What is a Kidney Stone (Renal Calculi)?
A kidney stone is a type of hard deposit which can form inside one or both of your kidneys. It’s made up of certain minerals or salts.
These build-ups are also known as nephrolithiasis or renal calculi. Anyone can develop a kidney stone, yet it poses more of a threat in men than it does in women.
Severity typically depends on the size and amount of stones. A smaller kidney stone can usually be passed painlessly from your urinary tract without intervention. (1, 2)
Kidneys are two organs on either side of your abdomen. They perform a number of vital functions within your body.
They are responsible for filtering waste products and excess water from your blood. These unnecessary substances are then passed from the body as urine. (3)
A kidney stone forms in the center of your kidney known as the renal pelvis. This is where urine is passed into the ureter, a tube connecting the kidney to your bladder. (4)
There are four different compounds a kidney stone can be made out of including: uric acid, minerals calcium and struvite, or an amino acid called cystine.
Calcium deposits are the most common, comprising an estimated 80 percent of kidney stones. Struvite and uric acid accumulations occur less frequently. Cystine stones are comparatively rare.
Conditions which alter the acidity of your urine can trigger the formation of a kidney stone. These include gout, diabetes and severe urinary tract infections such as cystitis.
A family history of kidney stones, eating a diet high in salt and dehydration can also increase your risk of developing these deposits.
A kidney stone only causes symptoms if it is large enough to block your ureter or renal pelvis. (5)
If this occurs, you may experience one or more of the following symptoms: (6)
Lower Back Pain
A kidney stone can cause lower back pain. This symptom can manifest as a persistent ache which may travel down to your groin.
Severe Abdominal Pain
A telltale symptom of a kidney stone is extreme abdominal pain. It typically occurs in the side or lower areas of the abdomen.
This debilitating pain can last for several minutes or hours. It may also periodically worsen and then ease in cycles.
Nausea and Vomiting
Some individuals with a kidney stone experience nausea and vomiting.
Blood in your urine can indicate the presence of a kidney stone. Dark urine is common, and it may turn pink, brown, or red.
Bloody urine can be caused by the kidney stone scratching against your ureter or kidney.
If you’re suddenly experiencing pain when you urinate, you could have a kidney stone.
Fever and Chills
Occasionally, a kidney stone can result in an infection of the kidney. Chills, shivering, and fever can occur if the stone is blocking your ureter.
If you have a fever of more than 38 degrees celsius, seek urgent medical attention.
A kidney stone can vary in material, location and size. The mechanisms of how a kidney stone forms can be described as follows: (7)
Nucleation is the first stage of kidney stone formation.
It involves molecules (or ions) gathering together to create microscopic particles inside your kidney.
These microscopic particles can solidify into crystals. This process is called crystallization.
Once crystals have developed, they can mass together in what is known as aggregation.
In some cases, new crystals can begin the process of nucleation on the surfaces of existing crystals.
Organic materials within the kidney help bind these crystals together. At this stage in the process, the kidney stone begins to solidify.
These organic materials consist of lipids, proteins and other substances derived from cells.
The solidified stone grows as a result of crystals accumulating together.
It can also grow when new crystals start the process of nucleation on the surface of old ones.
Doctors usually suspect a kidney stone if you present with telltale symptoms. If you also have a history of this condition, diagnosis is easier.
Your doctor will perform a series of tests to check the size, type and location of the kidney stone or stones. These include imaging tests such as a CT scan or ultrasound.
A urinalysis can reveal the presence of infection or tiny pieces of stones. Finally, blood tests can reveal which substances (e.g. calcium) could be causing your kidney stones.
Ideally, you should try to keep any stones which may pass through your urine. A laboratory analysis of the stone can help your doctor determine the best treatment. (8)
The goal of treatment is to help dissolve or remove the kidney stone.
You may also receive medication to manage pain and other disruptive symptoms. For
example, antiemetic medication can reduce nausea and vomiting. (9)
Treatment for a kidney stone includes the following options:
If you have a kidney stone which is not particularly large in size, you might not require medical intervention.
Your doctor will suggest drinking plenty of fluids (preferably water) to help pass the stone at home. You will have to consume enough to turn your urine totally colorless. (10)
A stone which has formed from uric acid can also be treated in this manner. These stones tend to be less hard than other kidney stones.
Drinking a minimum of three litres of water per day can reduce the size of a uric acid stone. In some cases, this method may help dissolve it entirely. (11)
Extracorporeal Shockwave Lithotripsy (ESWL)
ESWL involves the use of an ultrasound machine to break down a kidney stone into pieces. The small fragments can then be passed through your urine.
Ultrasound machines use sound waves of a frequency so high we cannot hear them. These sound waves (ultrasound) can target the location of a kidney stone.
This form of treatment can cause discomfort. You will likely receive medication to dull the pain before the process begins.
Depending on the size and quantity of your kidney stones, you might require multiple sessions.
ESWL is highly effective in breaking down a stone with a diameter of 20 millimeters or less. It’s the most common treatment method for kidney stones.
A ureteroscopy is a procedure to remove a kidney stone stuck in your ureter. It does require general anesthetic.
A ureteroscope, which is a type of slim telescope, will be inserted inside your urethra. The urethra is where urine exits your body.
Once the ureteroscope reaches the offending stone, it can be removed in one of two ways.
The first approach is to carefully remove the stone manually with another medical tool. The second method is to break the stone apart using lasers.
This procedure is between 50 and 80 percent successful in treating stones of a diameter of 15 millimeters or less.
Percutaneous Nephrolithotomy (PCNL)
PCNL is a type of surgical procedure to treat a larger kidney stone. As with ESWL, it is performed under general anesthesia.
It has a success rate of 86 percent in treating stones reaching a diameter of 21 to 30 millimeters.
A telescopic instrument called a nephroscope is inserted through a minor incision in your back. From there, it passes into your kidney. The kidney stone is then removed through the incision or broken apart with lasers.
Surgery is usually a last resort for treating an extremely large kidney stone. It is also performed on individuals with kidney abnormalities.
Through a surgical incision in your back, a surgeon will remove the stone from your kidney or ureter. (12)
What is a kidney stone (renal calculi)? A kidney stone is a solid deposit which can form in one or both of your kidneys.
What are the signs of a kidney stone (renal calculi)? The signs of a kidney stone can include lower back pain, severe abdominal pain and bloody urine. You may also experience nausea, vomiting, painful urination and fever.
How do you develop a kidney stone (renal calculi)? A kidney stone develops as a result of certain substances building up in your kidneys to form hard deposits. These substances include calcium, struvite, uric acid or cystine.
How are you diagnosed for a kidney stone (renal calculi)? A kidney stone can be diagnosed with imaging tests, urinalysis and blood tests.
What is the best treatment for a kidney stone (renal calculi)? You may be prescribed medication to manage pain and nausea. Other treatments include: drinking water, extracorporeal shockwave lithotripsy, ureteroscopy, percutaneous nephrolithotomy or surgery.
What are the long term complications of a kidney stone (renal calculi)? Recurring kidney stones can increase your chances of developing chronic kidney disease. (13)
Is a kidney stone (renal calculi) considered a disability? A kidney stone does not meet the definition of a disability because it can be resolved with treatment. To qualify, your condition must be chronic (i.e. last for longer than one year) or terminal. (14)
Is a kidney stone (renal calculi) life threatening? If untreated, a kidney stone can cause deadly complications. These include urosepsis (severe infection of the urinary tract) or infection of the kidney in question, both of which can be life threatening. (15)
A kidney stone can be extremely painful if it grows large enough. You can reduce your risk of developing a kidney stone by remaining hydrated.
If your urine is very dark, you are likely not consuming enough fluids. Make sure you drink water regularly throughout the day.
If you have already suffered from a kidney stone, consult your doctor for advice about how to manage your health and diet to prevent recurrence. (16)