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LARGE INTESTINE5 parts: ascending, transverse, descending, sigmoid colon and rectum Begins at the cecum - ileocecal valve Appendix projects from the convergence of the teniae at the lowest part of the cecum Ascending colon is retroperitoneal, suspended from above at the hepatic flexure by hepatocolic ligament

LARGE INTESTINE ANATOMYTransverse colon is intraperitoneal, from hepatic flexure to the splenic flexure, suspended by splenocolic and gastrocolic ligaments Descending colon is retroperitoneal, continued by sigmoid colon Sigmoid colon is intraperitoneal Rectum begins at the level of S3, 12-15 cm. in length, passes the pelvic diaphragm, ends in the anal canal

LARGE INTESTINE ANATOMYRectum describes 3 lateral curves Rectal ampulla is the most distal portion of the rectum Rectum ends at the anorectal junction Anal canal, 4 cm. in length, ends at the anal verge Internal sphincter- smooth inner muscle with involuntary control Striated external sphincter- under voluntary control

LARGE COLON HISTOLOGYColonic wall- 4 layers: mucosa, submucosa, muscularis propria, serosa Mucosa is lined by columnar epithelium, malignant cells confind to this are reffered to as carcinoma in situ 1-2 cm. above the dentate line is a zone of transitional epithelium having both columnar and squamous cells Below the dentate line, the anal canal is lined by modified skin- no hair follicle, no seb. glands

LARGE COLON HISTOLOGYSubmucosa contains blood vessels and lymphatics Tumor cells must penetrate this layer to gain access to the lymphatic system, enabling metastatic spread Submucosa is the strongest layer of the bowel wall Muscularis propria is made up of circular and longitudinal smooth muscles Rectum lacks a serosal layer According to the depth invasion- Dukes staging

LARGE BOWEL ARTERIAL SUPPLY1.- Ileocolic art.- terminal branch of SMA 2.- Right colic art.- from SMA or ileocolic 3.- Middle colic art.- from SMA 4.- Left colic art- from IMA 5.- Rectosigmoid art.- from IMA 6.- Superior rectal art.- from IMA 7.- Middle rectal art.- from internal ileal 8.- Inferior rectal art.- from internal pudental art.

LARGE BOWEL VENOUS RETURNColorectal veins parallel the arteries similarly named Colon veins drain into the portal system Rectal veins drain into the portal and systemic venous system

LARGE BOWEL PHYSIOLOGYStorage, transport, concentration of intestinal waste products Na, chloride, water are actively absorbed The absorbative capacity of the colon is about 2 l/ day Colonic mucosa secretes K and bicarbonateexcessive diarrhea may result in potassium and bicarbonate losses and metabolic acidosis Colonic gas originates from both swallowed air and the by-products of bacterial reactions

EVALUATION OF THE COLON, RECTUM AND ANUSHistory: Recent and past bowel habit Pattern of rectal bleeding Consistency of stool Family history of IBD, colonic polyps, cancer Nature of pain

PHYSICAL EXAMINATIONAnorectal examination in the left lateral decubitus: Inspection of the perianal region Digital rectal examination Anoscopy Sigmoidocopy Examination of stools

INVESTIGATIONS1. 2. 3. 4. 5. Plain abdominal X ray Barium enema Endoscopy +/- biopsy Abdominopelvic CT Endoscopic ultrasonography

PLAIN ABDO X RAYAssess the pattern of air and fluid Pneumoperitoneum Gaseous distention of small or large bowel Fluid level- topography

Routine examination of an acute abdomen Patient in stand up position during exam.

This upright abdominal x-ray shows multiple airfluid levels, which are indicative of a bowel obstruction.Dilation of the large intestine, indicated by the larger caliber of the air-filled segments and the transverse lines called haustra. The air extends into the left lower quadrant and pelvis, indicating that the obstructive lesion is quite distal, in the recto-sigmoid region. Therefore this is a distal large bowel obstruction

A 50 year old man underwent an above-knee amputation to remove his gangrenous leg. He developed nausea and dyspneoa on the 4th postoperative day. On examination he had tachypnoea and tachycardia, but was apyrexic. On chest auscultation air entry was reduced bilaterally at the lung bases. The abdomen, though distended, was not tender and the bowel sounds were audible. Digital rectal examination was unremarkable.

Acute colonic pseudo-obstruction or Ogilvie syndromeThe chest radiograph shows dilated loops of large bowel. This finding is confirmed on the plain abdominal film which shows a picture of large bowel obstruction. There is no evidence of free gas under the diaphragm. A subsequent CT scan of the abdomen did not reveal a mechanical cause of the condition and colonoscopic decompression was theraputic.

Differential Mechanical colonic obstruction Toxic megacolon Mesenteric ischaemia

Acute colonic pseudo-obstruction or Ogilvie syndrome is a condition with clinical and radiological features of colonic obstruction without any evidence of a mechanical cause.Abdominal distension in this patient accounted for the respiratory distress Pathophysiology of Ogilvie syndrome is not clearly understood, though it is thought to be due to an imbalance in the autonomic innervation leading to a functional bowel obstruction. Ogilvie syndrome typically occurs in patients hospitalized with a significant illness e.g. severe cardio-respiratory disorders, sepsis, electrolyte imbalance and postoperatively. Left untreated it can progress to colonic perforation and peritonitis.

Complete colonic obstruction from an obstructing carcinoma in the descending left colon with proximal airfluid levels. The absence of air distally in the rectum or the sigmoid is suggestive of complete obstruction. The ileocecal valve is competent, and thus, there is no small bowel air.

Upright radiograph: complete small bowel obstructionUpright radiograph shows multiple air-fluid levels of varying size arranged in inverted Us. In the right lower pelvis, a loop of small bowel is seen a finding suggestive of adhesive obstruction.

CONTRAST ENEMAIt is not an emergent investigation Requires bowel preparation Instant enema in rare occasions Indicated in assessing colon polyps, tumors or diverticulosis. If perforation is suspected- contrast substance used-gastrografin



ENDOSCOPIC STUDIESRigid proctorectoscopy- can examine 25 cm. from the anal verge Position of the patient-lateral decubitus or prone jacknife position Bowel preparation- 2 enemas only

COLONOSCOPYCan assess the entire length of the colon Concurrent biopsy and polypectomy is possible Inssuflation of air induces some discomfort for the patient Bowel preparation mandatory

COLONOSCOPYINDICATIONS: The treatment of polyps Suspicious colon cancer Evaluation of a positive fecal occult blood test Follow-up in pts. with IBD Bowel preparation: - Nil by mouth for 8 h. prior to the procedure - Laxatives - Enemas



IRRITABLE BOWEL SYNDROMENamed in the past spastic colon Clinical features: Episodic cramping abdo pain at any time of the day Episodes can last from 15 min.- several hours The pain is unrelated to meals It may occur anywhere in the abdomen Symptoms occur daily for weeks at a time Worse at times of sress Eratic bowel habit- loose stools/constipation Abdominal distention/excess flatus

IRRITABLE BOWEL SYNDROMEPathophysiology- low fiber diet seems to play a part Colonic motility studies abnormal rises in intraluminal pressure, disordered peristalsis

The small volume of feces-dehydrated, fragmented- rabbit pallets Imbalance in gut hormonal and autonomic control systems

IRRITABLE BOWEL SYNDROMEManagement Carcinoma and diverticulosis must be excluded by colonoscopy/barium enema Treatment: - reasurence - adjusting the diet to include adequate fibre - bulking agents, antispasmodic drugs - codeine phosphate-analgesic for occasional use - relaxation therapy

SIGMOID VOLVULUSPathophysiology Chronic constipation- enlarged, elongated, atonic sigmoid colon= dolicomegacolon Occasionally, the huge sygmoid loop, heavy with feces becomes twisted on its mesenteric pedicle- closed loop obstruction Venous infarction- perforation-peritonitis

SIGMOID VOLVULUSClinical features: Elderly, mentally handicaped Abdominal distension, abdominal pain Assymetrical distension, tympanism Variable degree of tenderness Absolute constipation for at least 24 hours Perforation- peritonitis PR- the rectum is empty

SIGMOID VOLVULUSManagement: Plain abdominal x ray- single grossly dilated sigmoid loop often reaching the xiphisternum An erect film- a characteristic inverted U of bowel gas in the upper abdomen with fluid level at the same height in the two bowel limbs in the lower abdomen An abdominal lateral decubitus x ray may reveal two parallel fluid levels running the full length of the abdomen

SIGMOID VOLVULUSManagement Rectoscope is passed as far as possible into the rectum and a flatus tube inserted through it The end of the flatus tube is then gently manipulated through the twisted bowel into the obstructed loop If this is successful there is a gush of liquid feces and flatus relieving the obstruction The flatus tube left in-situ for 24 hours

SIGMOID VOLVULUSAcute large bowel obstructioninstant enema may define the lesion Persistent volvulus- urgent operation Sigmoidectomy with colorectal anastomosis / Hartmann procedure After a period of recovery following Hartmann op.- redo colorectal anastomosis

DIVERTICULAR DISEASECommon condition- chronic lack of dietary fiber Patients over 60 years of age Female are more affected

DIVERTICULAR DISEASEPathophysiology Chronic constipation- hypertrophy of the colonic wall