| Descending colon | |
|---|---|
 Drawing ofcolon seen from front (descending colon coloured blue) | |
 | |
| Details | |
| Precursor | Hindgut |
| System | Digestive system |
| Artery | Left colic artery |
| Vein | Left colic vein |
| Identifiers | |
| Latin | colon descendens |
| MeSH | D044683 |
| TA98 | A05.7.03.006 |
| TA2 | 2986 |
| FMA | 14547 |
| Anatomical terminology | |
In theanatomy of humans and homologous primates, thedescending colon is the part of thecolon extending from theleft colic flexure to the level of theiliac crest (whereupon it transitions into thesigmoid colon). The function of the descending colon in thedigestive system is to store the remains of digested food that will be emptied into therectum.
The descending colon is on the left side of the body (barring any malformations). The termleft colon ishypernymous todescending colon in precise use; many casual mentions of the left colon chiefly concern the descending colon.
The descending colon extends from theleft colic flexure[2]: 1194 at the upper left part of theabdomen inferior-ward through the lefthypochondrium and lumbar regions, along the outer border of the leftkidney,[citation needed] ending at the level of theiliac crest[2]: 1194 at the lower left part of the abdomen,[citation needed] being continued thenceforth as thesigmoid colon.[2]: 1194
It is usuallyretroperitoneal (being lined by peritoneum on its anterior and lateral aspects), but may be suspended (usually short)mesentery in a minority of individuals.[2]: 1194
The arterial supply comes via theleft colic artery.[citation needed]
While the first part of the large intestine is responsible for the absorption of water and other substances from thechyme, the main function of the descending colon is to store waste until it can be removed from the body in solid form, when a person has abowel movement. Thestools gradually solidify as they move along into the descending colon.[3]
There are several diseases associated with the descending colon. Among the most common are theinflammatory bowel diseases (such asulcerative colitis orCrohn's disease) andcolon cancer.
Ulcerative colitis can affect any part of the colon (and othermucosa, such as the mouth), but when it affects the descending colon, it is calledleft-sided colitis.Inflammation andulcers on the lining of the intestine mark its presence. Symptoms of ulcerative colitis includediarrhea, bleeding, fever, abdominal pain, too much mucus in fecal material, and appetite and weight loss. Treatment methods can vary widely, ranging from changes in diet to drug therapy to corrective surgery, depending on the severity of the condition and the overall health of the patient.
When a person has Crohn's disease or Crohn's colitis, they have lesions on the tissues of the intestine; this makes it hard for the intestine to absorb water and salt. The symptoms which may develop from this disease include abdominal pain, diarrhea orconstipation, nausea and vomiting, fever,blood in the stool, weight loss, abscesses and fatigue. There is no cure for Crohn's disease although many treatments are available. Symptomatic treatment with antidiarrhoeals is common in low level cases where the inflammation is reasonably under control. Steroid and/or sulphasalazine treatment are usually the first line of drug based management, although newer drugs along theTNF inhibitor line (such asinfliximab andadalimumab) are becoming more widespread in the treatment of inflammatory colonic conditions. Diet and lifestyle changes can also be useful, as stress may exacerbate inflammatory processes.
Cancer of the descending colon is a serious disease. A person can have colon cancer yet have no symptoms in the early stages. As such, regular colorectal examinations or fecal occult blood testing are necessary for catching the disease in its early stages. However, there are some signs that can indicate colon cancer; they include abrupt changes in bowel habits, bleeding from the rectum, black stools, frequent constipation, and mucus in the stools. Treatment options depend on the stage of the cancer and the overall health of the patient.
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