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
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.
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).
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
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
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
60.
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
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)