Bowel Obstruction PDF

INTESTINAL OBSTRUCTION gallbladder through the bowel wall and can cause obstruction at the ileocecal valve. Intestinal obstruction is the inability of the Besid...

INTESTINAL OBSTRUCTION gallbladder through the bowel wall and can cause obstruction at the ileocecal valve. Intestinal obstruction is the inability of the Besides the findings of bowel obstruction, one intestinal tract to allow for regular passage of may note air in the biliary tree on abdominal food and bowel contents secondary to radiographs. Lymphomas may be the leading mechanical obstruction or adynamic ileus. point of intussusception and present as SBO. Adynamic ileus (paralytic ileus) is the more Bezoars are most commonly composed of common entity but is usually self-limiting and vegetable matter or pulp from persimmons. does not require surgical intervention. Patients who have undergone gastrointestinal Mechanical obstruction can be caused by either pylorplasty or pyloric resection are most intrinsic or extrinsic factors and generally susceptible to intraluminal obstruction by requires definitive intervention in a relatively bezoars. short period of time to determine the cause and minimize subsequent morbidity and mortality. Inflammatory bowel disease also may affect the small bowel at various sites. Likewise, infectious processes including abscesses may SMALL BOWEL OBSTRUCTION obstruct the bowel. Radiation enteritis is also a possible cause of SBO in patients who have The most common cause of SBO is adhesions undergone radiation therapy. following abdominal surgery. Although in most cases several months to years have passed from the time of the previous surgery, SBO LARGE BOWEL OBSTRUCTION may occur within the first few weeks following surgery. The second most common cause of Colonic obstruction is almost never caused by SBO is incarceration of a groin hernia. This hernia or surgical adhesions. Neoplasms are by can occur in infants as well as adults and should far the most common cause of LBO. Therefore, be suspected anytime there is a complaint of a anyone who has symptoms of colonic “knot” or growth in the inguinal region that obstruction should be evaluated for a neoplasm. fails to reduce with manipulation. Other sites Diverticulitis may create significant secondary that occasionally are responsible for SBO obstruction and mesenteric edema. Stricture secondary to hernia include the umbilicus, formation may occur with chronic femoral canal, and rarely, the obturator inflammation and scarring. Fecal impaction is foramen. Umbilical hernias are more readily a common problem in elderly, debilitated apparent and occur in any age group. Obturator patients and may present with symptoms of or femoral hernias are much less common. colonic obstruction. Elderly females are particularly susceptible to these hernias, which may present with femoral The next most frequent cause of LBO after or medial thigh pain. Finally, a defect in the cancer and Diverticulitis is sigmoid volvulus. mesentery itself may cause intestinal Elderly, bedridden, or psychiatric patients who obstruction. are taking anticholinergic medication are most often subject to this mechanical problem. A Other causes of SBO are much less common history of constipation may precede the and generally are the result of intraluminal or volvulus and presenting symptoms. intramural processes. Primary small bowel Radiographic appearance is usually classic. lesions include polyps, lymphoma, or Finally, although much less common, cecal adenocarcinoma. An unusual cause of volvulus also may cause LBO. There is a intraluminal obstruction is gallstone ileus. In higher incidence of cecal volvulus in gravid this situation, a gallstone has eroded from the patients. W:\Academy EMS\ACP yr1(ICP)\ACP Year One 2014-2015\Module 3 Resp_Gastro_BLS Recert\Day 9 Gastroenterology\Gastroenterology_Handouts\Bowel Obstruction.doc  less intense and more constant. If the PATHOPHYSIOLOGY obstruction is proximal, vomiting is usually present. The vomitus in proximal obstruction is Normal bowel contains gas as well as gastric usually bilious but is feculent in distal ileal secretions and food. Intraluminal accumulation obstruction. The pain of LBO is usually of gastric, biliary, and pancreatic secretions hypogastric, LBOs may be associated with continues even if there is no oral intake. As feculent vomitus. obstruction develops, the bowel becomes congested, and there is failure of intestinal Other features that are consistently present with contents to be absorbed. Vomiting and obstruction of small bowel or colon include the decreased oral intake follow. The combination inability to have a bowel movement or pass of decreased absorption, vomiting and reduced flatus. Care should be taken to avoid the intake leads to volume depletion with diagnosis of constipation because this symptom hemoconcentration and electrolyte imbalance is secondary to partial or complete obstruction. and ultimately can cause renal failure or shock. Partial bowel obstruction, however, is often associated with regular passage of stool and Bowel distension often accompanies flatus. mechanical obstruction. Distension is due to the accumulation of fluids in the bowel lumen, Physical findings vary depending on the site, an increase in intraluminal pressure with duration and etiology of the pathologic process. enhanced peristaltic contractions, and air Early symptoms usually are associated with swallowing. When intraluminal pressure some abdominal distension, often impressive exceeds capillary and venous pressure in the with colonic obstruction yet not readily bowel wall, absorption and lymphatic drainage apparent in cases of incarcerated hernia. decrease. At this stage, bacteria may enter the Abdominal tenderness may be minimal and bloodstream, the bowel becomes ischemic, and diffuse or localized and sever. Patients who septicaemia and bowel necrosis can develop. have developed peritonitis will have severe Shock ensures rapidly. Mortality approaches tenderness. The abdomen may be tympanitic to 70 percent if bowel obstruction has been percussion. Mechanical obstruction will allowed to progress this far. With a closed-loop produce active, high-pitched bowel sounds with obstruction, this sequence of events may occur occasional “rushes”. If obstruction has been more rapidly. In this instance, there is no present for several hours, peristaltic waves and proximal escape for bowel contents. Examples bowel sounds may be diminished. Patients of closed-loop obstruction include an with an adynamic ileus may have some incarcerated hernia and complete colon abdominal distension associated with obstruction in the presence of a closed ileocecal diminished or absent bowel sounds. Careful valve. search for localized or rebound tenderness is essential to rule out the possibility of CLINICAL FEATURES gangrenous or perforated bowel, which required immediate surgical intervention. The site and nature of the obstruction and the pre-existing condition of the patient will Elderly patients have signs and symptoms that determine the clinical presentation. Almost all are similar to younger patients with intestinal patients will have abdominal pain. The pain obstruction. Adhesions and hernias are generally is described as crampy and common causes for SBO in this age group, intermittent. Pain of mechanical SBO is often whereas carcinomas are the most likely etiology episodic, usually lasting for a few minutes at a of LBO because of the increased likelihood of time, and it may be periumbilical or more cancer as people age. Elderly patients who are diffuse. In adynamic ileus, the pain tends to be debilitated or confused or who are on multiple W:\Academy EMS\ACP yr1(ICP)\ACP Year One 2014-2015\Module 3 Resp_Gastro_BLS Recert\Day 9 Gastroenterology\Gastroenterology_Handouts\Bowel Obstruction.doc medications may be unable to give a detailed coverage preoperatively because the risk of history. Patients over 70 years old are more infection and septicaemia is significant in most likely to succumb secondary to complications conditions. There are many possible regimens. of bowel obstruction. Careful examination for Monotherapy could be tazobactampiperacillin characteristic bowel sounds and masses or 3.375 g IV q6h or ampicillin-sulbactam 3.00g blood in stool and radiographic investigation IV q6h. often will distinguish bowel obstruction from ileus. Emptiness of the left iliac fossa has been If adynamic ileus is the primary problem or the reported to be a reliable sign of sigmoid diagnosis is uncertain, conservative measures, volvulus. including intravenous fluids, nasogastric decompression, and observation, generally are All patients with abdominal pain or distension effective in allowing the bowel to resume should be examined for signs of organomegaly normal activity and function. Any medication or masses that may suggest a cause of the that inhibits bowel mobility should be obstruction. A rectal examination may identify discontinued. Abdominal CT contrast fecal impaction, rectal carcinoma, occult blood, radiography is used commonly to distinguish or stricture. The absence of stool or air in the partial SBO from ileus or for the differentiation vault may aid in the diagnosis of bowel of strangulated from simple SBO. obstruction, but its presence does not eliminate a more proximal obstruction because patients PSEUDO-OBSTRUCTION may not be able to evacuate pre-existing rectal contents. A pelvic examination should be Intestinal pseudo-obstruction (Ogilvie performed to identify and gynecologic syndrome) also may mimic bowel obstruction. pathology causing obstruction. A vaginal Although any segment of bowel may be pessary can cause colonic obstruction due to affected, low colonic obstruction is the most extrinsic compression of the colon. common clinical presentation. Large amounts of gas will be present in the large intestine. TREATMENT Radiographs reveal a dilated colon with well- defined septa and haustral markings and very If a true mechanical obstruction is diagnosed, little fluid, making air-fluid levels uncommon. then surgical intervention is often required. Patients may be using anticholinergic or Prior to surgical intervention, a nasogastric tube Tricyclic antidepressants, which depress should be inserted to remove excess bowel motility. One must avoid the use of barium contents and air. Intravenous fluid replacement studies because the patient may be unable to is needed because of loss of absorptive evacuate the barium. Preference should be capacity, decreased oral intake, and vomiting. given to colonoscopy after digital rectal Patients can be monitored prior to surgical examination as an early intervention to rule out intervention by the response of blood pressure true obstruction or significant lesions. and heart rate and measurement of urine output. Colonoscopy also will treat the pseudo- Surgery should not be delayed unnecessarily by obstruction by decompression. Surgery usually attempting to use long intestinal tubes (Baker is not helpful and may be harmful. Cantor, or Miller-Abbott) or excessive testing. Neostigmine infusion is reported to be effective A volvulus of the sigmoid colon usually will at relieving pseudo-obstruction in patients who decompress via sigmoidoscopy and insertion of had not responded to conservative means. a rectal tube. Should a closed-loop obstruction, bowel necrosis, or cecal volvulus be suspected, then surgical intervention should be performed without delay. All patients with mechanical obstruction require broad-spectrum antibiotic W:\Academy EMS\ACP yr1(ICP)\ACP Year One 2014-2015\Module 3 Resp_Gastro_BLS Recert\Day 9 Gastroenterology\Gastroenterology_Handouts\Bowel Obstruction.doc