A-side and B-side. The terms A-side and B-side refer to the two sides of 78, 45, and 33 1/3 rpm phonograph records, whether singles, extended plays (EPs), or long-playing (LP) records.
The two ureters connect to either side of the top of the bladder, which is the organ that stores urine until it is expelled from the body. Urine is expelled from each kidney into its respective ureter. Once it enters the ureters, peristalsis moves the urine down the tube and into the bladder.
(The ureter is the tube that carries urine from the kidney to the bladder.) The physician can then see the stone and remove it with a small basket at the end of a wire which is inserted through an extra tube in the ureteroscope.