What Does a Kidney Stone Look Like When It Is Passed?

Kidney stones are one of the most common problems associated with the kidneys. Millions of people have either had an episode with a kidney stone, or get them regularly. They are a painful condition. Sometimes they pass from your kidneys out of your urinary tract on their own, but sometimes they require in-depth treatment to get rid of them. Kidney stones can form anywhere along the urinary tract and they can be composed of several different types of material. Kidney stones also come in many shapes, colors and sizes.


The size of a kidney stone varies, ranging from as small as a pebble to as large as a golf ball. Larger stones are not be able to be passed on their own and require surgical intervention. The smaller stones, many times, can be passed on their own. There are tests, such as a KUB, an ultrasound, or an IVP that can determine the size of your stone. However, even smaller stones sometimes will require surgical intervention depending on where the stone is formed and if it is getting caught in a certain area along the urinary tract that is not allowing it to pass.


The shape of kidney stones vary. They can be round, oval or smooth, or they can be rough, bumpy and jagged. They can take on the appearance of starbursts, branch-like figures, or they can be multi-layered. They can even look like potatoes with the roots starting to branch out. Kidney stones can be a variety of textures as well, depending on the stone's composition. The shape of kidney stones depends on where in the urological tract they originally form, and what the stone is composed of.


The color of a kidney stones also varies. Although they are typically a yellow or brown color, they have been known to form in tans, black and even gold. The colors of the stones are influenced by the type of material the stone is made of. For example, a stone made of calcium whewellite will typically be brown or black. If calcium and magnesium combine, it results in a weddellite stone, which is usually light yellow.


The most common type of stone is a calcium stone and the most common of these is calcium oxylate. They make up approximately 70 percent of kidney stones. Calcium phosphate makes up about 5 to 10 percent of kidney stones, and struvite and uric acid both comprise approximately 10 percent of kidney stones.

It is not uncommon for physicians to see stones that are made up of a combination of these materials. Depending on the patient's history, diet and kidney function, any of these materials can come together and create a stone. You can even have more than one stone at a time, with each one made up of its own combination of substances. However, this is not as common as seeing multiple stones made up of the same materials.


Approximately 80 percent of people who have ever had a kidney stone will develop another kidney stone at some time in their lifetime. If you have had a stone composed of one type of material before, such as calcium, chances are you will form another one of the same material. However, this does not mean that you cannot form other stones of different materials in the future.

If you are prone to kidney stones, you should get regular urinary checkups with a urologist who can monitor your condition. You should also adhere to any special instructions, including a special diet that your doctor may put you on. This can help reduce the chances of forming new stones.