Treatment includes analgesia and immediate surgery to correct the volvulus and any underlying anatomical defect that may have given rise to the condition. The coffee bean sign on an abdominal x-ray can identify sigmoid volvulus. If volvulus remains for a significant period, the bowel may become ischaemic and necrotic, risking peritonitis. This results in pain and absolute constipation. It is more likely to occur when the sigmoid colon and its mesocolon are long. Sigmoid volvulus- Volvulus is when the bowel twists on itself, closing the lumen. The condition most frequently occurs in the elderly. They may present with blood in the faeces. If a faecolith is trapped in one of these herniations, or becomes infected, the patient will present with left iliac fossa pain. It usually occurs due to chronic constipation from a high fat, low fiber diet. In addition, another function of the sigmoid colon is to absorb water, vitamins and other nutrients from the feces, before they are moved to the rectum.ĭiverticulitis- A diverticulum is an outpouching of the wall of the bowel, and most frequently occurs in the sigmoid colon. This function is carried out with peristaltic waves that move the content of the sigmoid colon. Feces form in the descending and sigmoid colon and accumulate in the rectum before defecation. The main function of the sigmoid colon is to transports fecal matter from the descending colon to the rectum and anus. Lymphatic drainage follows the course of the inferior mesenteric vessels. The venous drainage of the sigmoid colon follows the arterial supply and venous blood is drained by the inferior mesenteric vein. The sigmoid colon receives its blood supply from the two to five sigmoidal branches of the inferior mesenteric artery, which is a branch of the abdominal aorta at 元. The sigmoid colon usually lies within the pelvis, but can be displaced into the abdomen due to its relatively mobile nature. Superior to it are loops of the ileum, and anterior to it are the bladder and uterus (in the female). It also lies anterior to the posterior abdominal wall (quadratus lumborum, iliacus, iliac crest). It runs in front of the sacrum, external iliac vessels, the left sacral plexus, left ureter, and the left piriformis muscle (a pear shaped external hip rotator that divides the greater sciatic foramen into two openings). It runs deep to the lesser (or true) pelvis, together with the bladder. As soon as the mesentery (sigmoid mesocolon) stops, the bowel is renamed the rectum (which is retroperitoneal). The lower part of the mesentery is shorter, meaning the rectum and descending colon are relatively stable. The mesentery is long in the center of the sigmoid colon, allowing it a significant range of mobility. It is intraperitoneal (unlike the rectum, ascending and descending colon, which are retroperitoneal) and is covered in mesentery, i.e. The sigmoid colon curves back on itself, and descends into the pelvis. It begins around the superior aperture of the pelvis, and is continuous with the descending colon. The S-shaped sigmoid colon is part of the hindgut and is the last region of the large bowel before the rectum. Large intestine excised with sigmoid colon highlighted Course Finally, visceral afferents relay the sensation of colonic distension. Both plexuses contain interstitial cells of Cajal, which generate the pacemaker activity of the gut essential for peristalsis. Meissner’s plexus can be found in the submucosa, while Auerbach’s myenteric plexus lies between the longitudinal and circular smooth muscle layers of the gut wall. The autonomic nervous system modulates the activity of the enteric nervous system innervating the large intestine, which includes motor and sensory neurons. Lumbar splanchnic nerves synapse in the abdominal aortic and inferior mesenteric plexuses to allow postganglionic sympathetic fibres to slow colonic motility and contract the internal anal sphincter. Most preganglionic parasympathetic neurons synapse in the wall of the hindgut, while postganglionic neurons innervate glands and muscle to increase colonic motility and to relax the internal anal sphincter. The cell bodies of the pelvic splanchnic nerves can be found in the sacral parasympathetic nucleus. The hindgut gets its blood supply from the inferior mesenteric artery, its parasympathetic nerve supply from the pelvic splanchnic nerves (S2-S4), and its sympathetic innervation from the lumbar splanchnic nerves (L1-L2).
The foregut stretches from the oesophagus to the major duodenal papilla, the midgut from the major duodenal papilla to two thirds of the transverse colon, and the hindgut from this point to the pectinate line of the rectum. The gastrointestinal system is divided into the foregut, midgut and hindgut.
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