Hi welcome to healthcare magic,
IgA Nephropathy is the most commonest cause of
Hematuria i.e bloodstained urine.In very few children it progresses to
nephritis . Yes children who develop nephritis can have
hypertension too . Treatment is just symptomatic i.e salt restriction , taking drugs to control hypertension and a regular check up to see the functioning of kidneys. There is no permanant cure though it can be controlled .Yeah there has been reported data that fish oils offer some benefit .