Gastroenterology is the specialty of medicine which deals with diseases of the digestive tract. The human digestive system consists of the food pipe (Esophagus), the stomach, the small intestine (Duodenum, jejunum and ileum), the large intestine (Colon and Rectum), The gallbladder and the bile duct and the two solid organs the liver and the pancreas.
The process of digestion starts in the mouth itself with the mastication of food and secretion of enzymes for the digestion of carbohydrates. The food bolus then travels down the esophagus which is a pipe connecting the mouth to the stomach. Esophageal disease manifests as obstruction to the passage of food (Dysphagia), chest pain, vomiting, heart burn chronic cough and wheezing. The common diseases of the esophagus are GERD, Esophageal Ulceration, Barretts esophagus, Esophagitis, Esophageal stricture, Esophageal infections and Motility disorders like Achalasia cardia.
From the esophagus, the food travels into the stomach which is a sac which stores food and pulverizes it into a paste which is then sent into the small intestine (duodenum) for further digestion. Protein digestion takes place in the stomach with the secretion of hydrochloric acid and pepsin by the stomach cells. Non ulcer dyspepsia (bloating and indigestion) Gastric or peptic ulcer (Pain, vomiting, blood vomiting and black tarry stools), stomach cancer (Pain, loss of weight and appetite, lump in the upper abdomen), H pylori infection (presents as indigestion and can lead to serious consequences as lymphoma, cancer) are the major diseases of the stomach.
The food then passes into the duodenum (the 1st part of the small intestine), here it is digested further with the help of secretion of bile from the liver and digestive enzymes from the pancreas. Major digestion as well as absorbtion of carbohydrates, proteins and fats takes place in the duodenum.
The process of digestion continues in the small intestine and food is broken down into smaller absorbable units by the action of the pancreatic and intestinal enzymes with the help of bile. Absorption of this digested food largely takes place in the jejunum or the second part of the small intestine. The food then continues to go to the third part of the intestine or the ileum, some nutrients like Vitamin B12 and bile acids are absorbed specifically in the ileum.
Diseases of the duodenum can vary from simple duodenitis or the more serious duodenal ulcer (presents with pain can result in blood vomiting, black stool, stricture causing obstruction and perforation). Acute and chronic diarrheas can be caused by a number of bacterial (E. Coli, Campylobacter, Shigella, Yersinia, Clostridium dificile, Mycobacteriun tuberculosis and Mycobacterium intracellulare, Vibrio cholera etc), Viral (Rotavirus, Norovirus, calcivirus, Adenovirus) Parasitic (Giardiasis, Amebiasis, Cryptosporidium, Cyclospora, Microsporidia, Entmobea etc). Infections, most diarrhoeas are self limiting however severe diarrhoeas need specific treatment
Most intestinal parasites like giardiasis, ancylostomiasis (hook worm), round worms (ascariasis, strongyloidiasis) are found in the small intestine. They can cause diarrhoea and abdominal pain. Diseases causing malabsorbtion (Celiac disease and tropical sprue) occur due to defect in the intestinal villi. They can cause deficiency of nutrients which results in anaemia, loss of weight and muscle mass and specific vitamin deficiencies. Intestinal cancer like lymphoma, Gastrointestinal stromal tumors (GIST), Carcinoid, Sarcoma and Leiomyoma can effect the jejunum or ileum. Crohns disease can effect the entire small intestine and cause pain and malabsorbtion. Small bowel obstruction can result from Adhesions, Intussuption, Volvulus, Hernia, Paralytic ileus etc.
The colon or the large intestine, it is primarily concerned with the absorption of water and the formation of stool. It consists of the caecum, ascending colon, transverse colon, descending colon, sigmoid colon and rectum. The stool is formed in the large intestine as the water is absorbed and is stored in the rectum and sigmoid colon.
The disease of the large bowel can vary from the less serious conditions like Haemorrhoids (Piles) and fissure (which can cause anal pain and bleeding), rectal prolapse (presents with the extrusion outside of a part of the rectum), colonic polyps, colonic cancers (weight loss bleeding an d lump are the common presentations), diverticulitis (can present with severe abdominal pain) constipation and IBS are all diseases of the colon.
The liver is the largest solid organ in the body and is responsible for a number of functions. It is a treated as a speciality in itself and is mentioned in the section on hepatology.
The Pancreas is the second major solid organ of the digestive tract. It has two functions endocrine and exocrine. The endocrine functions of the pancreas include the secretion of hormones like insulin directly into the blood stream. While the exocrine functions include the secretion of enzymes responsible for digestion of protein (The proteases), Fat (Lipase) and Carbohydrate (Amylase) into the intestine through the pancreatic duct.
Acute Pancreatitis is a abdominal catastrophe, it presents with severe abdominal pain and my need ICU admission. Repeated episodes of acute pancreatitis can lead to chronic pancreatitis which can also be the result of a number of other causes. Pancreatic cancer is the third major pancreatic disease which can present with pain, weight loss and.