RENAL FAILURE - ACUTE AND CHRONIC
Causes, symptoms and dietary management
Acute renal failure
There is sudden shutdown of renal function following injury to the normal kidney. This is a condition in which the kidneys are no longer able to maintain the normal composition of the blood.
1. Loss of blood due to accidents and internal hemorrhage. Ulcers can cause acute renal failure as the blood flow to the kidneys decreases.
2. Loss of plasma as in burns.
3. Inhalation or ingestion of poisons such as carbon tetrachloride or mercury
4. Shock from surgery
5. Nephritis and Nephrosis can result in acute renal failure.
6. Uremia - There is retention of urea and others urinary constituents in the kidney.
7. Azotemia - accumulation of nitrogenous constituents in the blood.
8. Oliguria - a scanty output of urine (less than 500 ml)
9. Anuria - minimal production or absence of urine (less than 100 ml per day).
10. Serum potassium levels are high when tissue proteins are broken down to provide calories.
11. There is increased phosphate and sulphate with decreased sodium, calcium and base bicarbonate.
12. Patients are lethargic, anorexic, have nausea and vomiting.
A minimum of 600-1000 kcal is necessary. In the initial period when oral intake is less due to vomiting and diarrhoea, 100 g per 24 hours intravenous glucose is given to reduce protein catabolism.
Initially a protein free diet is used in the non-dialysed patients. In the diuretic phase 20-40 g protein is given. The protein content of the diet varies depending on the urea content of the blood.
A minimum of 100g per day is essential to minimize tissue protein breakdown.
Fluid allowance is regulated in accordance with urinary output. The total fluid permitted is 500 ml + losses through urine and gastro intestinal tract. With visible perspiration an additional 500 ml may be given.
Sodium restriction is judged based on the sodium loss in the urine. For the non-dialysed patient 500 to 1000 mg per day is given. Patients on dialysis are permitted 1500 to 2000 mg per day.
Potassium allowance is based on serum levels. Hyperkalemia (potassium intoxication) has deleterious effects on the heart. Potassium sources like tomato juice, coffee, tea, cocoa are avoided.
Chronic Renal failure
It is also known as uraemia as the level of urea in blood is very high. This occurs when 90 per cent of the functioning renal tissue is destroyed. It may be the end result of acute glomerulonephritis and nephrotic syndrome.
1. Progression of acute nephritis or nephrosis
2. Chronic infection of the urinary tract.
3. Kidney stones
4. High blood pressure
5. Exposure to toxic substances.
Once chronic renal failure occurs, the normal functions of the kidneys like regulation of body fluids, electrolytes, pH and excretion of metabolites are disrupted.
In chronic renal failure symptoms appear when the glomerular filtration rate (GFR) is inadequate to excrete nitrogenous wastes. When the GFR is less than 10 ml per minute (normal 120 ml per minute) and the serum urea nitrogen (SUN) is more than 90 mg per day (normal 8 to 18 mg per day) dietary modification brings about improvement. As GFR falls, daily protein intake is restricted.
1. The symptoms of the gastrointestinal tract are nausea or vomiting. The breath has an ammoniacal odour. Ulcerations of the mouth and hiccups interfere with food intake.
2. The nervous system - Patients are drowsy, irritable and sink to coma.
3. If there is hypertension, headache, dizziness, muscular twitchings and failing vision occur.
4. The functioning of the heart is seriously disturbed
5. Death results when hyperkalemia (elevated serum potassium) block the contraction of the heart.
Dehydration, sodium depletion, high serum potassium, acidosis, increased susceptibility to infection are the most general manifestations.
The objectives of treatment are
1. To maintain optimal nutritional status
2. To minimize uremic toxicity
3. To prevent protein catabolism
4. To improve the patients well-being
5. To delay the progression of renal failure
6. To delay the need for dialysis
Adequate kilocalories are essential to spare protein for tissue protein synthesis. Without adequate calorie intake body tissues will be rapidly catabolized thus increasing the blood urea and potassium levels. For adults calorie needs range from 35 - 45 kcal per kg of ideal body weight or 2000 to 3000 kcal per day.
Failing kidneys need to be given rest. Protein intake can be reduced to 0.5 g/kg body weight per day. Haemodialysis patients need 1.0g protein per kg body weight daily to compensate for losses of amino acids in the dialysate. The aim is to provide half of the protein allowance as high biological value protein.
Carbohydrate and Fat
Elevated serum triglycerides common in chronic renal disease can be lowered by controlling carbohydrate intake, dietary cholesterol and polyunsaturated fat.
This is restricted to 1m mol / kg body weight. Potassium allowance is in accordance with the patients blood levels, urinary output and amount of potassium in the dialysate.
Dietary sodium intake depends on the amount of sodium in serum and urine. Restriction is necessary if edema, hypertension and threat of congestive heart failure is present.
Losses of ascorbic acid and many B vitamins occur during dialysis. Intake is likely to be low as raw fruits and vegetables are restricted. Folic acid and pyridoxine requirements are increased. Due to impaired vitamin D metabolism supplements are needed.
Intake of fluids needs to be monitored. 500 ml over the normal urinary output is allowed if there is no oedema and hypertension.