Imaging

Hydronephrosis

Preliminary Diagnosis: Hydronephrosis

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

  • Renal ultrasound with Doppler

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

Advantages

  • Ultrasound is safe, cheap, and fast.

  • Early in obstruction prior to collecting system dilatation, Doppler may show increased renal vascular resistance from obstruction compared to contralateral kidney (only valid if unilateral hydronephrosis).

Disadvantages

  • False positive rate of ultrasound is approximately 25% for hydronephrosis.

  • Effectiveness of ultrasound decreases with obese body habitus.

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

  • No contraindications to ultrasound

IV. What alternative imaging techniques are available?

  • CT abdomen and pelvis without contrast

  • Intravenous pyelogram

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

CT abdomen and pelvis without contrast

Advantages

  • High sensitivity and specificity for hydronephrosis; typically will identify cause

Disadvantages

  • Exposure to ionizing radiation

Intravenous pyelogram

Advantages

  • Identifies level of obstruction causing hydronephrosis

Disadvantages

  • Long filming sequence for patients

  • Exposure to intravenous contrast

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

CT abdomen and pelvis without contrast

  • CT abdomen and pelvis (without contrast): CT should be used conservatively in pediatric population and is contraindicated in pregnancy.

Intravenous pyelogram

  • IV contrast is contraindicated in renal insufficiency.

  • IV contrast is contraindicated in patients with previous anaphylaxis to contrast or iodine.

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