Urinary tract stones

Question 1

How common is it?

Answer 1

Prevalence of stones in the population is around 3% males>females

Question 2

Who does it affect?

Answer 2

Most common age of presentation: 20-50 years.

Question 3

What causes it?

Answer 3

Commonest reason for urological emergencies. 90% of calculi are radio-opaque. Several causes:

Metabolic: Hyperparathyroidism, idiopathic hypercalciuria, disseminated malignancy, sarcoidosis, hypervitaminosis D.

Familial metabolic causes: Cysturia, errors of purine metabolism, hyperoxaluria, hyperuricuria, xanthinuria

Infection

Impaired urinary drainage: e.g. medullary sponge kidney, pelvi-uteric junction obstruction, ureteric stricture, extrinsic obstruction.

Question 4

What risk factors are there?

Answer 4

Peak presentation in summer months. 75% of stones are calcium. 15% are struvite stones, triple phosphate. 5% uric acid stones. Cysteine stones, 1-2%. Are others even rarer.

Question 5

How does it present?

Answer 5

Ureteric/renal colic.

Severe, intermittent stabbing pain radiating from loin to groin.

Microscopic or rarely, frank haematuria.

Systemic symptoms such as nausea, vomiting, tachycardia, pyrexia.

Loin or renal angle tenderness due to infection or inflammation.

Iliac fossa tenderness if the calculas has passed into the distal ureter

Question 6

Investigations

Answer 6

Raised WCC and CRP suggests supradded infection or inflammation. Raised Cr suggests renal impairment. Stones often visible on plain abdo X-ray. Serum calcium, phosphate and uric acid. 24hr urine for Ca, phosphate, oxalate, urate, cysteine, and xanthine. Non-contrast CT is the gold standard for locating the stones.

Question 7

Treatment

Answer 7

Acute presentations: analgesia, if less than 0.5cm then conservatively. Percutaneous nephrostomy and or uteric stent insertion is necessary if either pain or obstruction are persistent.

Elective presentations: Extra-corpeal nephrolithotomy, endoscopic treatment or open nephrolithotomy.