A Colonoscopy is an examination used to look for changes such as swollen, irritated tissues, polyps or cancer in the large intestine/ colon and rectum. During a colonoscopy, a long, flexible tube (colonoscope) is inserted into the rectum.Gastroenterologists diagnose, treat and work to prevent gastrointestinal (stomach and intestines) and hepatological (liver, gallbladder, biliary tree and pancreas) diseases.
Before we study the procedure and diagnostic significance of Colonoscopy,it is necessary to understand the anatomy or structure and function of each part of large intestine.
It is briefly described in this article.
Introduction to anatomy of large intestine:
The digestive system includes the mouth, pharynx (throat), oesophagus, stomach, small intestine, large intestine, rectum, and anus. It also includes the salivary glands, liver, gallbladder, and pancreas, which make digestive juices and enzymes that help the body digest food and liquids.
Function of digestive system:
The digestive system breaks down food into nutrients such as carbohydrates, fats and proteins. They can then be absorbed into the bloodstream so the body can use them for energy, growth and repair. Unused materials are discarded as faeces.
Digestive system is also referred to as gastro-intestinal system includes the mouth, pharynx (throat), oesophagus, stomach, small intestine, large intestine, rectum, and anus. It also includes the salivary glands, liver, gallbladder, and pancreas, which make digestive juices and enzymes that help the body digest food and liquids.
The gastrointestinal tract and its function:
The digestive system is composed of the gastrointestinal (GI) tract or the alimentary canal, salivary glands, the liver, and the exocrine pancreas. The principal functions of the gastrointestinal tract are to digest and absorb ingested nutrients and to excrete waste products of digestion.
The large intestine includes the colon, rectum and anus. It's all one, long tube that continues from the small intestine as food nears the end of its journey through your digestive system. The large intestine turns food waste into stool and passes it from the body when you poop.
The function of a large intestine:
The purpose of the large intestine is to absorb water and salts from the material that has not been digested as food, and get rid of any waste products left over. By the time food mixed with digestive juices reaches your large intestine, most digestion and absorption has already taken place.
Length of the large intestine:
The large intestine (colon or large bowel) is about 5 feet long and about 3 inches in lumen diameter. The colon absorbs water from wastes, creating stool.
The main anatomical parts or portions of the large intestine:
The large intestine has four parts: cecum, colon, rectum, and anal canal and anus.Partly digested food moves through the cecum into the colon, where water and some nutrients and electrolytes are removed.
The large intestine is approximately 1.5m long.
About 1.5 litres of water arrives in the colon each day.
The role of large intestine:
The large intestine, also called the large bowel, is where food waste is formed into poop, stored, and finally excreted. It includes the colon, rectum and anus. Sometimes “colon” is also used to describe the entire large intestine.
The large intestine, which is the terminal part of gastrointestinal (GI) tract, is so called because its lumen (diameter) is larger, not because its length is greater, than that of the small intestine (duodenum, jejunum, ileum); in fact, small intestine is longer than the large intestine.
The small intestine is by far the longest section of the gastrointestinal tract, about 22 feet long. The lining also has a vast surface area that's scrunched into folds and peaks.The small and large intestines are a vital part of the human digestive system. The length of the small intestine is roughly 2.7 - 4.8m, while the large intestine is shorter, measuring about 1.5m long
Anatomy or structure of large intestine:
(1) Caecum:
It is a first portion/part of large intestine.Ceacum is a pouch that forms the first part of the large intestine. It connects the small intestine to the colon, which is part of the large intestine. The cecum connects the small intestine to the colon.
(2)Colon:
The colon is the longest part of the large intestine and its average length in the adult human is 65 inches or 166 cm or 5.5 (range of 80 to 313 cm) for males, and 61 inches or 155 cm or 5.08 feet (range of 80 to 214 cm) for females. The large intestine is about 1.5 m (5 feet) to 1.8 m (6 ft) long and about 7.5 cm (3 inch) in diameter.
The large intestine/large bowel absorbs chemicals such as sodium and chloride, nutrients, and water from the digested food. It also prepares waste (stool) to be expelled from the body.
The colon is found in the abdomen, below the stomach. The first part of the colon, the cecum, is in the lower right part of the abdomen. From there, the colon extends upward to beneath the ribcage, across the upper abdomen from right to left, then down the left side to the anus.
Colon is made up of four parts namely ascending colon, transverse colon, descending colon and rectum.
(2A) Ascending colon:
The ascending colon is one of the four major regions of the colon, which is itself one of the parts of our large intestine. The ascending colon carries feces from the cecum superiorly along the right side of our abdominal cavity to the transverse colon.The ascending colon/right colon lies on the right side of the abdominal cavity, in front of the quadratus lumborum and transversus abdominis muscle. It extends from the cecum to the hepatic flexure and averages 12 to 20 cm in length.
The ascending colon travels up the right side of the abdomen.
(2B) Transverse colon:
The transverse colon runs across the abdomen.
The transverse colon is the longest and most mobile part of the colon. It runs from the right to the left of the abdomen and connects the end of the ascending colon to the start of the descending colon.The transverse colon is the longest and most mobile part of the colon.The main role of the transverse colon is to absorb water and salts from indigestible food matter.The transverse colon is a section of the large intestine that runs across the abdomen. It is where the body absorbs water and salts from material that it cannot digest. Later, this becomes feces
Location of the transverse colon in relationship to the umbilicus that is belly button:
Average location of the superior its function is to store fecal wastes until they are ready to leave the body.
The sigmoid colon's function is to store fecal waste until it is ready to leave the body through the rectum and anus. Feces is stored in the sigmoid colon for seven hours or more and it is usually expelled from the body when new waste material enters the area.
The most common disorders of the colon are inflammatory bowel diseases such as ulcerative colitis, which causes pain in the sigmoid colon—the final part of the large intestine that leads to the rectum.
Crohn's disease, which typically causes pain around the belly button or on the lower right side of the abdomen.One cause of Crohn's disease may be an autoimmune reaction—when your immune system attacks healthy cells in your body. Experts think bacteria in your digestive tract can mistakenly trigger your immune system. This immune system response causes inflammation, leading to symptoms of Crohn's disease.
Six symptoms of Crohn's disease:
While symptoms vary from patient to patient, there are some common symptoms of inflammation of the GI tract caused by Crohn's disease.
•Persistent diarrhea.
•Rectal bleeding.
•Urgent need to move bowels.
•Abdominal cramps and pain.
•Sensation of incomplete bowel evacuation.
•Constipation, which can lead to bowel obstruction.
If there's a problem in your sigmoid colon, you'll probably feel abdominal pain. You might feel nauseated or lose your appetite, and you might experience either diarrhea or constipation. You might also notice blood in your stool.
The significance of the sigmoidoscopy test :
A sigmoidoscopy is a diagnostic test used to check the sigmoid colon, which is the lower part of your colon or large intestine. This section of your colon is close to your rectum and anus.
Flexible sigmoidoscopy can't detect cancer:
Flexible sigmoidoscopy doesn't allow the doctor to see the entire colon. As a result, flexible sigmoidoscopy alone can't detect cancer or small clumps of cells that could develop into cancer (polyps) farther into the colon.
Time required for the sigmoidoscopy :You typically do not need sedatives or anesthesia, and the procedure takes about 20 minutes. For the procedure, you'll be asked to lie on a table while the doctor inserts a sigmoidoscope into your anus and slowly guides it through your rectum and into your sigmoid colon.
Colectomy the surgery of colon:
You may need a colectomy if part or all of your colon has stopped working, or if it has an incurable condition that endangers other parts. Common reasons include colon cancer and inflammatory bowel diseases.
After a colectomy, bowel movements might be more frequent. Bowel movements usually become more normal after one year. Your doctor can recommend a bowel care plan to help normalize bowel movements. The most common time a cancer recurs is within the first two years following diagnosis and treatment.Bowel movements usually become more normal after one year. Your doctor can recommend a bowel care plan to help normalize bowel movements. The most common time a cancer recurs is within the first two years following diagnosis and treatment.
There may be is a serious complication. It is treated with antibiotics and often requires further surgery which may result in a stoma .
Recovery after Sigmoid Colectomy:
Most patients will be fully recovered after six weeks but should expect to feel sore around the incisions, and may feel weak for a week or two after surgery.
(3) Rectum:
The rectum is a chamber that begins at the end of the large intestine, immediately following the sigmoid colon, and ends at the anus .The rectum is the section of the digestive tract above the anus where stool is held before it passes out.
The rectum is a straight, 8-inch chamber that connects the colon to the anus. The rectum's job is to receive stool from the colon, let you know that there is stool to be evacuated (pooped out) and to hold the stool until evacuation happens.
Rectal cancer is a disease in which cancer cells develop in the rectum. The signs of rectal cancer include diarrhea, constipation or blood in your poop. The treatments include surgery, chemotherapy and radiation therapy. Rectal cancer is curable, especially when detected early through screening methods like colonoscopy.
(4) Anal canal:
The anal canal is a tube at the end of your rectum that The length of the anal canal : measures one and half inches in length (about 4 centimeters). Muscles (anal sphincters) that surround the anal canal relax to allow waste to leave your body.The anal canal is the part that connects the rectum to the anus, located below the level of the pelvic diaphragm. It is located within the anal triangle of the perineum, between the right and left ischioanal fossa.
In men the average length of anal canal is 4.4 cm (range 3.2-5.3 cm) compared with the average length of 4.9 cm (range 3.0-5.0 cm) in women.
The average length of the anatomic anal canal (dentate line to anal verge) was 2.1 cm (range 1.0-3.8 cm).
(5)Anus:
The anus is the opening at the lower end of the intestines. It's where the end of the intestines connect to the outside of the body. As food is digested, it passes from the stomach to the small intestine. It then moves from the small intestine into the main part of the large intestine called colon.Thus anus is the last part of the digestive tract. It's located at the end of the rectum. It's where stool comes out of the body. It consists of a muscular ring called a sphincter, that opens during a bowel movement to allow stool /feces to pass through, as well as flat cells that line the inside of the anus.
Of course, it's normal for the skin around your anus to look darker. It is most often not a cause for concern. "This can be due to genetics, everyday friction, sweat, diet, irritation, hormonal changes, among other reasons," said Dr. Kaado.
Information compiled by: Dr Bhairavsinh Raol
