4.5.2 Kidney Stones

Kidney stones are hard, crystalline mineral materials that form within the kidney or urinary tract. They can vary in size from grains of sand to golf balls and may cause severe pain. The condition of having stones in the kidney is termed nephrolithiasis.

Definition

Kidney Stones: Urinary stones are hard, crystalline mineral materials that stick together to form small "pebbles" within the kidney or urinary tract. They can be as small as grains of sand or as large as golf balls. They may stay in kidneys or travel out of the body through the urinary tract. The condition of having stones in the kidney is termed nephrolithiasis.

Main Idea

• Kidney stones are hard, crystalline mineral materials.
• They form within the kidney or urinary tract.
• They can be as small as grains of sand or as large as golf balls.
• They may stay in kidneys or travel out through the urinary tract.
• The condition is called nephrolithiasis.
• There are five major types of urinary stones.
• The type of stone can be hypothesized by studying the urine test.

Core Concept

• Kidney stones = hard, crystalline mineral materials
• Nephrolithiasis = condition of having stones
• Five types = calcium oxalate, calcium phosphate, magnesium ammonium phosphate, uric acid, cystine
• **Size** = 2–3 mm; can be larger
• Staghorn stone = branching stone
• Urine pH = determines stone type
• Calcium oxalate = acidic urine
• Calcium phosphate = alkaline urine
• Uric acid = persistently acidic urine
• Nephrology = study of kidneys

Detailed Explanation

What Are Kidney Stones?

• Urinary stones are hard, crystalline mineral materials.
• They stick together to form small "pebbles" within the kidney or urinary tract.
• They can be as small as grains of sand or as large as golf balls.
• They may stay in kidneys or travel out of the body through the urinary tract.
• The condition of having stones in the kidney is termed nephrolithiasis.

Types of Urinary Stones

There are five major types of urinary stones:

Size and Shape

• Uric stones are composed of a combination of uric acid and calcium oxalate.
• They are normally 2–3 mm in diameter.
• They have either a smooth or uneven surface.
• A branching stone is called a staghorn stone.

Hypothesizing Kidney Stone by Urine Test

• When urine is acidic (low pH), the stone is of calcium oxalate.
• When the urine is alkaline (high pH), the stone is of calcium phosphate.
• When urine is persistently acidic, the stone is of uric acid type.

Do You Know?

The science concerned with the structure, functions, and diseases of the kidneys is called nephrology.

Symptoms

• Severe pain in lower back
• Blood in urine
• Nausea
• Vomiting
• Fever and chills
• Urine that smells bad or looks cloudy

Causes

• Kidney stones may be caused by increased calcium level in the blood, which is termed hypercalcemia.
• It, in turn, causes high calcium in the urine, the hypercalciuria.
• Increased oxalate level in the urine is called hyperoxaluria.
• Hypercalciuria and hyperoxaluria cause calcium oxalate type of kidney stones which are present in 70% of kidney stone patients.
• Hyperuricemia is the increased amount of uric acid in the blood and it causes uric acid type of kidney stones which are found in 10% of kidney stone patients.
• High concentration of cysteine and phosphates in urine also cause kidney stones.
• Continuous state of dehydration increases the chances of kidney stone formation.

Treatment

- Extracorporeal Shock Wave Lithotripsy (ESWL) and Percutaneous Nephro Lithotripsy (PCNL) are common methods for kidney stone treatment.

• In ESWL, an instrument called lithotripter is used to generate shock waves from outside the patient's body focused on the stone, breaking it into small pieces.
• Most of the fragments then pass spontaneously via the urethra.

• In case of larger stone, PCNL is preferred.
• A tube is inserted from the patient's back into the kidney to create a tract.
• A scope is run through the tract to directly visualize the stone inside the kidney.
• Ultrasound equipment can then be inserted to break up the stone.
• While watching the stone through the scope, the stone fragments can be grasped with special equipment and pulled through the tract out from the kidney.

Open Surgery: - Open surgery is now almost never needed except for large bladder stone.

Intermediate Level

Types of Kidney Stones

Causes of Kidney Stones

Symptoms of Kidney Stones

Treatment of Kidney Stones

Size and Shape

Formula / Mathematical Form

Not applicable to this topic.

Solved Example

Not applicable to this topic (descriptive topic).

Important Points

• 1. Kidney stones are hard, crystalline mineral materials.
• 2. They form in the kidney or urinary tract.
• 3. They can be as small as grains of sand or as large as golf balls.
• 4. The condition is called nephrolithiasis.
• 5. There are five major types of urinary stones.
• 6. Calcium oxalate is the most common type (70%).
• 7. Uric acid stones are found in 10% of patients.
• 8. Calcium oxalate stones form in acidic urine.
• 9. Calcium phosphate stones form in alkaline urine.
• 10. Uric acid stones form in persistently acidic urine.
• 11. Hypercalcemia = high calcium in blood.
• 12. Hypercalciuria = high calcium in urine.
• 13. Hyperoxaluria = high oxalate in urine.
• 14. Hyperuricemia = high uric acid in blood.
• 15. Dehydration increases the risk of kidney stones.
• 16. Symptoms include severe pain, blood in urine, nausea, vomiting, fever, and chills.
• 17. ESWL uses shock waves to break stones.
• 18. PCNL uses a tube through the back to remove stones.
• 19. Open surgery is rarely needed.
• 20. Nephrology is the study of kidneys.

Remember

• - Kidney stones = hard, crystalline mineral materials
• - Nephrolithiasis = condition of having stones
• - Five types = calcium oxalate, calcium phosphate, magnesium ammonium phosphate, uric acid, cystine
• - Calcium oxalate = acidic urine; 70% of cases
• - Calcium phosphate = alkaline urine
• - Uric acid = persistently acidic urine; 10% of cases
• - Hypercalcemia = high calcium in blood
• - Hypercalciuria = high calcium in urine
• - Hyperoxaluria = high oxalate in urine
• - Hyperuricemia = high uric acid in blood
• - ESWL = shock waves
• - PCNL = tube through back
• - Staghorn stone = branching stone
• - Nephrology = study of kidneys

Common Mistakes

• 1. Thinking all kidney stones are the same — There are five major types.
• 2. Confusing the pH for stone types — Calcium oxalate = acidic; calcium phosphate = alkaline.
• 3. Mixing up hypercalcemia and hypercalciuria — Hypercalcemia = blood; hypercalciuria = urine.
• 4. Confusing hyperoxaluria and hyperuricemia — Hyperoxaluria = oxalate; hyperuricemia = uric acid.
• 5. Mixing up ESWL and PCNL — ESWL = shock waves; PCNL = tube through back.
• 6. Thinking open surgery is always needed — Open surgery is rarely needed.
• 7. Forgetting the role of dehydration — Dehydration increases stone risk.
• 8. Mixing up the symptoms — Pain, blood in urine, nausea, vomiting, fever, chills.
• 9. Thinking kidney stones only affect older people — They can affect people of all ages.
• 10. Confusing nephrology and urology — Nephrology = kidneys; urology = urinary tract.

Quick Revision

Kidney stones are hard, crystalline mineral materials that stick together to form small "pebbles" within the kidney or urinary tract. They can be as small as grains of sand or as large as golf balls. The condition of having stones in the kidney is termed nephrolithiasis. There are five major types of urinary stones: calcium oxalate, calcium phosphate, magnesium ammonium phosphate, uric acid, and cystine. The type of stone can be hypothesized by studying the urine test: when urine is acidic, the stone is calcium oxalate; when the urine is alkaline, the stone is calcium phosphate; when urine is persistently acidic, the stone is uric acid type. Causes include hypercalcemia, hypercalciuria, hyperoxaluria, hyperuricemia, high cysteine and phosphates, and dehydration. Symptoms include severe pain in lower back, blood in urine, nausea, vomiting, fever and chills, and cloudy urine. Treatment includes ESWL (shock waves) and PCNL (tube through back). Open surgery is rarely needed.

60-Second Revision

• Kidney stones = hard, crystalline mineral materials
• Nephrolithiasis = condition of having stones
• Five types = calcium oxalate, calcium phosphate, magnesium ammonium phosphate, uric acid, cystine
• Calcium oxalate = acidic urine; 70% of cases
• Calcium phosphate = alkaline urine
• Uric acid = persistently acidic urine; 10% of cases
• Hypercalcemia = high calcium in blood
• Hypercalciuria = high calcium in urine
• Hyperoxaluria = high oxalate in urine
• Hyperuricemia = high uric acid in blood
• ESWL = shock waves
• PCNL = tube through back
• Warning: Dehydration increases the risk of kidney stones

NEXT TOPIC

• Chapter:
• 4. Urinary System of Man

• Topic:
• 4.5.3 KIDNEY FAILURE

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