When urinary calculi are formed in the uriniferous tubules, they are called renal calculi. When calculi form in the pelvis of the kidney, they are known as pelvic calculi. If the bladder is the site of the production of the concretion it is designated as a vesical cauculus. Calculi may pass from the kidney into the ureter and from the bladder into the urethra. These are termed uretral and urethral calculi, respectively.