Page 2 - CUA guideline on the evaluation and medical management of the kidney stone patient

dion et al.

“urinary stone.” In total, 4603 article titles were reviewed and radiological investigations are necessary in this patient
and 698 were identified as potentially relevant for inclusion population.
in the literature assessment for this guideline. In addition, all
references from recently published guidelines were assessed In-depth evaluation
and relevant studies were included in our literature review.
Studies were evaluated and recommendations made For those patients where an in-depth evaluation is indicated,
based on Oxford levels of evidence and grades of recom- the workup should include serum and 24-hour urine tests, as
mendation as per the CUA’s Guidelines Committee’s direc- well as a thorough dietary history. These tests should include:
tive. Guideline statements with management recommenda- a) Serum:
tions were developed based on the highest level of evidence. • Creatinine, sodium, potassium, chloride, calcium,
albumin, uric acid, bicarbonate
Indications for metabolic evaluation • Parathyroid hormone (PTH) level if serum calcium
is high normal or abnormally elevated
It is generally accepted that even the first time stone-former, • Vitamin D if low normal serum calcium or ele-
without any identifiable risk factors for recurrent stone for- vated serum PTH
mation, should undergo a limited metabolic evaluation to b) 24-hour urine collection:
rule out potential systemic disorders, such as hyperpara- • Volume, creatinine, calcium, sodium, potassium,
thyroidism and renal dysfunction. This evaluation should oxalate, citrate, uric acid, magnesium
include a urinalysis ± culture, serum electrolytes (Na, K, Cl, • Cystine if suspect cystine stone or if the stone
HCO ), serum Ca, and serum creatinine (Level of Evidence analysis is cystine
3
4, Grade C Recommendation). c) Spot urine:
An in-depth metabolic investigation may be considered • Urine pH
for any patient who is interested and willing to participate in • Urinalysis
the endeavor to collect and analyze a 24-hour urine study • Specific gravity
and have blood work drawn, and is willing to alter his/
her diet or begin pharmacotherapy. There are, however, Number of 24-hour urine collections
patient populations with clearly known risk factors where
an in-depth metabolic investigation is highly recommended There is some controversy regarding the number of 24-hour
(Level of Evidence 3, Grade C Recommendation): 14-20 urine collections necessary to investigate patients. 21,22 Recent
• Children (<18 years of age) data suggests that up to 47.6% of patients had their clinical
• Bilateral or multiple stones management changed by an abnormality that was identified
• Recurrent stones (having had two or more kidney only when two samples were collected. 23,24 It is currently rec-
stone episodes in the past) ommended that two 24-hour urine collections be obtained
• Non-calcium stones (e.g., uric acid, cystine) in order to correctly identify metabolic abnormalities. The
• Pure calcium phosphate stones benefit of two collections should be balanced, however, by
• Any complicated stone episode that resulted in a the practicality and importance of obtaining at least one
severe (if even temporary) acute kidney injury, sepsis, collection (Level of Evidence 3, Grade C Recommendation).
hospitalization, or complicated hospital admission
• Any stone requiring percutaneous nephrolithotomy Importance of stone analysis
treatment
• Stones in the setting of a solitary (anatomical or func- Identification of stone composition will aid in determining
tional) kidney prevention and directing surgical options for future stones.
• Patients with renal insufficiency Furthermore, identification of struvite, ammonium urate,
• History of kidney stones and systemic disease that uric acid, calcium phosphate, or cystine stones would alter
increases the risk of kidney stones (e.g., gout, osteo- whether or not 24-hour urine tests are required. Efforts
porosis, bowel disorders, hyperparathyroidism, renal should, therefore, be made to have patients collect stones
tubular acidosis, etc.) they have passed or if stones are removed at the time of
• Occupation where public safety is at risk (e.g., pilots, surgical intervention, they should be submitted for analysis
air traffic controller, police officer, military person- (Level of Evidence 3, Grade C Recommendation).
nel, firemen) If a patient continues to form new stones, it is worthwhile
Due to the infectious nature and cause of struvite stones, to repeat a stone analysis of the patient’s subsequent stones.
routine metabolic evaluation of patients with struvite stones Stone composition changed in 21.2% of patients over time.
is not usually recommended; however, routine urine culture Patients interchanged between calcium oxalate and calcium

E348 CUAJ • November-December 2016 • Volume 10, Issues 11-12