This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: CT and MRI of the Kidney, Subject name: Radiology
Cobra head appearance is seen in: 
Select and explain. 
A. Ureterocele, B. Wilm's Tumor, C. Horse shoe kidney, D. Vesicoureteral reflux
A: Ureterocele
Answer: A: Ureterocele 
Explanation: Ans: A (Ureterocele) Ref: Harrison is online. 18th edExplanation:Some Important Features in ContrastRadiographsSpider leg appearance -- Polycystic kidneyCobra head appearance -- UreteroceleFlower vase appearance of ureters -- Horse shoe kidneySandy patches -- Schistosomiasis of bladderSoap bubble appearance -- HydronephrosisApple core lesion on barium -- Ca colonClaw appearance on barium enema -- IntussusceptionSaw tooth appearance -- Diverticula of colonBirds beak appearance of esophagus on barium meal -- AchalasiaCork screw appearance of esophagus on barium meal -- Diffuse esophageal spasmString sign of kantor -- Crohn's disseaseThumb printing sign -- Ischemic colitisEGG SHELL CALCIFICATION------ Silicosis, Sarcoidosis. Scleroderma, Histoplasmosis, Amyloidosis, lymphoma following radiotherapy