Swollen eyelids in infants

NMW :
Help please at least somehow figure out whatmay be the cause of swelling in the baby. To the child 1,5 months. were born prematurely for 31 weeks. 4 days for mechanical ventilation. We are on GW, we eat strictly the norm for our weight. Periodically there are edemas (the face, eyelids, legs strongly swell). With the kidneys they said everything was fine, they passed all the tests (a small amount of protein and white blood cells appeared periodically, but everything was within the norm) and examined by a nephrologist. We often write, the chair rarely 2-3 times a day. No one can say what the reason is. Before this edema was 3 weeks. back - slept due to diuretics. Now they have reappeared and are holding for 3 days already. Local pediatrician does not pay attention to it, saying, "Mom probably something not eaten" And then my mother food (although I strictly keep to a diet for hepatitis B) Please help to understand what could be wrong, very worried about it. Thank you.

Chernorutskaya Ekaterina Igorevna :
"a small amount of protein and white blood cells periodically appeared, but all within the limits of the norm" -the protein in the urine should not be. Give the survey data. Neuropathologist - treatment is?

NMW :
Have handed over again the analysis wet - all in norm or rate, only leucocytes 1-2. And the eyelids are still swelling. They were examined at the cardiologist - the cause of edema was not revealed, on the digestive tract - dysbiosis. There is no treatment for neurology.

Chernorutskaya Ekaterina Igorevna :
Given prematurity, you should be observed in a neurologist, more often edema in such kids as you are associated with problems of the nervous system.