Urinary tract calculi (Complete) Flashcards
What are the main types of renal calculi?
Calcium oxalate (85%)
Uric acid (5-10%)
Calcium phosphate (10%)
Struvite (2-20%)
Cystine (1%)
What is the most common type of renal stone?
Calcium oxalate (85%)
What are the main features of calcium oxalate stones?
Most common type of renal stone (85%)
Radiopaque (appear white on x-ray)
Hypercalciuria is major risk factor
Form in variable urine pH
What are the main features of calcium phosphate stones?
10% of stones
Radiopaque
Typically occurs in renal tubular acidosis type 1 & 3 [causes high urine pH which supersaturates calcium and phosphate]
Form in high urine pH (normal-alkaline)
What are the main features of cystine stones?
1% of stones
Semi opaque “ground glass” appearance (due to presence of sulfur)
Caused by inherited recessive inborn errors of metabolism which leads to disruption of cystine transport and decreased absorption from renal tubule.
Multiple stones may form
What are the main features of uric acid stones?
5-10% of stones.
Radiolucent.
Uric acid formed from purine product metabolism
Can be caused by diseases which result in extensive tissue breakdown (e.g. malignancy)
Precipitated when urinary pH is low.
What are the main risk factors for urate forming renal stones?
Gout
Ileostomy (loss of bicarbonate and fluid results in acidic urine, causing the precipitation of uric acid)
Why does ileostomy increase risk of urate renal stones?
Loss of bicarbonate and fluid results in acidic urine, causing the precipitation of uric acid
What are the main features of struvite stones?
2-20% of stones
Radio opaque
Formed from magnesium, ammonium and phosphate.
Occur as a result of urease producing bacteria, associated with chronic UTIs (ureaplasma, proteus).
Crystals precipitated in alkaline conditions
Tend to form staghorn calculi
Summary of urine pH conditions for precipitation of different types of stones
What are the main risk factors for renal stones?
Modifiable:
Obesity
Dehydration (urinating 1 litre a day increases risk vs 2 litres)
Diet
Non-modifiable:
Previous stone disease
Anatomical abnormalities of the collecting system
Family history
Hyperparathyroidism
Renal tubular acidosis
Myeloproliferative disorders
All chronic diarrhoeal conditions
What is renal tubular acidosis?
Syndrome characterized by hyperchloremic metabolic acidosis with a normal serum anion gap.
Results in buildup of acid in blood
What is the main presentation of renal colic?
Acute/subacute onset of severe pain
Pain radiates from loin to groin (testes or labia)
Colicky
Patients often unable to get comfortable and pace around/ hunch over in pain
Nausea
Vomiting
What investigations should be considered in patients with renal colic?
Bedside:
Basic obs: Check for sepsis signs such as hypotension
Urine dipstick and culture: Show very positive haematuria and may aid in determining type of stone
Urine pregnancy test: Rule out ectopic pregnancy
Bloods:
FBC: Check for inflammatory response (WCC) in case of infection such as UTI and pyelonephritis
Blood culture: If features of sepsis
CRP: Check for infective causes such as pyelonephritis or UTI
U&Es: Check for any subsequent renail impairment
Calcium: Check underlying cause hypercalaemia
Uric acid: Check for underlying cause hyperuricaemia
Clotting factors and G&S: If percutaenous intervention is planned.
Investigations:
Non-contrast helical CT KUB: gold standard
Renal ultrasound: If pregnant or child
Abdominal X-ray: Useful to check for visible stone which would require extracorporeal shockwave lithotripsy.
Should renal colic be ruled out if no evidence of haematuria on urine dipstick?
Should not rule out
What is the gold standard investigation for renal stones?
Non-contrast helical CT KUB
Non-contrast helical CT KUB is contraindicted in which patients? Which imaging is therefore prefered?
Pregnant women
Children
Urgent renal ultrasound instead
What pH values may be seen in dipstick which is suggestive of each type of calculi?
N.B. Mean is calculated as pH is effected prandially (meals can make pH fall due to purine metabolism)
What is the management plan for renal stones?
Conservative management if stone <5mm
Manage sepsis ASAP before treating stone if present
Medication:
Analgesia:
NSAIDs
Parenteral analgesics (e.g. Intramuscular/rectal diclofenac): If severe pain for rapid relief.
Medical expulsive therapy: Can speed up passage of stone
Surgery:
Nephrostomy: For emergency situations
Retrograde stent insertion: For emergency situations
Shockwave lithotripsy
Ureteroscopy
Percutaneous nephrolithotomy
Renal stones measuring less than 5mm in maximum diameter will typically pass within how many weeks of symptom onset?
4 weeks
List examples of types of medical expulsive therapy options.
Tamsulosin
Doxazosin
N.B. they relax the ureter to aid passage
Medical expulsive therapy is only used in which types of patients?
Patient is of the following:
Not spetic
Normal renal function
Stone is visible on AXR
What analgesia is reccomended for patients with severe renal colic?
Parenteral analgesia
E.g. Intramuscular diclofenac
What presentation of renal colic is considered a surgical emergency?
Stones together with infection (e.g. sepsis)
Which presentations of renal colic indicates more urgent and intensive treatment is required in these patients?
Presence of ureteric obstruction with subsequent renal impairment
Renal developmental abnormality such as horseshoe kidney
Previous renal transplant.
What surgical options are used in renal colic in a septic patient?
Nephrostomy
Retrograde stent insertion
What is a nephrostomy?
Radiological procedure where access to the renal pelvis is gained through the skin.
A drain is then inserted to decompress kidney
Antegrade stent can then be inserted to ensure kidney drains urine into bladder (can be inserted at same time as nephrostomy or later date)
What is retrograde stent insertion?
Stent inserted via urethra access to decompress kidney
What surgical options are offered in non-emergency management of renal stones?
Extra corporeal shock wave lithotripsy
Percutaneous nephrolithotomy
Ureteroscopy
What is shockwave lithotripsy?
Shock wave is generated external to the patient
Causes cavitation bubbles and mechanical stress which fragments the stone
Shockwave lithotripsy should be offered in presentations of renal stones?
Stone burden of less than 2cm in aggregate
This is because there is fragmentation of larger stones can cause ureteric obstruction.
What are some complications of shockwave lithotripsy?
Ureteric obstruction (if done on large stones)
Solid organ damage
Pain (Require analgesia during and post-procedure)
What is ureteroscopy?
Ureteroscope is passed retrograde through the ureter and into the renal pelvis
Stones can be removed by using a basket, or breaking it into smaller pieces using a laser.
When is ureteroscopy indicated?
Stone burden of less than 2cm in pregnant females or in patients in which lithotripsy is contraindicted.
What is percutaneous nephrolithotomy?
Involves accessing the renal pelvis via a percutaneous approach through the loin.
Stones can then be broken up and removed.
When is percutaneous nephrolithotomy indicated?
Complex renal calculi and staghorn calculi
What medications can be considered in patients with reccuent kidney stone disease to reduce risk?
Calcium stones: Thiazide diuretic (increases calcium reabsorption)
Oxalate stones: Cholestryamine or pyridoxine
Uric acid stones: Allopurinol or oral bicarbonate
