Renal stones

Question 1

Kidney stone : definition

Answer 1

1. Solutes in the urine precipitate out and crystallise
2. Occurs when certain solutes become too concentrated
3. Commonly form in the kidneys and ureters.

Question 2

Kidney stone : Clinical features

Answer 2

Dull or localised constant flank plain

Question 3

Kidney stone : Investigations

Answer 3

1. Urine dipstick and culture
2. Bloods incl calcium/urate
3. US and CT KUB

Question 4

Renal stone : Calcium oxalate

Answer 4

1. Calcium oxalate stone: calcium ion binds to oxalate ion
2. Description :Black or dark brown coloured stone
3. X-ray : radiopaque, looks white
4. Risk factor : More likely to form in acidic urine

Question 5

Renal stone : Calcium oxalate

Answer 5

1. Calcium phosphate : calcium ions bind to phosphate ions
2. Description : Dirty white in colour
3. X-ray : radiopaque, white.
4. Risk factor : More likely to form in alkaline urine

Question 6

Renal stone : Uric acid stone

Answer 6

1. Uric acid stone : uric acid becomes a urate ion which binds to sodium
2. Red-brown stones
3. X-ray : radiolucent under x-ray, non visible
4. Risk factor :
   High uric acid - causes gouty arthritis
   High purine diet - uric acid is breakdown of purine, high purine foods such as shellfish, red meat
   Gout
   Ileostomy - loss of bicarbonate and fluids results in acidic urine

Question 7

Renal stone : Uric acid stone - Mx

Answer 7

Allopurinol
Urinary alkalinization e.g. oral bicarbonate

Question 8

Renal stone : Cysteine stones

Answer 8

1. Cystine stones : composed of amino acid cysteine which leaks into the urine and crystallises
2. Yellow or light pink coloured stone
3. X-ray - radiolucent, not visible

Question 9

Renal stone : Xanthine stones

Answer 9

Xanthine stone - by product of purine breakdown
Red-brown in colour
X-ray : radiolucent, non visible

Question 10

Renal stone : Drugs precipitating kidney stones

Answer 10

1. Drugs that promote calcium stone : loop diuretics, steroids, theophylline
2. Thiazides that prevent calcium stone - increase distal tubular calcium resorption

Question 11

Kidney stone : Conservative management

Answer 11

1. IM diclofenac for pain relief
2. Alpha blockers - can be used in conservative management with greatest benefit amongst larger stone

Question 12

Kidney stone : Mx of renal stone <5mm

Answer 12

1. <5mm - renal stone pass spontaneously within 4 weeks - if infected or transplant needs intervention

Question 13

Kidney stone : Mx of renal stone <2cm

Answer 13

1. <2cm - Lithotripsy
   Shock wave generated leading to fragmentation of stones, larger stones may result in ureteric obstruction
2. <2cm in pregnancy females
   * Ureteroscope : passed retrograde through the ureter and renal pelvis, when lithotripsy is contraindicated such as in pregnancy and in complex stone disease. Stent is left inset for 4 weeks after procedure.

Question 14

Kidney stone : Mx of complex renal calculi

Answer 14

Complex renal calculi and stag horn calculi : Percutanoeus nephrolithotomy