Indications

flank pain, hydronephrosis, hematuria, acute renal failure, and/or urinary retention

To evaluate the kidneys if there is clinical suspicion for hydronephrosis or urinary retention in a patient with abdominal pain.

Ultrasound Anatomy

Documentation

At least 7 standard views should be submitted:

Longitudinal Views:
    1. Hilum
    2. Medial kidney
    3. Lateral kidney
Transverse Views:
    4. Hilum
    5. Superior pole
    6. Inferior pole
Bladder (7)

Approach

• Both kidneys should be evaluated in transverse and longitudinal views
• The bladder should be examined for evidence of distention or collection of stone
• When to US instead of CT for renal colic and suspected kidney stone?  

Probe & Positioning

• 2-5 MHz curvilinear abdominal probe
• Patient is supine. Right lateral decubitus positioning can help obtain left renal views

Clinical Question & Exam Interpretation

• Is there hydronephrosis or bladder distention?
  • Positive: Evidence of hydronephrosis, calculi, or bladder distension with the appropriate clinical setting
    • Hydronephrosis: dilation or the renal pelvis or calyses, loss of border between pelvis and calyses, cortical thinning, or renal atrophy
  • Negative: Similar kidney anatomy on each side with no evidence of hydronephrosis, calculi, or bladder distension
  • Equivocal/Inadequate: Technical or artifact problems make the exam difficult to interpret

Pearls and Pitfall

• May need to rotate the probe in between rib spaces to evaluate eliminate rib shadow artifact in the RUQ (counterclockwise rotation) and LUQ (clockwise rotation) views.
• May need to use the fanning technique to obtain the views of the medial and lateral kidney in longitudinal view.
• Renal cysts are typically seen in the periphery of the kidney.
• Both kidneys should be evaluated for hydronephrosis. Overly hydrated and pregnant patients may show hydronephrosis in both kidneys.