Husband 40+ y.o. taking 40mg nexium (esomeprazole). has been experiecing burn sensation in stomach. stomach ultrasound showed nothing wrong. what could be causing it?

Acid reflux: A small percentage of people with acid reflux do not respond to proton pump inhibitors such as Nexium (esomeprazole) and omeprazole. These people will still have symptoms of acid reflux while taking these ppis. To diagnose this a pH manometry study is helpful as well as an upper endoscopy to look for evidence of continued gastritis or esophagitis. Usually a gastroenterologist orders these more specific tests.