Renal sinus

Last revised by Raymond Chieng on 13 Jan 2023

The renal sinus is a fat-filled compartment of the kidney.

The renal sinus is a fatty compartment located within the medial aspect of the kidney. It communicates with the perinephric space. It contains the renal hilum and is bordered by renal parenchyma laterally. 

  • renal artery and vein (major branches) 4

  • major and minor calyces 4

  • adipose tissue (main component) 4

    • increases with age and obesity

  • lymphatic channels 4

  • autonomic nerves

  • fibrous tissue (variable amount) 4

  • junctional parenchymal defects - allow connection of fat in the renal sinus with intraparenchymal fat; may present as a renal pseudotumor 3

  • hypertrophied column of Bertin - normal renal cortex projecting into the renal sinus; can present as a renal pseudotumor

Renal sinus appears hyperechoic compared to the renal parenchyma, contains blood vessels 3 The urothelium layer within the renal sinus also appears as hyperechoic. On longitudinal section, it appears as an oval shaped hyperechoic area. On transverse section, its shape becomes round 4. Evaluation of the renal sinus is important in identification of hydronephrosis and evaluation of filling defect found on intravenous urography (which can be due to tumors, blood clots, or non-radioopaque stones) 4.

Small renal calculi may be difficult to be differentiate from the hyperechoic renal sinus. Therefore, Time Gain Compensation (TGC) or Gain should be adjusted to a lower level to visualize the posterior acoustic shadowing casted by the renal calculi are visible 4.

Calcifications located at the junction of the renal sinus and medulla may represents calcifications of branches of renal artery 5.

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