<prompt> A neonate presented with fever, lethargy, abdominal distension, vomiting and constipation. Clinically he was diagnosed as volvulus neonatarum with suspected perforation. Best investigation would be:Plain X-rayBarium enemaUpper GI endoscopyBarium meal follow through  <response>: In a case of suspected perforation plain x-ray should be performed. It shows free air under the diaphragm and confirms the diagnosis of perforation. Ref: Jones Clinical Paediatric Surgery : Diagnosis and Management By Peter G. Jones, John M. Hutson, Alan A Woodward, Page 40; Walkers Pediatric Gastrointestinal Disease : Physiology, Diagnosis By W. Allan Walker, Volume 2, Page 1420 