A kidney stone (or renal calculus) is a hard, crystalline deposit that forms in the kidneys when mineral and acid salts in the urine become highly concentrated and crystallize. They can occur anywhere in the urinary tract, from the kidneys to the bladder, but typically cause the most severe problems when they move into the ureters (the narrow tubes connecting the kidneys to the bladder).
Key Characteristics
Composition: Most kidney stones are made of calcium oxalate (the most common type). Other types include struvite, uric acid, and cystine stones.
Size: They can be as small as a grain of sand or as large as a pearl.
Pain: The condition is famous for causing renal colic, which is sudden, agonizing pain that occurs when a stone blocks the ureter.
Symptoms
The most prominent symptom is the severe pain experienced when the stone moves:
Severe, sharp pain in the side and back, below the ribs (flank pain).
Pain that radiates to the lower abdomen and groin.
Pain that comes in waves and fluctuates in intensity.
Painful urination (dysuria).
Urgency and frequent need to urinate.
Pink, red, or brown blood in the urine (hematuria).
Nausea and vomiting.
Fever and chills (if an infection is present—a medical emergency).
Causes and Risk Factors
Kidney stones form when there is an imbalance in the chemical composition of the urine. Risk factors include:
Dehydration: Not drinking enough water is the primary risk factor.
Diet: High intake of salt, sugar, animal protein, and foods rich in oxalate (for calcium oxalate stones).
Family or personal history of kidney stones.
Obesity.
Certain medical conditions: Such as urinary tract infections (leading to struvite stones), gout (leading to uric acid stones), and hyperparathyroidism.