What are Kidney Stones?
Kidney stones are hard deposits of minerals and salts that form within the kidneys when certain substances in the urine become highly concentrated and crystallise.
Stones may remain inside the kidney or travel into the ureter which is the tube connecting the kidney to the bladder, where they can obstruct the flow of urine and cause significant pain.
Kidney stones vary in size, from tiny crystals that pass naturally to larger stones that require medical treatment.
What are Kidney Stones Made Of?
Several different types of kidney stones exist. The most common include:
- Calcium oxalate stones (the most common type)
- Calcium phosphate stones
- Uric acid stones
- Struvite (infection-related) stones
- Cystine stones (a rare inherited condition)
Identifying the type of stone helps determine the most effective treatment and strategies to prevent recurrence.
Why Do Kidney Stones Develop?
Kidney stones form when the balance of minerals, salts, and fluids in the urine changes, allowing crystals to develop and grow.
A number of factors can increase the risk of stone formation, including:
- Not drinking enough water
- High salt (sodium) intake
- Diets high in animal protein
- High oxalate intake in susceptible individuals
- Recurrent urinary tract infections
- Obstruction of the urinary tract
- Certain medications
- Obesity
- Family history of kidney stones
- Medical conditions such as:
- Gout
- Hyperparathyroidism
- Inflammatory bowel disease
- Short bowel syndrome
- Certain metabolic disorders
Some people are naturally more prone to developing kidney stones due to genetic factors.
Symptoms of Kidney Stones
The most common symptom is sudden, severe pain, often referred to as renal colic.
Pain may:
- Begin in the side or back (flank)
- Radiate towards the lower abdomen or groin
- Come in waves of varying intensity
Other symptoms may include:
- Blood in the urine
- Pain or burning when passing urine
- Frequent or urgent urination
- Nausea and vomiting
- Recurrent urinary tract infections
Some stones cause no symptoms and are discovered incidentally during imaging studies.
When is a Kidney Stone an Emergency?
A kidney stone requires urgent medical attention if it causes:
- Fever or chills
- Severe pain that cannot be controlled
- Persistent vomiting
- Difficulty or inability to pass urine
- A blocked kidney, particularly when accompanied by infection
In these situations, emergency drainage of the kidney may be required using a ureteric (DJ) stent or a percutaneous nephrostomy before definitive stone treatment can be performed.
Treatment
Treatment depends on:
- The size of the stone
- Its location
- Your symptoms
- Whether infection or obstruction is present
Treatment options may include:
- Observation and allowing the stone to pass naturally
- Medication to assist stone passage and manage pain
- Shockwave lithotripsy (ESWL)
- Ureteroscopy with laser stone fragmentation
- Percutaneous nephrolithotomy (PCNL) for larger stones
- Robotic or laparoscopic surgery in selected cases
Your urologist will recommend the most appropriate treatment based on your individual circumstances.
Preventing Future Kidney Stones
People who have formed one kidney stone are at increased risk of developing another. Fortunately, simple lifestyle changes can significantly reduce this risk.
Stay Well Hydrated
The single most effective way to prevent kidney stones is to drink enough fluid.
Aim to:
- Drink enough water to produce 2–2.5 litres of urine each day
- Increase your fluid intake during hot weather or exercise
- Choose water as your primary beverage
Reduce Salt Intake
A high-sodium diet increases the amount of calcium excreted in the urine, increasing the risk of stone formation.
Try to:
- Avoid adding extra salt to meals
- Limit processed and packaged foods
- Reduce intake of cured meats, salty snacks, and fast food
Eat a Balanced Diet
A healthy diet helps reduce the risk of recurrent stones.
General recommendations include:
- Eat plenty of vegetables and fruit.
- Choose wholegrains and high-fibre foods.
- Moderate your intake of animal protein, including red meat.
- Maintain a healthy body weight.
Maintain a Normal Calcium Intake
Contrary to popular belief, most people should not avoid calcium-rich foods.
A normal dietary calcium intake actually helps reduce the absorption of oxalate from the intestine and lowers the risk of calcium stone formation.
Calcium supplements should only be taken if recommended by your healthcare professional.
Limit High-Oxalate Foods if Recommended
If you have calcium oxalate stones, your urologist or dietitian may advise reducing foods high in oxalate, such as:
- Spinach
- Beetroot
- Nuts
- Chocolate
- Cocoa
- Rhubarb
These foods do not need to be completely avoided unless specifically recommended.
Use Vitamin Supplements Carefully
Excessive vitamin supplementation may increase the risk of stone formation.
In particular:
- Avoid high-dose Vitamin C supplements unless medically advised.
- Only take calcium or Vitamin D supplements if recommended by your healthcare provider.
Long-Term Stone Prevention
If you have recurrent kidney stones, your urologist may recommend additional investigations to identify the underlying cause, including:
- Blood tests
- 24-hour urine analysis
- Laboratory analysis of the stone itself
These tests allow treatment and dietary advice to be tailored specifically to your individual risk factors, helping to reduce the likelihood of future stone formation.
