Nephrolithiasis accounts for significant morbidity and expense and is increasing in prevalence in the U.S.; an estimated 7% of females and 11% of males are affected during their lifetimes (Ingimarsson, 2016). Initial testing is usually a point-of-care urinalysis, followed by urinalysis with microscopy and/or culture, CBC, and basic metabolic panel to evaluate electrolytes and kidney function. Imaging is used to confirm presence of a stone and to determine whether intervention might be required for removal. A stone analysis and a 24-hour urine evaluation can help identify the cause of stone formation, although these are not often performed in adults experiencing a first stone. The first kidney stone in a child prompts a more complete workup.
Quick Answers for Clinicians
Diagnosis
Indications for Testing
- Hematuria
- Flank pain
- Colicky back pain
Laboratory Testing
- Initial testing
- Urinalysis
- Point-of-care testing for hematuria
- Urine microscopic testing
- Blood indicates injury due to crystal passage
- Crystals indicate the possibility of a stone
- Urine culture – consider to evaluate for concomitant urinary tract infection
- CBC – especially if symptoms of concomitant infection are present
- Serum electrolytes – evaluate for electrolyte abnormalities
- Blood urea nitrogen (BUN)/creatinine – evaluate for obstructive renal pathology
- Urinalysis
- 24-hour urine evaluation – use panel testing for most patients
- Not usually performed with first stone, except in children (refer to Pediatrics)
- Usually includes electrolyte analysis (eg, sodium) and metabolic analysis (eg, oxalate and calcium)
- Collection of two different urine specimens is recommended
Component |
Kidney Stone Risk Panel, 0020843 (Basic Urine Panel) |
Calculi Risk Assessment, 2008708 (Extended Urine Panel) |
Supersaturation Profile, 2008771 (Extended Urine Panel with Supersaturation Tests) |
---|---|---|---|
Total volume |
X |
X |
X |
pH |
N |
X |
X |
Calcium |
X |
X |
X |
Creatinine |
X |
X |
X |
Oxalate |
X |
X |
X |
Uric acid |
X |
X |
X |
Chloride |
N |
X |
X |
Citric acid |
X |
X |
X |
Magnesium |
N |
X |
X |
Phosphorus |
N |
X |
X |
Potassium |
N |
X |
X |
Sodium |
N |
X |
X |
Sulfate |
N |
N |
X |
Calcium oxalate supersaturation |
N |
N |
X |
Calcium phosphate supersaturation |
N |
N |
X |
Uric acid supersaturation |
N |
N |
X |
N, not included in panel; X, included in panel |
- Serum – uric acid, ionized calcium, and parathyroid hormone (PTH)-related peptide (PTHrP)
- PTH testing may be reserved for recurrent disease unless primary hypoparathyroidism is a concern
- Amino acids analysis – evaluate when cystinuria is a concern or in those with cystine stones
- Stone collection and analysis
- Repeat if there is lack of response to therapy, since stone composition may change
Differential Diagnosis
- Urinary tract infection
- Ectopic pregnancy
- Musculoskeletal pain
- Ovarian cyst rupture
- Ovarian torsion
- Peritonitis
- Prostatitis
- Acute pyelonephritis
- Interstitial cystitis
- Groin hernia
Screening
There is no evidence to support screening for stones in asymptomatic patients.
Monitoring
- Usually unnecessary in patients experiencing first stone
- If performed, usually includes a minimum of the following
- Assessment within 6 months after treatment begins or changes; annually thereafter, depending on stone activity (American Urological Association, 2014)
- 24-hour urine – kidney stone panel testing
- Should include testing for calcium oxalate, sodium, uric acid, citric acid, phosphorus, creatinine
- Quantitative cystine in patients with cystinuria
- Serum – urea nitrogen, creatinine, and ionized calcium
Background
Epidemiology
- Prevalence – 1-5/1,000
- 1/11 affected during lifetime (Pearle, 2014)
- Sex – M>F, 1.3:1
- Ethnicity – White men have highest incidence
- Geography – greater incidence in hotter and drier climates
Risk Factors
Type of Stone | Percentage of Stones | Risk Factors |
---|---|---|
Calcium oxalate/calcium phosphate | 70-90% (most common) |
Dehydration Thiazide diuretics Increased intestinal absorption Pregnancy Primary hyperparathyroidism Chronic bowel malabsorption Chronic use of calcium-containing products Excessive consumption of oxalate, phosphoric acid (cola products), or sugar-sweetened beverages |
Magnesium ammonium phosphate, also referred to as struvite stones (staghorn calculi) |
10-15% |
Frequent urinary tract infections Presence of alkaline urine |
Uric acid | 5-15% |
Family history of gout or stones Malignancy treated with chemotherapy Diet high in purines |
Cystine | 1-2% | Hereditary cystinuria |
Clinical Presentation
- Acute, colicky flank pain radiating into the pelvis and genitalia
- Hematuria – present in 90% of patients
- Nausea and vomiting
- Urinary urgency, frequency, and dysuria with stone passage
Pediatrics
Epidemiology
- Incidence – 4.7/100,000 hospitalized
- Lower incidence than in adults
Clinical Presentation
- Flank pain, abdominal pain
- <5 years of age – nonspecific; nausea, emesis
- Blood in urine, dysuria, urgency
Indications for Testing
Refer to Diagnosis
Laboratory Testing
- Refer to Diagnosis
- Differences in pediatric testing
- 24-hour urine evaluation recommended in the first episode due to high risk of metabolic problems underlying stone formation
- Amino acid analysis recommended
- Evaluate for cystinuria in patients with elevated urine cystine – more common in children with nephrolithiasis
Monitoring
- More important in children, even in those with first stone
- >75% of stones in children are secondary to metabolic problems
- Usually includes the following
- Assessment within 6 months after treatment begins or changes
- 24-hour urine evaluation – kidney stone panel testing
- Should include testing for calcium oxalate, sodium, uric acid, citric acid, phosphorus, creatinine
- Quantitative urine cystine or urine amino acids analysis in patients with cystinuria
- Serum – urea nitrogen, creatinine, ionized calcium
ARUP Laboratory Tests
Kidney stone risk assessment and monitoring
Quantitative Spectrophotometry/Quantitative Enzymatic/Quantitative Ion-Selective Electrode
Kidney stone risk assessment and monitoring; includes interpretation of data
Quantitative Spectrophotometry/Quantitative Enzymatic/Quantitative Ion-Selective Electrode
May use to monitor kidney stone formation
Preferred test is urine supersaturation profile or urinary calculi risk assessment, depending on calculation need
Quantitative Spectrophotometry/Quantitative Enzymatic
Panel includes calcium, citric acid, creatinine, oxalate, and uric acid
Initial test to diagnose or rule out cystinuria
Quantitative Liquid Chromatography/Tandem Mass Spectrometry
Panel includes arginine, cystine, lysine, and ornithine
Monitor treatment in patients previously diagnosed with cystinuria
To diagnose or rule out cystinuria, refer to the cystinuria panel or amino acids quantitative, urine
Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS)
Screen for disorders of amino acids transport (eg, cystinuria, lysinuric protein intolerance, hyperornithinemia-hyperammonemia-homocitrullinuria [HHH] syndrome)
Use for risk assessment if cystine stone is found
Quantitative Liquid Chromatography/Tandem Mass Spectrometry
Determine composition of calculi
Quantitative Reflectance Fourier Transform Infrared Spectroscopy/Quantitative Polarizing Microscopy
Determine composition and appearance of calculi
Quantitative Reflectance Fourier Transform Infrared Spectroscopy/Quantitative Polarizing Microscopy
Evaluate for concomitant infection
Automated Cell Count/Differential
Evaluate for obstructive pathology
Quantitative Chemiluminescent Immunoassay/Quantitative Enzyme-Linked Immunosorbent Assay
Panel includes albumin, calcium, carbon dioxide, creatinine, chloride, glucose, phosphorous, potassium, sodium, and BUN, and a calculated anion gap value
Detect urinary tract abnormalities, including crystals
Reflectance Spectrophotometry/Microscopy
Quantitative culture to identify bacterial causes of urinary tract infections
Culture/Identification
Screening test to evaluate kidney function
Assay interference (negative) may be observed when high concentrations of N-acetylcysteine (NAC) are present
Negative interference has also been reported with NAPQI (an acetaminophen metabolite) but only when concentrations are at or above those expected during acetaminophen overdose
Quantitative Enzymatic
Quantitative Spectrophotometry
Evaluate individuals with calcium oxalate renal calculi
Quantitative Spectrophotometry
Assess the body pool size of oxalate
Quantitative Spectrophotometry
Aid in diagnosis and monitoring of gout or kidney stones
Aid in monitoring uric acid levels in patients at risk for kidney stone development
Assay interference (negative) may be observed when high concentrations of NAC are present
Negative interference has also been reported with NAPQI (an acetaminophen metabolite) but only when concentrations are at or above those expected during acetaminophen overdose
Quantitative Spectrophotometry
Aid in the evaluation of unexplained hypercalcemia, particularly in suspected hypercalcemia, particularly if possible hypercalcemia of malignancy
Aid in the diagnosis of and monitoring of treatment for hypercalcemia
Highly specific test for PTHrP
Amino (N)- and carboxy (C)-terminus PTHrP fragments, such as those produced by some patients with renal insufficiency, do not interfere with this assay
Quantitative High Performance Liquid Chromatography-Tandem Mass Spectrometry
Quantitative Enzymatic
Quantitative Spectrophotometry
Ion-Selective Electrode/pH Electrode
Medical Experts
De Biase

Frank

Longo

Pasquali

References
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Fink HA, Wilt TJ, Eidman KE, Garimella PS, MacDonald R, Rutks IR, Brasure M, Kane RL, Monga M. Recurrent Nephrolithiasis in Adults: Comparative Effectiveness of Preventive Medical Strategies [Internet]. Rockville (MD): Agency for Healthcare Research and Quality (US) 2012; :PubMed
Panel includes calcium, chloride, citric acid, creatinine, magnesium, oxalate, pH, phosphorus, potassium, sodium, and uric acid