Separation of the collecting system in either the left or right kidney is often reported and detected during a renal ultrasound. Simply put, separation of the renal collecting system often indicates hydronephrosis, or hydronephrosis of the renal pelvis. Generally, a normal collecting system is not separated. If the separation is greater than 1 cm, the ultrasound will report it, often indicating hydronephrosis. If the separation of the collecting system is not severe, it may be due to a physiological cause, such as a congenital pot-bellied renal pelvis. If the separation is more severe, especially with thinning of the renal cortex, it often suggests obstruction of the urinary tract below the ureter. Most commonly, these are urinary stones, but may also be urinary tumors, inflammatory strictures of the urinary tract, malformations, etc. Separation of the collecting system often requires further consultation and treatment in the urology department of a regular hospital, where the cause of the obstruction should be detected and released in a timely manner. Otherwise, it is easy to cause renal insufficiency and affect kidney function.