renal sinus cyst

Renal sinus cysts are simple renal cysts that lie within the renal sinus.


It is worth noting that some authors  use the term renal lymphangiectasia interchangeably. It is likely that true renal lymphangiectasia is a separate and rare disorder, and is thus discussed separately.


Renal sinus cysts are benign. They can be subdivided into

  • parapelvic cysts: originate from the adjacent parenchyma and protrude into the renal sinus
  • peripelvic cysts: originate within the sinus itself and have a lymphatic origin
Parapelvic cysts

These are simple renal cysts that plunge into the renal sinus from the adjacent renal parenchyma. They are usually single or few and resemble simple renal cortical cyst in morphology. A parapelvic cyst at times may cause compression of the pelvicalyceal system resulting in hydronephrosis. They may also mimic hydronephrosis, termed pseudohydronephrosis.

Peripelvic cysts

These are frequently bilateral. They appear as fluid-density cysts closely abutting the pelvis and infundibula, rarely cause functional renal derangement by compression. When followed up they remain unchanged in size. They may be confused with hydronephrosis on NECT and ultrasonography, but on CECT the differentiation is obvious.

Differential diagnosis

Renal sinus cysts can mimic hydronephrosis but CT IVP studies will demonstrate a normal or narrowed/stretched/displaced (but not dilated) collecting system.

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