Urinary/Kidney Stones – Overview (Signs and Symptoms, Risk Factors, Pathophysiology, Treatment)
Urinary/Kidney Stones – Overview (Signs and Symptoms, Risk Factors, Pathophysiology, Treatment)
Kidney stones, also called renal calculi or urinary stones (urolithiasis), are hard deposits made of minerals and salts that form within the kidneys or urinary tract. They are a common condition, affecting approximately 1 in 10 people during their lifetime.
While some kidney stones are small enough to pass on their own without causing symptoms, others can become lodged in the urinary tract, leading to severe pain, urinary obstruction, infection, or kidney damage if left untreated.
Early diagnosis and appropriate treatment can help prevent complications and reduce the risk of future stones.
What Are Kidney Stones?
Kidney stones develop when certain minerals and waste products in the urine become highly concentrated and crystallize.
Over time, these tiny crystals can join together to form larger stones that may remain in the kidney or travel into the ureter—the tube connecting the kidney to the bladder.
Stone size varies from tiny grains of sand to several centimeters in diameter.
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Types of Kidney Stones
Different stones have different causes.
1. Calcium Stones (Most Common)
Approximately 80% of kidney stones are calcium stones, usually composed of:
Calcium oxalate
Calcium phosphate
Risk factors include dehydration, high sodium intake, excessive oxalate consumption, and certain metabolic disorders.
2. Uric Acid Stones
These develop when urine becomes too acidic.
Risk factors include:
Gout
High-purine diets
Obesity
Type 2 diabetes
Chronic dehydration
3. Struvite Stones
These stones are usually associated with urinary tract infections caused by certain bacteria.
They can grow rapidly and become very large.
4. Cystine Stones
These rare stones occur in people with cystinuria, an inherited disorder that causes excessive cystine to be excreted in the urine.
Signs and Symptoms
Small stones may cause no symptoms and are sometimes discovered incidentally during imaging for another reason.
Symptoms usually occur when a stone moves into the ureter or obstructs urine flow.
Common symptoms include:
Severe Flank Pain
The classic symptom is sudden, intense pain in the side or back, just below the ribs.
The pain may:
Come in waves
Be extremely severe (renal colic)
Move toward the lower abdomen or groin as the stone travels
Pain During Urination
As the stone approaches the bladder, urination may become painful or produce a burning sensation.
Blood in the Urine
Urine may appear:
Pink
Red
Brown
Sometimes blood is only detected through laboratory testing.
Frequent Urination
You may feel:
A frequent urge to urinate
Difficulty emptying the bladder completely
Urinating in small amounts
Nausea and Vomiting
Severe pain often triggers nausea and vomiting.
Cloudy or Foul-Smelling Urine
This may indicate an accompanying urinary tract infection.
Fever and Chills
Fever is not a normal symptom of an uncomplicated kidney stone.
Fever and chills suggest infection and require immediate medical attention, particularly if urine flow is blocked.
Risk Factors
Several factors increase the likelihood of developing kidney stones.
Dehydration
Not drinking enough fluids leads to concentrated urine, increasing crystal formation.
Family History
People with close relatives who have had kidney stones are more likely to develop them.
Previous Kidney Stones
Once you’ve had one stone, your risk of recurrence is significantly higher.
Diet
Higher risk has been associated with:
High sodium intake
High animal protein consumption
Excessive oxalate-rich foods (for susceptible individuals)
High sugar intake
Obesity
Obesity and metabolic syndrome increase stone risk.
Certain Medical Conditions
Examples include:
Hyperparathyroidism
Gout
Inflammatory bowel disease
Bariatric surgery
Type 2 diabetes
Renal tubular acidosis
Certain Medications
Some medications may increase stone formation in susceptible individuals.
Pathophysiology
Kidney stones develop through several steps.
1. Supersaturation
Urine becomes highly concentrated with minerals such as calcium, oxalate, uric acid, or cystine.
2. Crystal Formation
The minerals begin forming microscopic crystals.
3. Crystal Growth
Crystals enlarge as additional minerals attach.
4. Stone Formation
The crystals combine into larger stones.
5. Obstruction
If a stone enters the ureter, it may partially or completely block urine flow.
This blockage causes:
Increased pressure inside the kidney
Stretching of the urinary tract
Severe pain (renal colic)
If obstruction persists or infection develops, kidney damage may occur.
Diagnosis
Doctors may recommend:
Medical History and Physical Examination
The location and pattern of pain often provide important clues.
Urinalysis
Urine testing may detect:
Blood
Infection
Crystals
Abnormal urine pH
Blood Tests
These evaluate:
Kidney function
Calcium levels
Uric acid
Electrolytes
CT Scan
A non-contrast CT scan is considered the most accurate imaging test for diagnosing kidney stones.
Ultrasound
Ultrasound is often used in:
Pregnancy
Children
Patients requiring reduced radiation exposure
Treatment
Treatment depends on:
Stone size
Stone location
Symptoms
Presence of infection
Kidney function
Conservative (Non-Surgical) Treatment
Small stones (often less than 5 mm) frequently pass on their own.
Treatment may include:
Increased Fluid Intake
Drinking adequate fluids helps increase urine output and may facilitate stone passage, though fluid intake should follow your healthcare provider’s advice if you have other medical conditions.
Pain Relief
Doctors commonly recommend:
Nonsteroidal anti-inflammatory drugs (NSAIDs), when appropriate
Other pain medications depending on individual circumstances
Medical Expulsive Therapy
For selected patients with ureteral stones, medications such as alpha-blockers may help relax the ureter and increase the likelihood of stone passage.
Surgical Treatment
Larger stones or stones causing complications may require intervention.
Shock Wave Lithotripsy (SWL)
High-energy sound waves break the stone into smaller fragments that can pass more easily.
Ureteroscopy
A thin scope is passed through the urinary tract to locate and remove or fragment the stone using a laser.
Percutaneous Nephrolithotomy (PCNL)
Large or complex stones may require removal through a small incision in the back.
Emergency Drainage
If a kidney stone causes urinary obstruction with infection, urgent drainage using a ureteral stent or nephrostomy tube may be necessary before definitive stone treatment.
Prevention
Preventing recurrence is an important part of long-term care.
Doctors often recommend:
Drinking enough fluids to produce an adequate amount of urine daily
Limiting excessive sodium intake
Eating a balanced diet with adequate (not excessive) dietary calcium
Limiting excessive animal protein if advised
Maintaining a healthy weight
Taking prescribed preventive medications when indicated based on stone type and metabolic evaluation
The ideal prevention strategy depends on the type of stone and the underlying cause.
When Should You Seek Emergency Care?
Go to the emergency department immediately if you experience:
Severe flank pain that does not improve
Fever with suspected kidney stone
Chills
Persistent vomiting
Difficulty passing urine
Complete inability to urinate
Blood in the urine with severe pain
Symptoms affecting your only functioning kidney or a transplanted kidney
These symptoms may indicate obstruction, infection, or other serious complications.
The Bottom Line
Kidney stones are a common but often painful condition caused by the formation of mineral crystals in the urinary tract. Symptoms typically include sudden flank pain, blood in the urine, painful urination, nausea, and urinary urgency, although small stones may cause no symptoms at all. Major risk factors include dehydration, previous stones, obesity, certain dietary patterns, and specific medical conditions.
Most small stones pass without surgery, while larger or obstructing stones may require procedures such as shock wave lithotripsy, ureteroscopy, or percutaneous nephrolithotomy. Prompt medical evaluation is essential if symptoms are accompanied by fever, persistent vomiting, or difficulty passing urine, as these may signal a medical emergency. With appropriate treatment and preventive strategies, many people can successfully manage kidney stones and reduce their risk of recurrence.