A 45 year old lady is having persistent reflux symptoms. Most accurate investigation in establishing the diagnosis before surgical treatment is

GERDGERD is often associated with hiatus hernia type IClinical featuresInvestigationsClassical traid: retrosternal burning pain, epigastric pain, and regurgitation.HeaburnsRegurgitationAbdominal painCoughDysphagia for solidsBelchingBloatingManometry for measuring LES tone24 hrs pH monitoringEsophagogram TreatmentLifestyle modifications: cessation of smoking, decreased caffeine intake and avoidance of large meal at nightMedical management: double dose of PPI'SSurgical therapy: laparoscopic Nissen's fundoplication, modern fundoplication, 3600 floppy fundoplication (Refer: Sabiston's Textbook of Surgery, 19th edition, pg no: 1081)