Oliguria is defined as urine output -

Oliguria or hypouresis is the low output of urine specifically more than 80 ml/day but less than 400ml/day. The decreased output of urine may be a sign of dehydration, kidney failure, hypovolemic shock, HHNS hyperosmolar Hyperglycemic Nonketotic Syndrome, multiple organ dysfunction syndrome, urinary obstruction/urinary retention, DKA, pre-eclampsia, and urinary tract infections, among other conditions Normal: 1 - 2ml/kg/hr. Oliguria: <1.0ml/kg/hr. Anuria: no urine output. Polyuria: > 3ml/kg/hr. Older children: 30 ml/hr is the minimum normal output. Ref Harrison20th edition pg 277