What Is the Duration of Kidney Stones?

There's really no way to accurately predict the duration of kidney stones, although there are some guidelines and estimates that are helpful. A better understanding of the different ways that "duration" can relate to kidney stones can be gained by learning what they're made of and how they leave the body.

Definition

• Kidney storms form when the fluid and minerals that are in urine are out of balance. The minerals normally stay dissolved in the fluid, but if there isn't enough fluid, then minerals such as calcium and uric acid can easily form into crystals. Over time, these crystals stick together and develop into hard stones. This is especially likely to happen if the urine also doesn't have the right supply of the chemicals that prevent crystals from clumping together. Once they're formed, kidney stones are hard minerals.

Types

• Kidney stones are made of different types of minerals. According to the experts at the Mayo Clinic, about four out of every five kidney stones are made out of calcium oxalate. Another type of stone consisting of struvite is caused by urinary tract infections and is most often found in women. Uric acid is a byproduct of protein metabolism, so you have a higher risk of uric acid stones if you eat a high protein diet. Cysteine stones are rare and only form in people with a hereditary disorder that causes the kidneys to secrete large amount of amino acids.

Duration

• The duration of kidney stones can refer to the length of time they remain in the kidney, how long they take to leave your body, or how long the stone will last. There aren't any hard-and-fast answers. Since they are hardened minerals, kidney stones can last a long time. Also, they may be broken into small pieces in a procedure to help them pass through the body. As long as they stay in the kidney and aren't so large or numerous that they cause problems, they can stay inside your body indefinitely. If they move out of the kidney, then they must leave the body either naturally or with procedures to help make that happen, but the length of time it takes them to leave the body depends on their size.

Size

• Physicians at the Delaware Urological Associates state that kidney stones that are larger than 1 cm (0.39 inches) will "rarely pass through the urinary system without complications." Stones that are less than 3 mm (0.12 inches) have a high chance of naturally passing out of the body. Stones bigger than 8 mm (0.31 inches) in width have about a 20 percent chance of passing spontaneously within one year. A report from the American Academy of Family Physicians states that any stone larger than 5 mm (0.20 inches) has no chance of passing without intervention. While size predicts whether the stone will be able to pass spontaneously, estimates of how long that might take range from three days to three weeks.

Treatment

• If the kidney stones are too large to pass within a reasonable amount of time, or if they cause a blockage or bleeding, then intervention is necessary. A procedure called extracorporeal shock wave lithotripsy sends shock waves through the body. The waves are harmless to body tissues but when they hit the kidney stones, the stones are broken into smaller pieces that can flow through the urine. Percutaneous nephrolithotomy is a type of surgery used to remove a large stone using an instrument called a nephroscope inserted through an incision in the back.