What does it mean to have a mild left renal caliectasis?

Mild kidney swelling: Calices are the major urine ducts between collecting tubules and kidney pelvis, which 'funnel' draining all urine from kidney into the ureter. Mild caliectasis, often diagnosed prenatally, can signify mild partial kidney obstruction from an anatomic narrowing, kidney stoneor infection. Can also be from ureteral obstruction at bladder level or bladder reflux. In itself not serious.