Your child appears to have a multicystic dysplastic kidney on the left side. This is a structural abnormality in which the kidney has not developed properly and does not function at all. It would require removal sometime later.
It is unusual to get 76 ml fluid in the hydrocoele of a small baby. In any case, hydrocoele do not require surgical correction as an emergency. It can be done at your convenience since he will not have symptoms due to it. Sometimes, hydrocoeles resolve spontaneously in the first year of life.