Metabolic evaluation of urinary lithiasis 2

1. Metabolic
Evaluation of
Urinary Lithiasis
Dr G Praveen Chandra
MCh Urology Resident
Gandhi Medical College
Secunderabad

2. • Diagnostic Evaluation
• Use of Stone Analysis
• Role of Imaging
• Economics of Metabolic Evaluation
• Classification-Diagnostic Criteria

3. Diagnostic Evaluation
• Symptomatic episodes of urinary calculi are
a/w
• Significant patient discomfort.
• Morbidity of surgical treatments.
• Financial pain.

4. • How to prevent a recurrence of such an
episode…?!

5. • Metabolic Evaluation…

6. • Metabolic evaluation should be
• Simple to perform
• Economically viable
• Providing information that can be applied
toward a selective, rational therapy of stone
disease

7. • Metabolic problems include
• Distal RTA
• Primary HPT
• Enteric hyperoxaluria
• Cystinuria
• Gouty diathesis
• Selective medical therapy---
• To prevent further stone formation
• To correct underlying physiological disturbances
that may lead to nonrenal complications

8. How to select patients?
• Debatable……!
• Incidence of stone disease---escalating
• Males---
• Higher incidence of calculi overall
• Higher recurrence rate as well
• Increasingly higher percentage of female stone
formers ( 3:1 then Vs 1.3:1 now )

9. 1st time Stone Formers
• First-time stone formers have a 50% risk of
recurrence within the subsequent 10 years,
more so in the years immediately following their
1st episode.

10. First-Time Stone Formers
• Formation of a first stone may be the
harbinger of a more severe underlying
systemic disorder such as
• RTA
• Bone disease
• Hypercalcemia due to HPT

11. Evaluation
Recommended
• Patients @higher risk for recurrence..those with
• A family history of stones
• Intestinal disease ( Chr. diarrheal states )
• Pathological skeletal #s
• Osteoporosis
• UTI
• Gout
• Obese women with stones
• Poorly controlled diabetes with stones

12. • Any patients with stones composed of cystine,
uric acid or struvite…
• All children with urinary lithiasis

13. Indications for a
Metabolic Stone Evaluation

14. TIMING
When?
• At least 1 month after stone passage or stone
removal, allowing the patient to return to
normal routine.

15. How to do it…?

16. Abbreviated Protocol for
Low-Risk, Single Stone
Formers

17. Abbreviated
Protocol

19. Microscopy-Crystals
Apatite
Struvite
( Mg. Ammonium
Phospahate ) Ca.Ox.Dihydrate
Amorphous Rectangular Coffin-lid Tetrahedral-envelope

20. Ca.Ox.Monohydrate Cystine Ammonium urate
Hourglass Hexagonal Thorn apple shaped

21. Brushite
( Ca. Hydrogen
Phosphate Dihydrate )
-
Needle shaped

22. Abbreviated Protocol

23. STONE ANALYSIS

24. Use of Stone Analysis
• To determine metabolic abnormalities.
• Aids with preventive therapy.
• Most stones are a mixture of ≥1 component.
• Relative ratios / predominance of any
particular molecule—predictive value+

25. • Stone analysis may obviate the need for a
complete metabolic evaluation.
• Stone composition can direct metabolic
investigation.

26. Extensive Diagnostic
Evaluation

27. Extensive Diagnostic
Evaluation
• In patients with recurrent nephrolithiasis, and stone
formers at increased risk for further stone formation.
• Pt. to discontinue
• any medication that interferes with metabolism of
calcium, uric acid or oxalate (vitamin D, calcium
supplements, antacids, diuretics, acetazolamide & vitamin
C)
• any current medication for stone treatment (thiazides,
phosphate, allopurinol or magnesium).

28. Outline of
Extensive Ambulatory Protocol

29. How to validate a complete
24-hour urine specimen ?
• By checking total urinary creatinine.
• Production of creatinine
• In males – 15-20 mg / Kg BW / 24 hours
• In females--- 10-15 mg / Kg BW / 24 hours

30. Fast & Calcium Load Test
Differentiates between absorptive & renal hypercalciuria
• Essential before placing a patient on a calcium-binding
resin.
 Normal fasting urinary calcium < 0.11 mg/dL GF
 Normal postload urinary calcium < 0.2 mg/mg
creatinine

31. When & How to do it ?
• On the morning of the 2nd visit.

32. 7 days
before
•Restricted diet starts
12 hrs
before
•Fasting commences
•300 mL distilled water
9 hrs
before
•300 mL distilled water
2 h
before
•Empty bladder completely, discard urine
•+600 mL of distilled water
Over
2 hrs
•Pooled urine sample collected-Fasting urine
Over
10 min
•1 g oral calcium load
Over
4 hrs
•Pooled urine sample-Postload urine

33. Simplified Metabolic
Evaluation
• Calcium fast & loading tests excluded.
• No adherence to restricted diet.
• Single office visit.

36. IMAGING-
STONE COMPOSITION

37. CT Imaging
• Hounsfield unit ( HU ) measurement
• Significant diff. in HU b/n pure uric acid stones
& other stone types.

38. • DECT – Dual-Energy CT
• DECT slope algorithm-separates between
relatively pure cystine, struvite, Ca.ox,
Ca.phosphate & brushite stones.
• 92-100% accurate in diff b/n uric acid & non-uric
acid stones.

39. • Diagnostic Evaluation
• Use of Stone Analysis
• Role of Imaging
• Economics of Metabolic Evaluation
• Classification-Diagnostic Criteria

40. Economics
• The peak incidence of urolithiasis occurs in patients
between 20 and 60 years of age.
• The costs associated with the treatment of
nephrolithiasis are substantial.
• Hospital-based outpatient services.
• Emergency room charges
• Additional societal costs of lost productivity and social
service support.

41. • However, office visits, serum studies, and 24-
hour urine studies have their own costs.
• Is there a break-even point…?

42. • Medical management of a first stone episode is not
cost-effective and individual decisions should be
determined by local costs.
• However, recurrent stone formers should be treated
medically after a simplified evaluation, because of
the high recurrence rate of stone formation

43. • Diagnostic Evaluation
• Use of Stone Analysis
• Role of Imaging
• Economics of Metabolic Evaluation
• Classification-Diagnostic Criteria

44. Classification of
Nephrolithiasis
• 12 separate categories of nephrolithiasis
reflecting specific physiologic derangements

46. Diagnostic Criteria of
nephrolithiasis

48. Calcium – Based Calculi
• Hypercalciuria
• Hyperoxaluria
• Hypocitraturia
• Hypomagnesuria

49. Hypercalciuria
(>200 mg/day)

50. Calcium – Based Calculi
• Hypercalciuria
• Hyperoxaluria
• Hypocitraturia
• Hypomagnesuria

51. Hyperoxaluria
(>40 mg /day)
Primary
Hyperoxaluria
Mild metabolic
Hyperoxaluria-
Dietary
Enteric
Hyperoxaluria

52. Calcium –Based Calculi
• Hypercalciuria
• Hyperoxaluria
• Hypocitraturia
• Hypomagnesuria

53. Hypocitraturic Calcium
Nephrolithiasis
• <550mg in female
• <450mg in male
Hypo
Citraturia
Distal RTA
type 1
Chr. Diarrheal
states
Thiazide
induced
Idiopathic

54. Distal RTA Type 1
• Acquired / Inheritable
• Complete / Incomplete
• Lab hallmark:
• Low urine citrate ( < 100 mg / day )
• Inappropriately high urine pH ( ≥6.5 )
• Hypokalemia
• Hyperchloremia

55. Thiazide-induced
Hypocitraturia
Prolonged
Thiazide therapy
Hypokalemia
Intracellular
acidosis
HypoCitraturia

56. Calcium – Based Calculi
• Hypercalciuria
• Hyperoxaluria
• Hypocitraturia
• Hypomagnesuria

57. Hypomagnesuric Calcium
Nephrolithiasis
• Low urinary magnesium ( Importance? )
• Hypocitraturia
• Low urine volume
• a/w:
• Chr thiazide therapy
• IBD ( malabsorption )
• Excessive dependence on laxatives (
Chr.diarrhea )

59. Uric Acid-Based Calculi
• Gouty diathesis: Urine pH <5.5
HYPERURICOSURIC Calcium Nephrolithiasis
( HUCN )
Gouty Diathesis
Stones Form Ca oxalate stones
Can form either uric acid or
Ca oxalate calculi
Urinary pH NORMAL LOW ( Idiopathic )
Findings
Hyperuricosuria
Hypercalciuria +/-
High urinary Sodium
Normal Urinary uricacid
levels with
Hyperuricemia

61. Cystinuria
• Autosomal recessive error of transepithelial
transport involving the intestine & the kidneys
• Cystinuria : >250 mg / L
• Frequently a/w
• Hypercalciuria
• Hyperuricosuria
• Hypocitraturia
• Defective renal acidification

63. Infection Calculi
Urease producing
bacteria
Splitting of urea
Production of Ammonia
Alkaline Urine
( pH > 7.2 )
STRUVITE CALCULI
(MOST LIKELY STAGHORN CALCULI )

64. NO Disturbances
• In 3% of all patients undergoing a full metabolic
evaluation

65. Diagnostic Criteria

66. AUA Guidelines-
Metabolic Evaluation
1. Clinicians should perform a screening evaluation
consisting of a detailed medical and dietary history,
serum chemistries and urinalysis on a patient newly
diagnosed with kidney or ureteral stones.
(Clinical Principle)
2. Clinicians should obtain serum intact PTH level as part of
the screening evaluation if primary
hyperparathyroidism is suspected.(Clinical Principle)

67. 3. When a stone is available, clinicians should
obtain a stone analysis at least once.
(Clinical Principle)
4. Clinicians should obtain or review available
imaging studies to quantify stone burden.
(Clinical Principle)

68. 5. Clinicians should perform additional metabolic testing
in high-risk or interested first-time stone formers
and recurrent stone formers.
(Standard; Evidence Strength: Grade B)
6. Metabolic testing should consist of one or two 24-hour
urine collections obtained on a random diet and
analyzed at minimum for total volume, pH, calcium,
oxalate, uric acid, citrate, sodium, potassium
and creatinine. (Expert Opinion)

69. 7. Clinicians should not routinely perform "fast
and calcium load" testing to distinguish
among types of hypercalciuria.
(Recommendation; Evidence Strength:
Grade C)

70. Thank You