Compression of the renal parenchyma results in compression of the renal vessels, which leads to decreased blood flow and activation of the renin-angiotensin system. The renin-angiotensin system activation results in a rise in blood pressure and where this is prolonged, hypertension.
All modalities will demonstrate a collection surrounding the kidney, of variable density / intensity / echogenicity depending on the nature of the collection. Importantly, the adjacent renal parenchyma should be distorted.
History and etymology
This phenomenon was first described by Irvine H Page in 1939 2 when he discovered that hypertension could be produced in a dog by wrapping one or both kidneys in cellophane.