What is the normal appearance of the upper urinary tract on a retrograde pyelogram?
There are 8 to 14 calyces in a normal collecting system, which drain through infundibulae into the renal pelvis. The renal pelvis may sometimes protrude outside of the medial aspect of the renal parenchyma; this congenital variation is known as an extrarenal pelvis. An extrarenal pelvis may appear prominent because it is not compressed by the renal parenchyma, but it is important not to misconstrue this as hydronephrosis. The ureters insert on the posterior aspect of the bladder at the trigone.