Eighteenth-century

• Italian Lazzaro Spallanzani (1729–99) was among early physicians to disregard Galen's theories, and in 1780 he gave experimental proof on the action of gastric juice on foodstuffs.
• In 1767, German Johann von Zimmermann wrote an important work on dysentery.
• In 1777, Maximilian Stoll of Vienna described cancer of the gallbladder.^[7][8]

Nineteenth-century

• In 1805, Philipp Bozzini made the first attempt to observe inside the living human body using a tube he named Lichtleiter (light-guiding instrument) to examine the urinary tract, the rectum, and the pharynx. This is the earliest description of endoscopy.^[9][10]
• Charles Emile Troisier described enlargement of lymph nodes in abdominal cancer.^[11]
• In 1823, William Prout discovered that stomach juices contain hydrochloric acid.^[12]
• In 1833, William Beaumont published Experiments and Observations on the Gastric Juice and the Physiology of Digestion following years of experimenting on test subject Alexis St. Martin.
• In 1868, Adolf Kussmaul, a well-known German physician, developed the gastroscope. He perfected the technique on a sword swallower.
• In 1871, at the society of physicians in Vienna, Carl Stoerk demonstrated an esophagoscope made of two telescopic metal tubes, initially devised by Waldenburg in 1870.
• In 1876, Karl Wilhelm von Kupffer described the properties of some liver cells now called Kupffer cells.
• In 1883, Hugo Kronecker and Samuel James Meltzer studied oesophageal manometry in humans.

McClendon's pH-probe

Twentieth-century

• In 1915, Jesse McClendon tested acidity of human stomach in situ.^[13]
• In 1921–22, Walter Alvarez did the first electrogastrography research.^[14]
• Rudolf Schindler described many important diseases involving the human digestive system during World War I in his illustrated textbook and is portrayed by some as the "father of gastroscopy". He and Georg Wolf developed a semiflexible gastroscope in 1932.
• In 1932, Burrill Bernard Crohn described Crohn's disease.
• In 1957, Basil Hirschowitz introduced the first prototype of a fibreoptic gastroscope.

Twenty-first century

• In 2005, Barry Marshall and Robin Warren of Australia were awarded the Nobel Prize in Physiology or Medicine for their discovery of Helicobacter pylori (1982/1983) and its role in peptic ulcer disease. James Leavitt assisted in their research, but the Nobel Prize is not awarded posthumously so he was not included in the award.

Colonoscopy

Diagram of a colonoscopy procedure

A procedure using a long thin tube with a camera that is passed through the anus to visualize the rectum and the entire length of the colon. The procedure is performed either to look for colon polyps and/or colon cancer in somebody without symptoms, referred to as screening, or to further evaluate symptoms including rectal bleeding, dark tarry stools, change in bowel habits or stool consistency (diarrhea, pencil-thin stool), abdominal pain, and unexplained weight loss. Before the procedure the physician might ask the patient to stop taking certain medications including blood thinners, aspirin, diabetes medications, or Nonsteroidal anti-inflammatory drugs. A bowel prep is usually taken the night before and into the morning of the procedure which consists of an enema or laxatives, either pills or powder dissolved in liquid, that will cause diarrhea. The procedure might need to be stopped and rescheduled if there is stool remaining in the colon due to an incomplete bowel prep because the physician can not adequately visualize the colon. During the procedure the patient is sedated and the scope is used to examine the entire length of the colon looking for polyps, bleeding, or abnormal tissue. A biopsy or polyp removal can then be performed and the tissue sent to the lab for evaluation. The procedure usually takes thirty minutes to an hour followed by a one to two hour observation period. Complications include bloating, cramping, a reaction to anesthesia, bleeding, and a hole through the wall of the colon that may require repeat colonoscopy or surgery. Signs of a serious complication requiring urgent or emergent medical attention include severe pain in the abdomen, fever, bleeding that does not improve, dizziness, and weakness.^[15]

Sigmoidoscopy

Sigmoidoscopy

A procedure similar to a colonoscopy using a long thin tube with a camera (scope) passed through the anus but only intended to visualize the rectum and the last part of the colon closest to the rectum. All aspects of the procedure are the same as for a colonoscopy with the exception that this procedure only lasts ten to twenty minutes and is done without sedation. This usually allows for the patient to return to normal activities immediately after the procedure is finished.^[16]

Esophagogastroduodenoscopy (EGD)

Endoscopy

A procedure using a long thin tube with a camera that is passed through the mouth to view the esophagus ("esophago-"), stomach ("gastro-"), and the duodenum ("duodeno-"). It is also referred to as upper endoscopy or just endoscopy. The procedure is performed for further evaluation of symptoms including persistent heartburn, indigestion, vomiting blood, dark tarry stools, persistent nausea and vomiting, pain, difficulty swallowing, painful swallowing, and unexplained weight loss. It is also performed for further testing following a lab test that shows low hemoglobin levels without a known cause or an abnormal barium swallow. The procedure can be used to diagnose many disorders through direct visualization or tissue biopsy including esophageal varices, esophageal strictures, gastroesophageal reflux disease, Barrett's esophagus, cancer, celiac disease, gastritis, peptic ulcer disease, and a H. pylori infection. Intra-operative techniques can then be used for treatment of certain disorders like banding esophageal varices or dilating esophageal strictures. The patient will likely be required to not eat or drink anything starting 4 hours prior to the procedure. Sedation is usually required for patient comfort. This procedure usually lasts around thirty minutes followed by a one to two hour observation period. Side effects include bloating, nausea, and a sore throat for 1 to 2 days. Complications are rare but include reaction to the anesthesia, bleeding, and a hole through the wall of the esophagus, stomach, or small intestine which could require surgery. Signs of a serious complication requiring urgent or emergent medical attention include chest pain, problems breathing, problems swallowing, throat pain that gets worse, vomiting with blood or the appearance of "coffee-grounds", worsening abdominal pain, bloody or black tarry stool, and fever.^[17]

Endoscopic Retrograde Cholangiopancreatography (ERCP)

ERCP

A procedure using a long thin tube with a camera passed through the mouth into the first part of the small intestine to locate, diagnose, and treat disorders related to the bile and pancreatic ducts. These ducts carry fluids that help with digesting food from the liver, gallbladder, and pancreas and can become narrowed or blocked as a result of gallstones, infection, inflammation, pancreatic pseudocysts, and tumors of the bile ducts or pancreas. As a result one may experience back pain, yellowing of the skin, and an abnormal lab test showing an elevated bilirubin level which could necessitate this procedure. However, the procedure is not recommended if the patient has acute pancreatitis unless the level of bilirubin remains high or is increasing which could suggest the blockage is still present. The patient will likely be required to not eat or drink anything starting 8 hours prior to the procedure. After the patient is sedated, the physician will pass the scope through the mouth, esophagus, stomach, and into the duodenum to locate the opening where the ducts drain into the small intestine. The physician can then inject dye into these ducts and take X-rays which show a real time view, via fluoroscopy, allowing the physician to locate and relieve the blockage. This is done through multiple techniques including cutting the opening and creating a bigger hole for drainage, removing gallstones and other debris, dilating narrow parts of the ducts, or placing a stent which keeps the ducts open. The physician can also take a biopsy of the ducts to evaluate for cancer, infection, or inflammation. Side effects include bloating, nausea, or a sore throat for one to two days. Complications include pancreatitis, infection of the bile ducts or gallbladder, bleeding, reaction to the anesthesia, and perforation of any structures that the scope or its instruments pass but particularly the duodenum, bile duct, and pancreatic duct. Signs of a serious complication requiring urgent or emergent medical attention include bloody or black tarry stool, chest pain, fever, worsening abdominal pain, worsening throat pain, problems breathing, problems swallowing, vomit that is bloody or looks like coffee-grounds. Most of the time complications from this procedure require hospitalization for treatment.^[18]

Esophagus

Gastroesophageal reflux disease (GERD)

See also: Gastroesophageal reflux disease

Gastroesophageal reflux

A condition that is a result of stomach contents consistently coming back up into the esophagus causing troublesome symptoms or complications.^[19] Symptoms are considered troublesome based on how disruptive they are to a patient's daily life and well-being. This definition was standardized by the Montreal Consensus in 2006.^[20] Symptoms include a painful feeling in the middle of the chest and feeling stomach contents coming back up into the mouth. Other symptoms include chest pain, nausea, difficulty swallowing, painful swallowing, coughing, and hoarseness.^[21] Risk factors include obesity, pregnancy, smoking, hiatal hernia, certain medications, and certain foods. Diagnosis is usually based on symptoms and medical history, with further testing only after treatment has been ineffective. Further diagnosis can be achieved by measuring how much acid enters the esophagus or looking into the esophagus with a scope. Treatment and management options^[19] include lifestyle modifications, medications, and surgery if there is no improvement with other interventions. Lifestyle modifications include not lying down for three hours after eating, lying down on the left side, elevating head while laying by elevating head of the bed or using extra pillows, losing weight, stopping smoking, and avoiding coffee, mint, alcohol, chocolate, fatty foods, acidic foods, and spicy foods. Medications include antacids, proton pump inhibitors, H2 receptor blockers. Surgery is usually a Nissen fundoplication and is performed by a surgeon. Complications of longstanding GERD can include inflammation of the esophagus that may cause bleeding or ulcer formation, narrowing of the esophagus leading to swallowing issues, a change in the lining of the esophagus that can increase the chances of developing cancer (Barrett's esophagus), chronic cough, asthma, inflammation of the larynx leading to hoarseness, and wearing away of tooth enamel leading to dental issues.^[19][21]

United States

Gastroenterology is a subspecialty of internal medicine and therefore requires three years of internal medicine residency training followed by three additional years in a dedicated gastroenterology fellowship.^[1] This training is certified by the American Board of Internal Medicine (ABIM) and the American Osteopathic Board of Internal Medicine (AOBIM) and must be completed at a program accredited by the Accreditation Council for Graduate Medical Education (ACGME).^[25][26][27] Other national societies that oversee training include the American College of Gastroenterology (ACG), the American Gastroenterological Association (AGA), and the American Society for Gastrointestinal Endoscopy (ASGE).^[28][29][30]

Subspecialties

Some gastroenterology trainees will complete a "fourth-year" (although this is often their seventh year of graduate medical education) in transplant hepatology, advanced interventional endoscopy, inflammatory bowel disease, motility, or other topics.

Advanced endoscopy, sometimes called interventional or surgical endoscopy, is a sub-specialty of gastroenterology that focuses on advanced endoscopic techniques for the treatment of pancreatic, hepatobiliary, and gastrointestinal disease. Interventional gastroenterologists typically undergo an additional year of rigorous training in advanced endoscopic techniques including endoscopic retrograde cholangiopancreatography, endoscopic ultrasound-guided diagnostic and interventional procedures, and advanced resection techniques including endoscopic mucosal resection and endoscopic submucosal dissection. Additionally, the performance of endoscopic bariatric procedures is also performed by some advanced endoscopists.

Hepatology, or hepatobiliary medicine, encompasses the study of the liver, pancreas, and biliary tree, and is traditionally considered a sub-specialty of gastroenterology, while proctology encompasses disorders of the anus, rectum, and colon and is considered a sub-specialty of general surgery.