Urolithiasis Flashcards
staghorn stones are most frequently composed
magnesium ammonium phosphate (struvite) and/or calcium carbonate apatite and rarely due to calcium oxalate or phosphate stones.
Urea splitting organisms
Proteus
Pseudomonas
Klebsiella
Staphylococcus
Mycoplasma.Treatment options for Staghorn
Open pyelolithotomy open anatrophic pyelolithotomy ESWL flexible ureteroscopy PCNL (+ESWL,) or (PCNL+ESWL+PCNL) Endoscopic combined intrarenal surgeries (nephroscope + ureteroscope) Medical dissolution with RENACIDIN
give 3 stone scoring systems created with the aim of determining complications and stone-free rates
Guy’s stone score
S.T.O.N.E nephrolithometry system
CROES nomogram.
GUYS STONE SCORE
grade 1 - single stone in mid/lower pole or single stone in the pelvis with simple anatomy
grade 2 - single stone in upper pole or multiple stones in a patient with simple anatomy or a single stone in a patient with abnormal anatomy
grade 3 - multiple stones in a patient with abnormal anatomy or stones in a calyceal diverticulum or partial staghorn calculu
grade 4 - staghorn calculus or any stone in a patient with spina bifida or spinal injury
Proper diet for urolithiasis (diet)
(+)promote low-salt, low-protein diet combined with normal calcium intake,high intakes of fresh fruit, fibre from wholegrain cereals and magnesium were associated with decreased stone formation risk
(-) high oxalate, modern high-protein/low-carbohydrate dietary fads, fructose consumption
Physical properties of SWL
Shock waves
Spallation
Cavitation
DEFINE CAVITATION
occurs as a shock wave passes through fluid, creating microscopic air bubbles. These bubbles coalesce at the stone’s surface and as the next shock wave arrives the bubbles collapse and release microjets of energy against the surface of the stone
DEFINE SPALLATION
The wave of energy passes uninterrupted through media of similar density such as water. However, when the wave meets an object of differing density, like a stone, there is increased resistance to energy transmission, termed acoustic impedance.
Components of a shockwave lithotripter
- SHOCK WAVE
- FOCUSING DEVICE
- COUPLING MEDIUM’
- LOCALIZATION MEDIUM
etiology of New-onset htn from SWL
Shock wave injury to surrounding normal parenchyma results in vasoconstriction and ischaemia, while shear stress may also induce vascular injury–>Vascular damage and ischaemia results in an inflammatory cascade and free radical formation
Incidence of STreinstrasse in SWL for stones less than 2 cm
The incidence of steinstrasse depends on the size of the treated stone, but ranges are reported from 2-6% in stones less than 2cm
Patient Selection for Shockwave therapy –> composition, HU and size, SSD
Composition -> not cystine stones they are able to deform and absorb shock wave energy, Brushite and calcium oxalate are harder making them resistant to cavitation and spallation
HU - 900, 50% less likely to be Stone free
Size- <1 cm stones approaches 80% SFR, 2 CM do not attempt
Skin-to-stone distance <10 cm
LIP Variable on stone-free rates fir SWL
LIP angle >70%
IW >5mm
IL <3cm
Adjunctive measures for SWL
Success, defined as the patient being stone-free or having fragments smaller than 3mm on ultrasound, was higher at three months in the tamsulosin group
Conservative management of ureteric calculi, % of passage by size
4 mm: 78-95%
5 mm: 68%
5-10mm: 47%
when to use MET for ureteric stones
<10 mm
no evidence of sepsis,normal crea, adequate pain cntrol
when to use pre-SWL stenting?
for solitary kidney,obstruction,sepsis,uncontrollable pain otherwise stents impedes stone passage and does not prevent Steinstrasse
Surgical Management of stone for pregnant patients and what semester to avoid to do procedure
Failing conservative management, diversion via ureteric stenting or nephrostomy drainage is recommended.
URS with laser lithotripsy has been deemed safe during pregnancy.
When possible, deferring URS beyond the first trimester is preferred to avoid potential teratogenic effects of anaesthesia
medications linked with stone formation
Carbonic anhydrase inhibitors (such as topiramate and zonisamide) cause a renal acidification defect similar to RTA and increase the risk of calcium phosphate stones.
Excessive use of supplements such as calcium or vitamins C and D can promote calcium stone formation.
Probenecid increases urinary uric acid and poses a risk for calcium or uric acid stones.
On the other hand, triamterene, certain protease inhibitors and guaifenecine/ephedrine can cause formation of stones composed of the drug or its metabolites.
Interpretation of Ua and CS for stone formers
urease-producing bacteria suggests struvite stones
high urine pH suggests calcium phosphate or struvite stones
low urine pH suggests uric acid stones
hexagonal crystals indicate cystine stones
coffin-lid shaped crystals are pathognomonic for struvite stones.
serum panel for stone formers
sodium
potassium
chloride
bicarbonate
calcium
creatinine
uric acid
RTA --> High chloride, low bicarbonate and low K
hyperparathyroidism --> If high CA, suggest PTHwhen to order metabolic work-up for stone formers
High-risk patients include those with recurrent stones (including those with multiple or bilateral stones at initial presentation) and first time stone formers who have medical, genetic, anatomic or dietary predisposition to recurrent stone formation. In addition, any first time stone former who expresses interest in more extensive evaluation and directed medical therapy should be offered metabolic testing.
metabolic workup for stone
1. 24-hr urine x 2
then analysed with 9 criteria :
total volume
calcium, citrate, creatinine.
oxalate
potassium, pH
Sodium
uric acid
Urine urea nitrogen and urinary sulphate, which estimate animal protein intake, and urinary supersaturation, which provides an estimate of stone forming propensity, are considered optional tests.
