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Pts with augmented bladder constitute
-another risk group for urinary stones
Clacium oxalate stones
-70%
Hypercalciuria is defined
-24 urinary calcium excretion of more than 4 mg/kg/day
-in child weighing less than 60 kg
Hypercalciuria can be
-idiopathic
-secondary
Idiopathic hypercalciuria
-clincal, labaratory, and radiographic investigations fail to delineate an underlying cause
-with a normal calcium level
Secondary hypercalciuria
-increased bone resorption (hyperparathyroidism, hyperthyroidism, immobilization, acidosis, metastatic disease, gastrointestinal hyperabsorption)
A good screening test for hypercalciuria
-calcium-to-creatinine ratio
-should be less than 0.2
If calcium-to-creatinine ratio higher than 0.2
-repeat testing is indicated
If diagnosis of hypercalciuria (more than 4 mg/kg/day) confirmed futher evaluation includes
-serum bicarbonate
-creatinine
-alkaline phosphatase
-calcium
-magnesium
-pH
PTH if
-hypercalcemia
Initial management of hypercalciuria
-fluid intake and urinary flow
-dietary sodium restriction
-
Hydrochlorthiazide
-o.5-1 mg/kg/day
-in case of sustaining hypercalciuria up to 2 mg/kg/day
Side effects of thiazides
-hypocitraturia
-hypokalemia
-hyperuricemia
-hypomagnesemia
Oxalic acid
-metabolite excreted by the kidneys
oxalate from diet
-only 10-15%
Types of hyperoxaluria
-primary two types
-increased dietary intake
-enteric hyperabsorption
The treatment of hyperoxaluria
-promotion of urine flow
-restriction of dietary oxalate
-regular calcium intake
-pyridoxine (primary hyperoxaluria)
Citrate is
-urinary stone inhibitor
Hypocitraturia
-less than 320 mg/day
Treatment of hypocitraturia
-potassium citrate 1mEq/kg
-in two divided doses
Uric acid stones
-4-8%
Hyperuricosuria
-more then 10 mg/kg/day
Uric acid dissiciation and solubility
-is strongly reduced at pH less than 5.8
In familia or idiopathic form of hyperuricosuria
-usually normal serum uric acid levels
In other children hyperuricosuria due to
-overproduction secondary to inborn errors of metabolism
-myeloproliferative disorders
-high purine and proteine intake
The mainstay of therapy of uric acid stones
-alkalisation of urine
Allopurinol
-10 mg/kg
-than failed conservative treatment
Allopurinol side effects
-rash
-diarrhea
-eosinophilia
-chronic renal failure
Cystine stones
-recessive autosomal  disorder characterised by failure of renal tubules to reabsorb four basic amino acids (cystine,ornitine, lysine, arginine)
The medical treatment of cystine stones
-alkalising of urine
-alphamercaptopropionyl glycine (Thiola)
Cystine stones and SWL
-difficult
Infection stones
-bacteria prodcucing urease
Urease converts
-urea into ammonia and bicarbonate
-alkalising the urine and futher converting bicarbonate to corbonate
-formation magnesium ammonium phosphate stones
Imaging of stones
-US first study
-CT for noninformative US or plain abdominal roentgenogram
Metabolic evaluation includes
-family and patient history of met. problems
-analysis of stone composition
-electrolytes
-spot analysis , culture, calcium-creatinine ratio
-urine tests
-24 hour cystine analysis
Electrolytes
-BUN
-creatinine
-calcium
-phosphorus
-alk.phosphatase
-uric acid
-total protein
-carbonate
-albumin
-PTH if hypercalcemia
Urine tests
-calcium
-phosphorus
-magnesium
-oxalate-uric acid-citrate
-protein
-creatinine clearence
Cystine analysis
-positive sodium nitroprusside test
-cystine stone (hexagonal crystals in urine)
Cystine stones treatment
-high fluid intake
-potassium citrate 3-4 mEq/kg/day
-mercaptopropiyonilglycine 10-15 mg/kg/d
Uric acid stone treatment
-alkali replacement (K-citrate)
-allopurinol 10 mg/kg low purine diet
Mg Ammonium Phosphate (struvite)
-total elimination of stone (surgery/SWL)
-antibiotics
Calcium stones could be
-Calcium oxalate
-Calcium phosphate
Diagnostic evaluation of calcium stones blood
-calcium
-uric acid
-carbonate
-magnesium
-phosphate
-pH
Diagnostic evaluation of calcium stones urine
-calcium
-uric acid
-magnesium
-phosphate
-oxalate
-citrate
-pH
Urine pH less than 5.5 and calcium stones
-hypercalciuria
-hyperuricosuria
-hypocitraturia
-hyperoxaluria
Urine pH more than 5.5 and calcium stones
-futher investigation for RTA
Treatment of hypercalciuria
-K-citrate diet
-low sodium intake
-HCTZ -0.5-1mg/kg
Hyperoxaluria treatment
-regular calcium intake
-diet low in ox
-K-citrate
-pyridoxine
Hyperuricosuria treatment
-alkali replacement K-citrate
-allopurinol 10 mg/kg
Stenting and SWL is essential in
-solitary kidneys undergoing SWL
-large stone burden (risk of developing Steinstrasse) and urinary obstruction
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