Kidney Stone Basics by Siddhivinayak Hospital Maninagar Ahmedabad

1. Basic information by ::Basic information by ::
Siddhivinayak Hospital,Siddhivinayak Hospital,
Maninagar, AhmedabadManinagar, Ahmedabad

2.  IntroductionIntroduction
 Conditions causing kidney stone formationConditions causing kidney stone formation
 Types of kidney stonesTypes of kidney stones
 Calcium saltsCalcium salts
 Uric acidUric acid
 Mg ammonium POMg ammonium PO44
 CystineCystine
 Other (xanthine, etc.)Other (xanthine, etc.)
 Laboratory investigationsLaboratory investigations

3.  Renal calculi (kidney stones) are formed in renalRenal calculi (kidney stones) are formed in renal
tubules, ureter or bladdertubules, ureter or bladder
 Composed of metabolic products present inComposed of metabolic products present in
glomerular filtrateglomerular filtrate
 These products are in high conc.These products are in high conc.
 Near or above maximum solubilityNear or above maximum solubility

4.  High conc. of metabolic products in glomerularHigh conc. of metabolic products in glomerular
filtratefiltrate
 Changes in urine pHChanges in urine pH
 Urinary stagnationUrinary stagnation
 Deficiency of stone-forming inhibitors in urineDeficiency of stone-forming inhibitors in urine

5.  High conc. of metabolic products in glomerular filtrateHigh conc. of metabolic products in glomerular filtrate
is due to:is due to:
 Low urinary volume (with normal renal function)Low urinary volume (with normal renal function)
due to restricted fluid intakedue to restricted fluid intake
 Increased fluid loss from the bodyIncreased fluid loss from the body
 Increased excretion of metabolic products formingIncreased excretion of metabolic products forming
stonesstones
 High plasma volume (high filtrate level)High plasma volume (high filtrate level)
 Low tubular reabsorption from filtrateLow tubular reabsorption from filtrate

6.  Changes in urine pH due to:Changes in urine pH due to:
 Bacterial infectionBacterial infection
 Precipitation of salts at different pHPrecipitation of salts at different pH
 Urinary stagnation is due to:Urinary stagnation is due to:
 Obstruction of urinary flowObstruction of urinary flow

7.  Deficiency of stone-forming inhibitors:Deficiency of stone-forming inhibitors:
 Citrate, pyrophosphate, glycoproteins inhibitCitrate, pyrophosphate, glycoproteins inhibit
growth of calcium phosphate and calciumgrowth of calcium phosphate and calcium
oxalate crystalsoxalate crystals
 In type I renal tubular acidosis, hypocitraturiaIn type I renal tubular acidosis, hypocitraturia
leads to renal stonesleads to renal stones

8.  Calcium saltsCalcium salts
 Uric acidUric acid
 Mg ammonium POMg ammonium PO44
 CystineCystine
 Other (xanthine, etc.)Other (xanthine, etc.)

9.  80% of kidney stones contain calcium80% of kidney stones contain calcium
 The type of salt depends onThe type of salt depends on
 Urine pHUrine pH
 Availability of oxalateAvailability of oxalate
 General appearance:General appearance:
 White, hard, radioopaqueWhite, hard, radioopaque
 Calcium POCalcium PO44: staghorn in renal pelvis (large): staghorn in renal pelvis (large)
 Calcium oxalate: present in ureter (small)Calcium oxalate: present in ureter (small)

10. Causes of calcium salt stones:Causes of calcium salt stones:
 Hypercalciuria:Hypercalciuria:
 Increased urinary calcium excretionIncreased urinary calcium excretion
 Men: > 7.5 mmols/dayMen: > 7.5 mmols/day
 Women > 6.2 mmols/dayWomen > 6.2 mmols/day
 May or may not be due to hypercalcemiaMay or may not be due to hypercalcemia

11.  Hyperoxaluria:Hyperoxaluria:
 Causes the formation of calcium oxalates withoutCauses the formation of calcium oxalates without
hypercalciuriahypercalciuria
 Diet rich in oxalatesDiet rich in oxalates
 Increased oxalate absorption in fat malabsorptionIncreased oxalate absorption in fat malabsorption
 Primary hyperoxaluria:Primary hyperoxaluria:
 Due to inborn errorsDue to inborn errors
 Urinary oxalate excretion: > 400 mmols/dayUrinary oxalate excretion: > 400 mmols/day

12. Calcium oxalate stones

13.  Treatment:Treatment:
 Treatment of primary causes such as infection,Treatment of primary causes such as infection,
hypercalcemia, hyperoxaluriahypercalcemia, hyperoxaluria
 Oxalate-restricted dietOxalate-restricted diet
 Increased fluid intakeIncreased fluid intake
 Acidification of urine (by dietary changes)Acidification of urine (by dietary changes)
 Calcium salt stones are formed in alkaline urineCalcium salt stones are formed in alkaline urine

14.  About 8% of renal stones contain uric acidAbout 8% of renal stones contain uric acid
 May be associated with hyperuricemia (with or withoutMay be associated with hyperuricemia (with or without
gout)gout)
 Form in acidic urineForm in acidic urine
 General appearance:General appearance:
 Small, friable, yellowishSmall, friable, yellowish
 May form staghornMay form staghorn
 Radiolucent (plain x-rays cannot detect)Radiolucent (plain x-rays cannot detect)
 Visualized by ultrasound or i.v. pyelogramVisualized by ultrasound or i.v. pyelogram

15.  Treatment:Treatment:
 Purine-restricted dietPurine-restricted diet
 Alkalinization of urine (by dietary changes)Alkalinization of urine (by dietary changes)
 Increased fluid intakeIncreased fluid intake

16. Uric acid stones

17.  About 10% of all renal stones contain Mg amm.About 10% of all renal stones contain Mg amm.
POPO44
 Also called struvite kidney stonesAlso called struvite kidney stones
 Associated with chronic urinary tract infectionAssociated with chronic urinary tract infection
 Microorganisms (such as from Proteus genus)Microorganisms (such as from Proteus genus)
that metabolize urea into ammoniathat metabolize urea into ammonia
 Causing urine pH to become alkaline andCausing urine pH to become alkaline and
stone formationstone formation

18.  Commonly associated with staghorn calculiCommonly associated with staghorn calculi
 75% of staghorn stones are of struvite type75% of staghorn stones are of struvite type
 Treatment:Treatment:
 Treatment of infectionTreatment of infection
 Urine acidificationUrine acidification
 Increased fluid intakeIncreased fluid intake

19. Mg ammonium phosphate (struvite) stone

20.  A rare type of kidney stoneA rare type of kidney stone
 Due to homozygous cystinuriaDue to homozygous cystinuria
 Form in acidic urineForm in acidic urine
 Soluble in alkaline urineSoluble in alkaline urine
 Faint radio-opaqueFaint radio-opaque
Treatment:Treatment:
 Increased fluid intakeIncreased fluid intake
 Alkalinization of urine (by dietary changes)Alkalinization of urine (by dietary changes)
 Penicillamine (binds to cysteine to form a compound morePenicillamine (binds to cysteine to form a compound more
soluble than cystine)soluble than cystine)

21. Cystine stone

22. If stone has formed and removed:If stone has formed and removed:
 Chemical analysis of stone helps to:Chemical analysis of stone helps to:
 Identify the causeIdentify the cause
 Advise patient on prevention and futureAdvise patient on prevention and future
recurrencerecurrence

23. If stone has not formed:If stone has not formed:
 This type of investigation identifies causes thatThis type of investigation identifies causes that
may contribute to stone formationmay contribute to stone formation
 Serum calcium and uric acid analysisSerum calcium and uric acid analysis
 Urinalysis: volume, calcium, oxalates and cystineUrinalysis: volume, calcium, oxalates and cystine
levelslevels
 Urine pH > 8 suggests urinary tract infection (MgUrine pH > 8 suggests urinary tract infection (Mg
amm. POamm. PO44))
 Urinary tract imaging:Urinary tract imaging:
 Ultrasound and i.v. pyelogramUltrasound and i.v. pyelogram