Energy intake in children with chronic kidney disease

Each child is a complete individual. When the body is in a stable state, the phosphate intake from the diet and the phosphate excreted from the kidneys are balanced. When the blood phosphorus level in the body is too low or too high, a series of symptoms will appear. In severe cases, there will be subtle myopathy and muscle weakness, and the latter is a sign of worsening kidney disease.

There are many causes of hyperphosphatemia, and the most common cause in children is chronic kidney disease complicated by hyperphosphatemia. It is common to see children with chronic kidney disease who restrict protein intake and control their protein diet at 0.8g/kg/day. Parents are afraid to let their children eat more, which leads to a low level of growth and development. For this reason, this article summarizes the importance of dietary intake to children's growth and development, hoping to provide help for clinical work.

1. The three most important nutrients for children's growth and development are fat, protein, and carbohydrates. Among them, protein is the basic component of cell and organ function. In addition to providing enough protein, there must also be enough non-protein energy (i.e. carbohydrates, fat) to ensure that carbon skeleton amino acids are not converted to meet energy needs. For children, promoting weight gain and development is the first priority, and the guidelines recommend adjusting daily energy to the upper limit of dietary intake.

2. For children with hyperphosphatemia, there is a contradiction between growth and development and dietary restrictions. Growth and development requires a lot of food, and protein contains phosphorus. Restricting protein intake will inevitably hinder children's growth. For children, first ensure adequate energy intake, and it is recommended to give protein according to the upper limit of intake. If the child's biochemical indicators and urea nitrogen are significantly elevated, it indicates excessive protein intake. Reduce protein intake to the lower limit of the recommended amount. According to different age groups, the protein intake target is different. Among them, the newborn baby has the highest demand, which is 1.52-2.5g/kg/day. Adolescent children have the lowest demand, which is 0.9-1.14g/kg/day[1].

3. If it is a small baby, breastfeeding is the first recommended diet. If breastfeeding is not possible, whey protein formula is strongly recommended. If the child has a fluid restriction, then fortified breast milk or formula milk powder is needed (that is, the milk powder is thicker and the concentration can reach 13%). Milk powder can also be mixed with breast milk, and the concentration of milk powder is 3%-6%. If fortified nutrition is given, the tolerance of the child needs to be considered, because when the concentration increases, the osmotic fluid will increase, so symptoms such as diarrhea and vomiting may occur, and excessive phosphate, potassium or other fat-soluble vitamins will be ingested. Fat-soluble vitamin A has an accumulation effect and may cause poisoning, so special care should be taken. There is no such worry about water-soluble vitamins.

4. Peritoneal dialysis (PD) causes significant protein losses. Protein losses are higher in younger children with PD compared to older children, ranging from 0.28 g/kg/day in infancy to 0.1 g/kg/day in adolescence. Therefore, it is recommended that protein intake should be increased accordingly. However, there are no studies on protein losses in children on hemodialysis (HD). Protein losses in adults receiving HD are as high as 6-10 g/dialysis session.

5. Regularly monitor the growth and development percentiles of the child, and intervene immediately if the weight percentile is found to have regressed. For children with inadequate dietary intake, oral nutritional supplements should be started after considering the correctable reasons for reduced intake. Hyperkalemia occurs during the progression of CKD and is more obvious in patients with metabolic acidosis. It usually indicates the need to reduce potassium intake. However, when energy intake is insufficient, cellular catabolism can also lead to hyperkalemia. This can be solved by adding high-energy foods to the formula commonly used by infants.

References

[1] Vanessa Shaw, Nonnie Polderman, and José Renken-Terhaerdt, et al. Energy and protein requirements for children with CKD stages 2-5and on dialysis – clinical practice recommendations from the PediatricRenal Nutrition Taskforce. Pediatr Nephrol. 2020 Mar;35(3):519-531.

[2] Quan A, Baum M (1996) Protein losses in children on continuous cycler peritoneal dialysis. Pediatr Nephrol 10:728 – 731.

(Zhao Yiming, Beijing Children's Hospital, Capital Medical University)