Urinary Tract Calculi

Question 1

What do renal stones consist of and where do they form?

Answer 1

1. Crystal aggregates

2. Collecting ducts

Question 2

Where are the classic sites of renal stone deposits?

Answer 2

1. Pelviureteric junction
2. Pelvic brim (ureter over iliac vessels)
3. Vesicoureteric junction (most common place for impaction)

Question 3

What are the two main compositions of renal stones?

Answer 3

1. Calcium oxalate (calcium and phosphate, 75%) - hypercalciuria but not hypercalcaemia.
2. Uric acid stones (radiolucent on x-ray)

Question 4

What are the causes of hypercalciuria?

Answer 4

1. Absorptive - over absorption from the gut
2. Renal hypercalciuria - defect in PCT impairing calcium absorption.
3. Hypercalcaemia - usually due to primary hyperparathyroidism.

Question 5

What are the risk factors for developing renal stones?

Answer 5

1. High protein and salt intake
2. Caucasian, M:F 3:1
3. Dehydration, obesity, PMHx of renal stones
4. Antacids, steroids, aspirin

Question 6

What is this a presentation of?
Excruciating spasms of renal colic classically ‘loin to groin’, flank pain can radiate to groin and testicles. Cannot lie still. N&V. Frequency symptoms sometimes (bladder irritation). Proteinuria, sterile pyuria, anuria. May be signs of infection.

Answer 6

Renal stones

Question 7

What type of haematuria do kidney stones cause?

Answer 7

Microscopic

Question 8

How should suspected renal stones be investigated?

Answer 8

1. FBC, U&Es, calcium, phosphate, urate, bhCG
2. Exclude pregnancy
3. Urine dipstick (+ve for blood)
4. MSU for MCS
5. Non-contrast CT, 80% visible on KUB X-ray.
6. In pregnancy and children - renal USS 1st line.

Question 9

What is the indication for urgent surgical treatment in renal stones and how are they treated?

Answer 9

1. Sepsis and obstructing stone in kidney or ureter.
2. Antibiotics and renal decompression.
3. Ureteric stent or percutaneous nephrostomy tube.

Question 10

What is the treatment for renal stones with no complications?

Answer 10

1. Analgesia - diclofenac IV/IM/PR, morphine and anti-emetic.
2. IV fluids if cannot tolerate oral.
3. Antibiotics if infection - tazocin or gentamicin.
4. Stones <5mm in lower ureter - normally pass spontaneously with increased fluid intake.
5. Stones >5mm/pain not resolving - medical expulsive therapy, extracorporeal shockwave lithotripsy, percutaneous nephrolithotomy.

Question 11

Which medications are used in medical expulsive therapy in renal stones?

Answer 11

Nifedipine (Ca channel blocker) or Tamsulosin (alpha blocker)

Question 12

What is the difference between extracorporeal shockwave lithotripsy and percutaneous nephrolithotomy?

Answer 12

1. Shatters stone which can be collected/pass alone.

2. Keyhole surgery to remove stones (reserved for large proximal ureteric/renal stones).

Question 13

How are renal stones prevented?

Answer 13

1. 2L of water per day
2. In hypercalciuria - thiazide diuretic to decrease calcium excretion.
3. Normal dietary calcium intake
4. Decrease oxalate intake
5. Alkalinise the urine as urate is more soluble at pH >6
6. Allopurinol also for high urate