Crohn's and Colitis. Dr. Hillary Steinhart

       Rectum

      The last part of the large intestine is called the rectum. The wall of the rectum can stretch, up to a certain point, to allow stool to be kept inside until there is an appropriate time to evacuate. When the rectum is inflamed or somehow diseased in other ways, that ability to hold stool is reduced, and you may feel the need to go to the bathroom very frequently and urgently. In some instances, this can result in accidents with associated loss of control of bowel function, otherwise known as fecal incontinence. This need for frequent bathroom visits and the urgency that may go along with it can be one of the most troubling symptoms of inflammatory bowel disease.

       Related Parts of the Gastrointestinal Tract

      There are other parts of the gastrointestinal tract involved to a greater or lesser extent in digestion and nutrient absorption. These organs, which are typically connected to the tubular part of the gastrointestinal tract by small channels (or ducts), include the liver, gallbladder, and pancreas. The gallbladder and pancreas are usually not affected by inflammatory bowel disease. However, the liver may be affected in a small proportion of patients. Occasionally, this can lead to liver damage.

       Liver

      The liver has many functions, but the one that is most involved in digestion is bile production. Bile is similar to a detergent, in that it allows fat to be broken down and made into a form that can be dissolved or mixed with water. Normally, fat remains separate from water, like the fat floating on the top of chicken soup. This ability of bile to break up fat into small particles and disperse those particles in the watery contents of the small intestine is crucial to fat digestion and absorption.

       Gallbladder

      Bile that is produced by the liver is usually stored in the gallbladder, a small sac next to the liver, until it is needed after a meal. When the production of bile is not adequate or if bile is blocked from reaching the intestine, absorption of fat from the diet is reduced. As a result, fat may end up coming out in the stool. This appears as droplets of fat or oil in the stool.

       Pancreas

      The pancreas is a gland producing a number of digestive enzymes that enter the upper part of the small intestine. The pancreas lies very close to the duodenum and has a small duct running through it that carries the enzymes from the pancreas into the duodenum. These enzymes help break down protein, starch, and fat in the diet into components that can be easily absorbed by the intestine.

       Anus

      The anus (or anal canal) is the passageway that stool follows when it leaves the body. The primary role of the anus is to keep the stool that is present in the rectum from coming out when you don’t want it to come out. In other words, it helps to prevent fecal incontinence. Within the anal canal, there are two main muscular anal sphincters (or valves) that help to prevent the stool from coming out involuntarily.

      One of the sphincters, called the external anal sphincter, is under your conscious control. In other words, you can control or tighten this particular sphincter when trying to hold in stool or gas. The other sphincter, the internal anal sphincter, is not under voluntary control, but works reflexively at a subconscious level. Maintaining continence and ensuring the smooth and complete emptying of the rectum requires the coordination of the two anal sphincters. If either of these two sphincters is damaged or diseased, it can result in fecal incontinence.

       Signs of Inflammation

      Inflammation occurs in response to any sort of injury, whether it is from a serious or life-threatening infection or from something as small as a paper cut. The classic signs of inflammation are pain, swelling, redness, and loss of normal function.

What Goes Wrong in IBD?

      Crohn’s disease and ulcerative colitis involve inflammation of the gut. A healthy person normally has a certain degree of inflammation in the gastrointestinal tract, but in those with IBD, the inflammation is extensive and excessive.

       Excessive Inflammation

      Excessive or uncontrolled inflammation is central to the onset of Crohn’s disease and ulcerative colitis. As scientists learn more about the factors that control the degree of inflammation in the gut, they learn more about the causes of these disorders.

       Normal Intestinal Inflammation

      In the gut, the degree of inflammation that is normally present in healthy people is usually not enough to cause loss of function or to be seen by the naked eye, but when viewed under the magnification provided by a microscope, you can always see some white blood cells, called lymphocytes, present within the inner lining and just beneath the lining of the intestine.

      These defensive cells are part of the intestine’s immune system and help to protect you from potentially harmful bacteria, viruses, parasites, and proteins that aren’t normally present in the body. The amount of inflammation is closely regulated so that there is just enough immune response so as to protect against these dangers, but not so much that it will cause problems.

      Too much of a good thing may be bad, and the amount of inflammation in the intestinal lining is no exception. If there is too much inflammation or if it is not properly controlled, inflammation can cause swelling and damage to the tissues of the gastrointestinal tract. This damage can lead to problems with the normal functioning of the gastrointestinal tract, including absorption of nutrients and fluids and retaining and expelling stool at appropriate times.

      When the damage is particularly severe, the internal lining of the gastrointestinal tract can slough off, leading to a variety of symptoms, such as abdominal pain, diarrhea, blood in the stool, weight loss, and failure of children to grow properly.

       Ulcerative Colitis Signs

      Inflammation in ulcerative colitis is limited to the colon, but the extent of the inflammation within the colon varies from person to person and may vary within an individual over the course of the illness.

      Any portion of the colon may be inflamed in ulcerative colitis, leaving the remainder completely unaffected. However, the rectum is always inflamed or diseased.

       Pancolitis

      In many instances, the entire colon is inflamed. This is referred to as pancolitis. When the inflammation extends upward, it does so in a continuous fashion. In other words, there are no areas of inflammation separated from one another by normal areas of colon.

       Proctitis

      In some people with ulcerative colitis, only the rectum is inflamed. This particular form of the disease is often referred to as proctitis or ulcerative proctitis. Some differences have been observed between proctitis and the more extensive forms of the disease, such as pancolitis. Ulcerative proctitis is unusual in children and tends to be seen more often when the disease occurs for the first time in middle-aged or elderly individuals.

       Limited Extent

      Because the extent of inflammation in ulcerative proctitis is so limited — involving at most just the last 6 inches (15 cm) of the large intestine — patients suffering from that form of the disease are usually not as sick as patients with more extensive forms of ulcerative colitis.

       Crohn’s Disease Signs

      In Crohn’s disease, the inflammation can occur in any part of the gastrointestinal tract. Although it appears most often in the ileum and colon, Crohn’s disease can affect the esophagus, stomach, duodenum, and jejunum.

       Skip Lesions

      The areas of the gut affected by Crohn’s disease may