Child Having Abdominal Pain. USG Abdomen Test Done. Took Tetadox 100. Suggest Further Chek-up And Which Disease Can It Be?

my 3.6 year child was complaint abdominal pain then I consult to his Dr. he advised USG abdominal and Findings are slo mild thickening of terminal ileum and caecum with small mesenteric lymphadenopathy and minimal interbowelloops ascites , likely to be infective etiology. I went for follow up and Dr prescribed medicine ,Tab Tetadox 100 for 10 days and Syp metrogyl 2.5 mg thrice for 7 days and also advise for test CBC-ESR,Tb Quantiferon gold, Montonk test, S.WIDAL,Urine and chest X-ray. kindly suggest further chek-up and which disease can be possible.