Imaging

Nephrolithiasis

Preliminary Diagnosis: Nephrolithiasis

I. What imaging technique is first-line for this diagnosis?

  • Computed tomography (CT) scan without oral and without intravenous contrast

II. Describe the advantages and disadvantages of this technique for diagnosis of nephrolithiasis.

Advantages

  • Able to locate an obstructive radiopaque renal, collecting system, and urinary bladder calculi

  • Relatively quick imaging modalities that require minimal patient cooperation and are less susceptible to patient motion

  • Able to detail secondary complications from an obstructing collecting system calculi (ie, calyceal or forniceal rupture, hydroureter or hydronephrosis, or pyelonephritis)

Disadvantages

  • Exposure to ionizing radiation

  • May not be able to localize nonradiopaque collecting system calculi

III. What are the contraindications for the first-line imaging technique?

  • Contraindicated in pregnant patients especially within the first two trimesters

IV. What alternative imaging techniques are available?

  • Ultrasound (grayscale)

  • Radiography (plain film)

  • For pregnant patients, ultrasound is the first-line imaging modality.

V. Describe the advantages and disadvantages of the alternative techniques for diagnosis of nephrolithiasis.

Ultrasound (Grayscale)

Advantages

  • May be diagnostic for obstructive collecting system calculi

  • May detail secondary signs of obstruction such as hydroureter and hydronephrosis

  • Relatively inexpensive and portable imaging modality

  • Does not utilize ionizing radiation

Disadvantages

  • May not visualize the entire course of the ureter owing to overlying bowel gas and osseous structures

  • Limited in detailing deep structures in obese patients

Plain Films

Advantages

  • May be able to localize radiopaque calculi overlying the expected region of the kidneys, collecting system, and bladder

  • Quick

  • Inexpensive

  • Far less radiation exposure with plain radiographs than with CT

Disadvantages

  • Not very specific and has poor anatomic detail

  • Nonradiopaque obstructive uropathy and secondary complications of obstruction are not well identified on plain radiographs.

VI. What are the contraindications for the alternative imaging techniques?

Ultrasound

  • No significant contraindications exist to ultrasound.

Plain Films

  • No significant contraindications. Some institutions may require consent for pregnant patients.

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