Kidney stone disease (Nephrolithiasis)
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A kidney stone is hard mass that forms in the urinary tract. Nephrolithiasis or kidney stone disease occurs more commonly in men than in women and usually strikes men between the ages of 30 and 60. A stone lodged in the ureter will cause bleeding and intense pain. Kidney stone diseases causes’ considerable suffering and loss of time from work, and it may lead to kidney damage. Once a stone forma in a person, stone formation often occur.
Stones form when poorly soluble substances in the urine precipitate out of solution, causing crystal to form aggregate, and grow. Most kidney stones (75-85%) are made up of insoluble Ca2+ salts of oxalate and phosphate. There may be excessive amount of Ca2+or oxalate in urine as a result of diet, a genetic defect, or unknown cause. Stones may also form from precipitated ammonium magnesium phosphate (struvite), uric acid and cystine. Struvite stones (10 to 15%of all stones) are the result of infection with bacteria, usually proteus species. Uric acid stones (5-8%) may form in patients with excessive uric acid production and excretion, as occur in some patients with gout. Defective tubular reabsorption of cystine (in patients with cystinuria) leads to cystine stones (1% of stones). The rather insoluble amino acid cystine was first isolated from a urinary bladder stone by Wollaston in 1810, hence, its name. Because low urine flow rate raise the concentration of all poorly soluble substances in the urine, favoring precipitation, a key to prevention of kidney stones is to drink plenty of water and maintain a high urine output day and night.
Fortunately, most stones are small enough to be passed down the urinary tract and spontaneously eliminated. Microscopic and chemical examination of the eliminated stones is used to determine the nature of the stone and help guide treatment. Sometimes a change in diet is recommended to reduce the amount of potential stone-forming-material in the urine. Thiazide diuretics are useful in reducing in treating most stone disease because citrate complexes Ca2+ salts. It also makes the urine more alkaline (since citrate is oxidized to HCO3- in the body). This is helpful in reducing the risk of uric acid stones because urates (favored in alkaline urine) are more soluble than uric acid (the form favored in acidic urine). Administering an inhibitor of uric acid synthesis, such as allopurinol, can help reduce the amount of uric acid in the urine.
If the stone is not passed, several options are available. Surgery to remove the stone can be done, but extracorporeal shock wave lithotripsy is more common, using a device called a lithotriptor. The patient is placed in a tub of water, and the stone is localized by X-ray imaging. Shock waves are generated in the water by high-voltage electric discharges and are focused on the stone through the body wall. The shock waves fragment the stone so that it can passed down the urinary tract and eliminated. As some renal injury is produced by this procedure, it may not be entirely innocuous. Other procedure includes passing a tube with an ultrasound transducer through the skin into the renal pelvis; stone fragments can be removed directly. A ureteroscope with a laser can also be used to break up stones.
Frequently asked question.
Does eating stone cause renal stone?
Answer: There is no relation between eating stone and formation of renal stone.
References:
- Short practice of surgery, bailey and love, 25th edi.
- Harrison’s Principles of Internal Medicine, 17th edition.
- Davidson’s Principles and Practice of Medicine, 20th Edition
- The Washington Manual of surgery, 5th edition.
- Medical physiology, Lippincott Williams & Wilkins 3rd edi.
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