Pediatric Nephrolithiasis Justin Ahn M.D. PGY-1 Urology University of Washington

Overview Background Causes Evaluation Treatment Prevention

Background 10% of U.S. population – Prevalence  70% last 15 years PHIS: 42 pediatric hospitals, ‘99-’08 – Annual  10.6%, adjusted for volume  –  6x vs. appendicitis –  10x vs. bronchiolitis Short Stature, Bone Mineral Density – 31-65% lower BMD in adult stone formers, kids?

PHIS Data

Causes (contributors) Metabolic – Calcium, Citrate, Oxalate, Uric Acid Anatomic – Obstruction, urinary stasis Dietary – Dehydration, high protein, high salt Infectious – Urease splitting org. Medications – Vit C/D, Triamterine, Protease Inhibitors, Lasix, CAI Immobility

Evaluation: Imaging US – 25-81% sens, % spec – Use: Screening, r/o hydronephrosis – Limitations: nondiagnostic, overestimation, ureter, operator dep KUB: – 45-85% sensitivity – Use: Screening, Localization ESWL – Limitations: radiolucent stones (10%), other opacities Unenhanced CT scan: – >96% sens & spec – Gold Standard, acute and initial presentation – Limitations: radiation, expense

Evaluation: Labs Serum – Chem 10, Alk Phos, Uric Acid Urine – UA, UCx – 24 hour collection vs. Spot Volume, pH Metabolic profile Stone analysis

Evaluation: 24 hour urine

Treatment Conservative – < 3 mm pass spontaneously – Passage: hydration, flomax, pain meds Intervention (stent vs. lithotripsy) – ≥ 4 mm in ureter – Pain, Urosepsis, anorexia >24hrs, refractory pain, nausea/vomiting – solitary kidney

Extracorporeal Shock Wave Lithotripsy Stones < or = to 15 mm, outpatient, nonemergent ~80% effective with 1-2 sessions, better proximally Risk: minimal  steinstrasse, UTI, hematoma

Ureteroscopy, Laser Lithotrpsy Stones 15 mm or smaller, with acceptable anatomy ~80% effective with monotherapy, better distally Risk: minimal  UTI, perforation (prox ureter)

Percutaneous Nephrolithotomy Large upper tract stones >15mm, lower pole calculi > 10mm, anatomic abnormality, known cystine or struvite (hard stones) 90% sucess with monotherapy Risk: minimal-moderate  bleeding, PTX, intra/extraperitoneal injury, sepsis

Lap/Robotic Pyelolithotomy Large stone burden, Cystine staghorn refarctory to PCNL and SWL, concomitant UPJ obstruction Lap: Casale et al 2004, 8 patients Robotic: Lee et al 2007, 5 patients video

Residual Stone Fragments – Afshar et al pts w/ RF ≤ 5mm, mean f/u 46 mo 35.5% regrowth 34.5% clinical symptoms (hematuria, colic, UTI – Dincel et al 2013 (Journal Pediatric Surgery) 85 pts with RF ≤ 4mm, f/u 6 mo minimum, 22 mo median 57.1% passage pelvix stones, 16.1% passage lower pole 40% adverse outcomes (colic, hematuria, UTI) 18% regrowth 29.4% reoperation – “Residual stones associated with adverse clinical outcomes, try to achieve stone free status”

Medical Tx / Prevention Dietary Modification – FLUIDS: goal UOP >1cc/kg/hr (ex: 40kg : 960cc) Soda, coffee, tea, alcohol, soda, except grapefruit & apple juice – Salt Drags calciumDaily 1.2g (4-8yo), 1.5g (9-18yo) – Animal Protein Decreases urine pH, increases uric acid – Citrate (fruits and vegetables) Oranges and lemons Medical Therapy – K Citrate: potentially curative cystine and uric acid stones (dissolves with correction of urine pH) – Pyridoxine – Thiazides – Allopurinol

Oxalate Malabsorption (IBD, CF, short gut, etc.) – Diarrhea  dehydration Solution:  oxalate intake, consume with dairy, Ca carbonate supplementation

Oxalate Oxalate Food Offenders: 1.Spinach600 mg 2.Swiss chard645 mg 3.Rhubarb~500 mg 4.Beets675 mg 5.Chocolate (especially dark)~254 mg 6.Nuts~200 mg 7.Soy/Tofu/Milk alternatives 336 mg/8.5 oz

Thanks!