Metro Urology

A kidney stone is a literal description, a large crystal formed from the minerals in your urine that resembles a small pebble or rock. A stone can be quite dense and hard, while other stones are softer and more friable. The density of the stone is determined by the composition of the stone as well as how long it took the stone to form.

Most kidney stones contain calcium, combined with either oxalate or phosphate to form crystals. 85% of kidney stones contain calcium. Most of the rest of the stones are uric acid stones, another mineral in the urine. Only a few percent are other kinds of minerals. We can only determine what kind of kidney stone you have by having the stone crystals identified in a laboratory (crystallography) If you pass a kidney stone, bringing the stone in can help us determine what your next steps should be.

Most people don’t feel a growing stone. In fact, many of those diagnosed with a kidney stone felt well until the kidney stone tried to pass. Most kidney stones form slowly, over months to years, so most patients have had their stones for a long time before it casues them any trouble.

Why do kidney stones hurt so much? Why do they start hurting so fast?

Your kidneys are big filters that filter minerals from the bloodstream. Urine is produced and drains into a common, funnel-shaped area of the kidney, the renal pelvis, that tapers down to the ureter. The ureter is a long, thin, muscular tube that transports the urine down to the bladder by “milking” the urine down the tube. Getting the urine from the kidney to the bladder is an active process, the only place urine is supposed to stay for a while is in the bladder.

The ureter is narrow tube and continues to narrow as it gets toward the bladder. A kidney stone that tries to pass down the ureter will only get so far before it will get stuck. Only the small stones will pass without getting stuck. If the stone gets stuck in the ureter and blocks the flow of urine, pressure will build as the ureter and renal pelvis continue to actively try to transport the urine to the bladder. As pressure builds, the ureter and renal pelvis are forced to stretch. The stretching causes pain.

The pain of a kidney stone is often intense, and most patients are diagnosed when they come to the Emergency Room. Localized, acute, and severe back pain, nausea, and vomiting are typical symptoms. Fever and infection are not common and require urgent treatment.

I am having pain. How do I know if I have a kidney stone?

Kidney stones are best diagnosed with CT scans. Sometimes plain xrays can clearly show a stone, but a CT scan of the abdomen and pelvis is nearly 100% accurate to not only diagnose the stone but to tell us how big it is, where it got stuck, and how dilated the ureter and renal pelvis might be (hydronephrosis). Most all emergency rooms use CT technology because it will also diagnose other possible reasons for a patient’s symptoms, such as appendicitis.

A CT Scan is a lot of xray. Can’t I just have a plain xray or ultrasound?

A plain x-ray is helpful in some cases, and most commonly is used if you are going to have treatment by using shock waves. Many calcium stones can be identified on plain x-ray, but uric acid stones can not.

Are there other tests I need?

A urinalysis is important. Traces of blood are often found. Signs of infection may require more urgent surgical treatment. Sometimes blood will help determine if you need more urgent treatment.

Why am I straining my urine? Won’t I know if the stone is passed when the pain is gone?

When you have been diagnosed with a kidney stone, you should begin straining all of your urine to know whether or not you have passed your stone. Some stones will be stuck in the ureter but won’t cause pain because the urine is draining around the stone. Some patients will think they have passed their stone because the pain went away, only to be surprised later by another onset of pain. When you strain your urine you will know when your stone has passed, and you can also bring that stone to our office so we can have it analyzed for the type of stone you’ve made.

I have had a stone before. What’s the best way to determine if I have a stone now that I should be worried about?

The easiest way to know if you have another stone is by getting a CT scan. Your specialist will help you decide if a CT scan is appropriate. CT scans are expensive, and they are a lot of x-ray. We try to be careful about using CT scans in our office, getting them only when we feel it is appropriate and necessary.