This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Abdomen & Pelvis, Subject name: Anatomy
A 28-year-old female visits the outpatient clinic to receive the required physical examination for an insurance policy. Physical and laboratory examinations give evidence that she is probably a normal, healthy woman. A radiograph of the patient is shown below. Which of the following is the most likely diagnosis? 
Select and explain. 
A. Cholecystitis, B. Carcinoma of the liver, C. A caudal extension of the right hepatic lobe (Riedel lobe), D. Pancreatic carcinoma
C: A caudal extension of the right hepatic lobe (Riedel lobe)
Answer: C: A caudal extension of the right hepatic lobe (Riedel lobe) 
Explanation: Because physical and laboratory tests show a normal, healthy woman, the anomaly of the radiograph would be expected to be benign. Riedel's lobe is a normal variation of the liver, often an inferior extension of the right lobe of the liver, lateral to the gallbladder that extends about 4 or 5 cm below the rib cage. Carcinomas would present with abnormal laboratory examinations, and cholecystitis would present with an abnormal physical examination, as when the gallbladder is inflamed.