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:

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