Kidney Stones

A kidney stone forms when urine becomes supersaturated with stone-forming salts and there is not enough citrate or fluid to keep them dissolved. Calcium oxalate accounts for around 80% of stones, followed by uric acid, struvite from infection, and rare cystine stones. Passing a stone produces flank pain that comes in waves, often radiating to the groin, with nausea and blood in the urine. The recurrence rate is high — roughly half of people form another stone within five to ten years — which is why prevention matters more than treatment of the acute episode. The most persistent myth is that people who form calcium stones should cut dietary calcium. The opposite is true: dietary calcium binds oxalate in the gut so it is excreted in stool rather than absorbed and filtered by the kidney. Low-calcium diets raise urinary oxalate and increase stone risk. What does help is high fluid intake, reducing sodium, which drives calcium into urine, moderating animal protein, and limiting the highest-oxalate foods such as spinach, rhubarb, almonds and black tea in people with documented hyperoxaluria. Calcium supplements taken away from food are a different matter — they raise risk, whereas calcium eaten with meals lowers it.

• •Severe waves of flank pain radiating to the groin
• •Blood in the urine
• •Nausea and vomiting
• •Urinary urgency and burning as the stone nears the bladder
• •Restlessness and inability to find a comfortable position

• •Low fluid intake
• •High dietary sodium
• •High animal protein intake
• •Low urinary citrate
• •Primary hyperparathyroidism
• •Malabsorption or bariatric surgery
• •Obesity and metabolic syndrome

Chronically low urine volume, high sodium intake, high animal protein load, low urinary citrate, hyperparathyroidism, gut malabsorption or bariatric surgery causing enteric hyperoxaluria, obesity and insulin resistance, and hot climates or heavy sweating.