Abnormal renal rotation

Mr Andrew Murphy and Dr Henry Knipe et al.

Abnormal renal rotation (renal malrotation) refers to an anatomical variation in the position of the kidneys, in particular to anomalous orientation of the renal hilum. It may occur unilaterally or bilaterally. It is almost always an asymptomatic incidental finding. 

Malrotation is rare, perhaps under reported, and in one autopsy series a prevalence of ~1 in 2000 was reported 3. It is more common in males.

The renal hilum is normally directed anteromedially. The renal hilum is initially oriented anteriorly, but during its ascent from the pelvis the kidney rotates 90° along its longitudinal axis to its more typical orientation.

Anomalies in this process can result in 1-3:

  • incomplete rotation or nonrotation (most common): hilum faces anteriorly, ureters are located laterally
  • excessive rotation (hyper-rotation): hilum faces posteriorly; renal vessels are located posteriorly
  • reversed rotation: hilum faces laterally, renal vessels are located anteriorly, ureter is located laterally
  • malrotation can be demonstrated when the calyces project medially to the renal pelvis
  • on CT urography the renal pelvis may be seen projecting anteriorly 4

The exact cause of malrotation of the kidneys is unclear, though it has been hypothesised that malrotation may occur if the ureteric bud inserts into an abnormal region of metanephric mesenchyme. Its association with renal ectopia suggests that certain processes may interrupt both normal ascent and rotation.

Abdominal and pelvic anatomy
Share article

Article information

rID: 25938
System: Urogenital
Section: Anatomy
Synonyms or Alternate Spellings:
  • Rotational anomalies of the kidney
  • Rotational anomalies of the kidneys
  • Renal malrotation
  • Kidney malrotation

Support Radiopaedia and see fewer ads

Cases and figures

  • Drag
    excretory MRU
    Case 1: malrotated left kidney on MR urography
    Drag here to reorder.
  • Drag
    Case 2: malrotated right kidney
    Drag here to reorder.
  • Drag
    Case 3: posteriorly rotated right kidney
    Drag here to reorder.
  • Drag
    Case 4: anterolaterally malrotated duplex kidney
    Drag here to reorder.
  • Updating… Please wait.
    Loadinganimation

    Alert accept

    Error Unable to process the form. Check for errors and try again.

    Alert accept Thank you for updating your details.