Kidney Stones Flashcards
pathophys of kidney stones
dissolved salts in urine condense into solid and obstruct urtheral pathway
natural prevention of kidney stones
increasing amount of urine and decreasing amount of solute in urine
citrate and magnesium can block formation
types of stones (5)
- calcium
- struvite
- uric acid
- cystine
- miscellaneous
Calcium stones
occur when?
MC type of stone, occurs w/elevated Ca excretion
Hyperparathyroidism
resorptive hypercalcemia
renal hypercalciuria
immobilization syndrome
randall’s plaque
collection of subepithelilal calcification of renal papillae
serves as anchoring surface for calcium oxalate stones
diet restriction and calcium stones
diet that restricts calcium can increase calcium stone formation bc less Ca to bin to collate in lumen
this results in increased oxalate absorption in gut and recruitment of calcium in bones
struvite stones
typically in UTI infections caused by urea splitting bacteria
produce excess ammonia phosphate and elevate pH levels (decrease solubility of phosphate)
MC cause of stag horn calculi
urea splitting bacteria
UTI from these species cause struvite stones
Klebsiella, Proteus, Staphylococcal species
staghorn calculi
struvite stones MC cause
lg stones that form cast of renal pelvis
poor abx penetration, can lead to urosepsis
uric acid stones
10% of stones
radiolucent, urine is typically acidic
cystine stones
rare
founding pts with cystinuria (genetic disorder)
Misc. causes of stones
Indinavir (HIV drug) trimterine (Abx) Acetazolamide (glaucoma drug) Xanthine (caffeine) silicate
why are kidney stones so painful?
obstruction of hollow viscus organ and hydronephrosis causing pressure against GEROTA’s fascia
migrating but non obstructive stones can cause pain
stones in the KIDNEY don’t cause pain
Cr levels in obstructive kidney stones
no rise in serum CR
other kidney can compensate 185% of baseline
if Cr rises, suggests kidney dysfunction
determining probability of passage of stone:
size
shape
location
degree of urinal obstruction
bizarre/irregularly shaped stones have lower spontaneous passage rate
complete obstruction = lower rate of spontaneous passage
common sites of obstruction
ureteropelvic junction (UPJ)
Pelvic brim
UVJ
probability of spontaneous passage of kidney stones in 4 weeks
98% <5mm
60% 5-7
39% >7
stone size on radiograph is larger, stone on CT is actually smaller
classical clinical feature of kidney stone
acute onset of crampy intermittent flank pain that radiates to the groin
visceral pain, n/v
unable to find comfort
tachycardia, HTN, diaphoresis
hematuria
location of pain
upper utter refer pain to plank
mid ureter radiate to lower quadrant of abdomen
distal ureter refers to pain in groin
3 important things to clarify in history
asses risk factors for stone development
prior stone related outcome
important mimickers
risk factors for poor outcome
renal function at risk
history of difficulty stones
infections
serious mimickers to consider in kidney stone
AAA
renal artery infarction
aortic dissection
AAA is often misdiagnosed as kidney stone
distinguishing AAA from kidney stone
stones don’t usually present in men older than 60
stones dont cause hypotension
distinguish renal artery thrombosis from stone
swelling of infarcted kidney can cause hematuria BUT
non contrast CT can distinguish
patients with at risk renal function
DM HTN Renal insufficiency single kidney horseshoe kidney transplanted kidney
patient with difficult stones
extraction
stent
urterostomy tubes
liphotripsy
diagnosis of urologic stone disease
clinical suspicions
presence of hematuria
imaging (not often)
lab eval (4)
- pregnancy (ectopic consideration - all women = preg test)
- UA (rule out infection)
- renal function
- hematuria
imaging in kidney stones
confirms presence
r/o other diagnoses
identifies complications
defines stone location
who gets imaging in stone workup?
pts with first time stones
CT scanning reveals alternative diagnosis 33% of patients
non contrast CT of A and P
images obtained from top of kidney to bladder base
urterial dilation*
perinephric fat stranding*
dilation of collecting system
enlargement
faster, no need for contrast damage, an see other pathology
plan abdominal radiograph
90% of stones are radiopaque (density similar to bone) - calcium
struvite and cystine less able to see
uric acid stones are unable to be seen
not good to diagnose but good to see if stone is passing
US in stones
good if pt can’t use CT
may miss stones <5mm, mid arterial stones
information on size, renal blood and urine flow
ED tx
pain and n/v control
antibiotics for those w/evidence of infection
medical expulsion therapy
IV fluids to correct electrolyte imbalance
NSAIDs
primary choice of analgesics, direct action on ureter by inhibiting prostaglandin synthesis
avoid in its with high risk bleeding, DM, renal insufficiency, pregnancy
IV NSAID +dosing
ketorolac (Toradol)
<55 w.o. PMH of DM, renal insufficiency or GI bleeding - 30 mg
60-63 no CI - 15mg
> 65 - avoid
narcotics use
good analgesic
do not affect care of pain
second line
morphine, percocet
antiemetic agents
Odansteron (Zofran)
Metoclopradmide (Reglan)
Metoclopramide (Reglan)
blocks dopaminergic receptors in CNS
less sedating, can provide pain provide
medical expulsion therapy
alpha blockers are DOC
benefit in stones of distal third of ureter
(tamsulosin) Flowmax mc alpha blocker
surgical treatments used in kidney stones
Shock wave lithotripsy
Ureterscopy
Percutaneous nephrolithotomy
open surgery
SWL
renal calculi <3 cm
NOT recommended for stones >3 cm
utilized high energy shock waves to stone and break it down, then pass small fragments in urine
success of SWL depends on
number and density of stones
total number and rate of shocks
stone size
chemical composition
URS when is it used?
tx of choice for majority of middle and distal ureteral stones measuring > 3 cm
used in management of stones that have failed SWL, stones in proximal ureter and intrarenal
URS process
breaks up stones to less than 1 mm, pass painlessly
successful in 90% of cases
can place stents after to help passage
when is stenting performed
urinary tract abnormalities
solitary kidneys
residual edema or inflammation secondary to stone or endoscopic removal
PNL
placement of small caliber nephrostomy catheter thru flank into renal collecting system – cath is dilated and enter the kidney to grab and remove the stone
open stone surgery
used in management of complex renal and ureteral calculi
<1% of pts
indications for open stone surgery y
failed other procedures
complex (stag horn)
complex anatomy
morbid obesity
preventative treatment
thiazide diuretics (increased calcium reabsorption)
allopurinol or potassium citrate (uric acid)
disposition
<6 mm stone w/o impairment discharged with follow up
indications for hospitalization
intractable pain
stone > 6mm
evidence of infection
evidence of worsening renal impairment
irregular or proximal stone
return to ED
patients should return to ED if
fever
vomiting
intractable pain
urology follow up
w/in 7 days
allows etiology of stone to be evaluated and prophylactic strategy should be arranged
pregnancy
1 in 1500 pregnancies, most often in secondary third trimester
diagnostic study of choice: ultrasound
can use CT or MRI with OBGYN consult
NSAIDs can’t be used - narcotics instead
can use medical expulsive therapy
