Kidney Week 2012: Radiology of the Kidney

W. Charles O’Neill, MD
Emory University

Sonographic evaluation of the kidney

Kidney Length: The maximum kidney length is the single most important measurement to make

Normal range: 10-12 cm

There is no data on how to correct for body size

Other measurements are not very clinically useful

Kidney shape: This can be very helpful. An example: Swelling increases the width more than the length.

Cortical thickness: This is difficult to measure but is useful to assess for chronic kidney disease. The usual measurement from medullary pyramid to the renal capsule ranges between 5 and 9 mm.

Renal echogenicity: Usually compared to liver echogenicity, the kidney is usually less echogenic than liver (as long as liver is normal).

Urinary space evaluation:

  1.  The upper urinary tract is not visible unless dilated. This occurs in: pregnancy, large diuresis, ureteral stent with a full bladder, reflux and papillary necrosis and obstruction.

Filling defects:

  1. The most common cause is the presence of kidney stones, though very small stones may not be visualized. In acute renal colic, a sonogram is not very useful.
  2. Other causes: stents, blood clots, mass lesions, gas.

As a screening test:

  1. Sonography is best screening test for ADPKD, though very small cysts may not be visualized.
  2. Sonography should not be used as a screening for carcinoma for people with very high risk.

Vascular visualization:

  1. Renal artery: This is the most difficult artery to study due to overlying bowel gas, cases of multiple arteries, and poor angle.
  2. Interlobular artery: Most velocities are measured here as it is relatively easier to study. Resistive index is dependent on pre-renal factors (heart rate, SVR and valvular disease).

Post written by Dr. Kenar Jhaveri, eAJKD Blog Editor, and edited by Dr. Kellie Calderon, eAJKD Advisory Board member.

Check back for more eAJKD coverage of ASN’s Kidney Week 2012! Also, check out @eAJKD on Twitter for live updates!

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