Kidney Stones

Question 1

What are the two key complications of kidney stones?

Answer 1

Obstruction
Leading to AKI

Infection
With obstructive pyelonephritis

Question 2

What is the most common type of kidney stone?

Answer 2

Calcium-based stones
- Calcium oxalate (more common)
- Calcium phosphate

Question 3

What are the risk factors for calcium stone formation?

Answer 3

Raised serum calcium
Low urine output

Question 4

Asides from calcium-based stones, what other types of kidney stones are there?

Answer 4

Uric acid
Not visible on x-ray

Struvite
Produced by bacteria- associated with infection

Cystine
Associated with cystinuria- autosomal recessive disease

Question 5

What is a staghorn calculus?

Answer 5

Stone forms in the shape of the renal pelvis

Body sits in the renal pelvis with horns extending into renal calyces, seen on x-ray

Question 6

What are staghorn calculi stones commonly made of?

Answer 6

Struvite

In recurrent upper urinary tract infections, bacteria can hydrolyse urine to ammonia, creating solid struvite

Proteus Mirabilis

Question 7

What is renal colic?

Answer 7

Presenting complaint in symptomatic kidney stones

Unilateral loin to groin pain

Colicky (fluctuating severity) as stone moves and settles

Question 8

How can kidney stones present?

Answer 8

Renal colic

May also be:
- Haematuria
- Nausea or vomiting
- Reduced urine output
- Sepsis symptoms if infection is present

Question 9

What investigations can be used for kidney stones?

Answer 9

Urine dipstick

Blood tests

AXR (can show calcium stones as they are radiolucent)

CT KUB (non-contrast) NICE recommend within 24 hours of presentation

Ultrasound KUB, negative result does not exclude stones

Question 10

How are kidney stones managed?

Answer 10

NSAIDs
-Intramuscular diclofenac, IV paracetamol is an alternative if NSAIDs unsuitable

Antiemetics
Antibiotics
Watchful waiting
-If the stone is < 5mm 50-80% chance they will pass

Tamsulosin
Surgical intervention

Question 11

What surgical interventions are available for kidney stones?

Answer 11

Extracorporeal shock wave lithotripsy
Shockwaves directed at stone under X-ray guidance, breaks up stones

Ureteroscopy and laser lithotripsy
Camera into urethra, bladder and ureter to identify stone

Stone broken up by lasers

Percutaneous nephrolithotomy
General anaesthetic- nephroscope inserted via patient’s back

Scope inserted into kidney to look at ureters, stones broken into smaller pieces and removed

Question 12

What does NICE advise after one episode of renal stones?

Answer 12

• Increased fluid intake
• Add lemon juice to water (citric acid binds to urinary calcium)
• Avoid carbonated drinks (phosphoric acid promotes calcium oxalate formation)
• Reduce salt intake
• Maintain normal calcium (Low calcium increases kidney stones risk)

Question 13

What recommendations are there for calcium renal stones?

Answer 13

Reduce intake of oxalate-rich foods e.g.
- Spinach
- Beetroot
- Nuts
- Black tea

Question 14

What recommendations are there for uric acid stones?

Answer 14

Reduce purine intake e.g.
- Kidney
- Liver
- Anchovies
- Spinach

Question 15

What medications limit risk of recurring kidney stones?

Answer 15

Potassium citrate
Calcium oxalate stones and raised urinary calcium

Thiazide diuretics
Calcium oxalate stones and raised urinary calcium