urinary stones

Question 1

instrinsic factors for stones?

Answer 1

• Age
• Peak 20-50 years
• Gender
• Male: female 3:1
• Testosterone → oxalate production by liver
• Women higher urinary citrate

• Genetic
• Common in Caucasian/Asian
• Less common in native American/African/US
afrocaribean
• Renal tubular acidosis/cystinuria inherited

Question 2

extrinsic factors?

Answer 2

• Hot climates
• But complex!
• ‘Western Lifestyle’
• Excess food
• Poor fluid intake
• Limited exercise
• Summertime
• Dehydration → ↑Urinary concentration
• Vitamin D

• Water intake

• Diet
• Animal protein → high urinary oxalate, low urinary pH,
low urinary citrate
• Salt → hypercalciuria
• Low calcium diet → bone resporption → PO4- stones

• Sedentary occupation

Question 3

types of kidney stones

Answer 3

• Calcium oxalate 85%
• Uric acid 5-10%
• Mixed Ca phosphate/oxalate 10%
• Pure ca phosphate rare
• Struvite (Mg ammonium phosphate)2-20%
• Cystine stone 1%
• Indinavir rare

Question 4

meat and stones

Answer 4

Question 5

stone risks

Answer 5

Question 6

foods high in purine

Answer 6

Question 7

urolithiasis mechanisms

Answer 7

• ‘supersaturation’ of urine with respect to calcium
& oxalate

• I.e. exceeds Ksp
• Crystals should form but don’t!
• Stone inhibitors:
• Citrate
• Magnesium
• Tamm-Horsfall protein
• Glycosaminoglycans

• Meals/dehydration = periods of supersaturation

Question 8

risk factors for calcium stones?

Answer 8

• Hypercalciuria
• Hypercalcaemia – hyperparathyroidism
• Hyperoxaluria
• Hypocitraturia
• Hyperuricosuria
• Type 1(distal) Renal Tubular Acidosis

Question 9

uric acid stone (norm show on xray)

Answer 9

• Urate – soluble & Uric acid insoluble
• pKa 5.5
• I.e. uric acid insoluble in acid urine = uric acid
stones
• Gout = 1% form stones each year
• 50% uric acid stones have gout
• Myeloproliferative disorders & cytotoxic drugs
• idiopathic

Question 10

struvite stones

Answer 10

• ‘triple phosphate stones’
• Urease producing bacteria
• Hydrolyze urea into ammonium and CO2
• Alkalinizes urine
• Precipitates crystals of Calcium ammonium
phosphate
• = ‘stag horn calculi’

Question 11

organisms that facilitate urate production

Answer 11

Question 12

eval of stone

Answer 12

• U&E
• FBC
• Serum Ca
• Serum uric acid
• Urine pH
• Urine Culture
• 24hour urine collections
• Calcium, oxalate, citrate, uric acid, cystine

Question 13

diagnose stones

Answer 13

• Asymptomatic/incidental
• Symptoms - Loin pain, haematuria, UTIs
• Imaging
• Plain KUB xray
• Renal Ultrasound
• Intravenous urography
• Non contrast CT
• MR urography

Question 14

treatment option for kidney stones

Answer 14

• Watchful waiting
• Extracorporeal Shock Wave lithotripsy
• Flexible ureterorenoscopy
• Percutaneous nephrolithotomy (PCNL)
• Open surgery
• Medial ‘dissolution’ therapy

Question 15

ureteric colic

Answer 15

• Sudden onset flank pain

• Severe
• “worse than labour!”
• Colicky
• “come in waves”
• Radiates to groin
• “loin to groin pain”

• “can’t get comfortable”

Question 16

assessment in acute uretetic colic

Answer 16

• Examination
• Pt moves around
• Often ‘doubled up’
• NB peritonitic pt’s lie still!
• Pregnancy test
• DD = ruptured ectopic
• Ionising radiation
• Urine Dip
• 95% +ve to blood on 1st day of pain
• Temperature
• Infected obstructed kidney = septic shock = death!!!

Question 17

imaging uretetic colic

Answer 17

• Non-contrast CT KUB
• 95% specificity, 97% sensitivity
• Will diagnose other serious pathology!
• Leaking Aortic aneurysm
• Retrocaecal appendicitis

Question 18

mnage acute ureteric colic

Answer 18

• Diclofenac 100mg PR (‘voltarol suppository’)
• Reduces renal blood flow & renal pelvis pressure
• +/- opiate

• Normal fluid intake

Question 19

treat ureteric calculi

Answer 19

• Watchful waiting
• 90-98% <4mm will pass spontaneously
• Average time to passage of 4-6mm = 3 weeks
• Unlikely to pass after 2 months

• +/- medical expulsive therapy
– Tamsuloin 400mcg o.d.

Question 20

treatment of ureteri calculi

Answer 20

• Intervention if
• FEVER
• Failure to pass
• Poor pain control
• Social reasons e.g. pilot, submariner etc

Question 21

ureteric calculi interventions

Answer 21

• ‘double J-stent’
• Percutaneous nephrostomy
• If septic
• Shock Wave lithotripsy
• Ureteroscopy
• +/- basket extraction/laser fragmentation