Urolithiasis-Stones in the Urinary Tract

Stones or calculi can develop anywhere in the urinary tract. Most of them occur in the kidneys in a condition called nephrolithiasis or kidney stones. However, when these stones develop in any other part of the urinary tract, the condition is known as urolithiasis.

What causes urolithiasis?

Urolithiasis occurs when three specific mechanisms are at work:

-There is an excess of salt in urine that cannot be dissolved and eliminated. So the urine is over saturated with this insoluble substance and crystals begin to form. Under normal circumstances, these crystals would have dispersed and been eliminated in urine.

-More crystals begin to form that cannot be excreted. They join together and form a strong bond that develops into a stone.

-The body in unable to inhibit the crystallization of these substances in the urine and the stones continue to form.

Many times urolithiasis is idiopathic, meaning there is no identifiable cause. However there are some risk factors including dehydration, genetics, and excessive intake of calcium, oxalate, or protein.

What are the stones in urolithiasis made from?

The vast majority (75-80%) of the stones from urolithiasis are made from calcium oxalate or calcium phosphate. The rest are made up of uric acid (possibly resulting from gout), struvite (m agnesium ammonium phosphate) , and cystine (uncommon and most likely a genetic defect).

What are the signs and symptoms of urolithiasis?

If the stone blocks the ureter, a condition called renal colic can develop. Renal colic is defined by acute and severe back pain on the affected side that often radiates to the groin and external genitalia. The pain can be so severe that it causes nausea, vomiting, pallor, and cool/clammy skin. If the stone is in the bladder, the symptoms may resemble that of a urinary tract infection: painful and frequent urination, foul smelling or cloudy urine, and possibly hematuria (blood in urine.)

How do you treat and prevent urolithiasis?

Increasing fluid intake to 2-3L a day can help to pass the stone. Once the stone is passed, save it and bring it to your doctor so he can determine the makeup of the stone (calcium or otherwise.) Pain relievers can be taken as needed. Surgery options include laser disintegration of the stone or removal of the stone through the insertion a scope into the ureter or bladder.

Hydration and dietary changes are the best ways to prevent future urolithiasis. Maintaining a daily liquid intake of 2-2.5L can prevent stones from forming. Since most stones are calcium and oxalate based, avoiding foods high in these substances:

High calcium foods: Dairy, beans, lentils, canned fish (other than tuna)

High oxalate foods: asparagus, chocolate, celery, nuts, tomatoes

If your stones are uric acid based, try increasing your intake of alkalizing foods like green vegetables, milk, and rhubarb.

Sources:

National Kidney and Urologic Diseases Information Clearinghouse, Kidney Stones in Adults, October 2007

eMedicine, Nephrolithiasis/Urolithiasis, February 2010

Lemone, Pricilla and Burke, Karen (2008). Clinical Handbook On Medical Surgical Nursing (4^th ed). Upper Saddle River, NJ: Prentice Hall, pp 855-858