Preliminary Diagnosis: Hydronephrosis
I. What imaging technique is first-line for this diagnosis
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Renal ultrasound with Doppler
II. Describe the advantages and disadvantages of this technique for diagnosis of hydronephrosis.
Advantages
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Ultrasound is safe, cheap, and fast.
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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
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False positive rate of ultrasound is approximately 25% for hydronephrosis.
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Effectiveness of ultrasound decreases with obese body habitus.
III. What are the contraindications for the first-line imaging technique?
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No contraindications to ultrasound
IV. What alternative imaging techniques are available?
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CT abdomen and pelvis without contrast
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Intravenous pyelogram
V. Describe the advantages and disadvantages of the alternative techniques for diagnosis hydronephrosis.
CT abdomen and pelvis without contrast
Advantages
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High sensitivity and specificity for hydronephrosis; typically will identify cause
Disadvantages
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Exposure to ionizing radiation
Intravenous pyelogram
Advantages
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Identifies level of obstruction causing hydronephrosis
Disadvantages
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Long filming sequence for patients
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Exposure to intravenous contrast
VI. What are the contraindications for the alternative imaging techniques?
CT abdomen and pelvis without contrast
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CT abdomen and pelvis (without contrast): CT should be used conservatively in pediatric population and is contraindicated in pregnancy.
Intravenous pyelogram
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IV contrast is contraindicated in renal insufficiency.
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IV contrast is contraindicated in patients with previous anaphylaxis to contrast or iodine.
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