About Kidney Stones
Kidney stones, also known as renal calculi, are stone-like objects that form in the kidneys from waste products in the urine.
How is a Kidney Stone Made?
A primary function of the kidneys is to filter waste products out of the blood. These waste products are mixed with small amounts of water to form urine. Urine is formed one drop at a time, where it collects in the kidneys and travels down the ureters into the bladder. When the bladder becomes distended enough to be full, it squeezes and urine is expelled out of the urethra.
When urine is concentrated these molecules of waste products tend to bond together starting as small crystals that become larger stones. Kidney stones are classified by their type, and are treated differently based on that type. The most common type of kidney stone is calcium oxalate-- about 80 percent of all stones are made of calcium oxalate. Other types of kidney stones include calcium phosphate, uric acid, struvite and cystine.
What Happens to Kidney Stones? How Do They Cause Pain?
Kidney stones can stay dormant in the body for a long time or try to pass through the urine. Many stones are passed down through the ureters and out of the bladder without causing symptoms because of their small size.
If stones become large enough, they will cause obstruction as they attempt to pass. When a kidney stone obstructs urine flow, it can cause significant pain due to the pressure of the urine backflow. This pain will be felt in the flank and often will radiate down into the lower abdomen, groin and even the testicles in men. The pain can be so severe that it will cause nausea and vomiting.
Kidney stone pain will often come and go in waves. The ureters are made of smooth muscle tissue that expands and contracts in order to facilitate the downward flow of urine toward the bladder. As a segment of ureter contracts, it will tighten around the stone and cause obstruction making the urine back up and increase kidney pressure. When the ureter expands, this pressure will drop as urine flows around the stone and pain will subside.
Will I Be Able to Pass My Kidney Stone?
The smaller a kidney stone, the more likely it is that you will be able to pass it. Stones that are 2 millimeters or less are often passed painlessly. Stones 3 -4 mm in size can be passed about 80 percent of the time in less than a month. If the stone is 5mm or larger the chances are not good that you will be able to pass the stone without intervention.
As a kidney stone travels from the kidney into the bladder and to the "outside world", there are three spots that it has trouble moving beyond... the first is at the beginning of the ureter, where it narrows known as the ureteropelvic junction (UPJ). This is due to the narrowing of the ureter like a funnel from the kidney. The second area of the ureter is midway down, at a point where the ureter rests right next to the common iliac artery that runs to your leg. Every time your heart beats, it shakes the ureter, causing the stone to "rattle around" instead of traveling on its way. The third area of the ureter where kidney stones take their time passing is at the junction to the bladder, the ureterovesical junction (UVJ).
What Treatment Options Are There for Kidney Stones?