoid vitamin D supplements which can increase calcium oxalate levels.