This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Stomach and Intestines, Subject name: Pediatrics
A neonate presented with fever, lethargy, abdominal distension, vomiting and constipation. Clinically he was diagnosed as volvulus neonatorum with suspected perforation. Best investigation would be: 
Select and explain. 
A. Plain X-ray, B. Barium enema, C. Upper GI endoscopy, D. Barium meal follow-through
A: Plain X-ray
Answer: A: Plain X-ray 
Explanation: a. Plain X-ray(Ref: Nelson's 20/e p 1894-1897, Ghai 8/e p 285-286)Volvulus neonatorumWhat is it?Intestinal obstruction in a newborn due to twisting of bowel caused by malrotation or non-fixation of colonInvestigationsBarium meal follow-through is the investigation of choice as X-ray is not reliable in early stages of volvulus; However, if perforation is suspected, barium contrast should not be used because of risk of perotinitis