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A primer on urinary stones.

By Eduardo Gonzales, MD

What are urinary stones made up of? What can I and others do to prevent forming these stones?

Urinary stones are chemical sediments in urine that have condensed and solidified. Actually, urine contains compounds that prevent or inhibit the formation of stones, but in some people these are lacking or not working, so when urine gets concentrated, dissolved minerals and salts crystallize, stick together, and form stones. For still unknown reasons, urinary stones are four times more common in men than in women.

Types of urinary stones

Most, around 85 percent, of urinary stones are made up of calcium, the rest consist of struvite, uric acid, and cystine.

Calcium stones are usually in the form of calcium oxalate, but they also occur in the form of calcium phosphate. Consumption of food high in oxalate increases one's risk for this type of stone. Calcium phosphate stones, on the other hand, are more common in those with metabolic conditions such as renal tubular acidosis.

Struvite stones form in response to an infection, such as a urinary tract infection, while uric acid stones occur in people whose diet is high in purine and in those who have gout. Cystine stones, meanwhile, occur in people with a hereditary disorder that causes the kidneys to excrete an excess of certain amino acids.

Clinical course and treatment of urinary tract stones

Stones in the urinary tract invariably arise in the kidneys. If it stays in the kidney, a urinary stone will usually have no symptom. But if it drops from the kidney to the ureter, the tiny tube that conveys urine from the kidney to the urinary bladder, symptoms could develop.

The most common symptom of a ureteral stone is excruciating colicky pain that occurs suddenly. The pain is episodic rather than continuous in nature, and is not eased by assuming certain positions. It is felt on the flank, but may radiate over the abdomen and the testis (in men) or labium (in women). It is often accompanied by nausea and vomiting and, if there is an infection, fever. If the stone is in the lower part of the ureter, urgency and frequency of urination may likewise occur. The urine of patients with a ureteral stone usually contains some blood, but only rarely is the amount sufficient to discolor urine.

Most stones that find their way into the ureter pass out with urine in a few hours to several days. Hence, the initial treatment consists simply of a strong pain reliever while waiting for the stone to spontaneously pass out. But if the stone does not pass out after a reasonable period of time and causes constant pain or blocks urine flow, it has to be removed.

There are several options available for removing urinary tract stones, including ureteroscopic stone extraction and extracorporeal shock wave lithotripsy (ESWL). The former involves the passage of a small tube with a camera or fiber optic system through the urethra into the ureter and extraction of the stone under direct vision. The latter, which is especially effective in handling relatively large stones, involves the external application of shock waves to break down the stone into smaller pieces that can then pass out easily with urine. In certain cases, open surgery is performed.

How to prevent urinary stones

The most effective measure to prevent urinary stones is to drink plenty of water, at least 10 glasses per day. You know you are drinking enough water if your urine is light and clear all the time.

Eat fewer oxalate-rich foods, such as beets, okra, spinach, sweet potatoes, nuts, tea, chocolate, black pepper, and soy products.

Avoid purine-rich foods, which include steaks, innards (laman-loob), seafood, and beer.

Choose a diet that's low in salt and animal protein.

Take it easy on calcium and vitamin D supplements, but you can continue eating calcium-rich food. Calcium in food does not affect your risk for urinary stones.

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Title Annotation:Well-Being
Publication:Manila Bulletin
Date:Jun 19, 2018
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