Urinary Tract Calculi

Question 1

List 4 general risk factors for stones?

Answer 1

1. Dehydration
2. High dietary oxalate
3. Renal tubular acidosis
4. Polycystic kidney disease

Question 2

List the 2 key complications of kidney stones?

Answer 2

1. Obstruction leading to AKI
2. Infection with obstructive pyelonephritis

Question 3

What is the most common type of stone?

List the 2 types?

Answer 3

Calcium-based stones

• Calcium oxalate (more common)
• Calcium phosphate

Question 4

List 2 key risk factors for calcium stones

Answer 4

1. Hypercalcaemia
2. Low urine output

Question 5

How does hypercalcemia present?

Answer 5

Renal stones, painful bones, abdominal groans and psychiatric moans

Question 6

List 2 drugs which precipitate calcium stones

Answer 6

1. loop diuretics
2. steroids
3. acetazolamide
4. theophylline

Question 7

List the 3 key causes of hypercalcemia

Answer 7

1. Calcium supplementation
2. Hyperparathyroidism
3. Cancer (ie. myeloma, breast or lung cancer)

Question 8

Which drug may prevent calcium stones?

Answer 8

Thiazides (increase distal tubular calcium resorption)

Question 9

List 3 other types of kidney stones

Answer 9

• Uric acid (not visible on x-ray)
• Struvite
• Cystine

Question 10

List 2 risk factors for urate stones

Answer 10

1. gout
2. ileostomy (loss of HCO3 and fluid results in acidic urine)

Question 11

What are Struvite stones associated with?

Answer 11

Produced by bacteria, therefore, associated with infection

Question 12

What are the components of a Struvite stone?

Answer 12

Magnesium, ammonium and phosphate

Question 13

What are Cystine stones associated with?

Answer 13

Associated with cystinuria, an autosomal recessive disease

Question 14

What is a Staghorn Calculus?

Answer 14

Stone forms in the shape of the renal pelvis and extends into at least 2 calyces

(resemble antlers of a deer)

Question 15

Staghorn Calculus occur most commonly with what type of stone?

Why?

Answer 15

Struvite

In recurrent upper UTIs, bacteria hydrolyse urea in urine to ammonia, creating struvite

Question 16

Which stones appear opaque on X-ray?

Answer 16

1. Calcium Oxalate
2. Mixed calcium/ oxalate phosphate
3. Stag-horn calculi
4. Calcium phosphate

Question 17

Which stones appear radio-lucent on X-ray?

Answer 17

1. Urate stones
2. Xanthine stones

Question 18

How do cystine stones appear on x-ray

Answer 18

Semi-opaque, ‘ground glass’ appearance

Question 19

How do renal stones present?

Answer 19

Renal colic (excruciating unilateral loin to groin pain which is colicky) +/-

• Haematuria
• Nausea or vomiting
• Reduced urine output
• Symptoms of sepsis, if infection is present

Question 20

Initial Imaging of choice for Renal stones?

Answer 20

Non-contrast CT KUB should be performed on all patients within 24 hours of admission

Question 21

List 4 other initial investigations for suspected stones

Answer 21

1. urine dip and culture
2. Renal function (serum creatinine + electrolytes)
3. FBC / CRP
4. calcium/urate

Question 22

Management of kidney stones < 5mm

Answer 22

Will usually pass spontaneously within 4wks

Tamsulosin (alpha-blocker) can help aid the spontaneous passage of stones

Question 23

Management in patients with obstructive stones with signs of infection?

Answer 23

URGENT renal decompression + IV antibiotics

(Options incl nephrostomy tube, ureteric catheters and ureteric stent)

Question 24

What is the treatment of stones > 10 mm In the non-emergency setting?

Answer 24

1. Extracorporeal shock wave lithotripsy (ESWL)
2. Percutaneous nephrolithotomy (PCNL)
3. Ureteroscopy and laser lithotripsy
4. Open surgery (rarely used)

Question 25

What is the analgesia of choice for kidney stones?

Answer 25

NSAIDs eg. IM diclofenac (IV paracetamol is an alternative to NSAIDs)

Question 26

Advice to give patients to prevent Recurrent Stones

Answer 26

1. Increase fluid intake (2.5 – 3 litres/day) 2. Reduce dietary salt intake (\< 6g per day) 3. Add fresh lemon juice to water 4. Avoid carbonated drinks 5. Maintain a normal calcium intake

Question 27

List 2 foods you may recommend patients with calcium stones to AVOID

Answer 27

Oxalate-rich foods eg. spinach, beetroot, nuts, rhubarb and black tea

Question 28

List 2 foods you may recommend patients with uric acid stones to AVOID

Answer 28

Purine-rich foods eg. kidney, liver, anchovies, sardines and spinach

Question 29

List 2 medications which may be used to reduce the risk of recurrence in patients with calcium oxalate stones

Answer 29

1. Potassium citrate for calcium oxalate stones 2. Thiazide diuretics (e.g., indapamide)

Question 30

List 2 medications which may be used to reduce the risk of recurrence in patients with uric stones

Answer 30

1. Allopurinol 2. Oral bicarbonate