Renal ectopia

Key points

Simple Renal Ectopia

Found anywhere along the path of ascent, with the left pelvic location being the most common, situated below the aortic bifurcation

Often hypoplastic

Associations

• Absence of vagina

• Bicornate uterus

• Retrocaval ureter

• Ectopic ureteric orifice (UO)

• Mayer-Rokitansky-Küster-Hauser (MRKH) syndrome

• Fanconi’s anaemia

  
  

Horseshoe Kidney

• Isthmus:

  • Located at the level of L4, trapped below the inferior mesenteric artery (IMA)

  • May consist of fibrotic, dysplastic, or normal renal tissue

  • Frequently has a separate blood supply from the rest of the horseshoe kidney

• Blood Supply:

  • 70% of horseshoe kidneys are supplied by arteries other than the typical renal arteries, including the aortic, renal, mesenteric, iliac, or sacral arteries

• Radiological Features:

  • Imaging (MRU/IVU) often reveals bilateral renal malrotation with calyces positioned medially to the vertically oriented renal pelvis

  • Ureters are often positioned more laterally

• Associations:

  • Turner syndrome

    
    

• Pelvi-ureteric junction (PUJ) obstruction can occur, often due to the ureter crossing the isthmus, which may require ureterocalicostomy

  
  

Crossed Renal Ectopia

• Occurs in 85% of cases, while 10% have no fusion

• May present as a palpable mass

• Potential for misinterpretation as renal agenesis

• Ultrasound (USS) and MAG3 are typically sufficient for diagnosis

• No surgical intervention required for uncomplicated cases

References

Essentials of Pediatric Urology, 3rd edition, 2022, Chapter 14 Urologic Anomalies in Anorectal Malformations and Renal Ectopia