What is the definition or description of: hydronephrosis?

Kidney dilation: Hydronephrosis is a term used to describe dilation of the inner part of a kidney known as the collecting system. There are different severities of dilation and different causes, including stones, obstruction from infection, blood clots, tumors, scar tissues, etc. There are also non- obstructive causes of hydronephrosis.

Kidney swelling: Due to abnormal amount of urine retained by kidney due to swelling of internal renal collecting system consisting of cayces & renal pelvis. Urinary collecting ducts drain into calyces which dreain into pelvis (like a funnel) draining into ureter. Causes mostly blockage, congenital or acquired from stone, fibrous tissue, growth or external pressure of pelvis or lower down, or from bladder reflux.