medical management of renal stones
TRANSCRIPT
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Preventon of Renal Stones
Preetham Boddana
Renal Consultant
26 Feb 2014
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Outline
• Epidemiology
• Evidence for medical management
• Pathophysiology
• Preventon of stones by medical management
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Epidemiology
• Prevalence of kidney stones 8.5%
• Male-to-female rato 3:1 to < 2:1
• Increases with age
• Whites>black, asian or hispanic etnicity
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Clinical Risk Factors
• occupaton
• family history
• diet
• hydraton
• small bowel disease (i.b.d.)
• medical conditons causing hypercalcuria
• medical conditons causing aciduria
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STONE MANAGEMENT
OPTIONS
Open surgery
Percutaneous nephrolithotomy
Ureteroscopy
Shock wave lithotripsy
Medical therapy
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Metabolic Evaluaton
• Stone passage ≠ stone formaton
• Focused history for stone risk formers
• Urine analysis
• Stone analysis
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NEPHROLITHIASIS
Peak incidence age 30 - 60
Gender (Male : Female) 3 : 1
Family history 3 - fold risk
Body size risk with weight
Recurrence afer frst stone:
Year 1 10 - 15%
Year 5 50 - 60%
Year 10 70 - 80%
NATURAL HISTORY & RISK FACTORS
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Placebo/
Potassium
Conservatve Citrate
Stone formaton 0.54 0.25 0.52 0.02 rate (no/pt/yr)
Reducton in stone 54% 96%
formaton rate
Remission rate 61% 96%
MEDICAL MANAGEMENTOF NEPHROLITHIASIS
Preminger & Pak, 1985
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IMPACT OFMEDICAL THERAPY
Pre-On
Duraton (yr/pt) 3.0 3.7
Surgery rate (no/pt) 0.21 0.01
Patents requiring 58% 2%Surgery
NEED FOR STONE REMOVAL
Preminger & Pak, 1985
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SELECTIVE MEDICAL THERAPY
Sto
ne
Fo
rmat
ion
Rat
e
IMPACT OF MEDICAL RX
Pre-Rx On K-Citrate
0
1
2
3
4
5
6 Chronic Diarrh ea
RT A
Hyp erurico su ria
IdiopathicHyp oci tUric Aci d
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Conditons causingkidney stone formaton
• High conc. of metabolic products in glomerular fltrate
• Changes in urine pH
• Urinary stagnaton
• Defciency of stone-forming inhibitors in urine
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Conditons causingkidney stone formaton
• Defciency of stone-forming inhibitors:
– Citrate, pyrophosphate, glycoproteins inhibit growth of calcium
phosphate and calcium oxalate crystals
– In type I renal tubular acidosis, hypocitraturia leads to renal stones
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Pathogenesis of Renal Stones
• 99% of renal stones are composed of:
– calcium oxalate 75% (mono or di hydrate)
– calcium hydroxyl phosphate (15%)(apatte)
– magnesium ammonium phosphate 10% (struvite)
– uric acid 5%
– cystne 1%
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Calcium stone risk factors: 1) Hypercalciruia
• (>250mg/day in women, and >300mg/day in men)
– Seen in up to ½ of idiopathic calcium stone formers
– 3 types of hypercalciuria
• Absorptve: (most common form)
– increase in intestnal calcium absorpton from gut
• Resorptve: (5% of patents with recurrent stones)
– Secondary to primary hyperparathyroidism
– Risk of recurrent stones returns to baseline about 10 years afer parathyroidectomy
• Renal: (2%)
– Increased excreton of calcium secondary to defect in renal tubular calcium reabsoropton
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Calcium stone risk factors: 2) Hyperuricosuria
• (>750mg/day in women, 800mg/day in men)
– UA is end product of purine metabolism
– Uric acid is thought to act as a nidus for calcium stone formaton
– In most of these pts, a high purine diet is responsible rather than defect in uric acid metabolism
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Calcium stone risk factors: 3) Hypocitraturia
• (<320mg/day)
– Citrate thought to be a principal inhibitor of stone formaton by actng in tubular lumen by
combining with calcium to form soluble complex
– Women excrete more citrate and thus have lower incidence of stone formaton than men
– Chronic metabolic acidosis limits citrate excreton (by enhancing proximal reabsorpton)
• chronic diarrhea,
• RTA,
• carbonic anhydrase inhibitors
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Calcium stone risk factors: 4) Hyperoxaluria
• (>45mg/day)
– 1) Enteric hyperoxaluria
• Decolonisaton of Oxalobacter formigenes,
• Low calcium diet
• Small bowel disease or surgical resecton,
– malabsorpton of faty acids and bile saltsincrease in oxalate absorpton from:
» Increased free Ca to bind with oxalate (Ca is bound to faty acids in the intestnal lumen)
» increased colonic permeability to oxalate
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Principles of Medical Management
• instruct patent on adequate water consumpton ( enough to produce 2L of urine
in 24 hrs.)
• if hypercalciuric treat with hydrochlorothiazide (monitor urinary Ca)
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Principles of Medical Management (2)
• if hyperuricosuric
– allopurinol if serum uric acid elevated
– alkalinize urine if serum level is normal
• if actve Ca stone former not aided by diet, hctz add K citrate
• if magnesium ammonium phosphate stone afer reducton of burden treat
aggressively with antbiotcs.
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Principles of Stone Preventon
• Prevent supersaturaton
– water! water and more water enough to make 2L of urine per day
– prevent solute overload by low oxalate and moderate Ca intake and treatment of hypercalcuria
– replace “solubilizers” i.e... citrate
– manipulate pH in case of uric acid and cystne
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Drug therapy for calcium stones
• Hypercalciuria: thiazide diuretcs
– Thiazide therapy can lower calcium excreton by as much as 150mg/day
• Hyperuricosuria: allopurinol or K citrate
– Raising the urine pH above 6.0 will convert insoluble uric acid to much more soluble urate salt
• Hypocitraturia: K citrate
– Alkalinizing urine enhances citrate excreton
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Drug therapy for calcium stones (cont)
• Hyperoxaluria
– Aim to diminish intestnal oxalate absopton (high fuid, K citrate, oral calcium carbonate, low
fat, low oxalate diet)
– Possible drug therapy pending
• Pyridoxine may reduce producton of oxalate
• Cholestyramine reduces intestnal absorpton of oxalate
• Probiotc treatment with Oxalobacter has been shown to decrease urinary oxalate concentraton ,
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Treatment of Uric Acid Stones
• Hydraton, dietary purine moderaton (lower meat, poultry, fsh)
• Alkalinizaton urine with K citrate to maintain urine pH between 6.0-7.0
• If nocturnal urine pH falls, acetazolamide
• Can add allopurinol
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Cystne stones
• Treatment
– High fuid intake
– Urine alkalinizaton
– Sodium restricton
• Penicillamine, topronin, and captopril
– Cystne is formed from linkage of two cysteine
molecules by a disulfde bond. These meds by
decrease availability by forming complexes with
cysteine.
cysteine
cysteine
Disulfde bond
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THANK YOUTHANK YOU