The human gastrointestinal tract (GI tract), is the stomach an intestine, and is divided into the upper and lower gastrointestinal tracts. It can also include all the structures from the mouth to anus. (The digestive system is a broader term that includes other structures, including the digestive organs and their accessories).
The whole digestive tract is about nine metres long. The tract may also be divided into foregut, midgut, and hindgut, reflecting the embryological origin of each segment of the tract.
The GI tract constantly releases hormones to help regulate the digestive process. These hormones, including gastrin, secretin, cholecystokinin, and ghrelin, are mediated through either intracrine or autocrine mechanisms, indicating that the cells releasing these hormones are conserved structures throughout evolution.
Upper GI Endoscopy
Upper GI endoscopy (sometimes called a ‘gastroscopy’ or simply an ‘endoscopy’) is a test which allows the doctor to look directly at the lining of the esophagus, the stomach and around the first bend of the small intestine – the duodenum. In the test, an endoscope is passed through your mouth into the stomach. The endoscope is a long flexible tube with a bright light at the end. Looking down the tube, the doctor gets a clear view of the lining of the stomach and can check whether or not any disease is present. Sometimes the doctor takes a biopsy- a sample of tissue for analysis in the laboratory. The tissue is removed painlessly through the endoscope, using tiny forceps.
To allow a clear view, the stomach must be empty. You will therefore be asked not to have anything to eat or drink for at least six hours before the test. When you come to the hospital, doctor will explain the test to you. This is to ensure that you understand the test and its implications. Please tell the doctor or nurse if you have had any allergies or bad reactions to drugs or other tests. They will also want to know about any previous endoscopy you have had. If you have any worries or questions at this stage don’t be afraid to ask.
During the test
In the examination room you will be made comfortable on a couch, resting on your left side. A nurse will stay with you throughout the test. A spray of local anaesthetic on the throat to suck to numb the area. To keep your mouth slightly open, a plastic mouthpiece will be put gently between your teeth. When the doctor passes the endoscope into your stomach it will not cause you any pain, nor will it interfere with your breathing at any time. It may take up to fifteen minutes to examine all the areas of the stomach carefully. During this time some air will be passed down the tube to distend the stomach and allow the doctor a clearer view. When the examination is finished, the tube is removed quickly and easily.
After the test
You will be left to rest in the unit for at least thirty minutes. You will be given a drink but if you have had your throat numbed by a spray or lozenge, you will have to wait until your swallowing reflex is back to normal. This usually takes more than an hour. After this you can eat and drink normally.
Capsule Endoscopy involves ingesting a small (the size of the large vitamin pill) capsule, which contains a colour camera, battery, light source and transmitter. The camera takes two pictures every second for eight hours, transmitting images to a data recorder about the size of a portable CD player that patients wear around the waist.
Capsule endoscopy assists in diagnosing gastrointestinal conditions such as obscure gastrointestinal bleeding, malabsorption, chronic abdominal pain, and chronic diarrhea.
Once swallowed the camera moves naturally through the digestive tract while patients carry out their normal activities. 2 hours after ingestion of capsule clear fluids can be started and a light snack may then be eaten approximately 4 hours after swallowing the capsule and normal diet may be resumed after 8 hrs.
Approximately eight hours after ingesting the camera, patients return the recording device to their doctor so the images can be downloaded to a computer and evaluated. The Capsule endoscope is disposable and will be excreted naturally in your bowel movement.
Colonoscopy is a test that allows your doctor to look at the inner lining of your large intestine (rectum and colon). It is a thin, flexible tube called a colonoscope to look at the colon. A colonoscopy helps find ulcers, colon polyps, tumors, and areas of inflammation or bleeding. During a colonoscopy, tissue samples can be collected (biopsy) and abnormal growths can be taken out. Colonoscopy can also be used as a screening test to check for cancer or precancerous growths in the colon or rectum (polyps).
The colonoscope is a thin, flexible tube that ranges from 48 in. (122 cm) to 72 in. (183 cm) long. A small video camera is attached to the colonoscope so that your doctor can take pictures or video of the large intestine (colon). The colonoscope can be used to look at the whole colon and the lower part of the small intestine.
Before this test, you will need to clean out your colon (colon prep). If it is not, certain areas may be obscured and the test may have to be repeated. It is important to take the entire laxative prescribed and also considerably increase your intake of clear fluids on the day before the examination, which will help clean the bowel.
Plan to stay home during your prep time since you will need to use the bathroom often. The colon prep causes loose, frequent stools and diarrhea so that your colon will be empty for the test. The colon prep may be uncomfortable and you may feel hungry on the clear liquid diet. If you need to drink a special solution as part of your prep, be sure to have clear fruit juices or soft drinks to drink after the prep because the solution tastes salty.
The doctor will then pass the colonoscope through the anus into the rectum, and advance it through the colon. You may experience some abdominal cramping and pressure from the air which is introduced into your colon. This is normal, and will pass quickly. You may also be asked to change position during the examination, and will be assisted by a nurse. The examination takes 15-60 minutes.
Colonoscopy is one of many tests that may be used to screen for colon cancer.
Sigmoidoscopy is a procedure in which the inner lining of the lower large intestine is examined. It is commonly used to evaluate gastrointestinal symptoms, such as abdominal pain, rectal bleeding, or changes in bowel habits.
During the procedure, a doctor uses a sigmoidoscope, a long, flexible, tubular instrument about 1/2 inch in diameter, to view the lining of the rectum and the lower third of the colon (the sigmoid colon).
There are no diet or fluid restrictions before a sigmoidoscopy. But, your bowel must be cleansed in order for sigmoidoscopy to be successful. You will receive two enemas before the procedure since the rectum and lower intestine must be empty so that the intestinal walls can be seen. You will need to try to hold the enema solution for at least five minutes before releasing it.
A sigmoidoscopy procedure takes usually 10 minutes to 20 minutes. No sedation is required. Your doctor will have you lie on your left side, with your knees drawn up. The sigmoidoscope is inserted through the rectum and passes slowly into the sigmoid colon. A small amount of air is used to expand the colon so the doctor can see the colon walls. You may feel mild cramping during the procedure. You can reduce the cramping by taking several slow, deep breaths during the procedure. When the doctor has finished, the sigmoidoscope is slowly withdrawn while the lining of your bowel is carefully examined.
An endoscopic retrograde cholangio pancreatogram (ERCP) is a test that combines the use of a flexible, lighted scope (endoscope) with X-ray pictures to examine the tubes that drain the liver, gallbladder, and pancreas.
Your throat will be numbed with a special spray . A fine soft tube will be placed into one nostril to give you a little oxygen to breathe during the test. You will be given an injection into your drip which will make you very sleepy. Once you are sleepy, an endoscope is inserted through the mouth and gently moved down the throat into the esophagus, stomach, and duodenum until it reaches the point where the ducts from the pancreas (pancreatic ducts) and gallbladder (bile ducts) drain into the duodenum. X-ray dye will be injected down the endoscope so that the pancreas and bile ducts may be seen on X-ray films.
ERCP can treat certain problems found during the test. If an abnormal growth is seen, an instrument can be inserted through the endoscope to obtain a sample of the tissue for further testing (biopsy). If a gallstone is present in the common bile duct, the doctor can sometimes remove the stone with instruments inserted through the endoscope. A narrowed bile duct can be opened by inserting a small wire-mesh or plastic tube (called a stent) through the endoscope and into the duct.Occasionally it may be necessary to replace the tube some months later if it becomes blocked.
ERCP is done to:
- Check persistent abdominal pain or jaundice.
- Find gallstones or diseases of the liver, bile ducts, or pancreas.
- Remove gallstones from the common bile duct if they are causing a problem such as blockage (obstruction), inflammation or infection of the common bile duct (cholangitis), or pancreatitis.
- Open a narrowed bile duct or insert a drain.
- Get a tissue sample for further testing (biopsy).
- Measure the pressure inside the bile ducts (manometry).
Spy Glass Cholangioscopy
The Spy Glass system (Boston Scientific) is a recently developed system for performing Cholangioscopy, the visual examination of the bile ducts.
The capital equipment of the system consists of a fairly small cart with a light source, water pump, computer monitor, and electrohydraulic lithotripsy generator. The disposable portion of the system, the SpyScope itself, is a 10 Fr catheter. To perform cholangioscopy, the SpyScope is inserted through the channel of a standard endoscopic retrograde cholangiopancreatography (ERCP) scope and then introduced into the bile duct to visually inspect the bile duct. The single-use SpyScope also has a dedicated irrigation channel as well as a dedicated accessory channel for obtaining biopsies or applying electrohydraulic lithotripsy fibers.
The main indications for the use of the SpyGlass system include indeterminate or unexplained biliary strictures, difficult-to-remove bile duct stones, primary sclerosing cholangitis, cholangiocarcinoma, and common bile duct nodules or masses.
The main advantage over standard ERCP is that with the SpyGlass system, the scope can be inserted directly into the bile duct and the pathology can be directly visualized, rather than using radiographs to visualize the bile ducts. This direct visualization allows the endoscopist to obtain a targeted biopsy, if needed, or to use electrohydraulic lithotripsy to crush stones under direct vision.
Another advantage of the SpyGlass system is that it is a single-operator system, as opposed to standard ERCP, which requires two physicians.
Endoscopic ultrasound (EUS)
Endoscopic ultrasound (EUS) is a procedure that allows a doctor to obtain images and information about the digestive tract and the surrounding tissue and organs. Ultrasound testing uses sound waves to make a picture of internal organs.
During the procedure, a small ultrasound device is installed on the tip of an endoscope. An endoscope is a small, lighted, flexible tube with a camera attached. By inserting the endoscope and camera into the upper or the lower digestive tract, the doctor is able to obtain high-quality ultrasound images of organs. Because the EUS can get close to the organ(s) being examined, the images obtained with EUS are often more accurate and detailed than images provided by traditional ultrasound which must travel from the outside of the body.
Endoscopic ultrasound may be used to:
- Evaluate stages of cancer / chronic pancreatitis or other disorders of the pancreas.
- Study abnormalities or tumors in organs, including the gallbladder and liver.
- Study the muscles of the lower rectum and anal canal to determine reasons for fecalincontinence.
- Study nodules (bumps) in the intestinal wall.
A person undergoing an endoscopic ultrasound will be sedated prior to the procedure. After sedation, the doctor inserts an endoscope into the person’s mouth or rectum. The doctor will observe the inside of the intestinal tract on a TV monitor and the ultrasound image on another monitor. Additionally the sound wave testing may be used to locate and help take biopsies (small piece of tissue to examine by microscope). The entire procedure usually takes 30 to 90 minutes and the patient usually can go home the same day of the procedure.
Enteroclysis is a fluoroscopic X-ray of the small intestine. Radio-contrast is infused through a tube inserted through the nose to the duodenum, and images are taken in real time as the contrast moves through aided by administration of methyl cellulose.
Any problems of the small intestine can be found with Enteroclysis. Some of these include:
- Inflammation of the small bowel (such as Crohn’s disease)
- Narrowing or stricture of the intestine
- Small bowel blockage
- Tumors of the small intestine
A barium meal, also known as an upper gastrointestinal series is a procedure in which radiographs of the oesophagus, stomach and duodenum are taken after barium sulfate is ingested by a patient. Barium meals are useful in the diagnosis of structural and motility abnormalities of the foregut.
The gastrointestinal tract, like other soft-tissue structures, does not show clearly enough for diagnostic purposes on plain radiographs. Barium salts are radio opaque: they show clearly on a radiograph. If barium is swallowed before radiographs are taken, the barium within the oesophagus, stomach or duodenum shows the shape of the Lumina of these organs.
Liquid suspensions of barium sulfate are non-toxic, apart from a small risk of producing a disturbance in bowel function for 48 hours after ingestion. They usually have a chalky taste that can be disguised by adding flavors.
GI Physiology Lab
Anorectal and oesophageal Manometry
Anorectal Manometry measures the tone in the anal sphincter and rectal muscles. This test can diagnose problems with defecation (moving your bowels).
This test examines the movement and pressures of your esophagus. This test will involve the placement of a tube through your nasal passage, or nostril, and then swallowed into your esophagus with drinks of water.
This test monitors the acidity in your esophagus during a 24-hr period.
Bedfont Breath test
This is a test for bacterial overgrowth, or intolerances to lactose, fructose, or sucrose. Glucose is a sugar that will be broken down by bacteria if present in the small bowel with hydrogen or methane gas as a by-product. The breath sample will be analyzed for hydrogen or methane content to determine if you are able to properly break down the lactose, fructose, or sucrose, or if you have bacterial overgrowth.