Urinary calculi (kidney stones)
Kidney stones are crystals that grow in concentrated urine. The biggest diet step is plenty of fluid; the rest depends on the stone type.
At a glance
Types of stones and specific diet
| Stone | Cause or setting | Diet |
|---|---|---|
| Calcium oxalate (most common) | Concentrated urine, high oxalate, high salt, low calcium intake | Fluids; normal calcium with meals; limit high-oxalate foods, salt and animal protein; no high-dose vitamin C |
| Calcium phosphate | Alkaline urine, some kidney and hormone disorders | Fluids; limit salt; older books advise an acid-ash diet |
| Uric acid | Gout, high purine intake, acidic urine | Fluids; limit purines (organ meats, sardines, meat extracts, shellfish) and alcohol; alkaline-ash foods (fruits, vegetables) |
| Struvite (magnesium ammonium phosphate) | Urinary infection; can form large 'staghorn' stones | Treat infection; fluids; older books advise an acid-ash diet |
| Cystine | Inherited defect (cystinuria) | Very high fluid (at least 3.5-4 litres a day, so urine is over 3 litres); limit salt; alkaline urine |
Dietary principles (calcium oxalate stones)
| Nutrient | Recommendation | Why |
|---|---|---|
| Fluid | 2.5-3 litres a day, spread through the day and at night; water, lemon water, barley water | Dilute urine cannot form crystals easily |
| Calcium | Normal intake (about 1,000 mg) from milk and curd, taken with meals | Calcium binds oxalate in the gut so less is absorbed |
| Oxalate | Limit high-oxalate foods | Less oxalate reaches the urine |
| Sodium | Salt under 5 g a day | More salt means more calcium in urine |
| Protein | Moderate animal protein (about 0.8-1 g/kg total protein) | Excess meat raises urine calcium and uric acid and lowers citrate |
| Citrate | Lemon, sweet lime and orange juice | Citrate stops calcium crystals from forming |
| Vitamin C | Avoid high-dose supplements (over 1 g a day) | Extra vitamin C is changed to oxalate |
Foods to include and avoid (calcium oxalate stones)
| Food group | Include | Avoid or limit |
|---|---|---|
| Fluids | Water, lemon water, barley water, buttermilk | Colas, strong tea in large amounts, alcohol |
| Vegetables | Bottle gourd, ridge gourd, cabbage, cauliflower, cucumber, carrot, beans | Spinach (palak), amaranth leaves, beetroot, colocasia leaves |
| Fruits | Lemon, sweet lime, orange, banana, apple, watermelon | Large amounts of strawberries |
| Protein foods | Milk, curd, paneer, dal, egg in moderate amounts | Large meat portions, organ meats |
| Others | Home-cooked food with little salt | Nuts and sesame in large amounts, chocolate, cocoa, pickles, papad, chips |
Sample one-day menu (calcium oxalate stones)
| Meal | Menu |
|---|---|
| Early morning | 2 glasses of water; lemon water |
| Breakfast | Idli (3) with sambar (bottle gourd); milk (1 glass) |
| Mid-morning | Barley water; sweet lime |
| Lunch | Rice, dal, cabbage poriyal, cucumber salad, curd |
| Evening | Buttermilk; banana |
| Dinner | Chapati (2), ridge gourd curry, paneer or egg curry (little salt) |
| Bedtime | A glass of water (and another if awake at night) |
Ask stone patients to look at their urine colour: pale yellow means enough fluid. Many patients wrongly stop milk; explain that normal calcium protects against oxalate stones.
2 marks: “Name four types of urinary calculi.” Calcium oxalate, calcium phosphate, uric acid, struvite (also cystine).
5 marks: “Explain the dietary management of calcium oxalate stones.” Fluid 2.5-3 L, normal calcium with meals, limit oxalate foods, salt under 5 g, moderate animal protein, citrate, no high-dose vitamin C.
10 marks: “Discuss the types, causes and dietary management of urinary calculi.” Define, types table with specific diets, causes, symptoms, principles for oxalate stones, foods to include and avoid, menu.
Stone diet: 'Drink more, salt less, keep calcium, cut oxalate'. Pale urine is the goal.