present EUA 2021 and AUA guidelines on the metabolic work up for stone disease

1. METABOLIC EVALUATION
OF UROLITHIASIS-CURRENT
GUIDELINES
Dr SRIKANTH VALASAPALLI
DNB RESIDENT
MMHRC , MADURAI

2. OUTLINE
Introduction
Epidemiology
First time and High risk stone formers
Metabolic work up – components and indications
24 hour urinary analysis- evidence
Is metabolic work up essential for first time stone formers ?
Alternatives
Stone Analysis

3. INTRODUCTION
Urolithiasis is one of the oldest and longest recognized
urologic afflictions, yet it still remains one of the most
common urologic conditions.
Lifetime risk of stone formation 5-10%
Recurrence rate after formation of initial stone – 50 % within
next 10 years
First time stone formers – likely to have metabolic
abnormalities compared to healthy population
Recurrent stone formers – significant metabolic
abnormalities than with a single stone episode

4. EPIDEMIOLOGY
World prevalence rates vary ranging
from 7% to 13% in North America, 5%
to 9% in Europe, and 1% to 5% in Asia
In US : 1 in 11 will have calculus/i in
lifetime ( scales et al.,2012)
Previously male >> female .. Recent
trend is male = female(Lieska et
al.,2006)

6. FIRST TIME
STONE
FORMER
50 % risk for recurrence in next 10 years ( Uribarri ., 1989)
Few suggests, first-time stone formers should be provided
empirical fluid and dietary recommendations until they suffer a
recurrence.
Studies of single stone formers placed on a conservative program
of high fluid intake alone OR combined with avoidance of dietary
excess, revealed a low incidence of recurrent stone disease –
STONE CLINIC EFFECT
Others like - Pak 1982, Strauss et al., 1982b suggests that single
stone formers have an equally high incidence of metabolic
abnormalities as recurrent stone formers

7. AUA – Additional metabolic
testing in high risk or
interested first time stone
formers .
Stone can be the harbinger of
more severe underlying
disorder .

8. ROKS NOMOGRAM
• ROKS – Recurrence Of Kidney Stone

9. HIGH RISK
STONE
FORMER
Patients identified as high-risk stone formers include those
with :
Family history of stone disease,
Obesity and/or metabolic syndrome,
Patients with medical conditions that predispose to stone
formation such as
•Primary hyperparathyroidism
•Sarcoidosis,
•Gastrointestinal (GI) disease or prior surgical resection
•Type 2 diabetes mellitus,
•Renal tubular acidosis,
•Gout
•Urinary tract infection (UTI)

10. METABOLIC
EVALUATION
Simple to perform
It must be economically viable
It should provide information that can be applied
toward a selective, rational therapy of stone
disease
Any evaluation should be able to identify
associated metabolic disorders responsible for
recurrent stone disease.

11. INDICATIONS
• After stone passage, every patient
should be assigned to a low- or high-
risk group for stone formation
• For correct classification, two items are
mandatory:
Reliable stone analysis by infrared
spectroscopy or X-ray diffraction;
 Basic analysis
• Only high-risk stone formers require
specific metabolic evaluation
EAU 2021.

14. INDICATIONS

15. TIMING OF
METABOLIC
EVALUATION
• For the initial specific metabolic work-
up, the patient should stay on a self-
determined diet under normal daily
conditions and should ideally be stone
free for at least twenty days
• First follow up : 8-12 weeks after
starting pharmacologic treatment.
• Once urinary parameters are
normalized – every 12 months
EAU 2021

16. URINE
SAMPLING
• Specific metabolic evaluation requires
collection of two consecutive 24-hour
urine samples
• The collecting bottles should be prepared
with 5% thymol in isopropanol or stored at
< 8°C during collection
• Boric acid (10 g powder per urine
container) can also be used.
• Spot urine samples are an alternative
method of sampling
EAU 2021

17. DETAILED
INSTRUCTIONS
• Patient should choose a day when all voids
can be completely captured and when the
specimen will represent a typical day
• First morning void is discarded
• Urine must be collected in the appropriate,
laboratory provided container(ice, and/or
preservatives)
• Next morning, the first morning void is
collected with the rest of the specimen.
• Note- Total urinary creatinine should be
measured to provide an internal check.
• Males - 20 to 25 mg of creatinine for
every kg
• Females - 15 to 20 mg of creatinine for
every kg of body weight in 24 hour

18. • Patient is instructed to discontinue any
medication known to interfere with the
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) should be discontinued
• Two random 24-hour urine samples are
collected. These 24-hour specimens are
obtained with the patient on a random diet

19. COMPONENTS OF MBW

20. REPORT

21. CAUSES OF
ERRONEOUS
COLLECTION
• Error in collection technique (e.g.,
improper use of preservatives, ice)
• Failure to collect a full 24 hours’ worth
of urine
• Changes in the patient’s diet for the
sake of the study
• Intermittent indiscretions in diet
• Failure of specimen to accurately
represent typical day
• Bacterial contamination

22. EVIDENCE

23. IS METABOLIC
EVALUATION
NEEDED ??
• Basic evaluation with serum
chemistry and urinary analysis is
recommended for all ( LE :4,GR:B)
• Metabolic evaluation including
24-hr urine collection-for high
risk of stone recurrence or
formation ( LE :4,GR:B)
• Medical treatment of stone
disease – reduces the risk of
stone rcurrences in a meta-
analysis of RCTs ( LE :4,GR:B)

24. 24 hour analysis
– how and
when ??
EUA 2021
• For the initial specific
metabolic work-up, the
patient should stay on a self-
determined diet under
normal daily conditions and
should ideally be stone free
for at least twenty days
• First follow up : 8-12 weeks
after starting pharmacologic
treatment.
• Once urinary parameters are
normalized – every 12
months
AUA
• Recommends testing in a
motivated first time stone
former
• Recommends one collection
initially and 6 months after
the intervention – to assess
adherence and response

25. SINGLE URINE ANALYSIS – WORTH IT ?

26. PROS & CONS PROS
• Guidelines supported
• Objective and quantifiable
• Can check compliance
• Gives hope of prevention of
recurrence
CONS
• Limited ability to predict
response / recurrence
• Inconvenient
• Needs repeat testing
• Cost

27. ALTERNATIVES
Urine Spot Samples
• Alternative when 24 hour sample
collection is difficult
• Spot urine normally link the excretion
rates to creatinine
Bonn Risk Index(BRI)
• Ratio of ionized urinary calcium to the
amount of ammonium oxalate required
to induce calcium oxalate crystallization
in 200 ml of urine
• Predict recurrent calcium oxalate stone
formation

28. FIRST TIME
STONE
FORMERS
Pak et al in 1982- 80% have metabolic
abnormality
Commonest – Hypercalciuria

29. FIRST TIME
STONE
FORMERS-
INDIAN STUDY
Joshi A, Gupta SK, Srivastava A. Metabolic
evaluation in first-time renal stone formers in
North India: a single center study. Saudi J
Kidney Dis Transpl. 2013 Jul;24(4):838-43. doi:
10.4103/1319-2442.113916. PMID: 23816746.
92 % had metabolic abnormality
Commonest – Hypocitraturia .

30. STONE
ANALYSIS
• Stone analysis may be more practical to
obtain than a 24-hour urine collection.
• It is a good adjunct to serum and urine
metabolic evaluation.
• AUA guidelines recommend - stone
analysis at least once when one is
available to help classify patients and
guide preventive measures
• EUA 2021 – stone analysis and
biochemical work up is mandatory
after every stone passage

31. REFERENCES
• EUA update march 2021
• AUA guidelines
• Campbell Walsh Wein Urology 12th
edition

32. •THANK YOU