Urinary tract calculi

Question 1

How do renal stone present?

Answer 1

1. Asymptomatic
2. Haematuria
3. Proteinuria
4. Sterile pyuria
5. Anuria
6. Renal colic - excrutiating ureteric spasms (loin to groin) with nausea and vomiting

Renal obstruction felt in the loin

Obstruction of mid-ureter may mimic appendicitis/diverticulitis

Obstruction of lower ureter = bladder irritability and pain in scrotum, penile tip or labia majora.

Obstruction in bladder or urethra = pelvic pain, dysuria, strangury (desire but inability to void)

Pyelonephritis = Fever, rigors, loin pain, nausea, vomiting

Question 2

What are the causes of renal stones?

Answer 2

Metabolic (50%)
– Type 1 Renal tubular acidosis (hypercalciuria)
– Hyperparathyroidism (hypercalciuria)
– Cystinuria (inherited defect: cystine stones)
– Sarcoidosis
– Crohn’s disease (enteric hyperoxaluria)

Urological 20%
– Pelvic – ureteric junction obstruction

Infection (15%)

Immobilization (5%) causing bone decomposition

Question 3

What is the composition of renal stones?

Answer 3

• 75% - Calcium oxalate (visible on an x-ray)
• 10% - Struvite ‘staghorn’
• 10% - Urate (radiolucent)

Question 4

Where do renal stones normally occur?

Answer 4

Stones form in collecting ducts and may be deposited anywhere from the renal pelvis to the urethra, though classically at 3 points:

1. Pelviureteric junction
2. Pelvic brim
3. Vesico-ureteric junction

Question 5

How do you test for urinary tract calculi?

Answer 5

FBC
U&E
Calcium
Phosphate
Glucose
Bicarbonate
Urate

Urine dipstick: positive for blood
Urine pH
24 hour urine for calcium oxalate, urate, citrate, sodium, creatinine, stone biochemistry

Question 6

How do you image urinary tract calculi?

Answer 6

Spiral non-contrast CT

Kidneys, urine and bladder X-ray

Question 7

How do you treat urinary tract stones?

Answer 7

Analgesia

Increase fluid intake (to reduce solute load)

Treat infection

Bendroflumethiazide, Allopurinol, Penicillamine

Stones <5mm in lower ureter
–> approx 90-95% will pass spontaneously

Stones >5mm/pain not resolving

• ->Medical expulsive therapy e.g. nifedipine
• -> most pass within 48hours
• -> Extracorporeal shockwave lithitripsy (US waves shatter stone)
• -> Percutaneous nephrolithotomy (Keyhole surgery to remove stones, when large, multiple or complex)
• -> Open surgery (rare)

Question 8

What are the side effects of extracorporeal shockwave lithitripsy?

Answer 8

Renal injury
Hypertension
Diabetes mellitus

Question 9

How can renal stones be prevented?

Answer 9

Drink plenty
Normal dietary Calcium intake

Calcium stones –> thiazide diuretic is used to decrease calcium excretion

Oxalate –> pyridoxine used to decrease oxalate

Struvite: treat infection promptly

Urate: allopurinol

Cystine: vigorous hydration to keep urine output >3l/day and urinary alkalinisation