Why do we make kidney stones, how are they evaluated and how are they prevented? Dr. Britton E. Tisdale, MD, Urologist, UBMD Urology Buffalo Niagara / Western New York Area

1. .
Kidney Stone Causes,
Evaluation and Prevention
Dr. Britton Edgett Tisdale, MD, Urologist
Assistant Professor of Urology
State University of New York at Buffalo

2. Dr. Britton Edgett Tisdale, MD
UBMD Urology
Assistant Professor of Urology, State University of New York at Buffalo
Male Genitourinary Reconstruction, Female Genitourinary Reconstruction,
Urogynecology, Pelvic Prolapse Management Incontinence, Voiding Dysfunction
Neurourology, Laparoscopic and General Urology
Offices:
4233 Maple Road, Amherst, NY, Phone: (716) 725-6277
1020 Youngs Rd, #110, Williamsville, NY Phone:(716) 725-6277
2816 Pleasant Avenue, Hamburg, NY Phone (716) 725-6277
Surgical and Inpatient Services:
Millard Fillmore Suburban Hospital
Buffalo General Hospital
Erie County Medical Center

3. Objectives
1. Why do we make kidney stones
2. Evaluation of those that have recurrent
kidney stones
3. Prevention of kidney stones
Keep in mind, this is the basics only, not a
comprehensive review

4. What are kidney stones made of?
Composition Male Female All
Calcium Oxalates
Calcium Phosphates
Uric Acid & Urates
Struvite
Cystine
Others
73.2
4.7
17.4
1.6
1
2.1
62.9
14.4
10.3
5.0
2.5
4.9
70.1
7.6
15.2
2.8
1.5
4.8
Dr. Britton E. Tisdale, MD, Urologist 716-725-6277 ubmdurology.com/contact/

5. Why do stones form, in general?
1. Not enough of things that prevent
stones.
2. Too much of things that cause
stones
Dr. Britton E. Tisdale, MD, Urologist 716-725-6277 ubmdurology.com/contact/

6. Why do stones form in general?
Not enough of things that prevent stones
1.Not enough fluid intake causes low urine volume
 Low urine volume is often seen in 24 hour urine
collections in stone formers
 Need to drink enough to make 1.5 – 2.0 liters/quarts of
urine per day
 Dilutes things in the urine that cause stones.
1.Not enough citrate, magnesium, potassium, etc.
Dr. Britton E. Tisdale, MD, Urologist 716-725-6277 ubmdurology.com/contact/

7. Why do stones form in general?
Too much of things that cause stones in the urine
 Too much acid
 Too much calcium
 Too much oxalate
 Too much sodium
 Too much uric acid
Dr. Britton E. Tisdale, MD, Urologist 716-725-6277 ubmdurology.com/contact/

8. Why do calcium stones form?
Too much calcium in the urine = Hypercalciuria
 Idiopathic = we don’t know why
• 50% of calcium stones
 Intestinal issue = absorptive hypercalciuria
• High intestinal calcium absorption, more than one cause
 Bone issue = resorptive hypercalciuria
• Increased bone resorption putting more calcium in blood
 Kidney issue
• Not reabsorbing calcium during urine production
Dr. Britton E. Tisdale, MD, Urologist 716-725-6277 ubmdurology.com/contact/

9. Why do calcium stones form?
Too much calcium in the urine = Hypercalciuria
1.Parathyroid gland problem = Primary Hyperparathyroidism
 5% of calcium stones
 Inherited syndrome
1.Too much vitamin D
 Taking too much
 Producing too much: sarcoidosis
1.Too much calcium intake/absorption (or not enough intake)
2.Too much thyroid hormone
3.Too much sodium intake
Dr. Britton E. Tisdale, MD, Urologist 716-725-6277 ubmdurology.com/contact/

10. Why do calcium stones form?
Hypocitraturia =Not enough citrate in the urine
1.Normal Excretion is 300 - 900mg/day, (> 1.2
mmol/day)
2.Citrate binds calcium in the urine, preventing stone
formation
3.Lower in High Protein Diets
Dr. Britton E. Tisdale, MD, Urologist 716-725-6277 ubmdurology.com/contact/

11. Why do oxalate stones form?
Too much oxalate in the urine = hyperoxaluria
1.Too much oxalate intake
2.Not enough calcium intake with meals
3.Too much absorption from intestines
 Inflammatory bowel disease
 Gastric bypass surgery
1.Not enough pyridoxine (B6) intake
2.Specific genetic mutations affecting oxalate metabolism
Dr. Britton E. Tisdale, MD, Urologist 716-725-6277 ubmdurology.com/contact/

12. Calcium Oxalate crystals and stone
Dr. Britton E. Tisdale, MD, Urologist 716-725-6277 ubmdurology.com/contact/

13. Why do uric acid stones form?
Hyperuricosuria = too much uric acid in the urine
1.Low/acid pH in urine decreases solubility
2.Solubility not high in the first place, is ~90mg/L
3.Normal excretion 5-600mg/day = 4-4.5 mmol/day
 Intake of certain foods can increase
 Some medications can increase
 Medical conditions can increase
1.Low urine volume
Dr. Britton E. Tisdale, MD, Urologist 716-725-6277 ubmdurology.com/contact/

14. Uric Acid crystals can cause Calcium
Oxalate Stones
 Small uric acid cystals are a nidus for calcium
oxalate stone formation
 Bind Calcium Oxalate
 Promote Crystal Growth
Dr. Britton E. Tisdale, MD, Urologist 716-725-6277 ubmdurology.com/contact/

15. Uric Acid
Dr. Britton E. Tisdale, MD, Urologist 716-725-6277 ubmdurology.com/contact/

16. Struvite Stones = “Infection Stones”
1. Ammonium magnesium phosphate stones form in
infected urine
2. pH is High [> 7]
3. Bacterial Urease
 urea → ammonia → ammonium
1. Proteus, Klebsiella, Pseudomonas, many others
Dr. Britton E. Tisdale, MD, Urologist 716-725-6277 ubmdurology.com/contact/

17. Struvite Stones
Dr. Britton E. Tisdale, MD, Urologist 716-725-6277 ubmdurology.com/contact/

18. Other Stones
1. Calcium phosphate
2. Cystine
 Genetic “COLA” abnormality
1. Drug Stones
 triamterene
 Indinavir
 Many others
1. Xanthine
Ciprofloxacin
Indinavir
Dr. Britton E. Tisdale, MD, Urologist 716-725-6277 ubmdurology.com/contact/

19. Renal Tubular Acidosis
1. Distal RTA (Type 1)
 Defective Excretion & Retention of
Hydrogen Ions in Urine
 Problem with excretion, problem with
trapping
 Calcium phosphate stones
 Nephrocalcinosis
 Non-anion gap metabolic acidosis
 Relatively alkaline urine pH
Dr. Britton E. Tisdale, MD, Urologist 716-725-6277 ubmdurology.com/contact/

20. Evaluation of stone formers
What to Measure
1.24 Hour Urine Collection
2.Blood tests
3.Imaging
Dr. Britton E. Tisdale, MD, Urologist 716-725-6277 ubmdurology.com/contact/

21. Evaluation of stone formers
24 Hour Urine Collection
 Things that cause stones
 calcium, phosphate, uric acid, oxalate, sodium
 Things that prevent stones
 citrate, magnesium, potassiuim
 Other things
 Volume, creatinine, pH
Dr. Britton E. Tisdale, MD, Urologist 716-725-6277 ubmdurology.com/contact/

22. Evaluation of stone formers
Blood tests
 BMP
 Ionizied Calcium & PTH
 Vitamin D
 TSH
Dr. Britton E. Tisdale, MD, Urologist 716-725-6277 ubmdurology.com/contact/

23. Evaluation of stone formers
Imaging Studies to evaluate stone size, number, location
 Non-contrast CT of the abdomen and pelvis
 >/= 95% sensitivity and specificity
 Ultrasound + Xray of kidneys + ureters + bladder =
“KUB”
 50% sensitive for small stones
 Intravenous pyelogram = “IVP” – can be done, but
mostly historical
Dr. Britton E. Tisdale, MD, Urologist 716-725-6277 ubmdurology.com/contact/

24. Prevention of Calcium Oxalate Stones
1. Dietary and Fluid Intake Modification
2. Medications
Dr. Britton E. Tisdale, MD, Urologist 716-725-6277 ubmdurology.com/contact/

25. Prevention of Calcium Oxalate Stones
Dietary Modification
 Fluid Intake
 Animal Protein Intake
 Sodium Intake
 Calcium Intake
 Not what you might think
 Oxalate Intake
Dr. Britton E. Tisdale, MD, Urologist 716-725-6277 ubmdurology.com/contact/

26. Prevention of Calcium Stones
Medications
 Hydrochlorthiazide
 Reduce calcium in the urine
 Phosphates
 Bind calcium in the intestines
 Potassium Citrate
 CaOx, RTA (CaP), Uric acid, Cystine
Dr. Britton E. Tisdale, MD, Urologist 716-725-6277 ubmdurology.com/contact/

27. Prevention of oxalate stones
1. Calcium taken with meals
 binds oxalate in the gut from food
1. Cholestyramine
2. Pyridoxine
3. Magnesium
 magnesium oxalate is soluble
Dr. Britton E. Tisdale, MD, Urologist 716-725-6277 ubmdurology.com/contact/

28. Prevention of Uric Acid Stones
1. Drink more water
2. Restrict dietary purines
3. Medications
 Allopurinol
• prevents formation of uric acid
 Alkalinize the urine
Dr. Britton E. Tisdale, MD, Urologist 716-725-6277 ubmdurology.com/contact/

29. Prevention for other types of stones
1. Drink more water
2. Medications
 Antibiotics for struvite/“infection” stones
 Penicillamine for cystine stones
 Other medications
1. Stop medications that may be causing stone
formation.
Dr. Britton E. Tisdale, MD, Urologist 716-725-6277 ubmdurology.com/contact/

30. Take Home Messages
1. Kidney stones are common (10% lifetime
risk in North America)
2. Kidney stone formation & growth can be
prevented or slowed to reduce the frequency
of need for surgical intervention
Dr. Britton E. Tisdale, MD, Urologist 716-725-6277 ubmdurology.com/contact/

31. Take Home Messages
Prevention of Kidney Stone Formation &
Growth
 Increase urine volume by drinking more water
 Avoid excess dietary sodium and animal protein
 “Normal” Calcium (1 - 1.5 g/day) intake with
meals (not low or high intake)
 Potassium Citrate
 CaOx, RTA (CaP), UA, Cystine
Dr. Britton E. Tisdale, MD, Urologist 716-725-6277 ubmdurology.com/contact/

32. Scenario: Calcium Oxalate Stones
60 year old male
 2 episodes of renal colic from ureteral stones
 Calcium oxalate stones
 Blood tests - normal
 Non-contrast CT/CAT scan: no more stones
BEFORE looking at the next slide, what other
test(s) would you order?
Dr. Britton E. Tisdale, MD, Urologist 716-725-6277 ubmdurology.com/contact/

33. Urine Chemistry from 24 hour urine
collection
1. Volume 1.75 L
2. Calcium 2.9 mmol/day (N 2.5 - 7.5 mmol/d)
3. Oxalate 270 µmol/day (N < 450 µmol/day)
4. Urate 5.5 mmol/day (N < 4.5 mmol/day)
5. Citrate 0.6 mmol/day(N > 1.2 mmol/day)
BEFORE looking at the next slide, what
treatment/prevention measures would you
order?Dr. Britton E. Tisdale, MD, Urologist 716-725-6277 ubmdurology.com/contact/

34. Prevention of Calcium Oxalate Kidney
Stones
1. Drink more fluid = water
2. Avoid excess intake of sodium/salt, oxalate
3. “Normal” animal protein/meat intake
 No more than 3 “deck of card” sizes per day
1. “Normal” calcium intake, with meals
2. Take in more citrate (diet or prescription)
3. Medications
 Consider hydrochlorothiazide, chlorthalidone
 Consider allopurinol (high urine uric acid also can help cause
calcium oxalate stones)
Dr. Britton E. Tisdale, MD, Urologist 716-725-6277 ubmdurology.com/contact/