Renal calculi can vary in size from as small as grains of sand to as large as a golf ball. Kidney stones
typically leave the body by passage in the urine stream, and
are formed and passed without causing symptoms.
The resulting obstruction with dilation or stretching of the upper ureter and renal pelvis as well as spasm of muscle, trying to move the stone, can cause severe episodic pain, most commonly felt in the flank, lower abdomen and groin (a condition called renal colic).