DIETARY GUIDELINES IN DIALYSIS AND KIDNEY TRANSPLANT
Dialysis is a procedure that replaces some of the kidneys normal functions. It is performed when a person has kidney failure. Dialysis helps to remove waste products including salt, excess fluids and maintain a safe level of blood chemicals such as potassium, sodium and chloride in the body and also controls blood pressure.
In haemodialysis the patients blood circulates outside the body through coils or sheets of semipermeable membranes that are constantly bathed by a hypotonic dialyzing fluid so that nitrogenous wastes are removed into the dialysate. The membranes do not permit bacteria to enter the blood nor can proteins escape from the blood. However some aminoacids are lost into the dialysate. As haemodialysis is performed 3 times a week for 3 - 4 hrs, it may be necessary to regulate the protein intake based on the level of nitrogen waste products. If diet is not controlled dialysis will need to be more frequent.
This consists of introducing 1 to 2 litres of dialysis fluid into the peritoneal cavity and 30 to 90 minutes later withdrawing the fluid. The process is repeated until the blood urea level drops to tolerable levels. Some blood proteins and amino acids are lost and compensation must be made. Fig. represents peritoneal dialysis.
In continuous ambulatory peritoneal dialysis (CAPD), the dialysate is introduced into the abdominal cavity 3 - 5 times each day through a permanent indwelling catheter. The dialysate remains in the abdominal cavity for 4 - 8 hrs after which it is drained and fresh dialysate instilled. Protein losses occur but can be replaced by dietary protein.
Source : Srilakshmi B., (2000). Dietetics. 4th ed. New Age International Publishers.
The diet of a patient on kidney dialysis is important to maintain biochemical control. The objectives are to
1. Maintain protein and kilocalorie balance.
2. Prevent dehydration or fluid overload.
3. Maintain normal serum potassium and sodium blood levels and
4. Maintain acceptable phosphate and calcium levels.
For adults 1 g/kg body weight provides nutritional needs, maintains positive nitrogen balance and replaces amino acids lost during dialysis treatment. 75 percent of daily protein allowance should be protein of high biological value such as eggs, meat, fish and poultry. Milk is restricted as it has a high content of sodium, phosphate and potassium.
Carbohydrates are given to supply energy and prevent protein breakdown. The usual need is 40 kcal / kg lean body weight. Simple carbohydrate foods should be given.
Fluid is limited to 400 to 500 ml / day plus an amount equal to urinary output.
To control body fluid retention and hypertension, sodium is limited to 1000 to 2000 mg / day.
Potassium accumulation can cause cardiac arrest and hence potassium restriction is necessary. A dietary allowance of 1500 to 2000 mg /d ay is given.
During dialysis water soluble vitamins from the blood are lost. A daily supplement of all water soluble vitamins is given. Fat soluble vitamins especially vitamin A and D may build up.
Diet for a person with kidney transplant
Initially after the kidney transplant, it is necessary to maintain dietary restrictions. Diet modification can help to keep the blood pressure, blood sugar and cholesterol levels within the normal limits. Optimal protein and energy intake with restriction of salt, simple sugars, total fat, cholesterol and saturated fat is necessary. The healthy diet pyramid advocates eating more cereals, bread, legumes, vegetables and fruit, eating moderate amounts of milk, cheese, lean meat, poultry, fish and eggs and eating least quantities of sugar, oil and butter.