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, hyperosmolar hyperglycemic nonketotic syndrome (HHNS), multiple organ dysfunction syndrome, urinary obstruction/urinary retention, diabetic ketoacidosis (DKA), pre-eclampsia, and urinary tract infections, among other conditions.
Beyond oliguria is anuria, which represents an absence of urine, clinically classified as below 80 or 100 ml/day.