Kidney stones in adults

Overview

Kidney stones are one of the most painful disorders to afflict humans. This ancient health problem has tormented people throughout history. Scientists have even found evidence of kidney stones in an Egyptian mummy estimated to be more than 7,000 years old.

Kidney stones are one of the most common disorders of the urinary tract. More than I million cases of kidney stones were diagnosed in 1985. It is estimated that 10 percent of all people in the United States mill have a kidney stone at some point in time. Men tend to be affected more frequently than women.

Most kidney stones pass out of the body without any intervention by a physician. Cases that cause lasting symptoms or other complications may be treated by various techniques, most of which do not involve major surgery. Research advances also have led to a better understanding of the many factors that promote stone formation.

An Introduction to the Urinary Tract

The urinary tract, or system, consists of the kidneys, ureters, bladder, and urethra. The kidneys are two bean-shaped organs located below the ribs toward the middle of die back. The kidneys remove extra water and wastes from the blood, converting it to urine. They also keep a stable balance of salts and other substances in the blood. The kidneys produce hormones that help build strong bones and help form red blood cells.

Narrow tubes called ureters carry urine from the kidneys to the bladder, a triangle-shaped chamber in the lower abdomen. Like a balloon, the bladder's elastic walls stretch and expand to store urine. They flatten together when urine is emptied through the urethra to outside the body.

What Is a Kidney Stone?

A kidney stone develops from crystals that separate from urine and build up on the inner surfaces of the kidney. Normally, urine contains chemicals that prevent or inhibit the crystals from forming. These inhibitors do not seem to work for everyone, however, and some people form stones. If the crystals remain tiny enough, they will travel through the urinary tract and pass out of the body in the urine without even being noticed.

Kidney stones may contain various combinations of chemicals. The most common type of stone contains calcium in combination with either oxalate or phosphate. These chemicals are part of a person's normal diet and make up important parts of the body, such as bones and muscles.

A less common type of stone is caused by infection in the urinary tract. This type of stone is called a strived or infection stone. Much less common are the uric acid stone and the rare cystine stone.

Urolithiasis is the medical term used to describe stones occurring in the urinary tract. Other frequently used terms are urinary tract stone disease and nephrolithiasis. Doctors also use terms that describe the location of the stone in the urinary tract For example, a ureteral stone for (or ureterolithiasis) is a kidney stone found in the ureter. To keep things simple, the term "kidney stones" is used throughout this booklet.

Gallstones and kidney stones are not related. They form in different areas of the body. If a person has a gallstone, he or she is not necessarily more likely to develop kidney stones.
Pamphlet by: National Institute of Diabetes & Digestive & Kidney Diseases, April, 1994