Urinary tract calculi (URO) Flashcards
What is nephrolithiasis?
Presence of crystalline stones (calculi) within the urinary system (kidneys and ureter)
Describe the epidemiology of nephrolithiasis. (2)
- M>F
- 45-70y
What are the different types of stones (urinary tract calculi)? (4)
- calcium stones (80%) - calcium oxalate and calcium phosphate
- struvite (15%)
- uric acid (5%)
- cysteine (1%)
How do calcium stones appear on X-rays/CT (nephrolithiasis)?
Radiopaque = white
What are the differences between calcium oxalate and calcium phosphate stones?
- calcium oxalate - black/dark brown, acidify urine pH
- calcium phosphate - dirty white, alkaline
- (both radiopaque/white on scans)
What is a risk factor for calcium oxalate calculi?
Hypercalciuria
How do struvite stones (nephrolithiasis) appear on X-rays/CT scans?
White (radiopaque)
What do struvite stones (nephrolithiasis) do to urine pH?
Alkalises urine pH (alkaline)
What can struvite stones (nephrolithiasis) form into?
Staghorn calculi (big stones)
What do struvite stones (nephrolithiasis) contain?
Magnesium, ammonium and phosphate
What is a predisposing factor for struvite stones (nephrolithiasis)?
Recurrent UTIs (chronic Proteus/Pseudomonas/Klebsiella infection)
How do uric acid stones (nephrolithiasis) appear on X-rays/CT scans?
Radiolucent = black (not visible vs calcium oxalate/phosphate and struvite stones)
What condition may uric acid stones (nephrolithiasis) be associated with?
Gout/hyperuricaemia
What urinary pH is commonly associated with uric acid stones (nephrolithiasis)?
Urinary pH<5.5
What are cysteine stones (nephrolithiasis)?
Inborn error of abnormal renal tubular reabsorption of the amino acids cysteine, ornithine, lysine and arginine (yellow, light pink stones that are white on XR)
Where do kidney stones classically deposit? (3)
- pelviureteric junction (PUJ)
- pelvic brim
- vesicoureteric junction (VUJ)
What are some contributing factors to nephrolithiasis? (4)
- high urinary solutes - calcium, uric acid (by-product of purines), oxalate, sodium
- decreased stone inhibitors - citrate, magnesium
- low urinary volume e.g. dehydration
- low/high urinary pH
What foods are high in oxalate, potentially contributing to kidney stones? (6)
- chocolate
- tea
- rhubarb
- strawberries
- nuts
- spinach
When do urinary tract calculi become symptomatic?
Asymptomatic until they get stuck
What are the clinical features of urinary tract calculi? (5)
- renal colic - severe, acute flank pain that radiates to groin (loin –> groin) that may be colicky
- N&V
- urinary frequency/urgency (stone dislodged in distal ureter –> bladder irritation)
- haematuria
- testicular pain
What may be found on examination in urinary tract calculi?
Systemic signs of sepsis if urinary obstruction and infection above stone
What are some risk factors for urinary tract calculi? (10)
- chronic dehydration
- diet - chocolate, tea, rhubarb, strawberries, nuts, spinach (oxalate-rich)
- high salt intake
- white ancestry
- male
- obesity
- positive Fx
- crystalluria
- specific medicines
- various metabolic abnormalities
What are the first-line investigations for urinary tract calculi? (4)
- non-contrast CT KUB
- renal ultrasound (pregnant or child)
- urinalysis / urine dipstick
- FBC
What bedside test can we initially do in urinary tract calculi and what might it show?
Urine dipstick - may show microhaematuria