urolithiasis

Question 1

how common is urolithiasis?

Answer 1

5% of population

Question 2

risk factors

Answer 2

more prevalent in men

Question 3

how are urinary stones formed?

Answer 3

By precipitation of urinary solutes e.g. calcium salts, uric acid or cystine.

Question 4

types of stones, in order of commonness

Answer 4

calcium
struvite
uric acid
cystine

Question 5

rf normocalcaemic stones

Answer 5

immobilisation (paraplegia, quadriplegia), renal tubular acidosis

Question 6

rf hypercalcaemic stones

Answer 6

hypercalcaemia, excess vitamin D, sarcoidosis

Question 7

key rf to ask on hx

Answer 7

UTI, gout, immobility

Question 8

radio-opacity of stones

Answer 8

calcium and struvite are radio-opaque. uric acid is radioluscent. cystine is faintly radio-opaque (“ground glass”)

Question 9

acidity/alkalinity of stone formation

Answer 9

calcium oxalate forms in acidic urine
calcium phosphate forms in alkaline urine
struvite forms in alkaline urine with urea-splitting bacteria (proteus, klebsiella)
uric acid forms in acidic urine
cystine can form in either

Question 10

appearance of calcium phosphate stones

Answer 10

elongated, blunt crystals

Question 11

calcium oxalate appearance

Answer 11

dumbbell-shaped or appear as paired pyramids (envelope shape when viewed on end)

Question 12

struvite appearance

Answer 12

Soft and grow to fill the renal pelvis, taking on staghorn configuration

Question 13

uric acid appearance

Answer 13

Variety of shapes, with needles and rhomboid forms being most common

Question 14

cystine appearance

Answer 14

Appear as hexagonal crystals in urine

Question 15

presentation of stones

Answer 15

Presents with loin or loin-to-groin pain

May have haematuria with nondysmorphic RBCs

Question 16

complications of stones

Answer 16

Oliguria/ARF uncommon but can result if there is bilateral obstruction (e.g. struvite stones) or if solitary functioning kidney is affected

Question 17

ix workup

Answer 17

dipstick and MCS
strain urine and analyse stones
24h urine collection - calcium, phosphate, oxalate, citrate, uric acid, cystine (outpatients)
FBE, UEC, LFT, CRP/ESR, CMP, PTH, uric acid
x-ray/CTKUB

Question 18

rx principles

Answer 18

analgesia + hydration
if obstruction complete or associated with infection, do nephrostomy and stone removal (extracorporeal shockwave lithotripsy, cystoscopy, percutaneous techniques, or surgery)