This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: General anatomy, Subject name: Anatomy
[{'content': 'Which of the following is true about Horseshoe kidney? \nSelect and explain. \nA. Fused at upper pole lies in pelvis, B. Fused at lower pole, lies in pelvis, C. Fused at upper pole, lies in front of L1, D. Fused at lower pole, lies in front of L4', 'role': 'user'}, {'content': "Answer: D \nExplanation: The lower poles of the two kidneys (or sometimes the upper poles) may be fused. The connecting isthmus may lie either in front of, or behind, the aoa and inferior venacava. The ureters pass anterior to the isthmus. The inferior mesenteric aery also passes anterior to the isthmus which limits the ascent of the horseshoe kidney. (Reference : I B Singh's Embryology , 10th edition, pg 288)", 'role': 'assistant'}]