Aetiology
Result
from crystal
formation in urine: increased concentration of solute (Calcium,
oxalate,
cysteine, urate, xanthine), reduced volume of urine or low
levels of inhibitors
of stone formation (Citrate, Mg, nephrocalcin).
Epitaxy
– Urinary
calculi have a mixture of crystals amoungst which one
predominates. A foreign
body (catheter, organic matrix of proteins (Tamhorsfall),
another stone,
necrotic renal papilla, schistosome ova) forms a nucleus around
which stone
forms.
Calcium stones
Calcium
stones
(70%) are either calcium oxalate (40%) or calcium phosphate
(15%) or mixed
(Calcium oxalate-phosphate).
Causes:
—
Increased calcium in
urine. Can be associated with
normal serum calcium (absorptive hypercalciuria, tubular calium
leak) or
hypercalcaemia.
—
Increased uric acid in
urine may encourage formation
of calcium stones.
—
Increase urinary oxalate
(inherited or acquired – from
increased intake, fat malabsorption or excessive Vit C)
—
Reduced urinary citrate
Uric
acid stone
(8%). Radiolucent. Acid urine. Can occur in hyperuricaemic
patients or patients
with normal serum Urate.
Struvite
stone
(Magnesium ammonium phosphate and carbonate apetite) 15%. Urease
splitting UTI
with proteus, klebsiella or mycoplasma. Staghorn calculus.
Alkaline urine
Cysteine
stones
(2%). Very hard stones forming in acid urine. Due to congenital
disorder of
cyteine resportion.
Clinical
· Pain
—
Renal
Loin,
unbilicus,
testis
—
Mid ureter
Iliac
fossa
—
Lower ureter
Scrotum,
tip of
penis / labia
±
bladder
irritability
· Haematuria
Ix
For
all first time
stone formers
· MSU, microscopy for
RBC, WBC, casts, cyrstals
· Blds
—
U&E, Ca++,
uric acid, PO4-
· Retrieve and
analyse stone
· Spot urinary
cysteine test
· Xrays
—
IVP
· CTU
—
Gold standard
—
Non-contrast
enhanced spiral CT
—
Thick slices
—
Aim to visualise stone
For
patients with
recurrent stones, multiple stones, nephrocalciuosis perform 2 24
hour urine
collections for calclium, oxalate, urate, phosphorous, citrate,
creatinine,
volume and pH.
Complications
· Obstruction
· Infection
—
pyonephrosis
v
Obstruction +
infection® urgent
decompression with
percutanous nephrostomy
Rx
· General
—
Analgesia
—
Antiemetics
Size
and
probability of spontaneous resolution
—
4mm – 90%
—
4 – 6mm: 40%
—
>6mm: 25%
—
Absolute indications for
intervention: obstruction and
sepsis, obstruction and deteriorating renal function
—
Relative indication: stone
>6mm, continuing pain,
failure to resolve after adequate period of observation
Interventions for renal
stone
—
ESWL: Stones <2cm (less
than 1cm in lower pole
calyx).
o
Absolute contra-indication: AAA,
Pregnancy, obstruction
o
Relative
contra-indication : obesity, cystein
stones, horseshoe kidney, solitary kidney.
o
Complications: infection,
stein strasse obstruction,
pain, bruising, intra-renal haematuria.
—
PCNL: Stones >2cm.
Stone fragmented with US,
pneumatic or electrohydrolic device.
—
Open surgery: Removal of
stone either through renal
sinus (Gil-Vernet) or nephrotomy. Nephrectomy is used when
kidney contributes
<15% of renal function and is infected
Interventions
for
ureteric stones
—
Ureteric stent: can be
used to relieve obstruction
when associated with infection or deteriorating renal function.
Prophylactic
before ESWL for renal stones, Push-bang to displace mid-ureteic
stones
proximally for ESWL.
—
ESWL: Least successful for
mid-ureteric stones (65%)
compared to lower and upper 1/3 stones (80%).
—
Ureteroscopy. Can use
flexible (laser only) or rigid
(laser, pneumatic device or US for fragmentation). Most
successful for upper
1/3 (96%) vs middle 1/3 (75%) vs lower 1/3 (55%).
—
Dormia basket can be used
only with stones 5mm in size
no more than 5cm from ureteric orifice
o
All ureteric procedures
can be complicated by ureteric
perforation, avulsion or late stricture.
Follow-up
· 2 x fluid intake
· Metabolic
evaluation
—
Stone analysis
—
24hr urine
calcium,
uric acid,
oxalate, citrate, sodium, volume, pH
—
Bloods
Urea,
creatinine,
calcium, phosphate, uric acid