The causes of children not urinating for half a day include the following: First, it is caused by children drinking too little water. If children consume too little water, especially in the hot summer when they sweat more, it can cause children not to urinate for half a day. Second, the symptoms are caused by children suffering from diarrhea. If a child has diarrhea caused by acute enteritis, the number of stools will increase and the stool will be dilute, and the amount of urine will be low due to excessive water loss from the stool. Finally, the symptoms are caused by children with renal failure. If a child has severe impairment of kidney function, he or she may not urinate for half a day.