Renal Stone Analysis (Nephrolithiasis)

What sample is needed for Renal Stone Analysis?

1. Renal stones passed in the urine.
2. Renal stones were taken at the time of surgery.

What are the Indications for Renal Stones Analysis?

1. This analyses the constituents of renal stones.
2. It helps to treat the underlying cause of stone formation.
3. For the prevention of future stone formation.

What is the Epidemiology of renal stone formation?

1. In the USA, about 5% of women and 20% of men may develop renal stones during their life.
2. About 20% of people with stones have elevated serum calcium concentration due to hyperparathyroidism.
3. Prolonged deposition causes irreversible damage to kidneys.
4. If a stone passes through the ureter or by surgery, it may be checked, and the patient’s diet may be guided.

What is the composition of renal stones?

1. Calcium oxalate stones are 80%.
2. Calcium phosphate is 10%.
3. Uric acid is 9%.
4. Rest 1% is cysteine, ammonium acid urates, or magnesium ammonium phosphate. Etc.
5. These substances crystalize within the organic matrix.

What is the Mechanism of urinary stone formation?

1. It depends upon various factors like:
   1. Urine output depends upon fluid intake.
   2. Excretion of relatively insoluble substances.
   3. The absence of a substance inhibits the stone formation.
2. Stones form by concentric deposition of the poorly insoluble substance around some nuclei.
3. This nucleus may be blood clots, bacteria, fibrin, or sloughed epithelial cells.
4. The precipitation of the insoluble substances is initiated by infection, dehydration, urinary obstruction, or excessive intake or production of the compound.
5. Once the stone forms, then it starts to grow by accretion unless it is dislodged or removed by surgery.

What are the factors leading to renal stone formation?

1. Renal stone formation promoters are:
   1. Albumin.
   2. Globulin.
   3. Matrix substance A.
2. Renal stone inhibitors are:
   1. Magnesium.
   2. Citrate.
   3. Glycoprotein (Tamm-Horsfall).
   4. Pyrophosphate.
   5. RNA.
3. Predisposing factors are:
4. Pre-urinary is:
   1. More common in the female sex.
   2. Hot climate. This is due to decreased fluid intake.
   3. Stress.
   4. Immobilization.
   5. Protein-rich diet.
5. Urinary factors are:
   1. Increased Calcium.
   2. Increased oxalate.
   3. Increased urate.
   4. Decreased citrate.
   5. Decreased Magnesium.
   6. Increased pH.
   7. Decreased volume.
6. Metabolic abnormalities are:
   1. Milk-alkali syndrome.
   2. Renal tubular acidosis.
   3. Primary hyperparathyroidism.
   4. Cushing’s disease.
   5. Hereditary hyperoxaluria.
   6. Medullary sponge kidney.

What is the role of pH in renal stone formation?

1. Calcium oxalate is the most common stone, and it forms in 80% of the population when urine is acidic (low pH).
2. Calcium phosphate stone forms when urine is alkaline (high pH).
3. Uric acid is 5% to 10%, and it forms when urine is persistently acidic.
4. Cystine stones are rare and are a genetic disorder.

Calcium oxalate stones:

How will you discuss the calcium oxalate stones?

1. Calcium oxalate stones are the most common. They may be associated with concentrated urine or consistently increased urinary calcium or oxalate excretion.
2. Kidney stones may be as small as 1mm in diameter and larger than 2.5 cm in diameter.
3. Sometimes, small stones may pass into the ureter from the kidney and from there to the urinary bladder and, ultimately, through the urethra, which goes out.
4. Stones produce obstruction and pain.
5. 90% of the stones are seen on X-Ray.
6. What is the mechanism of Calcium Oxalate stone formation?
   1. There is a possibility that a person is excreting an excess of Calcium or oxalate.
   2. Or there is a very small amount of citrate, which binds the calcium and does not form the stone.
   3. An inherited tendency to absorb more than the normal amount of calcium from the diet leads to hypercalciuria.
   4. Taking food with a high concentration of calcium or oxalate increases the amount of these substances in the urine.
   5. Inflammatory bowel disease or intestinal surgery may lead to a nutrient imbalance of absorption and may result in excess urinary calcium.
   6. A raised parathyroid hormone level leads to an increased calcium level in the urine and blood.
   7. Metabolic disorders leading to metabolic acidosis cause increased calcium excreted in the urine.

Calcium Phosphate stone formation:

• This has the same factors as calcium oxalate stones.

Uric acid stone formation:

What is the mechanism of uric acid stone formation?

1. This is due to increased production of uric acid or excess secretion, seen in the following conditions:
   1. Gout.
   2. Disorders of uric acid metabolism.

Cystine stone formation:

What is the mechanism of cystine stone formation?

• This is due to increased production and excretion of cystine, a hereditary disease.

How will you do the renal stone analysis?

Physical examination:

1. Describe the shape of the stone.
2. Weigh and measure the size.
3. Note the color, surface appearance, and consistency.

What will be the appearance of calcium stones?

1. Calcium stones =   65%.
2. Calcium oxalate stones = 30%
3. calcium phosphate = 10%
4. Calcium mixed (oxalate+phosphate) = 25%
   1. These are hard, small to medium sizes, and often multiple.
   2. An X-ray will show the radiopaque shadow.

What will be the appearance of uric acid stones?

1. These are 5%.
   1. These are small, yellow, and friable.
   2. These may be large staghorn shapes.
   3. On the  X-ray are radiolucent.

What will be the appearance of magnesium-ammonium phosphate?

1. These are 25%.
   1. These may be large.
   2. These may be staghorn.
   3. These are on X-ray are radiopaque.

What will be the appearance of Cystine stone?

1. These are 2%.
   1. On X-ray radiolucent.
   2. These may be brown.
   3. These may be large and may be staghorn.

What Reagents are needed for renal stone analysis?

1. Sodium carbonate solution.
   1. 2 mol/L. Dissolve 20 grams of Na_² CO₃ in 100 mL of distal water.
2. Phosphotungstic acid.
   1. 50 grams of molybdenum-free sodium tungstate in 350 mL of water, add 20 mL of 85% H₂PO₄, and reflux (the process of boiling a liquid so that any vapor is liquefied and returned to the stock) for 2 hours.
   2. Add 1 drop of liquid bromine, cool to room temperature, and makeup to 1 L volume with water.
3. Ammonium Molybdate in HNO_3^. 
   1. Dissolve 5 grams of ammonium molybdate in 123 mL water and add 12 mL concentrated HNO₃ with stirring.
4. Sodium cyanide, 50 grams/L.
   1. Dissolve 5 grams NaCN in 100 mL water and add 0.2 mL in concentrated NH₄OH.
5. Ammonium hydroxide in concentrated form.
6. Nitric acid (HNO₃) concentrated is needed.
7. Sulphuric acid.
   1. Concentrated H₂SO₄ is needed.
8. Hydrochloride (HCL).
   1. 1 mol/L. Add 8 mL concentrated HCl to water and make up to 100 mL volume.
9. Sodium nitroferricyanide.
   1. Dissolve 5 grams in 100 mL. Discard when the color fades.
10. Ammonium Thiocyanate.
    1. Dissolve 3 grams in 100 mL water.
11. Sodium oxalate.
    1. Add 5 grams of salt to 100 mL water to saturate it with sodium oxalate, shaking well and allowing it to settle.
12. Sodium hydroxide (NaOH) 5 mol/L.
    1. Dissolve 20 grams of NaOH in water and make it up to 100 mL volume when it is cool.
13. Manganese Dioxide (MnO₂)  powdered reagents.
14. Titan yellow.
    1. Dissolve 0.1 grams in 100 mL water. Add 3 drops (5 mol/L) to make it alkaline.
    2. Store it in an amber bottle and prepare it every 30 days.
15. Alkaline Hypochlorite.
    1. 0.5 mol/L NaOH, and 30 mmol/L of NaOCl.
    2. When the solution cools, dissolve 25 grams of NaOH in 600 mL water, then add 43 mL of commercial-grade Hypochlorite solution (52 grams/L NaOCl).
    3. The reagent is stable for at least 3 months when protected from light and stored at 4 to 8 °C.
16. Phenol-Nitroferricyanide.
    1. 0.5 mol/L phenol and 0.8 mmol/L sodium nitroferricyanide.
       1. Add 50 grams of reagent-grade phenol to 500 mL water in a flask and 0.25 grams of sodium nitroferricyanide.
       2. Dilute to the mark with water.
       3. The reagent is stable for at least 2 months when stored at 4 to 8 °C.
17. Sodium nitrite (NaNO₂).
    1. 0.1 gram/dL in water.
    2. Prepare just before use.
18. N-(1-naphthyl) Ethylenediamine Dihydrochloride.
    1. Dissolve 0.1 gram /100 mL of the above reagent in water.
    2. Prepare fresh solution on the day of the procedure.
19. Acetic anhydride.
20. Chloroform.
21. p-Methylaminophenol sulfate.

What is the Procedure for renal stone analysis?

1. If the stone is larger than 25 mg, it is pulverized in the mortar and crushed in a test tube.
   1. If this is less than 25 mg, crush it in a test tube with a glass rod.
   2. Dissolve the stone in 1 mol/L HCl.
2. Add 2 mL of HCl 1 mol/L, and stir to dissolve.
3. Take the supernatant for the analysis.

How will you find Calcium?

1. 3 drops of the supernatant on a slide or plate.
2. 4 drops of sodium oxalate.
3. 2 drops of NH₄OH.
   1. Result: White precipitate positive for calcium.

How will you detect Oxalate?

1. Take a pinch of MnO2 and add it to the supernatant fluid.
2. If there is the release of tiny gas bubbles.
   1. Result: Positive for oxalate.

How will you detect Urate?

1. Stone powder or residue adds one drop of Na₂CO_3.
2. Add 2 drops of phosphotungstate solution.
   1. Result:  Positive prompt blue color develops.

How will you detect Carbonate?

1. Observe the supernatant fluid for bubbles when the acid is added.
   1. Result: Positive when you see effervescence.

How will you detect Phosphate?

1. Place a few mg of the crushed stone on the plate (or slide).
   1. For very small stones can use 3 drops of the supernatant.
2. Add 2 drops of the ammonium molybdate.
3. Add 2 drops of p-methylaminophenol sulfate.
   1. Result: Positive deep blue color.
      1. You can run the blank (negative control) with the test.

How will you detect Magnesium?

1. Place 3 drops of the supernatant on a white spot plate or slide.
2. Add 3 drops of NaOH.
3. Add one drop of Titan yellow solution.
   1. Result: Positive when seeing a red precipitate.

How will you detect Ammonia?

1. Take 3 drops of the supernatant off the white spot plate or slide.
2. Add 2 drops of NaOH.
3. Add one drop of phenol-nitroferricyanide solution.
4. Add one drop of alkaline hypochlorite solution.
5. Mix and place in a 37 °C incubator for 3 to 5 minutes.
   1. Result: Positive blue color develops.

How will you detect Cystine?

1. A few mg of stone powder on a spot plate or slide.
   1. Or take the residue from the acid solution.
2. Add one drop of NH₄OH.
3. Add one drop of NaCN.
4. Wait for 15 minutes.
5. Add 2 drops of sodium nitroferricyanide.
   1. Result: Positive is a brick red color.

How will you detect Cholesterol?

1. Take small powder in the small test tube.
2. 5 drops of chloroform and stir it.
3. Add 10 drops of acetic anhydride.
4. One drop of concentrated sulphuric acid.
   1. Result: Positive when bluish-green color develops.

How will you detect Xanthine?

1. Place the stone powder in the evaporating dish.
2. Add 0.5 mL of concentrated HNO₃.
3. Heat to dryness in the fumes hood.
4. Add concentrated NH₄OH to a residue in the dish.
   1. Result: Positive when the yellow residue turns orange on the addition of NH₄OH.

How will you detect Iron?

1. Make powder of the stone.
2. Add 3 drops of HNO₃.
3. Add 3 drops of NH₄SCN.
   1. Result: Positive when red color develops.

How will you follow the patient with stone formation?

1. Other tests needed to evaluate the renal stone formation include:
   1. Urinalysis to see the pH, presence of RBCs or WBCs, and type of crystals.
   2. Blood and Urine were collected for 24 hours to evaluate the amount of calcium, uric acid, and creatinine. It can evaluate oxalate, phosphates, citrate, or cystine.
   3. Complete blood count to rule out acute infection.

How will you diagnose stones in a patient?

1. Urine analysis.
2. Ultrasound.
3. CT scan.
   1. A blood test is used to guide the patient in the formation of stones.

What is the outcome of renal stones?

1. <5 mm in D stones have a high chance of passing out.
2. Stones 5 to 7 mm in diameter have a 50% chance of passing out.
3. Stones of >7 mm in diameter need treatment.

Questions and answers: