Lecture 8b 24 February 2014 Renal Disease Kidney stones Affect about 50,000 Canadians each year Mostly males over the age of 20 years

Kidney stones occur because of urinary concentration of components making up the stones is right to form the stones. The components are: -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

Get excess calcium, uric acid and cystine in the urine due to: -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 called cystinuria in which renal tubules are unable to reabsorb amino acid cystine-get abnormally high concentrations of cystine in the urine-then get crystallisation followed by stone formation

Magnesium ammonium phosphate stones -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 drink lots of fluid - to prevent a recurrence-consume 3-4 litres of fluid (mostly water) each day (possibly more in warm climates) to produce litres of urine daily-why ? -people with fevers, diarrhea or vomiting need more fluid why?

Nutritional prevention of calcium oxalate kidney stones -for people who have never had a stone, an intake of calcium(800 mg male, 1200 mg female/day) may lower risk but not if high oxalate foods are taken with calcium

Nutritional prevention of kidney stones (table 28-9) -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 get calcium removed 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 - 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, VLDL, Lp(a) -platelets clot more easily

Nephrotic syndrome Treatment via diet: -ensure adequate energy intake- (35 kcal/kg body weight/d) as this sustains weight and spares proteins -if have accompanying weight loss or infections then one needs more energy to fight the weight loss and the infections -if obese, lose weight to control lipids and blood glucose as elevated blood lipids and blood glucose will exacerbate nephrotic syndrome

Nephrotic syndrome Treatments via diet -watch protein intake ( about 0.8 g/kg body weight/day –no more than 1.00 g/kg body weight/day)- protein must be from high quality protein sources -dietary fat- TLC diet first then antilipemic drugs

Nephrotic syndrome Treatment via diet -sodium-restricted due to sodium retention as the kidney is not clearing sodium as well compared to the healthy person (sodium restriction depends on response to diuretics but generally 1-2 g of sodium per day) Table 28-1