Pain is the most common symptom of kidney stones, and, unfortunately, it can be excruciating.Many women describe the pain of passing a kidney stone as “worse than childbirth,” notes Seth K. Bechis, MD, an associate professor of urology at UC San Diego Health.
That said, the pain does vary from person to person, adds Dr. Bechis. If the stone does not cause a blockage as it moves through the urinary tract, a person may not experience any pain. Others may have pain in their back near the kidneys, which sit on either side of the spine below the rib cage, or in their lower abdomen or groin, he says.
Why Passing a Kidney Stone Can Be So Painful
Think of the urinary tract system as your body’s plumbing system, explains Timothy F. Lesser, MD, a urologist at Torrance Memorial Medical Center in Los Angeles. The kidney makes urine, which spills into the ureter, a tiny tube that transports the urine from the kidney down to the bladder. The bladder fills, then empties. The concept of “passing a stone” means a stone travels from the kidney down to the bladder, and then through the length of the ureter, he says. The stone leaves the urinary tract through the urethra, the tube that transports urine outside the body from the bladder.
A stone passing is so painful because the kidney itself is “exquisitely sensitive,” explains Dr. Lesser. When a stone blocks the flow of urine through the urinary tract, backed-up urine can put pressure on the kidney, resulting in pain.
“It is thought that the kidney itself does not have nerves with classical pain fibers,” says John C. Lieske, MD, a consultant in the division of nephrology and hypertension at the Mayo Clinic in Rochester, Minnesota. But the tissue surrounding the kidney — called the capsule — does contain nerve fibers that transmit pain. Backed-up urine swells and expands the capsule, he says.
This swelling activates those nerve fibers, causing signals that are interpreted by the brain as intense, visceral pain, says Prakash N. Maniam, MD, a urologist affiliated with Oviedo Medical Center Doctors Hospital in Florida.
Stones can also be painful as they enter or are traveling down the ureter because the ureter spasms as it tries to push the stone along, says Dr. Lieske. (Ureters also contain nerves that register pain.)
