urinary tract calculi Flashcards
definition of urinary tract calculi
crystal deposition in the urinary tract
also known as nephrolithiasis
stones form in collecting ducts and deposited anywhere from renal pelvis to urethra.
classically at pelviureteric junction, pelvic brim, vesicoureteric junction
aetiology of urinary tract calculi
many cases idiopathic
metabolic - hyperclaciuria, hyperuricaemia, hypercystinuria, hyperoxaluria
infection - hyperuricaemia
anatomic factors - hypercystinuria, hyperoxaluria
drugs - indinavir - only stones that dont show on CT, look more like a filling defect
RF for urinary tract calculi
low fluid intake
structural urinary tract anomalies (eg horseshoe kidney, medullary sponge kidney)
FH increase risk 3fold - x-linked nephrolithiasis and Dent’s disease (proteinuria, hypercalciruria and nephrocalcinosis), cystinuria/cystine stones
pathophysiology of urinary tract calculi
calculi formed by supersaturation of urine by stone forming compounds
allowing crystallisation around a focus (eg infection, tumour, foreign bodies)
main types of renal tract calculi
calcium oxalate - commonest, sharp projections = cause trauma - known as ‘mulberry stones’
struvite (Mg, ammonia, phosphate) - common, smooth and dirty white, associated with urea splitting bacteria eg proteus, pseudomonas, klebsiella, may form ‘staghorn’ stones in kidneys
calcium phosphate
urate - uncommon, hard, smooth, brown, faceted, occurs in acidic urine
hydroxyapatite
brushite
cystine - uncommon, white and translucent, occurs in acidic urine
mixed
importance of renal tract calculi
Pain
Infection – life threatening, gram -ve sepsis (pyelonephrosis)– ITU/surgery
Renal damage if blockage – kidney wont drain well = damage
Underlying met problems – gout uraemic acid stones, cystenuria – predispose hard stones, hyperparathyroidism
Anatomical problems – pelvioutero junction obstruction, urine stagnant/stasis, MSK, horseshoe kidney, ureteric stricture – more chance could form stones
area of stone impaction
o PUJ – between pelvis and ureter
o Midureter – where ureter crosses iliac vessels, natural constriction of ureter
o Intramural ureter at entrance to bladder
• If go through all 3 constrictions = pass
epidemiology of renal tract calculi
- common
- Caucasian
- 1% of hospital admissions
- prevalence: 2-3% of the population per year
- male
- lifetime risk 10-15% in men, 5-10% women
- 20-50yrs
- bladder stones more common in developing countries, upper tract stones in developed countries
sx of urinary tract calculi
often asymptomatic
severe ‘loin to groin’ flank pain (renal, caliceal or ureteric colic)
often cant lie still (differentiates from peritonitis)
may be associated with nausea and vomiting when severe
urinary urgency, frequency or retention
haematuria
obstruction of kidney - felt in loin between rib 12 and lateral edge of lumbar muscles (like intercostal nerve irritation pain, not colicky, worsened by specific movements/pressure on a trigger spot)
obstruction of mid-ureter - mimic appendicitis/diverticulitis
obstruction of lower-ureter - symptoms of bladder irritability, pain in scrotum, penile tip or labia majora
obstruction of bladder or urethra - cause pelvic pain, dysuria, strangury (desire but inability to void) +- interrupted flow
infection can co-exist - increased risk if impaired voiding eg UTI, pyelonephritis (fever, rigor, loin pain, nausea, vom), pyonephrosis (infected hydronephrosis)
proteinuria
sterile pyuria
anuria
nausea and vom
signs of urinary tract calculi
loin or lower abdominal tenderness, without signs of peritonism
leaking AAA is most important ddx to consider
signs of systemic sepsis if there is obstruction and infection above a stone
abdo soft
pain is spectrum - if acutely blocking kidney = pain
Ix for urinary tract calculi
bloods
urine
radiology
IVU
US
non-enhanced spiral CT
isotope renography - eg with DPTA or DMSA; assessment of kidney function in complex stone disease
bloods for urinary tract calculi
FBC - raised WCC indicates possible infection
U&E
urate
PO3-4 (if raised - need more investigation for causes)
Ca
glucose
bicarb
urine for urinary tract calculi
dipstick (if no haematuria diagnosis is questionable)
culture and senstivity
24hr urine collection - for calculi and measure calculi-forming ion levels, ca, oxalate, urate, citrate, Na, creatinine
MC&S
pH and nitrites - show UTI
radiology for urinary tract calculi
KUB - 80% stones are radio-opaque and will show on plain radiograph of lower abdo or pelvis
- w/o contrast because the contrast and stones are white
plane XR - radioopaque shadow between transverse processes because ureter runs across tip of the transverse processes of lumbar vertebrae
IVU for urinary tract calculi
enables visualistion of the kidneys and ureters
if ureteric stone, can be a delayed dense nephrogram phase, later films showing a dilated pelvicaliceal system and a standing column of contrast down to the stone
US for urinary tract calculi
ureteral dilation or hydronephrosis from an obstructive uropathy
not sensitive for detecting smaller stones
used when IVU contrast is CI
Mx of acute urinary tract calculi
analgesia (NSAID and opiate) eg diclofenac
AB eg poperacillin/tazobactam or gentamycin if infection
fluids - IV or oral
urine collection to collect any calculi for analysis
suitable for stones not causing obstruction (<5mm will pass)
obstructed infected kidney = emergency - need urgent relief of obstruction
placement of percutaneous nephrostomy under radiological guidance with AB and other supportive measures
what size stones pass spontaneously
stones <5mm in lower ureter 90-95% pass spontaneously
medical expulsive therapy for urinary tract calculi
nifedipine or a-blockers (tamsulosin) promote expulsion and reduce pain relief requirements
- distal ureter rich in a receptors, so this relaxes sm of distal ureter
alkanise urine: K citrate if uric acid to dissolve
removal of calculi
active intervention indicated if calculi obstructs or there is continuing pain or pyrexia
urethroscopy
- flexible or rigid urethroscope passed into the bladder and up ureter to visualise the stone
- removed by basket, grasper or broken up with laser, US or other methods
- if stone is impacted and cannot be removed a JJ stent is placed to ensure urine drainage
extracorporeal shock wave lithotripsy
- non-invasive, quick, no anaesthesia
- electromagnet or piezoelectric shock wave is focused onto calculus to break it up into smaller fragments - they can pass spontaneously
- suitable if <2cm as long as no obstruction - if bigger = too many fragments = stuck
- if stone hard - wont break
- have to pass the stone themselves - might be painful
percutaneous nephrolithotomy
- for large complex stones eg stag-horn calculi
- following creation of nephrostomy tract, a nephroscope is introduced and allows disintegration and removal of stones
- nephrostomy tube left in situ for 1-2 days post op with a nephrostogram perfomed to ensure stone removal and confirm normal ureteric drainage
open nephro-, pyelo-, ureterolithotomy
- less commonly performed
- usually for complex stones
nephrectomy - may be indicated in a non-functioning kidney
treatment of cause of urinary tract calculi
parathyroidectomy
dietary ca or oxalate restriction - dont cut out dairy just no supplements
less salt, animal protein (red meat)
allopurinol
urine alkanisation with oral potassium citrate - dissolves urate and cystine stones
treat UTI
indications for urgent intervention with urinary tract calculi
infection and obstruction - percutaneous nephrostomy or ureteric stent may be needed to relieve obstruction
urosepsis
intractable pain or vomiting
impending AKI
obstruction of solitary kidney
bilateral obstructing stones
admit to hospital for urinary tract calculi if:
- Single kidney
- Pyrexia
- Continuing pain
- Renal impairment
- Pregnancy
- Large stone/severe obstruction – need removal
- infected and obstructed
- vomiting/dehydration
- social circumstance
otherwise discharge with stone clinic
complications of urinary tract calculi
of stones - infection especially pyelonephritis, septicaemia, urinary retention
of ureteroscopy - perforation, false passage
of lithotripsy - pain, haematuria, Steinstrasse (ureteric obstruction caused by a column of stone fragments), renal injury, raised BP and DM
Px of urinary tract calculi
generally good
infection of renal calculi can potentially lead to irreversible renal scarring
recurrence rate is about 50% within 5yrs
classification of urinary tract calculi
size <5mm, 5-20mm, >20mm, staghorn
location - renal (calcyceal, pelvic, diverticular), ureteric
XR characteristics - radiolucent (uric acid), radioopaque
stone composition: CaOx, CaP, uric acid, cysteine, indinavir, infection magnesium ammonium phosphate/struvite
Blocked R kidney – not on XR – uric acid stone
Stone in VUJ lowest part of ureter
conservative Mx of urinary tract calculi
observe if non-sx and non-obstructive
metabolic screen
follow up issues with urinary tract calculi
renal deterioration if complete obstruction
JJ encrustation <6mo in stone formers
50% recurrent stones - fluid intake advice
40% of conservatively managed stones will enlarge - monitor by imaging
summarise obstructive pyonephrosis
= obstruction and infection
risk of fatal gram -ve sepsis
immediate resus and IV AB
culture
urgent imaging - KUB and US
discuss with urology
consider urgent nephrostomy or JJ stent
monitor in HDU
Mx of obstructive pyonephrosis once stable
Imaging to determine cause - CT KUB, nephrostigram
antegrade stent
plan uretoscopy/ESWL/PCNL
may need drainage if perinephric abscess
may need nephrectomy if XGP or EPN
