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
Which stones are radio-opaque?
Calcium oxalate
Calcium phosphate
Mixed calcium oxalate/phosphate stones
Triple phosphate stones
Which stones are radioo lucent
Urate stones
Xanthine stones
stag-horn calculi involve the renal pelvis and extend into at least 2 calyces.
true
Staghorn calculi arise due to?
develop in alkaline urine and are composed of struvite (ammonium magnesium phosphate, triple phosphate). Ureaplasma urealyticum and Proteus infections predispose to their formation
BAUS endorse the use of alpha-adrenergic blockers to aid ureteric stone passage routinely.
FALSE
They do however acknowledge a recently published meta-analysis advocates the use of α-blockers for patients amenable to conservative management, with greatest benefit amongst those with larger stones
How to manage analgesia in renal colic?
BAUS recommend an NSAID as the analgesia of choice for renal colic
whilst diclofenac has been traditionally used the increased risk of cardiovascular events with certain NSAIDs (e.g. diclofenac, ibuprofen) should be considered when prescribing
the CKS guidelines suggest for patients who require admission: ‘Administer a parenteral analgesic (such as intramuscular diclofenac) for rapid relief of severe pain’
Intial ix for renal colic?
urine dipstick and culture
serum creatinine and electrolytes: check renal function
FBC / CRP: look for associated infection
calcium/urate: look for underlying causes
also: clotting if percutaneous intervention planned and blood cultures if pyrexial or other signs of sepsis
BAUS now recommend that what should be performed on all patients with renal colic
non-contrast CT KUB
How soon should non-contrast CT KUB be performed in renal colic
within 14 hours of admission
if a patient has a fever, a solitary kidney or when the diagnosis is uncertain an immediate CT KUB should be performed.
In the case of an uncertain diagnosis, this is to exclude other diagnoses such as ruptured abdominal aortic aneurysm
Describe sensitivity & specificity of CT KUB for renal stones
CT KUB has a sensitivity of 97% for ureteric stones and a specificity of 95%
US is diagnostic renal stones
false
ultrasound still has a role but given the wider availability of CT now and greater accurary it is no longer recommend first-line. The sensitivity of ultrasound for stones is around 45% and specificity is around 90%
Stones ? size will usually pass spontaneously.
Typically pass within ? weeks?
< 5 mm
Most renal stones measuring less than 5mm in maximum diameter will typically pass within 4 weeks of symptom onset
More intensive and urgent treatment is indicated in the presence of what pmh
(in renal stones)
ureteric obstruction
renal developmental abnormality such as horseshoe kidney
previous renal transplant.
Mx ureteric obstruction due to stones?
Ureteric obstruction due to stones together with infection is a surgical emergency and the system must be decompressed. Options include nephrostomy tube placement, insertion of ureteric catheters and ureteric stent placement.
In the non-emergency setting, the preferred options for treatment of stone disease include
extra corporeal shock wave lithotripsy
percutaneous nephrolithotomy
ureteroscopy
open surgery remains an option for selected cases. However, minimally invasive options are the most popular first-line treatment.
Describe Shockwave lithotripsy
A shock wave is generated external to the patient, internally cavitation bubbles and mechanical stress lead to stone fragmentation.
The procedure is uncomfortable for patients and analgesia is required during the procedure and afterwards.
The passage of shock waves can result in the development of solid organ injury. Fragmentation of larger stones may result in the development of ureteric obstruction.