Lecture 8b 7 March 2011 Renal Disease Kidney stones Affect about 50,000 Canadians each year Mostly males over the age of 20 years

Kidney stones occur because of concentration of components making up the stones -calcium, oxalate and phosphate -oxalate is the salt of oxalic acid (eg calcium oxalate) -oxalic acid comes from vitamin C metabolism

-most common stones are calcium oxalate and calcium oxalate combined with phosphate -less common stones are comprised of : -uric acid (from purine metabolism (purine is part of the nucleotide bases)), -the amino acid cystine -or magnesium ammonium phosphate

-excess urinary calcium caused by overly efficient calcium absorption in the intestine or overly efficient calcium excretion in the urine -uric acid stones caused by gout –gout causes build up of uric acid in the blood and urine -cystine buildup in the urine caused by an inherited disorder of amino acid metabolism called cystinuria

-magnesium ammonium phosphate stones (struvite) caused by repeated urinary tract infections -bacterial enzymes cause struvite formation -cranberry juice may limit struvite formation in females ( limited number of studies done)

Nutritional prevention of kidney stones - to prevent in the first place lots of fluid - to prevent a recurrence-consume 3-4 litres of fluid (mostly water) each day (possibly more in warm climates) to produce 2 litres of urine why ? -people with fevers, diarrhea or vomiting need more fluid why?

Nutritional prevention of kidney stones -for people who have never had a stone a high intake of calcium may lower risk but not if high oxalate foods are taken with calcium -whether it is something in the high calcium foods beside the calcium is not clear -calcium and oxalate bind together to form an easily excretable complex (usually- discussion about this?)

Nutritional prevention of kidney stones (table 28-7) -high oxalate foods include: -beans- green and wax -beets* -celery -leeks -legumes -blackberries -blueberries -raspberries -spinach*

Nutritional prevention of kidney stones -rhubarb* -strawberries* -chocolate and chocolate beverages* -nuts, nut butters* -tea* -wheat bran* -cocoa -coffee -nuts * documented to raise urinary oxalate- avoid if at risk of oxalate stones

Nutritional prevention of kidney stones - people with hypercalcuria should avoid excessive calcium intakes -but not below recommended intakes or calcium from bone - avoid excessive vitamin C intakes ( in excess of recommended intakes)- why?

Nutritional prevention of kidney stones - to prevent uric acid stones -diets restricted in purines eg red meats in particular- organ meats, anchovies,sardines and meat products)- this is unproven but suggested alcohol - prevent cystinuria by limiting methionine intake –why?

Nutritional treatment once a stone has formed - once a stone has formed drinking plenty of fluid may help it pass - people with calcium oxalate stones should avoid high oxalate foods

Nephrotic syndrome -not a disease but a distinct cluster of symptoms caused by damage to the glomerular capillaries -damage due to diabetes, hypertension, infections (kidneys and elsewhere), immunological and hereditary disorders, chemicals (medications, illicit drugs or contaminants) and some cancers –there are others; this is only a partial list

Nephrotic syndrome -consequences -loss of blood proteins to urine -edema-retention of sodium -altered blood lipids-elevated cholesterol, triglycerides, LDL, and VLDL -platelets clot more easily

Nephrotic syndrome Treatments - adequate energy- (35 kcal/kg body weight/d) sustains weight and spares proteins -weight loss or infections -need more energy -if obese lose weight to control lipids and blood glucose

Nephrotic syndrome Treatments -watch protein ( about 0.8 g/kg body weight/day –no more than 1.00 g/kg body weight/day) -dietary fat- TLC diet first then antilipemic drugs

Nephrotic syndrome Treatments -sodium-restricted due to sodium retention (sodium restriction depends on response to diuretics but generally 1-2 g of sodium per day)