protein-, mineral- & fluid-modified diets for kidney diseases

Nutrition & Diet Therapy, 7th Edition

Protein-, Mineral- & Fluid-Modified Diets for Kidney

DiseasesChapter 23


Roles of Kidneys

• Filtration of blood & removal of excess fluid & wastes for elimination in urine

• Regulation of fluid volume & osmolarity, electrolyte concentration & acid-base balance

• Excretion of metabolic wastes, drugs & toxins• Secretion of enzyme renin to regulate blood pressure• Production of hormone erythropoietin to stimulate

production of RBCs• Conversion of vitamin D to active form, helping to

maintain bone tissue


I. Nephrotic Syndrome• Not a specific disease—

kidney disorders that result in urinary protein losses in excess of 3 grams/day

• Occurs most often in children between 1 ½-4 years old

• Damage to glomeruli increases permeability to plasma proteins, allowing protein to escape into the urine

• Can progress to renal failure

• Causes– Infection– Chemical damage– Immunological &

hereditary disorders– Diabetes mellitus– Other disorders involving

glomerulus• Clinical findings

– Proteinuria– Low serum albumin levels– Edema– Elevated blood lipids– Blood coagulation

disorders


Nephrotic Syndrome• Treatment goals:

include relief of symptoms & prevention of kidney damage

• Drugs– Anti-inflammatory drugs

(usually corticosteroids)– ACE inhibitors– Diuretics– Antihypertensives– Immunosuppressants– Lipid-lowering

medications

• Nutrition– Meet protein (.8-1g/Kg)&

energy (35 kcal/Kg)needs to minimize muscle tissue loss

– Low sat fats, cholesterol– Low refined sugars– Sodium restriction(1-2g/d)– Potassium-rich foods (if

potassium-wasting diuretics are used)

– Vitamin & mineral supplements


II. Acute Renal Failure

• Rapid deterioration of kidney function– Reduction of urinary output– Accumulation of nitrogenous wastes in blood– Degree of renal dysfunction varies from mild to

severe

• Causes– Can result from number of disorders– Often develops as consequence of severe illness,

infections, injury or surgery– Causes usually classified as prerenal, intrarenal or

postrenal


Acute Renal Failure• Consequences

– Fluid & electrolyte imbalance

• Oliguria: production of <400 mL urine/day

• Hyperkalemia: elevated serum potassium levels

• Hyperphosphatemia: elevated serum phosphate levels

– Uremia• Accumulation of nitrogen-

containing waste products in blood

– Blood urea nitrogen (BUN)– Creatinine– Uric acid

• Treatment– Drug therapy

• Diuretics• Correction of hyperkalemia

– Nutrition• Meet protein (.6-.8g/Kg)&

energy (35kcal/Kg) needs• Restoration of fluid

balance (urine+500ml)• Replacement of

electrolytes (2-3g Na/d, K & P restricted)

• Enteral & parenteral nutrition (cal, pro and electrolytes)

– Renal dialysis


III.Chronic Renal Failure• Characterized by gradual & irreversible

deterioration in kidney function; may follow acute renal failure

• Causes– Diabetes mellitus (about 43% of cases)– Hypertension (about 26% of cases)– Inflammatory, immunological or hereditary

diseases that directly affect kidneys

• End-stage renal disease (ESRD): advanced stage of chronic renal failure in which dialysis or kidney transplant is necessary to sustain life


Chronic Renal Failure Consequences

Early Stages• Anorexia• Fatigue• Headache• Hypertension• Itching• Kidney inflammation or

nephrotic syndrome• Nausea & vomiting• Proteinuria, hematuria

Advanced Stages• Anemia, bleeding tendency• Cardiovascular disease• Confusion, mental impairment• Electrolyte abnormalities• Fluid retention• Metabolic acidosis• Peripheral neuropathy• Protein-energy malnutrition• Reduced immunity• Renal osteodystrophy


Chronic Renal Failure

• Uremic syndrome– Cluster of symptoms & complications that

develops during final stages of chronic renal failure

• GFR (rate of kidneys form filtrate)<15 mL/minute• BUN exceeds 60 mg/dL• Anemia• Bone disease• Hormonal imbalance• Bleeding impairment• Increased risk of cardiovascular disease• Reduced immunity


Chronic Renal Failure• Treatment goals: slow

disease progression & prevent or alleviate symptoms

• Drug therapy– Antihypertensives– Erythropoetin– Phosphate binders(P)– Na bicarbonate(acidosis)– Cholesterol-lowering drugs– Vitamin D

supplementation(Ca)• Dialysis

– Hemodialysis– Peritoneal dialysis

• Nutrition– Energy intake to maintain

healthy weight & prevent wasting

– Low-protein (unless dialysis), low sat fat

– Regulation of fluid & sodium intakes based on total urine output, changes in body weight, blood pressure & serum sodium levels

– Regulation of potassium intake based on potassium levels & use of diuretics

– Vitamin & mineral supplementation

– Enteral & parenteral nutrition


Chronic Renal Failure• Kidney transplants

– Preferred alternative to dialysis in ESRD

• Restores kidney function

• Allows more liberal diet• Frees patient from

routine dialysis– Barriers to

transplantation• Supply of suitable

kidneys vs. demand (<20% are recipients)

• Patient-related barriers: age, financial difficulties, abnormalities of urinary tract

– Immunosuppressive drug therapy

• Used to prevent tissue rejection

• Include side effects that alter nutrition status (FDI)

– Nutrition• Increased E & protein

requirements after surgery

• Control of hyperglycemia, blood lipids, electrolyte balances, calcium levels

• Avoidance of foods that can cause food-borne illnesses


IV. Kidney Stones• Crystalline mass that forms within urinary tract• May be asymptomatic or may cause severe pain or

blockage of urinary tract as the stone passes• Tend to recur, but can be prevented with diet &

medical treatment• Formation of kidney stones

– Develop when stone constituents become concentrated in urine

– Allows formation & growth of crystals– Composed of calcium oxalate (75%) or uric acid, amino

acid cystine, magnesium ammonium phosphate– Formation promoted by factors that reduce urine volume,

block urine flow or increase concentrations of stone-forming substances


Kidney Stones• Calcium oxalate stones

– Usually associated with hypercalciuria

– Results from excessive or impaired calcium reabsorption, elevated levels of parathyroid hormone or vitamin D

– Reduction of dietary intake of oxalate recommended

• Uric acid stones– Develop in highly acidic urine

or in presence of high amounts of uric acid or both

– Frequently associated with gout

– Diet rich in purines also contributes


Kidney Stones

• Consequences– Renal colic– Hematuria– Urinary tract complications

• Prevention & treatment– Increased fluid intake of 12-16 cups daily

• Water, tea, coffee, wine, beer acceptable• Avoid apple & grapefruit juices( risk)

– Diet & drugs to reduce urinary calcium & oxalate levels, uric acid levels

– Adjustment in calcium (moderate), oxalate ( levels), moderate protein & sodium intakes, ?purine restriction for uric acid stones


Nutrition in Practice—Dialysis

• Dialysis offers life-sustaining treatment for chronic renal failure– Permanent treatment or temporary measure– Can restore fluid & electrolyte balances

• Removes excess fluids & wastes through processes of diffusion, osmosis & ultrafiltration– Hemodialysis– Peritoneal dialysis



• Dialysate (solution similar in composition to normal blood plasma) delivered to compartment beside semi-permeable membrane

• Blood flows along other side of membrane• Concentrations of dialysate & blood affect

movement of solutes across the semi-permeable membrane

• Semi-permeable membrane acts as filter– Small molecules (i.e. urea & glucose) can pass

through membrane pores– Large molecules are unable to cross



• Hemodialysis– Dialyzer used to cleanse blood– Treatments usually require 3-4 hours, at least

3 times per week– Most patients receive treatment in dialysis

centers; some (about 2%) are treated at home– Complications

• Infection & blood clotting at vascular access site• Hypotension• Muscle cramping• Blood losses, worsening anemia• Other: headaches, weakness, n&v, agitation



• Peritoneal dialysis– Peritoneal membrane surrounding abdominal

organs serves as the semi-permeable membrane• Dialysate infused through catheter into peritoneal

space (4-6 hrs)• Dialysate solution drained & exchanged (avg.4x/d,

30min.)

– Advantage over hemodialysis: vascular access not required, fewer dietary restrictions

– Complications• Infection (peritonitis)• Blood clotting in catheter, catheter migration• Abdominal hernia

protein-, mineral- & fluid-modified diets for kidney diseases

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