Chapter 28
CHAPTER 28 – NUTRITION AND RENAL DISEASES
CHAPTER SUMMARY
Kidneys are primarily responsible for eliminating waste products and maintaining fluid and electrolyte
balance. Other critical roles of kidneys include regulating blood pressure, production of the hormone
erythropoietin which stimulates the production of red blood cells in the bone marrow, and the conversion
of vitamin D to its active form. Under circumstances when kidney function is altered, severe side affects
develop. Disorders that affect the kidneys include the nephrotic syndrome, acute and chronic renal
failure and kidney stones.
The nephrotic syndrome, a term used to describe any kidney disorder that results in proteinuria
exceeding 3.5 grams per day, can develop when damage to the glomerular capillaries increases their
permeability to plasma proteins, allowing protein to escape in the urine. Consequences of nephrotic
syndrome include edema, increased risk of developing heart disease and stroke due to elevated LDL and
VLDL levels, and loss of immunoglobulins and vitamin-D binding protein in the urine. The nephrotic
syndrome is managed with mediations and medical nutrition therapy. Drug therapy includes antiinflammatory agents, ACE inhibitors, immunosuppresants, antihypertensive agents, diuretics and lipidlowering medications. Medical nutrition therapy includes a daily protein intake of 0.8-1.0 g/kg, adequate
kcalorie intake and a diet low in saturated fat, cholesterol and refined sugars.
Acute renal failure has a sudden onset (over hours or days) and the loss of kidney function reduces urine
output, resulting in nitrogenous wastes building up in the blood. Causes of acute renal failure include a
wide variety of conditions, often due to severe illness, injury or surgery. The causes are classified as
prerenal, intrarenal or postrenal. Consequences of acute renal failure include fluid and electrolyte
imbalances (sodium retention, hyperkalemia, hyperphosphatemia) and uremia. The treatment of acute
renal failure is a combination of medical nutrition therapy, drug therapy and dialysis, most often
continuous renal replacement therapy. Drug therapy includes diuretics, potassium exchange resins,
insulin (along with glucose) and possibly bicarbonate. Medical nutrition therapy involves careful
consideration of protein, energy, fluid, sodium, potassium, and phosphorus intakes. Sometimes enteral or
parenteral nutrition support is needed to provide adequate energy. Enteral products available for acute
renal failure are kcalorically dense and have lower concentrations of protein and electrolytes.
In contrast, chronic renal failure has a gradual onset with extensive, and irreversible, damage to nephrons
before symptoms appear. Symptoms of renal failure may not appear until 75% of the kidney function is
lost. The most common causes of chronic renal failure include diabetes mellitus and hypertension.
Consequences of chronic renal failure include altered electrolytes and hormones, uremic syndrome,
bleeding abnormalities, increased cardiovascular disease risk, reduced immunity and protein-energy
malnutrition. Clients have an altered nutritional status due to loss of nutrients, anorexia, nausea,
vomiting, diarrhea, and altered absorption ability. Treatment of chronic renal failure includes drug
therapy, medical nutrition therapy, dialysis and possibly kidney transplant. Drug therapy includes
diuretics, antihypertensive medications, erythropoietin injections, phosphate binders, sodium
bicarbonate, cholesterol-lowering medications and supplements containing active vitamin D. Dietary
modifications for chronic renal failure depend on whether the patient is on dialysis or not, and whether
they are on hemodialysis or peritoneal dialysis. Medical nutrition therapy includes modifications in
energy, protein, lipids, fluids, sodium, potassium, calcium, phosphorus, vitamin D, and other vitamins
and minerals. A meal planning system, similar to the exchange system for diabetes, has been developed.
Dietitians specializing in renal disease are best suited to provide medical nutrition therapy.
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Chapter 28
Clients in severe renal failure require dialysis to take over the function of the kidneys. An alternative to
dialysis is a kidney transplant, which brings about a new set of dietary challenges. Because kidney
recipients receive immunosuppressive drug therapy, they experience fluid retention, carbohydrate
intolerance, altered blood lipids, hypertension, and infection. Diet interventions include increased intakes
of protein and kcalories, controlling carbohydrate intake, possibly fat modifications, generally liberalized
intakes of sodium, potassium and phosphorus that are modified as needed based on serum electrolyte
values, and calcium supplementation.
Kidney stones are the most common disorder affecting the kidneys and urinary tract. Kidney stones
develop when stone constituents become concentrated in urine, allowing crystals to form and grow. The
majority of kidney stones (75%) are made up primarily of calcium oxalate. Other types of stones are made
up of uric acid, the amino acid cystine or magnesium-ammonium phosphate (known as struvite stones).
Factors that predispose to stone formation include dehydration or low urine volume, obstruction, renal
disease, urine acidity, and metabolic factors. Consequences of kidney stones include renal colic and
urinary tract complications. Prevention and treatment of kidney stones includes increased fluid intake,
and dietary and drug treatments based on the type of stones the individual forms.
Highlight 28 examines the basics of dialysis.
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