1. Lab 4
Renal Calculi

3. What are kidney stones?
Renal calculi (kidney stones) are formed in renal tubules, ureter or bladder.
They are composed of metabolic products present in glomerular filtrate.
These products are in high conc. near or above maximum solubility.

5. How it is formed ? Conditions leads to kidney stones
High conc. of metabolic products in glomerular filtrate is due to:
Low urinary volume (with normal renal function) due to restricted fluid intake
Increased fluid loss from the body
Increased excretion of metabolic products forming stones
High plasma volume (high filtrate level)
Low tubular reabsorption from filtrate

6. 2. Changes in urine pH due to:
Bacterial infection
Precipitation of salts at different pH
3. Urinary stagnation is due to:
Obstruction of urinary flow
4. Deficiency 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

8. Kidney stones

9. Calcium oxalate crystal
Types of kidney stones
1. Calcium salt stones
80% of kidney stones contain calcium
The type of salt depends on
Urine pH
Availability of oxalate
General appearance:
White, hard, radio-opaque
Calcium PO4: stag-horn in renal pelvis (large)
Calcium oxalate: present in ureter (small)
Calcium oxalate crystal

10. Causes of calcium salt stones:
1. Hypercalciuria:
Increased urinary calcium excretion
Men: > 7.5 mmols/day Women > 6.2 mmols/day
May or may not be due to hypercalcemia
2. Hyperoxaluria:
Causes the formation of calcium oxalates without hypercalciuria
Diet rich in oxalates
Increased oxalate absorption in fat malabsorption
3. Primary hyperoxaluria:
Due to inborn errors
Urinary oxalate excretion: > 400 mmols/day

11. Treatment:
Treatment of primary causes such as infection, hypercalcemia, hyperoxaluria
Oxalate-restricted diet
Increased fluid intake
Acidification of urine (by dietary changes)
Note:
Most of Calcium salt stones are formed in alkaline urine

12. 2. Uric acid stones General appearance:
About 8% of renal stones contain uric acid
May be associated with hyperuricemia
(with or without gout)
Form in acidic urine
General appearance:
Small, friable, yellowish
May form stag horn
Radiolucent (plain x-rays cannot detect)
Visualized by ultrasound or i.v. pyelogram
Uric acid crystal

13. Treatment: The last 2 choices Purine-restricted diet
Alkalinization of urine (by dietary changes)
Increased fluid intake
The last 2 choices

14. 3. Mg ammonium PO4 stones
About 10% of all renal stones contain Mg amm. PO4
Also called struvite kidney stones
Associated with chronic UTI
From Microorganisms (such as Proteus genus) that metabolize urea into ammonia
Causing urine pH to become alkaline and stone formation
Commonly associated with staghorn calculi
75% of staghorn stones are of struvite type

15. Treatment: Treatment of infection Urine acidification
Increased fluid intake

16. 4. Cystine stones Treatment: A rare type of kidney stone
Due to homozygous cystinuria
Form in acidic urine
Soluble in alkaline urine
Faint radio-opaque
Treatment:
Increased fluid intake
Alkalinization of urine (by dietary changes)
Penicillamine (binds to cysteine to form a compound more soluble than cystine)

17. Laboratory investigations
If stone has formed and removed:
Chemical analysis of stone helps to:
Identify the cause
Advise patient on prevention and future recurrence
If stone has not formed:
This type of investigation identifies causes that may contribute to stone formation

18. Tests are performed for this purpose:
1. Blood chemistry
2. Serum
Calcium, Phosphate.
Uric acid.
Alkaline phosphates.
sodium potassium chloride.
Magnesium.
Creatinine.
3. Urinalysis
Volume, calcium, oxalates and cystine levels
Urine pH > 8 suggests urinary tract infection (Mg amm. PO4)

19. Microscopy of urine
Urine examination is recommended on a freshly voided morning sample using dip stick test and microscopic examination and culture. Microscopy may reveal the following crystals:
oxalate (envelope)
calcium phosphate (amorphous)
triple phosphate (coffin lid)
uric acid (needle shaped) and
cystine (hexagonal)
as well as any other formed elements.

20. Stone analysis X-ray/imaging techniques
The content of the stone may determine the subsequent evaluation of the patient by this method.
The presence of uric acid, cystine or struvite will have therapeutic consequences. Chemical qualitative analysis is generally adequate.
X-ray/imaging techniques
If a calculus is suspected, intravenous pyelography (urogram) should be included. It may also reveal structural abnormalities

21. X-ray/imaging techniques
Renal Calculi

22. Chemical Examination
Wash the calculi well with tap water followed by distilled water
Dry well by oven
Grand the calculi to obtain a smooth powder
Take a small part of the powder and burn on direct flame to determine if the stone contain organic components or not.

23. Test for uric acid 1-Powder+ Uric acid indicator(U.A).
2-Incubation for 5 min. in RM.
3-Color pink will be appear if the U.A form it.

24. Test for oxalate, calcium, magnesium and phosphate
Powder + 6% HNO3+heat to boil then leave it to cooled ppt .then filtrated it. The filtrate make the following on it:
Filtrate + (2.5 %)CaCL2 +ammonia: If white ppt appeared. so there is oxalate
Filtrate + Reagent(phosphor) ammonium molibdate : Blue Color will be appear if the there is phosphor.
Filtrate + HCL: after a good mixing filter it and add H2SO4 to the precipetate on the filter paper to dissolve it, and heat then add KMO4 drop by drop if the permanganate color disappeared the calculi contains Calcium if there is no change in color the calculi is Mg.