A horseshoe kidney discovered incidentally on imaging. Which statement about its anatomy is correct?
- A The ureters pass medially around the isthmus
- B The isthmus consists entirely of fibrous tissue without functioning parenchyma
- C The isthmus usually crosses anterior to the aorta at the level of the inferior mesenteric artery origin ✓
- D It carries a lower incidence of pelviureteric junction obstruction than a normal kidney
Correct answer: C. The isthmus usually crosses anterior to the aorta at the level of the inferior mesenteric artery origin
Explanation
In horseshoe kidney the lower poles fuse across the midline, and the isthmus of functioning parenchyma lies anterior to the aorta and IVC, typically held at the level of the L3-L4 vertebra by the root of the inferior mesenteric artery, which prevented further ascent. The ureters hook over the isthmus and pass laterally then medially, producing a high insertion that predisposes to impaired drainage, stones and pelviureteric junction obstruction, making option D false. The isthmus contains functioning renal tissue, not merely fibrous bands.
Reference: Gray's Anatomy, 42nd ed.
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