renal stones

Question 1

what are the types of renal stones?

Answer 1

Calcium stones – 80%
– Calcium oxalate
– Calcium phosphate – high density

Struvite- 10%
– A.ka. Magnesium Ammonium Phosphate
– Urease-producing organisms (proteus, Klebsiella): Convert urea to ammonia, causes alkaline urine and crystals form. Forms quickly and extensive – Staghorn calculi

Uric acid stone - 5%
– not seen on x-ray
– May be treated with urine alkalinisation by oral potassium citrate/sodium bicarbonate

Others -1%: cysteine, xanthine, silica, indinavir (not seen on CT)

Question 2

what are the causes of renal stones ?

Answer 2

• Metabolic - Hyperparathyroidism, idiopathic hypercalciuria, disseminated malignancy, sarcoidosis, hypervitaminosis D.
• Familial metabolic causes - Cystinuria, errors of purine metabolism, hyperoxaluria, hyperuricuria, xanthinuria.
• Infection.
• Impaired urinary drainage, e.g. medullary sponge kidney, pelviureteric junction (PUJ) obstruction, ureteric stricture, extrinsic obstruction.

Question 3

what are the S&S of renal stones?

Answer 3

• ‘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 calculus has passed into the distal ureter.

Question 4

what InV are done for renal stones ?

Answer 4

Urinalysis - Can show haematuria, leucocytes or nitrates.

FBC - May show infective cause with increased WCC and CRP

U&E’s - Calcium, phosphate or uric acid may be raised. There may be renal impairment and AKI.

Stone analysis - Used to assess composition of the stone if the patient brings a passed stone.

Non-contrast CT KUB - Gold standard for diagnosis. Non contrast as renal impairment may be present.

Renal tract US – can show hydronephrosis.

Question 5

where do the stones typically lodge?

Answer 5

Pelviureteric junction (PUJ)

Crossing the pelvic brim where the iliac vessels travel across the ureter in the pelvis.

Vesicoureteric junction (VUJ)

Question 6

how is an acute presentation of stones managed ?

Answer 6

• Analgesia, e.g. diclofenac 100mg PR or 5-10mg morphine orally; antiemetic, e.g. metoclopramide 10mg

IV; IV fluids. Antibiotics if infection suspected.

Tamsulosin - relaxes muscle and helps pass

• Small stones (<5mm) may be managed expectantly as most will pass spontaneously.
• Emergency treatment with percutaneous nephrostomy and/or ureteric stent insertion is necessary if either pain or obstruction is persistent.

Question 7

what are the elective surgical options available for stones?

Answer 7

Extracorporeal shock wave lithotripsy (ESWL).
- small proximal uteric stones (<1cm) or renal stones <2cm. Needs analgesia

Percutaneous nephrolithotomy (PCNL). 
- larger renal stones >2cm. Needs GA 

Flexible Ureteroscopy.
- small uteric or renal stones. Needs GA

retrograde uteric stent or nephrostomy

Question 8

what are the complications of renal stones ?

Answer 8

• Post renal AKI
• Obstruction and hydronephrosis
• Infection and sepsis
• Ureteric stricture