Urology Flashcards
Renal Stones Hydronephrosis Benign Prostatic Hyperplasia LUTS & Urinary Incontinence Testicular & Scrotal Issues
Renal stones: risk factors?
dehydration
hypercalciuria, hyperparathyroidism, hypercalcaemia
cystinuria
high dietary oxalate
renal tubular acidosis
medullary sponge kidney, polycystic kidney disease
beryllium or cadmium exposure
Risk factors for urate stones
gout
ileostomy: loss of bicarbonate and fluid results in acidic urine, causing the precipitation of uric acid
drugs that promote calcium stones
loop diuretics, steroids, acetazolamide, theophylline
Which drugs can prevent calcium stones?
thiazides can prevent calcium stones (increase distal tubular calcium resorption)
What are the different types of renal stones?
Calcium oxalate Calcium phosphate Uric Acid Struvate Cystine
Commonest type of renal calculi?
Calcium oxalate
Risk factors for oxalate stones?
Hypercalciuria is a major risk factor (various causes)
Hyperoxaluria may also increase risk
Hypocitraturia increases risk because citrate forms complexes with calcium making it more soluble
Are calcium oxalate stones lucent or opaque?
Stones are radio-opaque (though less than calcium phosphate stones)
Hyperuricosuria may cause calcium oxalate stones?
Hyperuricosuria may cause uric acid stones to which calcium oxalate binds
Which is the least common stone?
Cystine 1%
How do cystine stones arise?
Inherited recessive disorder of transmembrane cystine transport leading to decreased absorption of cystine from intestine and renal tubule
Cystine stones present with multiple stones
true
Cystine stones radiolucency?
Relatively radiodense because they contain sulphur
Semi-opaque, ‘ground-glass’ appearance
Uric acid stones arise due to
Uric acid is a product of purine metabolism
May precipitate when urinary pH low
May be caused by diseases with extensive tissue breakdown e.g. malignancy
Uric acid prevalence? Most common in
5-10%
More common in children with inborn errors of metabolism
Uric acid radiology
Radiolucent
Calcium phosphate stones arise due to
May occur in renal tubular acidosis, high urinary pH increases supersaturation of urine with calcium and phosphate
Renal tubular acidosis types 1 and 3 increase risk of stone formation (types 2 and 4 do not)
Calcium phosphate prevalence?
10%
Calcium phosphate radiology?
Radio-opaque stones (composition similar to bone)
Struvite stones arise due to
Stones formed from magnesium, ammonium and phosphate
Occur as a result of urease producing bacteria (and are thus associated with chronic infections)
Under the alkaline conditions produced, the crystals can precipitate
Struvite stone prevalence
2-20%
Struvite radiology
Slightly radio-opaque
How does urine ph vary?
Urine pH will show individual variation (from pH 5-7).
Post prandially the pH falls as purine metabolism will produce uric acid.
Then the urine becomes more alkaline (alkaline tide).
When the stone is not available for analysis the pH of urine may help to determine which stone was present.
Describe stone types vs urine acidity and ph
Calcium phosphate Normal- alkaline Calcium oxalate Variable Uric acid Acidic Struvate Alkaline Cystine Normal