Kidney Stones

You may have had a kidney stone or know someone who has had one.  They are becoming more common, with the prevalence of kidney stones in the US jumping from 3.8% in the late 1970s to 10% or higher over the past several years.  Each year in the US, kidney stones are responsible for more than a half a million people going to the emergency room.  Let’s talk more about what a kidney stone is, what causes them, and how you might prevent them from happening to you.

What is a kidney stone?

A kidney stone is a hard object that is made up of salts and minerals that form within urine.  They can be as small as a grain of sand or as large as a pea.  They have a pebble-like appearance, which is the reason they are called stones.  

What causes a kidney stone?

There is not a single specific cause for a kidney stone, but several things can increase your risk for developing them.  Kidney stones develop when the urine contains more substances that can form into crystals than it has liquid to dilute them.  Sometimes the urine may not have enough of the necessary substances to prevent crystals from sticking together.

Things that may increase your risk of developing kidney stones include:

• Family history (or personal history) – If you have a family member with kidney stones, or if you have had a kidney stone in the past, then you are more likely to develop them.
• Dehydration – Not drinking enough water every day increases your risk.  The amount of water that you need daily depends on many things, including weather conditions, your level of exertion (how much you are sweating), the medications you take (such as diuretics), etc.
• Dietary factors – Too much salt in your diet increases the amount of calcium your kidneys need to filter, and significantly increases the risk of kidney stones.  Diets high in protein or sugar also increase your risk.  Sugar includes table sugar and high-fructose corn syrup.
• Certain supplements and medications – This includes vitamin C, calcium-based antacids, laxatives, some migraine medications, some antidepressants, and other dietary supplements.
• Obesity – High body mass index (BMI), significant weight gain, and large waist size, are all associated with an increased risk of kidney stones.
• Certain medical conditions – Certain kidney diseases, parathyroid overactivity, inflammatory bowel disease, chronic diarrhea, and frequent urinary tract infections can all increase your risk.  People who have had gastric bypass surgery are also at increased risk.
  

Are there different types of kidney stones?

There are four main types of kidney stones:

• Calcium oxalate – This is the most common type, which develops when calcium and oxalate combine within the urine.  You may think this would be from getting too much calcium, but it actually happens when your diet does not contain enough calcium, or enough water.  Some other conditions may contribute to these stones as well.
• Uric acid – Another common type of stone, these are more common in people who have gout, or people whose diets are high in purines (high in foods such as organ meats and shellfish).
• Struvite – Caused by infections in the upper urinary tract.
• Cystine – A rare cause of stones, which is usually hereditary.  

What are the Symptoms of a Kidney Stone?

Pain from a kidney stone usually starts after the stone leaves the kidney and gets into the ureter (the tube that connects the kidney to the bladder).  The ureter is a fairly small tube and is easily irritated by a stone.  The stone may get lodged within the ureter, causing a blockage of urine.  Pain from a kidney stone often builds rapidly to severe pain.  The bigger the stone, the worse the symptoms will be.  Here are the possible symptoms:

• Severe pain on either side of your flank or lower back, which may radiate to the lower abdomen or groin.  Pain often comes in waves, fluctuating in intensity.
• Vague pain in the abdomen that does not go away
• Blood in the urine, which gives the urine a pink, red, or brownish color
• Urinating more often, feeling a persistent need to urinate, or urinating small amounts
• Nausea and/or vomiting
• Fever and chills
• Urine that is cloudy or has a bad smell

Next week, we will talk more about how the diagnosis of a kidney stone is made and how they are treated. 

If you have any questions about kidney stones, please log into your account and send us your question. We are here to help.

Dr. Anita Bennett MD - Health Tip Content Editor