The urinary system is made up of the kidneys, the ureters, the bladder, and the urethra. Each plays an important role in helping your body to eliminate waste products in the form of urine.
A kidney stone can develop when certain chemicals in your urine form crystals that stick together. The crystals may grow into a stone ranging in size from a grain of sand to a golf ball. Most stones form in the kidneys. Very small stones can pass through the urinary system without causing problems. However, larger stones, when traveling from the kidney through the ureter to the bladder, can cause severe pain called colic.
Most stones (70 to 80 percent) are made of calcium oxalate. A smaller number are made of uric acid or cystine.
One out of ten Canadians will have a kidney stone at some point in their life. Kidney stones occur much more commonly in men than in women. They tend to affect people in middle age, and occur more frequently hot climates.
The Urinary System
What causes kidney stones to form?
Normally, urine contains chemicals which prevent crystals from forming. However, some people seem to be more prone to kidney stones than others. If you are prone to kidney stones, there are several factors which contribute to their formation:
- Consuming too much calcium oxalate or food high in uric acid in your diet
- Drinking too little fluid
- Blockage of the urinary tract
- Certain metabolic diseases
- Recurrent urinary tract infections
- Consuming too much Vitamin C or D
- Bed rest for several weeks or more
- Certain medications
Sometimes, no causes can be found.
Symptoms of kidney stones
- Severe pain that usually starts suddenly in the small of the back under the ribs or in the lower abdomen, and which may move to the groin; the pain may last for minutes or hours, followed by periods of relief.
- Blood in the urine
- Nausea and vomiting
If you have a urinary tract infection, you may also experience:
- Burning during urination and the urge to urinate frequently
- Cloudy or foul-smelling urine
- Fever, chills and weakness
How are kidney stones diagnosed?
Kidney stones are diagnosed by a complete medical examination, X-rays and other tests. You will first be given a physical examination and asked questions about past kidney illness, your diet, use of medications, your lifestyle and family background. Your doctor will then perform a urine test to see if there is blood in the urine, and a blood test to check your kidney function and whether you have any metabolic abnormalities; an ultrasound, X-ray or a CT scan will also be scheduled.
An X-ray of the kidneys, ureters and bladder can reveal the presence of most stones. Sometimes, stones which are less common can be seen using an intravenous injection of dye or an ultrasound test.
Treating kidney stones
Most small stones pass through your body by themselves within hours or a few days. To help this process, your doctor will prescribe painkillers and advise you to drink lots of fluids and follow a special diet.
Stones that do not pass by themselves may have to be removed if they are stuck in the lower part of the ureter, or crushed with Extra-corporeal Shock Wave Lithotripsy (ESWL). This treatment is a non-surgical technique that uses high-energy shock waves to break the stones into small fragments (about the size of grains of sand). You can then pass them when you urinate during the next few weeks. This treatment is successfully used in many cases where the stones are less than two centimetres in size. When stones are larger than two centimetres, a surgical procedure is often needed.
The stones that you pass at home and those that are surgically removed should be sent to a laboratory for analysis.
Certain types of stones can be dissolved using medication. However, the most common stones (those containing calcium) can not be dissolved.
Preventing the formation of kidney stones
There are steps you can take, in consultation with your doctor and dietitian, to help prevent kidney stones.
- Drink at least two litres of water during the day and a glass of water whenever you get up at night to pass urine. Be sure to drink plenty after meals and after exercise.
- If you have calcium oxalate stones, be sure to stay within the recommended dietary allowance for calcium and avoid foods high in oxalate content (such as tea or chocolate). Do not take very large doses of Vitamin C (4 grams or more daily) and avoid heavy use of antacids. Vitamin B6 (not exceeding 50 mg/day) may protect against recurrent calcium oxalate stones.
- Decrease protein and salt intake.
- If you have uric acid stones, cut down on the amount of red meat you eat.
With acknowledgement to D.G. Oreopoulos MD, PhD, FRCPC, FACP, Professor of Medicine, University of Toronto, and Director, Kidney Stone Clinic, Toronto Western Hospital, for his assistance in compiling this information.