Urolithiasis

Question 1

pathophysiology of urolithiasis

Answer 1

• ↑ concentration of urinary solute
• ↓ urine volume
• Urinary stasis

Question 2

most common sites to find renal stones

Answer 2

• Pelviureteric junction
• Crossing the iliac vessels at the pelvic brim
• Under the vas or uterine artery
• Vesicoureteric junction

Question 3

renal stone types

Answer 3

1. Calcium oxalate: 75%
   - ↑ risk in Crohn’s
2. Triple phosphate (struvite): 15%
   - Assoc. with proteus infection
3. Urate: 5% (radiolucent)
4. Cystine: 1% (radiofaint)

Question 4

factors associated with formation of renal stones

Answer 4

• Dehydration
• Hypercalcaemia: 1O HPT, immobilisation
• ↑ oxalate excretion: tea, strawberries
• UTIs
• Hyperuricaemia: e.g. gout
• Urinary tract abnormalities: e.g. bladder diverticulae
• Drugs: frusemide, thiazides

Question 5

general presentation of renal stones

Answer 5

• ureteric colic
• bladder or urethral obstruction
• UTI
• Haematuria
• sterile pyuria
• anuria

Question 6

features of ureteric colic

Answer 6

• Severe loin pain radiating to the groin
• Assoc. with n/v
• Pt. cannot lie still

Question 7

features of bladder or urethral obstruction

Answer 7

• Bladder irritability: frequency, dysuria, haematuria
• Strangury: painful urinary tenesmus
• Suprapubic pain radiating → tip of penis or in labia
• Pain and haematuria worse at the end of micturition

Question 8

urine investigations for renal stones

Answer 8

• dip: haematuria

- MC&S

Question 9

blood investigations for renal stones

Answer 9

FBC, U&E, Ca, PO4, urate

Question 10

imaging for renal stones

Answer 10

• Kidney, Ureter, Bladder (KUB) X-ray
• Ultrasound
• spiral non-contrast CT-KUB
• Intravenous Urogram (IVU)

Question 11

usefulness of KUB X-ray

Answer 11

• 90% of stones radio-opaque

- Urate stones are radiolucent, cysteine stones are faint

Question 12

what does ultrasound help to identify?

Answer 12

hydronephrosis

Question 13

usefulness of CT-KUB

Answer 13

• 99% of stones visible

- GOLD standard

Question 14

features of Intravenous Urogram (IVU)

Answer 14

• 600x radiation dose of KUB
• IV contrast injected and control, immediate and serial
  films taken until contrast @ level of obstruction

Question 15

abnormal findings of Intravenous Urogram

Answer 15

• Failure of flow to the bladder
• Standing column of contrast
• Clubbing of the calyces: back pressure
• Delayed, dense nephrogram: no flow from kidney

Question 16

contraindications to Intravenous Urogram

Answer 16

• Contrast allergy
• Severe asthma
• Metformin
• Pregnancy

Question 17

functional scans for renal stones

Answer 17

• DMSA: dimercaptosuccinic acid
• DTPA: diethylenetriamene penta-acetic acid
• MAG-3

Question 18

prevention of renal stones

Answer 18

• Drink plenty
• Treat UTIs rapidly
• ↓ oxalate intake: chocolate, tea, strawberries

Question 19

initial treatment of renal stones

Answer 19

1. Analgesia
   - Diclofenac 75mg PO/IM or 100mg PR
   - Opioids if NSAIDs CI: e.g. pethidine
2. Fluids: IV if unable to tolerate PO
3. Abx if infection: e.g cefuroxime 1.5mg IV TDS

Question 20

conservative management of renal stones

Answer 20

• 90-95% pass spontaneously
• Can discharge pt. c¯ analgesia
• Sieve urine to collect stone for out-patient analysis

Question 21

indications for medical expulsive therapy (MET)

Answer 21

• stone 5-10mm

- stone expected to pass

Question 22

drugs used in medical expulsive therapy

Answer 22

• Nifedipine or tamsulosin
• ± prednisolone
• Most pass w/i 48h, 80% w/i 30d

Question 23

indications for active stone removal

Answer 23

• Low likelihood of spontaneous passage: e.g. >10mm
• Persistent obstruction
• Renal insufficiency
• Infection

Question 24

methods of active stone removal

Answer 24

• Extracorporeal Shockwave Lithotripsy (SWL)
• Ureterorenoscopy (URS) + Dormier Basket Removal
• Percutaneous Nephrolithotomy (PNL)
• laparoscopic or open surgery (rare)

Question 25

indication for Extracorporeal Shockwave Lithotripsy (SWL)

Answer 25

Stones <20mm in kidney or proximal ureter

Question 26

side effects of Extracorporeal Shockwave Lithotripsy (SWL)

Answer 26

renal injury may → ↑BP

Question 27

contraindications to Extracorporeal Shockwave Lithotripsy (SWL)

Answer 27

pregnancy, AAA, bleeding diathesis

Question 28

indications for Ureterorenoscopy (URS) + Dormier Basket Removal

Answer 28

- Stone >10mm in distal ureter or if SWL failed | - Stone >20mm in renal pelvis

Question 29

indications for Percutaneous Nephrolithotomy (PNL)

Answer 29

- Stone >20mm in renal pelvis | - E.g. staghorn calculi: do DMSA first

Question 30

treatment of patient who is febrile with renal obstruction

Answer 30

- Surgical emergency - Percutaneous nephrostomy or ureteric stent - IV Abx: e.g. cefuroxime 1.5g IV TDS

Question 31

treatment summary for renal stones

Answer 31

- Conservative: stone <5mm in distal ureter - MET: stone 5-10mm and expected to pass - Active: stones >10mm, persistent pain, renal insufficiency

Question 32

1st line treatment for stone in renal pelvis

Answer 32

- >20mm = PNL or URS | - <20mm = SWL

Question 33

2nd line treatment for stone in renal pelvis

Answer 33

- >20mm = SWL | - <20mm = PNL or URS

Question 34

1st line treatment for stone in proximal ureter

Answer 34

- >10mm = URS or SWL | - <10mm = SWL

Question 35

2nd line treatment for stone in proximal ureter

Answer 35

<10mm = URS

Question 36

1st line treatment for stone in distal ureter

Answer 36

- >10mm = URS | - <10mm = URS or SWL

Question 37

2nd line treatment for stone in distal ureter

Answer 37

- >10mm = SWL