Disorders of Colonic Physiolog


The term constipation is often used by patients to describe a number of different defecatory symptoms (infrequent bowel movements, difficult or painful    movements, etc.). Constipation is generally defined clinically as one or fewer spontaneous bowel movements or stools per week.

  1. Etiologies include medications (narcotics, anticholinergics, antidepressants, calcium channel blockers), hypothyroidism, hypercalcemia, dietary factors (low fluidor fiber intake), decreased exercise, neoplasia, and neurologic disorders (e.g., Parkinson disease, multiple sclerosis). Abnormalities of pelvic floor function (obstructed defecation), such as paradoxical puborectalis muscle function or intussusception of the rectum (internal or external rectal prolapse), may result in constipation, as may idiopathic delayed transit of feces through the colon (dysfunction of the intrinsic colonic nerves or colonic inertia).
  2. Evaluation. Change in bowel habits is a common presentation of colorectal neoplasia. The initial evaluation of constipation should include digital rectal exam and colonoscopy. If this workup is negative and the patient fails to respond to a trial of fiber supplementation and increased fluid intake, the next step is a colonic transit time study. On day 0, the patient ingests an enteric-coated capsule containing 24 radiopaque rings. Abdominal plain x-rays are obtained on days 3 and 5. Normal transit results in 80% of the rings in the left colon by day 3 and 80% of all the rings expelled by day 5. The persistence of rings throughout the colon on day 5 indicates colonic inertia. When the rings stall in the rectosigmoid region, functional anorectal obstruction (obstructed defecation) may be present. This may be evaluated with cine defecography, anorectal manometry, or both; the task is to look for nonrelaxation of the puborectalis muscle or internal intussusception of the rectum
  3. Treatment of colonic inertia initially includes laxatives (polyethylene glycol, 12 oz/day), fiber (psyllium 9 g/day), increased exercise, and avoidance of predisposing factors. In patients with long-standing, debilitating symptoms refractory to nonopetive measures, total abdominal colectomy with ileorectal anastomosis may prove curative. The risk of total intestinal inertia after surgery is significant, and the patient should understand this.

B. Colonic pseudo-obstruction (Ogilvie syndrome)


  1. A. Colonic pseudo-obstruction (Ogilvie syndrome)   is a profound colonic ileus without evidence of mechanical obstruction. It most commonly occurs in critically ill or institutionalized patients. Colonic obstruction or volvulus must be ruled out; Hypaque enema is often therapeutic as well as diagnostic. The initial management consists of nasogastric decompression, rectal tube placement, an aggressive enema regimen (e.g., cottonseed and docusate sodium enema), correction of metabolic disorders, and discontinuation of medications that decrease colonic motility. Neostigmine intravenous infusion (2 mg/hour) in a monitored setting has been shown to be useful in resistant cases (N Engl J Med 1999;341:137). Rapid cecal dilation or a cecal diameter greater than 12 cm on plain abdominal x-rays requires prompt colonoscopic decompression. This is successful in 70% to 90% of cases, with a recurrence rate of 10% to 30% (recurrence is usually amenable to repeat colonoscopic decompression). Laparotomy is reserved for patients with peritonitis, at which time a total abdominal colectomy with end ileostomy should be performed.                                                                              3.Volvulus  is the twisting of an air-filled segment of bowel about its mesentery and accounts for nearly 10% of bowel obstruction in the United States
  2. 1  Sigmoid volvulus accounts for 80% to 90% of all volvulus and is most common in elderly or institutionalized patients and in patients with a variety of neurologic disorders. It is an acquired condition resulting from sigmoid redundancy with narrowing of the mesenteric pedicle.
  3. Diagnosis is suspected when there is abdominal pain, distention, cramping, and obstipation. Plain films often show a characteristic inverted-U, sausage-like shape of air-filled sigmoid pointing to the right upper quadrant. If the diagnosis is still in question and gangrene is not suspected, water-soluble contrast enema usually shows a bird’s-beak deformity at the obstructed rectosigmoid junction.
    • In the absence of peritoneal signs, treatment involves sigmoidoscopy, with the placement of a rectal tube beyond the point of obstruction. The recurrence rate after decompressive sigmoidoscopy approaches 40%; therefore, elective sigmoid colectomy should be performed in acceptable operative candidates. If peritonitis is present, the patient should undergo laparotomy and Hartmann procedure (sigmoid colectomy, end-descending colostomy, and defunctionalized rectal pouch). An alternative in the stable patient without significant fecal soilage of the peritoneal cavity is sigmoidectomy, on-table colonic lavage and colorectal anastomosis with or without proximal fecal diversion (loop ileostomy).
    • 2. Cecal volvulusoccurs in a younger population than does sigmoid volvulus, likely due to congenital failure of retroperitonealization of the cecum (in axial volvulus) or a very redundant pelvic cecum that flops into the left upper quadrant to kink the right colon (in bascule volvulus).
      • Diagnosis. Presentation is similar to that of distal small-bowel obstruction, with nausea, vomiting, abdominal pain, and distention. Plain films show a coffee bean–shaped, air-filled cecum with the convex aspect extending into the left upper quadrant. A Hypaque enema may be performed, which shows a tapered (in axial volvulus) or linear cutoff (in bascule volvulus) of the ascending colon.
      • Management involves urgent laparotomy and right hemicolectomy. Ileocolostomy is preferred; otherwise, ileostomy and mucous fistula are performed if concern about patient stability or bowel viability exists. Cecopexy has an unacceptably high rate of recurrent volvulus, and although cecectomy will prevent recurrence, it is technically more challenging than formal right hemicolectomy.
      • 3.Transverse volvulus is rare and has a clinical presentation similar to that of sigmoid volvulus. Diagnosis is made based on the results of plain films (which show a dilated right colon and an upright, U-shaped, dilated transverse colon) and contrast enema or computed tomography (CT). Endoscopic decompression has been reported, but operative resection is usually required.
    • Diverticular disease
      • General considerations. Colonic diverticula are false diverticula in which mucosa and submucosa protrude through the muscularis propria. Outpouchings occur along the mesenteric aspect of the antimesenteric taenia where arterioles penetrate the muscularis. The sigmoid colon is most commonly affected, perhaps owing to decreased luminal diameter and increased luminal pressure. Diverticula are associated with a low-fiber diet and are rare before age 30 years (<2%), but the incidence increases with age to a 75% prevalence after age 80 years. Right-sided diverticula are rare, comprising less than 10% of diverticular disease.
      • Complications
        • Infection (diverticulitis). Microperforations can develop in long-standing diverticula, leading to fecal extravasation and subsequent peridiverticulitis. Diverticulitis develops in 10% to 25% of patients with diverticula.
          • Presentation is notable for left-lower-quadrant pain (which may radiate to the suprapubic area, left groin, or back), fever, altered bowel habit, and urinary urgency. Physical examination varies with severity of the disease, but the most common finding is localized left-lower-quadrant tenderness. The finding of a mass suggests an abscess or phlegmon.
          • Evaluation by CT scan and complete blood count (CBC) is the standard of care. CT findings may include segmental colonic thickening, focal extraluminal gas, and abscess formation. Neither sigmoidoscopy nor contrast enema is recommended in the initial workup of diverticulitis because of the risk of perforation or barium or fecal peritonitis, respectively.
          • Treatment is tailored to symptom severity.
            • Mild diverticulitis can be treated on an outpatient basis with a clear liquid diet and broad-spectrum oral antibiotics for 10 days.
            • Severe diverticulitis is treated with complete bowel rest, intravenous fluids, narcotic analgesics, and broad-spectrum parenteral antibiotics (e.g., ciprofloxacin and metronidazole). If symptoms improve within 48 hours, a clear liquid diet is resumed, and antibiotics are given orally when the fever and leukocytosis resolve. A high-fiber, low-residue diet is resumed after 1 week of pain-free tolerance of a liquid diet. Fiber supplements and stool softeners should be given to prevent constipation. A colonoscopy or water-soluble contrast study must be performed after 4 to 6 weeks to rule out colon cancer, inflammatory bowel disease, or ischemia as a cause of the segmental inflammatory mass.

          • The lifetime likelihood of recurrence is 30% after the first episode and more than 50% after the second episode of diverticulitis. Therefore, resection is considered 4 to 6 weeks after treatment of a complicated initial attack of diverticulitis or after treatment of the first recurrence. The belief that diverticulitis in young patients (<50 years) somehow is more virulent is largely anecdotal. Large retrospective reviews have demonstrated that young patients have the same risk of recurrent diverticulitis following an uncomplicated attack as their older counterparts (Dis Colon Rectum 2006;49:1341).
          • Elective resection for diverticulitis usually consists of a sigmoid colectomy. The proximal resection margin is through uninflamed, nonthickened bowel, but there is no need to resect all diverticula in the colon. The distal margin extends to normal, pliable rectum, even if this means dissection beyond the anterior peritoneal reflection. Recurrent diverticulitis after resection is most frequently related to inadequate distal margin of resection.
        • Diverticular abscess is usually identified on CT scan. A percutaneous drain should be placed under radiologic guidance. This avoids immediate operative drainage, allows time for the inflammatory phlegmon to be treated with intravenous antibiotics, and turns a two- or three-stage procedure into a one-stage procedure. A low pelvic abscess may be drained into the rectum via a transanal approach.
        • Generalized peritonitis is rare and results if diverticular perforation leads to widespread fecal contamination. In most cases, resection of the diseased segment is possible (two-stage procedure), and a Hartmann procedure is performed. The colostomy can then be reversed in the future. An alternative in the management of the stable patient undergoing urgent operation for acute diverticulitis without significant fecal contamination is sigmoidectomy, on-table colonic lavage, and colorectal anastomosis with or without proximal fecal diversion (loop ileostomy).
        • Fistulization secondary to diverticulitis may occur between the colon and other organs, including the bladder, vagina, small intestine, and skin. Diverticulitis is the most common etiology of colovesical fistulas. Colovaginal and colovesical fistulas usually occur in women who have previously undergone hysterectomy. Colocutaneous fistulas are uncommon and are usually easy to identify. Coloenteric fistulas are likewise uncommon and may be entirely asymptomatic or result in corrosive diarrhea.
          • The presentation of enterovesical fistula includes frequent urinary tract infections and often is unsuspected until fecaluria or pneumaturia is noted. CT findings of air and solid material in a noninstrumented bladder confirm the diagnosis. Lower endoscopy, barium enema, intravenous pyelography, and cystoscopy often fail to demonstrate the fistula.
          • A colovaginal fistula is usually suspected based on the passage of air or gas per vagina. The fistula may be difficult to identify on physical examination or the previously mentioned tests. The presence of methylene blue staining on a tampon inserted in the vagina following dye instillation in the rectum is diagnostic.
          • Immediate treatment of the inflammatory mass adjacent to the bladder is as previously described for severe diverticulitis [Section II.D.2.a(3)(b)]. Colonoscopy is performed after 6 weeks to rule out other possible etiologies, including cancer or inflammatory bowel disease. Elective sigmoid resection is performed after preoperative placement of temporary ureteral catheters. Ureteral catheters can be very helpful in identifying the distal ureter in the inflammatory pericolonic mass, thereby shortening the operative time. Usually, the fistula tract can be broken using finger fracture, and the bladder defect can be repaired in a single layer. A Foley catheter is left in place for 7 to 10 days to allow this defect to heal. A colovaginal fistula is managed in a similar fashion. It may be helpful to interpose omentum between the colorectal anastomosis and the bladder or vaginal defect.

    • Acquired vascular abnormalities and lower gastrointestinal (GI) bleeding are more common in elderly patients than in younger individuals. Most cases of massive lower GI hemorrhage stop spontaneously, but surgery is required in 10% to 25% of cases.
      • Etiologies (with relative approximate incidence) of lower GI bleeding in industrialized nations include the following:
        • Diverticulosis (60%). The media of the perforating artery adjacent to the colonic diverticulum may become attenuated and eventually erode. This arterial bleeding usually is bright red and is not associated with previous melena or chronic blood loss. Bleeding most commonly occurs from the left colon. Urgent resection of the affected colonic segment should be considered in patients with active ongoing bleeding [>6 units packed red blood cells (RBCs)/24 hours]. Elective resection of the affected colonic segment should be performed in patients with recurrent bleeding or need for long-term anticoagulation or in those in whom excessive blood loss may be poorly tolerated.
        • Inflammatory bowel disease (IBD) (13%). Bleeding due to IBD tends to occur in a younger population; it is more commonly due to ulcerative colitis than Crohn disease.
        • Benign anorectal disease (11%) is discussed later in this chapter.
        • Neoplasia (10%) of the colon and rectum rarely presents with massive blood loss, but rather with chronic microcytic anemia and possible syncope. Hemorrhage following polypectomy can occur up to 1 month postprocedure and has an incidence of 3% in some series.
        • Angiodysplasias (< 5%) are small arteriovenous malformations composed of small clusters of dilated vessels in the mucosa and submucosa. An acquired condition, they rarely occur before age 40 years and are more common in the right colon (80%). Diagnosis can be made by colonoscopy or angiographic features (delayed filling of a dilated venule).
      • Massive lower GI bleeding is defined as hemorrhage distal to the ligament of Treitz that requires more than 3 units of blood in 24 hours. Management consists of simultaneously restoring intravascular volume and identifying the site of bleeding so that treatment may be instituted.
        • Resuscitation is performed using a combination of isotonic crystalloid solutions and packed RBCs as needed, administered via short, large-bore peripheral intravenous catheters.
        • Diagnosing the site of bleeding is more important initially than identifying the cause. Gastric lavage via a nasogastric tube must be performed to rule out an upper GI source of bleeding. Digital rectal exam can eliminate hemorrhoidal bleeding. The choice of localizing study depends on the estimate of bleeding rate.
          • Nuclear scan using technetium-99m sulfur colloid or tagged RBCs can identify bleeding sources with rates as low as 0.1 to 0.5 mL/minute. Tagged RBC scan can identify bleeding up to 24 hours after isotope injection, which may be important in patients who bleed intermittently. Although these scans can accurately demonstrate ongoing bleeding, they do not definitively identify the anatomic source of bleeding; hence, planning a segmental gastrointestinal resection based on this study is not entirely reliable. A rapidly positive scan indicates that angiography has a high likelihood of identifying the source.
          • Mesenteric angiography should be performed in the patient with a positive nuclear medicine bleeding scan with massive lower GI bleeding to definitively identify the anatomic source of bleeding. Angiography can localize bleeding exceeding 1 mL/minute and allows either therapeutic vasopressin infusion (0.2 unit/minute) or embolization, which together are successful in stopping the bleeding in 85% of cases. The advantage is that this can convert an emergent operation in an unstable patient with unprepared bowel to an elective one-stage procedure.

          • Colonoscopy frequently fails to identify the source of massive lower GI bleeds. With slower bleeding after the administration of an adequate bowel preparation over 2 hours, colonoscopy offers the therapeutic advantages of injecting vasoconstrictive agents (epinephrine) or vasodestructive agents (alcohol, morrhuate, sodium tetradecyl sulfate) or applying thermal therapy (laser photocoagulation, electrocoagulation, heater probe coagulation) to control bleeding.
          • In the rare patients who continue to bleed with no source identified, laparotomy should be considered. Intraoperative small-bowel enteroscopy may be performed if the source is not obvious at the time of exploration. If the source is still not identified, total colectomy with ileorectostomy or end-ileostomy is performed. This is associated with an incidence of recurrent bleeding of less than 10%, but the mortality rate for patients who rebleed is 20% to 40%. It is now rare for a patient to undergo resection for lower GI bleeding without preoperative localization.
      • Ischemic colitis results from many causes, including venous or arterial thrombosis, embolization, iatrogenic inferior mesenteric artery (IMA) ligation after abdominal aortic aneurysm repair, thromboangiitis obliterans, and polyarteritis nodosa. It is idiopathic in the majority of patients. Patients are usually elderly and present with lower abdominal pain localizing to the left and melena or hematochezia. The rectum often is normal on proctoscopy, owing to its dual vascular supply. Contrast enema may show thumbprinting that corresponds to submucosal hemorrhage and edema. Diagnosis depends on the appearance of the mucosa on colonoscopy. Although it may occur anywhere in the colon, disease is present most frequently at the watershed areas of the splenic flexure and sigmoid colon. In the presence of full-thickness necrosis or peritonitis, emergent resection with diversion is recommended. Patients without peritonitis or free air but with fever or an elevated white blood cell count may be treated with bowel rest, close observation, and intravenous antibiotics. Up to 50% of patients develop focal colonic strictures eventually. These are treated with serial dilations or segmental resection once neoplasm is ruled out.
      • Radiation proctocolitis results from pelvic irradiation for uterine, cervical, bladder, prostate, or rectal cancers. Risk factors include a dose of greater than 6,000 cGy, vascular disease, diabetes mellitus, hypertension, prior low anterior resection, and advanced age. The early phase occurs within days to weeks; mucosal injury, edema, and ulceration develop, with associated nausea, vomiting, diarrhea, and tenesmus. The late phase occurs within weeks to years, is associated with tenesmus and hematochezia, and consists of arteriolitis and thrombosis, with subsequent bowel thickening and fibrosis. Ulceration with bleeding, stricture, and fistula formation may occur. Medical treatment may be successful in mild cases, with the use of stool softeners, steroid enemas, and topical 5-aminosalicylic acid products. If these measures fail, transanal application of formalin 4% to affected mucosa may be efficacious in patients with transfusion-dependent rectal bleeding. Patients with stricture or fistula require proctoscopy and biopsy to rule out locally recurrent disease or primary neoplasm. Strictures may be treated by endoscopic dilation but often recur. Surgical treatment consists of a diverting colostomy and is reserved for medical failures, recurrent strictures, and fistulas. Proctectomy is rarely required and is usually associated with unacceptable morbidity and mortality.