This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Radiology
[{'content': 'Cobra head  deformity is characterstic of \nSelect and explain. \nA. Posterior urethral valve, B. Carcinoma of bladder, C. Bladder tumor, D. Ureterocele', 'role': 'user'}, {'content': 'Answer: D \nExplanation: A ureterocele is a congenital abnormality found in the ureter. In this condition the distal ureter balloons at its opening into the bladder,\nforming a sac-like pouch. It is most often associated with a duplicated collection system, where two ureters drain their respective kidney instead of one.', 'role': 'assistant'}]