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Snapshot
  • A 30-year-old man presents to the emergency department with severe, colicky left flank pain of acute onset that radiates to the left groin. He also reports urinary frequency and urgency. Physical examination is significant for left-sided costovertebral angle tenderness. Urine dipstick is heme positive. Urinalysis also shows envelope-shaped crystals. A non-contrast abdominal CT is shown.
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 Finding(s)
Stone Shape
Treatment
Calcium
  • Hypercalciuria
    • e.g., idiopathic hypercalcemia
  • Hypocitraturia
    • precipitates calcium oxalate stones
  • Ethylene glycol (antifreeze)
  • Vitamin C abuse
  • Crohn disease
  • Urine alkalinization
    • precipitates calcium phosphate stones
  • Radiography
    • radiopaque
  • Computerized tomography
    • radiopaque
  • Envelope or dumbbell shape
    • calcium oxalate
  • Wedge-shaped prism
    • calcium phosphate
  • Hydrochlorothiazide
  • Citrate
  • Low-sodium diet
Cystine
  • Impaired cystine reabsorption in the proximal convoluted tubule
    • this results in cystinuria
  • Precipitates in acidic urine
  • Diagnosis
    • cyanide-nitroprusside test 
  • Radiography
    • radiopaque
  • Computerized tomography
    • visible at times
  • Hexagonal 
  • Dietary modification
    • low sodium
  • Urine alkalinization
  • Chelating agents
    • in refractory cases
Struvite (magnesium ammonium phosphate)
  • Urease-positive organisms such as
    • Proteus mirabilis
    • Staphylococcus saphrophryticus
    • Klebsiella
  • Urease-positive organisms subesequently alkalinize the urine
    • this causes struvite stones due to precipitation
  • Radiography
    • radiopaque
  • Computerized tomography
    • radiopaque
  • Can result in a staghorn calculi
  • Coffin lid
  • Removal of underlying infection
  • Surgical removal of the stone
Uric acid
  • Hyperuricemia
    • e.g., states of increased cell turnover and gout 
  • Precipitates in acidic urine
  • Radiography
    • radiolucent
  • Computerized tomography
    • minimally visible
  • Rhomboid/rosette
  • Urine alkalinization
  • Allopurinol
  • Adequate 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
Treatment
  • Medical
    • analgesia, bed rest, and intravenous fluids
      • indication
        • considered first-line treatment for uncomplicated urolithiasis < 10 mm
    • α-blockers or calcium channel blockers
      • indication
        • can be considered to facilitate the passage of ureteral stones
          • appears to relax the ureter
  • Operative
    • extracorporal shock wave lithotripsy
      • indication
        • preferred for renal stones < 2 cm
    • percutaneous nephrolithotomy
      • indication
        • preferred for renal stones > 2cm
      • note
        • flexible ureterorenoscopy can be an option if percutaneous nephrolithotomy cannot be done
Complications
  • Ureteral obstruction
  • Ureteral stricture
  • Urinary tract infection
  • Renal deterioration
 

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