An esophageal 24hour pH test measures how often stomach acid or non-acid fluid flows into the lower esophagus and the degree of acidity during a 12-24 hour period.

Endoscopic Retrograde Cholangiopancreatography, or ERCP, is a specialized technique  used to study the ducts of the gallbladder, pancreas and liver.

The esophageal manometry test measures the motor action of the muscles that are the upper and lower ends of the esophagus, as well as the motor function of the esophageal body.

Upper GI endoscopy, sometimes called EGD (esophagogastroduodenoscopy), is a visual examination of the upper intestinal tract using a lighted, flexible fiberoptic or video endoscope.

Flexible Sigmoidoscopy lets your doctor examine the lining of the rectum and a portion of the colon (large intestine).

The doctor uses a lighted tube to look inside all or your colon. The doctor will be looking for a growth that could be cancer or a polyp that could turn into cancer. If he sees something that concerns him, he can take a piece of the growth and test it for cancer.