Renal Ultrasound


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


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)


  • 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.