The sigmoid colon is the last section of the bowel — the part that attaches to the rectum. It’s about a foot and a half long (around 40 centimeters) and is shaped like the letter “s.” Its job is to hold feces until you’re ready to go to the bathroom.
The sigmoid contains a lot of muscle tissue. The muscles in the sigmoid are arranged two ways: Some bundles of muscle tissue run up and down the length of the sigmoid tube, and some bundles are arranged in circular bands around the tube.
The circular bands of muscle pinch the tube into small sacs called haustra, making the sigmoid look a little bit like a string of plump beads. As the muscles contract, the haustra shift and move, pushing feces along the bowel tract.
The colon contains four layers of tissue. The inside layer is a mucous membrane. The mucus keeps the body from absorbing all the bacteria in fecal matter, and it also helps the feces glide along through the tube.
Next to the mucus membrane is a layer of connective tissue, blood vessels, and nerves. This layer of tissue carries away any remaining nutrients in the digested food. The nerves control your impulse to go to the bathroom.
A third layer is made of muscle to propel feces along the sigmoid tube, and a fourth layer of smooth epithelial tissue called the serosa protects the outside of the colon by secreting a liquid that keeps the organ from being torn by friction as you move.
The sigmoid portion of the bowel sits down low in the abdominal cavity, near the uterus in in women and near the bladder in men.
The primary job of the sigmoid is to act as a holding chamber for fecal matter until it can be moved out of your body.
By the time digested food reaches the sigmoid, most of the nutrients have already been extracted by the stomach and small intestines, but the sigmoid can extract water and vitamins from the feces while it’s waiting to be expelled.
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. Sometimes people with sigmoid colon problems also feel fatigued, become anemic, or lose weight.
Polyps
Polyps are lumps of tissue in the colon, most of which are not cancerous. Anyone can get them, but they are more likely to form as you get older. Smoking and being overweight also increase your risk.
It’s important to have a colonoscopy to find and remove polyps because they can get bigger over time, and the larger the polyp, the more likely it is to become cancerous.
Colorectal cancer
The American Cancer Society reports that colorectal cancer is the third most common cancer in the United States, with more than 145,000 new cases expected to be diagnosed this year.
Colon cancer occurs when abnormal cells develop inside the colon, usually in polyps. The cancerous cells can spread from the inner layers of the colon through the walls of the organ and eventually into the blood vessels and lymph system, if left untreated.
Early diagnosis improves your chances for recovery, so it’s a good idea to get regular colon screenings, especially if you have any of the risk factors or symptoms.
Ulcerative colitis
This disease causes open sores to form inside the intestinal tract, causing pain that can be severe at times. It’s a long-term disease, but people who have it may experience periods of remission where they feel no symptoms whatsoever.
According to the National Institute of Diabetes and Digestive and Kidney Diseases, you may be at higher risk for ulcerative colitis if you eat a high-fat diet, if the disease seems to run in your family, or if your intestinal immune system is overly sensitive. Jewish people are also at higher risk for developing ulcerative colitis.
If you’re concerned about ulcerative colitis, a gastroenterologist might be able to help diagnose your symptoms.
Crohn’s disease
Like ulcerative colitis, Crohn’s disease causes inflammation, swelling, and pain in the intestinal tract. Most of the time, Crohn’s disease affects the upper gastrointestinal tract, but it can occur anywhere, including the sigmoid colon.
Crohn’s disease can lead to infections in your intestines and in other parts of your body, and it can become life-threatening for some people, so it’s important to talk to a doctor and start treatments early to prevent severe complications from happening.
Fistulae
A gastrointestinal fistula is an opening in your bowel that allows gastric fluid to leak into other parts of your body. These openings usually occur after you’ve had surgery or a procedure in your abdominal area.
Fistulae may also develop if you’ve had an inflammatory bowel disease like Crohn’s for a long time. Gastrointestinal fistulae can lead to sepsis, an extremely dangerous systemic infection.
It’s possible to repair or treat fistulas to keep them from causing you serious problems. They can be stitched, glued, drained, and treated effectively with antibiotics, so get help if you suspect you may have developed one.
Diverticular disease
Diverticula are small balloon-like sacs that push outward through weak spots in your intestinal wall. Most of the time diverticula don’t cause any symptoms at all, but they can occasionally become painful and problematic.
Diverticula can become blocked. They can form abscesses, tear open, and leak pus or blood into other parts of your body. These complications can be dangerous, so if you develop a fever, start vomiting, or feel tender in your abdominal region, get to a doctor for help.
Volvulus
Volvulus is a problem with the way a baby’s intestines are formed, resulting in a section of intestine twisting or folding over on itself. This condition can cause blockage and blood supply to be cut off.
Babies who have this condition will have pain, belly bloating, nausea, and vomiting. They can also have dark or red bowel movements.
It’s really important to respond quickly if these symptoms occur, because this condition can be life-threatening. Doctors can often repair the damaged part of the baby’s bowel.
Depending on the nature of your colon issue, you could see a gastroenterologist, an oncologist, a radiologist, or a colorectal surgeon.
Colonoscopy
Colonoscopies allow your doctor to check the health of your colon. A thin, flexible tube with a tiny camera on it is inserted into your anus. The doctor can see the lining of your colon on a screen in the examining room. You might be sedated for this procedure.
Sigmoidoscopy
A sigmoidoscopy lets a doctor check just the sigmoid part of your intestine, using a slender tube with a light source and camera attached to it. During the procedure, air will be used to open up your intestine so the doctor can see it clearly. You may or may not be sedated for this procedure.
Biopsy
During a rectal biopsy, your doctor will remove a small section of your rectum or sigmoid to have it tested in a lab. The procedure is usually done during a sigmoidoscopy, so you’re likely to be awake, but the biopsy does not usually hurt.
Surgery
If your sigmoid has been injured or damaged by disease, you may have to have it surgically repaired or re-sectioned. These procedures may be done with a traditional incision or they may be performed via laparoscopy.
The sigmoid is the lower third of your large intestine. It’s connected to your rectum, and it’s the part of your body where fecal matter stays until you go to the bathroom.
If you have a sigmoid problem, you’re likely to feel pain in your lower abdomen. You may also have other symptoms like blood in your stool, loss of appetite, anemia, abdominal bloating, or fatigue.
It’s important to see a gastroenterologist if you have these symptoms because a range of diseases can affect the colon, including life-threatening conditions like cancer and Crohn’s disease.
