Nephrolithiasis

Snapshot

• A 36-year-old woman presents to the emergency department with severe and colicky left flank pain that radiates to the left groin. She reports increased urinary frequency and urgency. She is sexually active with multiple men and uses condoms inconsistently. On physical exam, there is left-sided costovertebral angle tenderness and lower abdominal tenderness. 

Introduction

• Clinical definition
  • calculi (stones) affecting the kidneys; however, these stones can also affect the ureter
• Epidemiology
  • prevalence
    • 12% in men and 7% in women
  • risk factors
    • hyperparathyroidism
    • hypocitraturia 
    • sarcoidosis
    • hyperoxaluria
    • renal tubular acidosis type I
    • nephrocalcinosis
    • cystic fibrosis
    • hyperuricosuria
    • indwelling catheter
    • urinary tract infections
    • malabsorption (e,g., Crohn disease)
    • horseshoe kidney
    • obesity
    • low fluid intake
    • gout
    • medications
      • e.g., allopurinol, indinavir, acetazolamide, and topiramate
• Pathogenesis
  • substance precipitation affecting the kidney and ureter
    • e,g., hypercalciuria and low urine volume forms calcium cystals
• Prognosis
  • small stones are more likely to spontaneously pass

Nephrolithiasis Stones
Stone Type	Etiology	Imaging Findings	Stone Shape	Treatment
Calcium	Calcium oxalate stones (most common)hypercalciuriahypocitraturiaethylene glycol (antifreeze)vitamin C abusecrohn diseaseCalcium phosphatein states of urine alkalinizatione.g., type I renal tubular acidosis	RadiographyradiopaqueComputerized tomographyradiopaque	Envelope or dumbbell shapecalcium oxalate Wedge-shaped prismcalcium phosphate	HydrochlorothiazideCitrateLow-sodium diet
Cystine	Impaired cystine reabsorption in the proximal convoluted tubulethis results in cystinuriaalso results in decreased reabsorption of ornithine, lysine, and arginine Precipitates in acidic urineDiagnosiscyanide-nitroprusside test	RadiographyradiolucentComputerized tomographyvisible at times	Hexagonal	Dietary modificationlow sodiumUrine alkalinizationChelating agentsin refractory cases
Struvite (magnesium ammonium phosphate)	Urease-positive organisms such asProteus mirabilisStaphylococcus saphrophryticusKlebsiellaUrease-positive organisms subesequently alkalinizes the urinethis causes struvite stones due to precipitation	RadiographyradiopaqueComputerized tomographyradiopaqueCan result in a staghorn calculi	Coffin lid	Removal of underlying infectionSurgical removal of the stone
Uric acid	Hyperuricemiae.g., states of increased cell turnover and gout Precipitates in acidic urine	RadiographyradiolucentComputerized tomographyminimally visible	Rhomboid/rosette	Urine alkalinizationAllopurinolAdequate hydration prior to chemotherapy treatment

Presentation

• Symptoms
  • colicky flank pain
    • pain may radiate to the groin or lower abdomen
  • dysuria
  • urgency and frequency
• Physical exam
  • low abdominal tenderness
• costovertebral angle (CVA) tenderness

Imaging

• Renal ultrasound
  • indication
    • in patients who are pregnant and children who are suspected to have nephrolithiasis
  • modality
    • abdomen and pelvis to visualize the kidney and bladder
• Non-contrast computerized tomography (CT)
  • indication
    • preferred imaging for most adults presenting with signs and symptoms concerning for nephrolithiasis
  • modality
• abdomen and pelvis

Studies

• Labs
  • serum
    • creatinine, uric acid, and ionized calcium should be obtained
  • urine studies
    • urinalysis/dipstick
      • in order to check for red and white blood cells, nitrites, and urine pH
    • urine culture
  • stone composition analysis
    • perform in patients who developed their first stone
    • straining the urine
• Diagnostic criteria
• based on clinical presentation and confirmed by imaging

Differential

• Urinary tract infections
• Acute pyelonephritis
• Groin hernia

Complications

• Ureteral obstruction
• Ureteral stricture
• Urinary tract infection
• Renal deterioration