A radiologist reports that the lower poles of both kidneys are fused across the midline by an isthmus of parenchyma. At what vertebral level does the isthmus of a horseshoe kidney typically lie, and which structure passes anterior to it?

• A L4 to L5 level, anterior to the abdominal aorta and inferior vena cava
• B L1 to L2 level, anterior to the coeliac trunk
• C S1 level, posterior to the iliac vessels
• D L3 level, anterior to the aorta and inferior vena cava ✓

Explanation

In horseshoe kidney the ascent is arrested by the inferior mesenteric artery, so the isthmus comes to lie at the L3 level, anterior to the aorta and IVC. The isthmus is supplied by accessory arteries arising from the aorta or iliac vessels. Option A is tempting because the kidneys are low-lying overall, but the classical teaching location of the isthmus itself is L3, trapped below the inferior mesenteric artery.

Reference: Bailey and Love's Short Practice of Surgery, 27th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.