Diagnostic Ultrasound - Abdomen and Pelvis

Renal Ectopia
TERMINOLOGY
Abbreviations
• Renal ectopia (RE), crossed fused ectopia (CFE)
Definitions
• Aberrant location of kidney
• Separated into multiple categories, of which simple RE and
CFE represent most common forms
○ Crossed nonfused RE, solitary crossed RE, and bilateral
crossed RE represent rare variants
IMAGING
General Features
• Best diagnostic clue
○ Absence of kidney in expected renal fossa
○ In both CFE and RE, affected kidney noted in abnormal
location
• Location
○ Normal renal position: Between transverse processes of
T12-L3
○ RE can range in location from pelvic (most common) to
thoracic (rare)
○ Simple RE: Kidney located ipsilateral to its ureteral
insertion
○ CFE: Kidney located contralateral to its ureteral insertion
• Size
○ Ectopic kidneys vary in size
Ultrasonographic Findings
• Grayscale ultrasound
○ Simple RE
– Aberrant location of kidney, from thorax to pelvis,
with kidneys on contralateral sides
– Ectopic kidney small and malrotated, often with
dysmorphic features
– Morphology described as "pancake," "disc," or "lump"
– Collecting system located near surface of kidney
(anterior orientation)
□ Normal sinus echo complex absent or eccentrically
positioned
– Intrathoracic RE
□ Mediastinal location
□ Note intact diaphragm below kidney
○ CFE
– Both kidneys located on same side of spine
– Empty contralateral renal fossa
– 90% of crossed ectopia involves fusion to normally
located kidney
□ Crossed nonfused RE rare
– Left kidney more often ectopic than right
– Ectopic kidney is malrotated
□ Usually fusion of upper pole of ectopic kidney to
lower pole of normally positioned kidney
□ S-shaped mass with 2 renal sinuses
□ While normal ipsilateral ureter enters ipsilateral
trigone, ureter of ectopic kidney crosses midline
and enters at contralateral trigone
• Color Doppler
○ RE:Arterial supply from regional arteries
– For example, pelvic kidney supplied by common or
internal iliac arteries
– Often with multiple arterial supply
○ CFE
– Separate vascular supply to each kidney, with aberrant
supply to ectopic kidney
□ Aberrant arteries may cross ureter and cause
obstruction
– Ureteric jets from ureterovesical junctions located in
their normal position
– Color Doppler may aid in prenatal diagnosis
Nuclear Medicine Findings
• Can confirm location and assess function of ectopic kidney
CT Findings
• CECT
○ Arterial phase for optimal delineation of vascular supply
in both CFE and RE
○ Excretory phase for ureteral course and number
MR Findings
• MR arteriography/urography
○ Can appreciate course of ureters without use of ionizing
radiation or intravenous contrast
○ Dilated ureters easier to follow
○ Contrast-enhanced sequences can delineate vascular
anatomy and allow for assessment of crossing vessels
DIFFERENTIAL DIAGNOSIS
Renal Transplant (Iatrogenic Ectopia)
• Most common location for transplant is right lower
quadrant
• Atrophic echogenic kidneys appreciated in bilateral renal
fossae
• Renal vessels anastomosed to ipsilateral external iliac artery
and vein
Horseshoe Kidney
• Fusion of lower poles of kidneys in low mid-abdomen
• Isthmus connecting kidneys in midline: Fibrous or renal
tissue
Ptotic Kidney
• Mobile, low-lying kidney
• May mimic pelvic kidney
• Low position due to poor fascial reinforcement
Abdominal, Pelvic, or Thoracic Mass
• Do not have characteristic renal morphology or function
Acquired Renal Displacement
• Secondary to mass effect from hepatomegaly,
splenomegaly, or abdominal mass lesion
• Autotransplantation for vascular diseases such as renal
artery stenosis
• Diaphragmatic hernia can result in acquired intrathoracic
kidney
PATHOLOGY
General Features
• Etiology
Diagnoses: Urinary Tract
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