Nephrolithiasis - Kidney Stone

Diagnosis

Indications for Testing

  • Patient with symptoms of a stone

Laboratory Testing

  • Initial testing
    • CBC – evaluate for concomitant infection
    • Electrolytes – evaluate for electrolyte abnormalities associated with vomiting
    • BUN/creatinine – evaluate for obstructive pathology
    • Urinalysis with possible urine culture – evaluate for concomitant urinary tract infection
  • Urine – kidney stone risk assessment on 24-hour urine
    • Not usually done with first stone
    • May delay this risk assessment until stone disease reoccurs
    • Initial testing should include 2 different specimens
  • Amino acids analysis – evaluate for cystinuria
  • Serum – uric acid, ionized calcium, and parathyroid hormone-related peptide (PTH)
    • PTH may be reserved for recurrent disease
  • Stone – calculi analysis

Imaging Studies

  • Helical CT scan can confirm presence and location of stones

Differential Diagnosis

  • Peritonitis
  • Pyelonephritis
  • Ovarian torsion
  • Ovarian cyst
  • Ectopic pregnancy
  • Prostatitis
  • Musculoskeletal pain

Screening

  • No evidence to support screening for stones in asymptomatic patients

Monitoring

  • Unnecessary in first-time stone former
  • Usually includes the following
    • Assessment 4-8 weeks after treatment begins or changes
    • Urine – kidney stone risk assessment
      • 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

Clinical Background

Nephrolithiasis is a worldwide problem that accounts for significant morbidity and expense.

Epidemiology

  • Prevalence – 1-5/1,000
  • Age – peaks in 20s
  • Sex – M>F, 2-3:1
  • Ethnicity – Caucasian men have highest incidence
  • Geographic – hotter and drier climates

Pathophysiology

  • Calcium oxalate/calcium phosphate stones – most common (70-90%)
    • Risk factors – dehydration, thiazide diuretics, increased intestinal absorption, excessive oxalate consumption, excessive phosphoric acid consumption (cola products), pregnancy, primary hyperparathyroidism, chronic bowel malabsorption, and chronic use of calcium-containing products
  • Magnesium ammonium phosphate stones (10-15%)
    • Risk factors – frequent urinary tract infections and presence of alkaline urine
    • Also referred to as struvite stones (staghorn calculi)
  • Uric acid stones (5-15%)
    • Risk factors – gout, family history, malignancy treated with chemotherapy, and high purine diet
  • Cystine stones (1-2%)
    • Risk factor is hereditary cystinuria

Clinical Presentation

  • Acute, colicky flank pain radiating into the pelvis and genitals associated with nausea and vomiting
  • Urinary urgency, frequency, and dysuria may develop with stone passage
  • Hematuria – present in 90% of patients

Prevention

  • All stones – maintain urine volume ≥2 L/24-hours
  • Uric acid stones – limit protein intake, allopurinol (AHQR, 2012)
  • Cystine stones – limit protein and salt intake
  • Calcium stones (AHQR, 2012)
    • Increased fluid intake
    • Reduced soft drink consumption
    • Thiazide diuretics
    • Citrate pharmacotherapy

Pediatrics

Clinical Background

Epidemiology

  • Incidence – 4.7/100,000 hospitalized
  • Lower than in adults

Clinical Presentation

  • Flank pain, abdominal pain
    • <5 years – nonspecific; nausea, emesis
  • Blood in urine, dysuria, urgency

Diagnosis

Indications for Testing

  • Patient with symptoms of a stone

Laboratory Testing

  • Initial testing
    • CBC – evaluate for concomitant infection
    • Electrolytes – evaluate for electrolyte abnormalities associated with vomiting
    • BUN/creatinine – evaluate for obstructive pathology
    • Urinalysis with possible urine culture – evaluate for concomitant urinary tract infection
  • Urine – kidney stone risk assessment on 24-hour urine
    • May delay this risk assessment until stone disease reoccurs
    • Initial testing should include 2 different specimens
  • Amino acids analysis – evaluate for cystinuria

Monitoring

  • More important in children, even with first-time stone former
    • >75% of stones in children are secondary to metabolic problems
  • Usually includes the following
    • Assessment 4-8 weeks after treatment begins or changes
    • Urine – kidney stone risk assessment
      • 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, and ionized calcium

Indications for Laboratory Testing

  • Tests generally appear in the order most useful for common clinical situations
  • Click on number for test-specific information in the ARUP Laboratory Test Directory
Test Name and Number Recommended Use Limitations Follow Up
Calculi Risk Assessment, Urine 2008708
Method: Quantitative Spectrophotometry/Quantitative Enzymatic/Quantitative Ion-Selective Electrode

Acceptable initial urine test for kidney stone risk assessment and monitoring

Panel includes calcium, chloride, citric acid, creatinine, magnesium, oxalate, pH, phosphorus, potassium, sodium, and uric acid

   
Supersaturation Profile, Urine 2008771
Method: Quantitative Spectrophotometry/Quantitative Enzymatic/Quantitative Ion-Selective Electrode

Acceptable initial urine test for kidney stone risk assessment and monitoring; includes interpretation of data

Panel includes calcium, magnesium, sodium, sulfate, citric acid, oxalate, uric acid, potassium, creatinine (24-hour) chloride, and phosphorous

Assessment for risk of magnesium ammonium phosphate (struvite) calculi is not included in this profile

Does not test for urine cystine

If magnesium ammonium phosphate calculi are suspected, order plasma ammonia testing

If cystine calculi are suspected, order cystinuria panel, cystine quantitative urine or amino acids quantitative urine tests

Kidney Stone Risk Panel, Urine 0020843
Method: Quantitative Spectrophotometry/Quantitative Enzymatic

Preferred test is urine supersaturation profile or urinary calculi risk assessment, depending on calculation need

Panel includes calcium, citric acid, creatinine, oxalate, and uric acid

May be used to monitor kidney stone formation

   
Cystinuria Panel 0081105
Method: Quantitative Liquid Chromatography/Tandem Mass Spectrometry

Evaluate for cystinuria

Panel includes arginine, cystine, lysine, and ornithine

   
Cystine Quantitative, Urine 0081106
Method: Liquid Chromatography/Tandem Mass Spectrometry
Monitor treatment in patients with cystinuria
   
Amino Acids Quantitative by LC-MS/MS, Urine 2009419
Method: Quantitative Liquid Chromatography/Tandem Mass Spectrometry

Use for risk assessment if cystine stone is found

   
Calculi (Stone) Analysis 0099460
Method: Quantitative Reflectance Fourier Transform Infrared Spectroscopy/Quantitative Polarizing Microscopy

Determine composition of calculi

Determine causative agent of calculi

   
Calculi (Stone) Analysis with Photo 2005231
Method: Quantitative Reflectance Fourier Transform Infrared Spectroscopy/Quantitative Polarizing Microscopy

Determine composition of calculi

Determine causative agent of calculi

For specimens smaller than 2 mg, refer to Calculi (Stone) Analysis

   
Additional Tests Available
 
Click the plus sign to expand the table of additional tests.
Test Name and NumberComments
CBC with Platelet Count and Automated Differential 0040003
Method: Automated Cell Count/Differential

Evaluate for concomitant infection

Renal Function Panel 0020144
Method: Quantitative Chemiluminescent Immunoassay/Quantitative Enzyme-Linked Immunosorbent Assay

Evaluate for obstructive pathology

Panel includes albumin, calcium, carbon dioxide, creatinine, chloride, glucose, phosphorous, potassium, sodium, and BUN

Urinalysis, Complete 0020350
Method: Reflectance Spectrophotometry/Microscopy

Detect urinary tract abnormalities, including crystals

Urine Culture 0060131
Method: Culture/Identification

Evaluate for concomitant infection

Creatinine, Serum or Plasma 0020025
Method: Quantitative Enzymatic
Creatinine, 24-Hour Urine 0020473
Method: Quantitative Spectrophotometry
Oxalate, Urine 0020482
Method: Quantitative Spectrophotometry
Citric Acid, Urine 0020852
Method: Quantitative Enzymatic
Urea Nitrogen, Serum or Plasma 0020023
Method: Quantitative Spectrophotometry
Uric Acid, Serum or Plasma 0020026
Method: Quantitative Spectrophotometry
Calcium, Ionized, Serum 0020135
Method: Ion-Selective Electrode/pH Electrode
Parathyroid Hormone-Related Peptide (PTHrP) by LC-MS/MS, Plasma 2010677
Method: Quantitative High Performance Liquid Chromatography-Tandem Mass Spectrometry