This document discusses kidney stones, including their causes, types, and treatments. It notes that kidney stones form when metabolic products in the glomerular filtrate crystallize in the renal tubules, ureters, or bladder. The main types of stones are calcium salts, uric acid, magnesium ammonium phosphate, and cystine. Treatment depends on the type of stone but generally involves increasing fluid intake, modifying diet, and addressing underlying causes like infection or metabolic abnormalities. Laboratory tests on stones or urine can help identify stone composition and risk factors.

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