Kidney, or urinary, stones are hard deposits that may occur in the kidney, ureter or bladder.
It is a common condition.
- Approximately 1 in 10 people will develop a urinary stone at some point in their life
- Every person runs a 5-10% risk of developing urinary stones at some point in their life
- Men develop urinary stones more often than women; the ratio is 3:1
- Urinary stones formation occurs more often in people aged between 30 and 50
- Patients with kidney stones often experience recurrence at some point in their life
The stones are formed when urine becomes more concentrated, allowing inorganic substances to crystallize and aggregate.
The passing of kidney stones through the ureter can be really painful; however, stones do not typically result in permanent damage.
Depending on the condition, the patient may only need analgesics and plenty of water intake to facilitate the excretion of the stone.
In different cases, surgical treatment may be required.
Kidney stones often are not due to a single cause.
Usually, several factors can increase the risk of developing kidney stones.
Stones are formed when urine contains increased levels of crystal-forming substances, such as calcium, oxalates and uric acid, which, above a specific concentration, cannot dissolve in the urine.
At the same time, our body may lack certain substances which prevent the formation of crystals, thus creating an ideal environment for the stones to form.
Types of stones
Knowing the composition of the stones can help determine the cause, and the knowing the cause in turn helps determine the treatment method.
Urinary stone types are:
- Calcium stones
The majority of kidney stones are calcium stones which often consist of calcium oxalate.
Oxalic acid is a substance found in food.
Some fruit and vegetables, as well as nuts and chocolate, contain high levels of oxalic acid.
Our liver also produces oxalates.
Dietary factors, such as high doses of vitamin D, surgical procedures in the bowel and several metabolic disorders may increase the concentration of calcium or oxalic acids in the urine.
Calcium stones may also occur in the form of calcium phosphate.
- Struvite stones
Struvite stones are formed due to urinary tract inflammations.
They may increase in size and become quite large, often with few symptoms.
- Uric acid stones
They may form in people who do not drink plenty of fluid or who lose significant amounts of fluid, as well as in those who consume large amounts of proteins or suffer from kidney failure.
Specific genetic factors may increase the risk of developing uric acid stones.
- Cystine stones
They develop in patients with congenital diseases which cause increased excretion of certain amino acids in the urine (cystinuria).
- Other rare types of stones may also form
Factors increasing the risk of developing urinary system stones include:
- Family history / heredity
If a family member has urinary stones, it is likely that other family members will also develop stones.
If a patient has developed stones in the past, he then runs an increased risk of developing other stones, too.
Stones are more commonly formed in patients aged 40 years and over, though they may occur at any age.
Reduced daily water intake can increase the risk of kidney stones.
Patients who live in warmer climates, as well as those who sweat more than normal, are at an increased risk compared to others.
- Eating habits
A diet rich in proteins, sodium and sugar can increase the risk of developing certain types of stones.
This is true, especially for diets rich in sodium.
The excessive amount of sodium in a diet increases calcium amounts which the kidneys have to filter; which is why it increases the risk of stone formation.
High Body Mass Index (BMI) and large waist circumference have been linked to increased risk of kidney stones.
- Gastrointestinal tract diseases and surgical procedures
Gastric bypass, inflammatory bowel disease and chronic diarrhea may cause changes in the digestive process, and affect calcium and water absorption, thus increasing the amounts of substances forming stones in the urine.
- Other pathological conditions
They include renal tubular acidosis, cystinuria, hyperparathyroidism, specific drug intake and urinary system inflammations.
A stone may not cause symptoms until it moves and passes into the ureter (the tube connecting the kidney with the bladder).
In this case, the following signs and symptoms may be present:
- Severe pain on the back and sides
- Pain progressing and spreading to the lower part of the abdomen and scrotum
- Pain which comes in waves and varies in severity (colicky pain)
- Pain during voiding
- Pink, red or brown urine
- Cloudy or smelly urine
- Nausea and vomiting
- More frequent urination than usual
- Fever and shivering when infection co-exists
The pain caused by a kidney stone may relocate and may change in intensity when the stone travels within the urinary system.
To diagnose the presence of a kidney stone in the urinary system, the following tests are required:
- Blood tests
May reveal high levels of calcium or uric acid in the blood.
Assist in the monitoring of renal health and can also assist in the diagnosis of pathological conditions related to kidney stones.
- Urine tests
A 24-hour urine collection and investigation helps measure the quantity of the excreted salts in the urine, as well as of substances which prevent the formation of kidney stones.
- Imaging tests
They can show stones present in the urinary tract.
Several options are available:
- simple X-ray of kidneys-ureter-bladder (KUB), which may, however, not show small stones
- high-resolution CT scan, which can reveal even small stones
- ultrasound examination
- intravenous pyelogram
In a pyelogram, a contrast agent is administered and then images are obtained as the contrast agent travels from the kidneys to the bladder.
- Stone analysis
It provides information to determine the cause of kidney stone formation and helps in the drawing up of the prevention and treatment plan.
It differs according to the type of stone and cause.
Small stones with few symptoms
Most kidney stones do not require aggressive therapy.
A small stone may be excreted in one of the following ways:
- Drinking water
Drinking 2 to 3 liters of water on a daily basis can help excrete the stone.
- Analgesic intake
Excreting a small stone can be painful. Which is why analgesics are recommended.
- Medication intake
Drugs, known as alpha-blockers, relax the muscles of the ureter and help excrete the stone more quickly and less painfully.
Large stones causing symptoms
Stones which cannot be conservatively treated, either because they are too large to excrete spontaneously or because they cause bleeding, obstruction and recurrent urinary tract infections, require aggressive treatment.
Invasive methods include:
- Ultrasound-guided extracorporeal lithotripsy
Percussion beams are targeted onto the stone, causing it to break down into small fragments.
It is a procedure well tolerated by the patient and its success rate is around 90%.
- Ureteroscopy and intracorporeal lithotripsy
Applied on stones located in the ureter.
It is performed via an endoscopy instrument called ureteroscope which, once inserted through the urethra and the bladder, enters the ureter and reaches the stone.
There, a laser beam breaks the stone down into small pieces.
- Percutaneous nephrolithotripsy
The method is applied on large kidney stones or stones not treatable with extracorporeal lithotripsy.
It is conducted through an incision on the skin which extends all the way to the kidney.
The nephroscope is inserted through the incision, and the stone is broken down into small fragments, using various energy sources.
- Open surgery
Today, open surgery is less common and is used only in complex cases.