Urostones Flashcards
What are the risk factors for developing urostones?
Intrinsic - male - genetics - metabolic - medical conditions (hyperthyroid, malabsorption, drugs, sarcoidosis) Extrinsic - climate - occupation - fluid intake - diet
How are bladder stones formed?
Under-saturated
Supersaturated byt stable - metastable
Supersaturated with spontaneous precipitation - unstable
What are the saturation and formation products?
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
What is the free-particle model of stone formation?
Urine containing crystals flows down the collecting ducts
Crystals grow and agglomerate
A critical particle gets trapped in the tubule
What is the fixed-particle model of stone formation?
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
Name some stone inhibitors.
Citrate
Magnesium
Pyrophosphate
Glycoproteins
Name some stone promoters.
THP
Matrix substance A
What factors affect stone formation?
Decrease liklihood of stone formation - Low volume - Low pH - Low citrate - Low magnesium Increase stone formation - high uric acid - high calcium - high oxalate
What types of stones occur in the bladder?
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
How do bladder stones present?
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
What initial investigation are done if you suspect bladder stones?
History and examination Bloods - CRP, FBC, U&Es Urine - non-visible haematuria (85%) Imaging - CT KUB (non-contrast) is best
What biochemical workup would you do if someone presented with their first stone?
U&Es Calcium Urate Urine dip Sodium nitroprusside (cysteine) Stone analysis
What biochemical workup would you do if someone presented with a recurrent stone?
U&Es Calcium Urate Venous bicarbonate 24 hour sodium urine analysis
How are stones managed?
Passing naturally
- <4mm 75% chance
Medical therapy
Surgical therapy
Describe the medical therapy for bladder stones.
Analgesia
- NSAIDs reduce pain due to reduced GFR, renal pressure and ureteric peristalsis
Medical expulsion therapy
- possibly
What are the surgical options for bladder stones?
Ureteroscopy and basket Ureteroscopy and fragmentation Flexible ureteroscopy ESWL - extracorporeal shockwave lithotripsy PCNL - percutaneous nephrolithotomy Emergency stent
What is a ureteroscopy?
Best for ureteric stones or renal <2cm
Can be rigid or flexible
Basket, laser and lithoclast
General anaesthetic
What is percutaneous nephrolithotomy?
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
What is extracorporal shockwave lithotripsy?
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
How are infected obstructed systems delt with?
Sepsis 6 Culture and Abx Imaging CT or USS Urgent decompression of an obstructed infected collecting system - nephrostomy - ureteric stenting
