Urostones

Question 1

What are the risk factors for developing urostones?

Answer 1

Intrinsic
- male
- genetics
- metabolic 
- medical conditions (hyperthyroid, malabsorption, drugs, sarcoidosis)
Extrinsic
- climate
- occupation
- fluid intake
- diet

Question 2

How are bladder stones formed?

Answer 2

Under-saturated
Supersaturated byt stable - metastable
Supersaturated with spontaneous precipitation - unstable

Question 3

What are the saturation and formation products?

Answer 3

Saturation product - level at which no more solute will dissolve without a change in pH or temperature
Formation product
- level at which spontaneous formation occurs

Question 4

What is the free-particle model of stone formation?

Answer 4

Urine containing crystals flows down the collecting ducts
Crystals grow and agglomerate
A critical particle gets trapped in the tubule

Question 5

What is the fixed-particle model of stone formation?

Answer 5

Urine containing crystals flows down the collecting ducts
Crystals grow and agglomerate
Particle adheres to the damaged site on the tubule wall and other crystals agglomerate with it

Question 6

Name some stone inhibitors.

Answer 6

Citrate
Magnesium
Pyrophosphate
Glycoproteins

Question 7

Name some stone promoters.

Answer 7

THP

Matrix substance A

Question 8

What factors affect stone formation?

Answer 8

Decrease liklihood of stone formation
- Low volume
- Low pH
- Low citrate 
- Low magnesium
Increase stone formation
- high uric acid
- high calcium
- high oxalate

Question 9

What types of stones occur in the bladder?

Answer 9

Calcium stones (80%)
- calcium oxalate monohydrate
- calcium phosphate 
Infection stones (10%)
- struvite 
Uric acid stone (5%)
- not seen on X-Ray
Others (1%)
- cysteine, silica

Question 10

How do bladder stones present?

Answer 10

Incidental
- imaging being done for a different reason
Pain
- colic, radiates from loin to groin, can’t settle and unable to stay still
Haematuria
- visible or non-visible
Sepsis/infection

Question 11

What initial investigation are done if you suspect bladder stones?

Answer 11

History and examination
Bloods
- CRP, FBC, U&Es
Urine
- non-visible haematuria (85%)
Imaging
- CT KUB (non-contrast) is best

Question 12

What biochemical workup would you do if someone presented with their first stone?

Answer 12

U&Es
Calcium
Urate
Urine dip
Sodium nitroprusside (cysteine)
Stone analysis

Question 13

What biochemical workup would you do if someone presented with a recurrent stone?

Answer 13

U&Es
Calcium 
Urate
Venous bicarbonate 
24 hour sodium urine analysis

Question 14

How are stones managed?

Answer 14

Passing naturally
- <4mm 75% chance
Medical therapy
Surgical therapy

Question 15

Describe the medical therapy for bladder stones.

Answer 15

Analgesia
- NSAIDs reduce pain due to reduced GFR, renal pressure and ureteric peristalsis
Medical expulsion therapy
- possibly

Question 16

What are the surgical options for bladder stones?

Answer 16

Ureteroscopy and basket
Ureteroscopy and fragmentation
Flexible ureteroscopy 
ESWL - extracorporeal shockwave lithotripsy 
PCNL - percutaneous nephrolithotomy 
Emergency stent

Question 17

What is a ureteroscopy?

Answer 17

Best for ureteric stones or renal <2cm
Can be rigid or flexible
Basket, laser and lithoclast
General anaesthetic

Question 18

What is percutaneous nephrolithotomy?

Answer 18

Best for stones larger than 2cm in the kidney
Direct access to the kidney via the skin to fragment or extract the stones
General anaesthetic

Question 19

What is extracorporal shockwave lithotripsy?

Answer 19

Best for proximal ureteric stones <10mm or renal stones <2cm depending on the location
Generation of shockwaves externally to break up the stones
Requires analgesia

Question 20

How are infected obstructed systems delt with?

Answer 20

Sepsis 6
Culture and Abx 
Imaging CT or USS
Urgent decompression of an obstructed infected collecting system
- nephrostomy 
- ureteric stenting