THIS MONTH'S ARTICLE OF INTEREST - KIDNEY STONES - EVALUATION AND PREVENTION
Kidney stones are composed of crystals that form from chemicals within the urine. Eighty percent of patients have calcium stones with either oxalate or phosphate. Calcium is obtained from food and stored in bone where it provides strength. Oxalate is a metabolic breakdown product of the protein unit glycine and ascorbic acid of vitamin C.
First time stone former or infrequent stones require a blood test for calcium, phosphate, urate and kidney function - creatinine, and analysis of the stone if you are able to catch it. You have a 30% chance of forming another stone in the next five years.
Active stone disease is the formation of a new stone within 18 months, enlargement of old stones, multiple residual stones or the passage of gravel. This requires a complete evaluation three months after stone passage or treatment with repeat blood tests, 24 hour urine collection and repeat x-ray or ultrasound to monitor response to treatment.
Prevention: The time to prevent forming another kidney stone is now while you remember how bad the pain was. There are four components to this:
1. High fluid intake
2. Protein intake
3. Avoid adding salt
4. Calcium
Oxalate is the other common chemical within kidney stones. It is absorbed from chemical processes that occur within the body. Only 10% comes from the diet. For most people, dietary restriction of oxalate will not affect stone formation.
Short bowel syndrome and malabsorption from inflammation of the large bowel results in an increase in oxalate absorption. Specific dietary advice is required.
A small group of people with active calcium oxalate stone disease (>1 per 18mths) may absorb excessive amounts from the diet. Restriction of oxalate in the diet can reduce stone formation. Oxalate is present in rhubarb, beetroot, silverbeet or spinach, nuts and chocolate. The recommendation is to restrict intake to four servings of the above items/week.
Uric acid calculi can be dissolved within the urinary tract by decreasing the acid in the urine. This requires oral bicarbonate of soda, two tsp every four hours or one Ural sachet per four hours. You can monitor the urine pH or acidity using chemical agent strips aiming to maintain pH 7 or above. The stone should dissolve within one month. Allopurinol will reduce uric acid levels.
Drug therapy: Prevention of active calcium oxalate stone disease. The Thiazide diuretic can lower calcium excretion and increase bone calcium density.
Follow-up: Small stones that remain unchanged in size over two years are unlikely to alter in the future. Concerns on any of the information provided above can be discussed either with your family doctor or through a consultation with Tony Beaven.
(Article written by Tony Beaven - Urologist - ph; 488 6662)
