Renal stones Flashcards
What are the main types of renal stones?
- Calcium oxalate
- Cystine
- Uric acid
- Calcium phosphate
- Struvite
What is a major risk factor for calcium oxalate stones?
Hypercalciuria is a major risk factor.
What percentage of all calculi do calcium oxalate stones represent?
85%
What causes cystine stones?
Inherited recessive disorder of transmembrane cystine transport.
What percentage of all calculi do cystine stones represent?
1%
What is uric acid a product of?
Uric acid is a product of purine metabolism.
What percentage of all calculi do uric acid stones represent?
5-10%
What conditions may lead to calcium phosphate stones?
May occur in renal tubular acidosis.
What percentage of all calculi do calcium phosphate stones represent?
10%
What are struvite stones formed from?
Magnesium, ammonium, and phosphate.
What percentage of all calculi do struvite stones represent?
2-20%
How does urine pH affect stone formation?
Urine pH varies individually and can indicate stone type.
What is the mean urine pH for calcium phosphate stones?
> 5.5
What is the mean urine pH for calcium oxalate stones?
6
What is the mean urine pH for uric acid stones?
5.5
What is the mean urine pH for struvite stones?
> 7.2
What is the mean urine pH for cystine stones?
6.5
Type of stone: features & percentage of all calculi
Which renal stone?
What guidelines were published for the management of acute ureteric/renal colic?
The British Association of Urological Surgeons (BAUS) published guidelines in 2018 and NICE in 2019.
What is the recommended analgesia for renal colic according to BAUS and NICE?
Both BAUS and NICE recommend an NSAID as the analgesia of choice.
What should be considered when prescribing NSAIDs for renal colic?
The increased risk of cardiovascular events with certain NSAIDs (e.g. diclofenac, ibuprofen) should be considered.
What does NICE recommend if NSAIDs are contraindicated or ineffective?
NICE recommends IV paracetamol.
What is recommended for patients requiring admission for severe pain?
‘Administer a parenteral analgesic (such as intramuscular diclofenac) for rapid relief of severe pain.’
What is the role of alpha blockers in renal colic management?
Alpha blockers promote smooth muscle relaxation and dilation of the ureter, potentially easing stone passage.
For which type of stones does NICE recommend alpha blockers?
NICE recommends considering alpha blockers for distal ureteric stones less than 10 mm in size.
What initial investigations are recommended for renal colic?
Urine dipstick and culture, serum creatinine and electrolytes, FBC/CRP, calcium/urate, and stone analysis after stone passage.
What imaging is recommended for patients with renal colic?
Non-contrast CT KUB should be performed on all patients within 24 hours of admission.
When should an immediate CT KUB be performed?
If a patient has a fever, a solitary kidney, or when the diagnosis is uncertain.
What is the sensitivity and specificity of CT KUB for ureteric stones?
CT KUB has a sensitivity of 97% and a specificity of 95%.
What is the recommended management for renal stones < 5 mm?
Watchful waiting if < 5mm and asymptomatic.
What is the management for renal stones 5-10 mm?
Shockwave lithotripsy.
What is the management for renal stones 10-20 mm?
Shockwave lithotripsy OR ureteroscopy.
What is the management for renal stones > 20 mm?
Percutaneous nephrolithotomy.
What is the typical outcome for stones < 5 mm?
They will usually pass spontaneously within 4 weeks of symptom onset.
What is a surgical emergency related to renal stones?
Ureteric obstruction due to stones together with infection requires surgical intervention.
What is shockwave lithotripsy?
A procedure where a shock wave is generated externally to fragment stones.
What are the risks associated with shockwave lithotripsy?
It can lead to solid organ injury and ureteric obstruction from fragmented stones.
What is ureteroscopy?
A procedure where a ureteroscope is passed retrograde through the ureter into the renal pelvis.
When is ureteroscopy indicated?
In individuals where lithotripsy is contraindicated and in complex stone disease.
What is percutaneous nephrolithotomy?
A procedure that gains access to the renal collecting system for stone fragmentation.
What are some prevention strategies for calcium stones?
High fluid intake, adding lemon juice to water, avoiding carbonated drinks, limiting salt intake, potassium citrate, and thiazide diuretics.
What can reduce urinary oxalate secretion for oxalate stones?
Cholestyramine and pyridoxine.
What treatments are available for uric acid stones?
Allopurinol and urinary alkalinization (e.g. oral bicarbonate).
What are the risk factors for renal stones?
Dehydration, hypercalciuria, hyperparathyroidism, hypercalcaemia, cystinuria, high dietary oxalate, renal tubular acidosis, medullary sponge kidney, polycystic kidney disease, beryllium or cadmium exposure.
What are the risk factors for urate stones?
Gout, ileostomy: loss of bicarbonate and fluid results in acidic urine, causing the precipitation of uric acid.
What drugs promote calcium stones?
Loop diuretics, steroids, acetazolamide, theophylline.
What drug can prevent calcium stones?
Thiazides can prevent calcium stones by increasing distal tubular calcium resorption.
What is the appearance of Calcium oxalate stones on x-ray?
Opaque
What is the frequency of Mixed calcium oxalate/phosphate stones?
25%
What is the appearance of Triple phosphate stones on x-ray?
Opaque
Triple phosphate stones can form stag-horn calculi that involve the renal pelvis and extend into at least 2 calyces.
What is the frequency of Calcium phosphate stones?
10%
What is the appearance of Urate stones on x-ray?
Radio-lucent
What is the frequency range of Cystine stones?
1%
What is the appearance of Cystine stones on x-ray?
Semi-opaque, ‘ground-glass’ appearance
What is the frequency of Xanthine stones?
<1%
What is the appearance of Xanthine stones on x-ray?
Radio-lucent
What predisposes to the formation of stag-horn calculi?
Ureaplasma urealyticum and Proteus infections
Renal stones: types, frequency, radiograph appearance
