renal variants in appearance and location

compensatory hypertrophy

enlargement of the unaffected contralateral kidney with unilateral renal agenesis or compromised renal function

dromedary hump

• bulge on the lateral border of the kidney (often on the left kidney)

• will have the same echogenicity as the adjacent renal cortex

duplex/duplicated collecting system

• division of the renal sinus

• there are 2 separate renal sinuses → upper pole moiety and lower pole moiety

• obstruction to one or both can occur

• 2 ureters drain separate portions of the kidney

• a kidney with this anomaly will typically measure longer than a normal size kidney

ectopic kidney - pelvic kidney

one or both kidneys may be located within the pelvis

ectopic kidney - cross fused ectopia

both kidneys are fused and on the same side of the body

ectopic kidney - thoracic kidney

kidney sits partially or completely in the chest

extrarenal pelvis

the renal pelvis is located outside of the renal hilum

fetal lobulation

• lobulated or bumpy outline to the kidney(s)

• can be seen in adults

horseshoe kidney

• 2 kidneys that cross the midline and connect their lower poles by an isthmus

• the isthmus travels anterior to the abdominal aorta and IVC

hypertrophic column of Bertin

• enlargement of a renal column seen as an indentation of the renal sinus

• actually are double layers of renal cortex

junctional parenchymal defect (junctional line)

• results from the incomplete fusion of the 2 embryologic components (renunculi) of the kidney

• appears as a hyperechoic, wedge-shaped structure on the anterior portion of the kidney → located between the upper and middle sections of the kidney

malrotated kidney

the kidney sits in the renal fossa but is positioned off of the normal axis

renal agenesis

• congenital absence of the kidney

• bilateral renal agenesis is typically not consistent with life

renal hypoplasia

• the underdevelopment of the kidney in which there are too few nephrons

• kidney will be smaller than normal

renal sinus lipomatosis (fibrolipomatosis)

• excessive fat within the renal pelvis

• renal sinus will be large and echogenic

supernumerary kidney

a third, smaller kidney