Which condition is described as fusion at the lower poles of the kidneys?

Which condition is described as fusion at the lower poles of the kidneys?

• A. Horseshoe kidney
• B. Duplex kidney
• C. Renal agenesis
• D. Polycystic kidney disease

Answer: (A)

When two kidneys fuse at their lower poles, the result is a horseshoe kidney. During development, the kidneys migrate upward from the pelvis, but in this condition the lower poles fuse across the midline to form an isthmus. That fusion tends to arrest the ascent as the fused organ sits lower than normal, usually anterior to the aorta and IVC. On ultrasound you’d typically see the kidneys connected by an inferior pole isthmus and located in the lower abdomen rather than the usual flank position. This distinguishes it from a duplex kidney (duplication of the collecting system without pole fusion), renal agenesis (absence of a kidney), and polycystic kidney disease (kidneys with multiple cysts rather than fused poles).

When two kidneys fuse at their lower poles, the result is a horseshoe kidney. During development, the kidneys migrate upward from the pelvis, but in this condition the lower poles fuse across the midline to form an isthmus. That fusion tends to arrest the ascent as the fused organ sits lower than normal, usually anterior to the aorta and IVC. On ultrasound you’d typically see the kidneys connected by an inferior pole isthmus and located in the lower abdomen rather than the usual flank position. This distinguishes it from a duplex kidney (duplication of the collecting system without pole fusion), renal agenesis (absence of a kidney), and polycystic kidney disease (kidneys with multiple cysts rather than fused poles).