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A. Mechanical obstruction
Mechanical obstruction can be partial, allowing some distal passage of gas or fluid, or complete, with total occlusion of the lumen. In a strangulated obstruction, the involved bowel has vascular compromise, which can ultimately lead to infarction and perforation of the intestinal wall. No clinical or laboratory values reliably differentiate simple from strangulated obstructions, although constant, as opposed to crampy, abdominal pain, fever, leukocytosis, and acidosis should raise the index of suspicion considerably. Ileus implies failure of peristalsis without mechanical obstruction. It can be caused by recent abdominal operations, electrolyte disturbances, peritonitis, systemic infections, bowel ischemia, trauma, or medications.
- Adhesions are the most common cause of small-bowel obstruction in U.S. adults. Most adhesions result from previous abdominal operations or inflammatory processes, although isolated congenital adhesions can occur as well.
- Incarcerated hernias are the second-most-common cause of small-bowel obstructions in industrialized nations. They are the most common cause of SBO worldwide. In industrialized nations, they are the most common cause of SBO in children and in patients without prior abdominal surgery.
- Intussusception occurs when one portion of bowel (the intussusceptum) telescopes into another (the intussuscipiens). Tumors, polyps, enlarged mesenteric lymph nodes, or even a Meckel diverticulum may serve as lead points of the telescoped segment. Unlike in children, intussusception in an adult should always prompt a workup for bowel pathology.
- Volvulus is often caused by adhesions or congenital anomalies such as intestinal malrotation. It more commonly occurs in the colon.
- Strictures secondary to ischemia, inflammation (Crohn disease), radiation therapy, or prior surgery may cause obstruction.
- Gallstone ileus occurs as a complication of cholecystitis. Fistulization between the biliary tree and the small bowel allows gallstones to travel distally and become lodged, typically at the ileocecal valve.
- External compression from tumors, abscesses, hematomas, or other masses can cause functional SBO.
- Foreign bodies typically pass without incident. Items presenting with obstruction may require operation if they cannot be retrieved endoscopically. Pathology due to swallowing foreign bodies is more common in institutionalized patients.
Diagnosis of SBO incorporates the full range of history, exam, and radiographic findings.
Signs and symptoms
- Proximal small-bowel obstructions present with early bilious vomiting. Distal obstructions present later, and vomit can be thick and feculent.
- Abdominal distention typically increases the more distal the obstruction.
- Abdominal pain is poorly localized and often characterized as crampy and intermittent (i.e., colicky).
- Obstipation, complete absence of flatus and bowel movement, occurs after the bowel distal to a complete obstruction is evacuated.
- With a persistent obstruction, hypovolemia progresses due to impaired absorption, increased secretion (“third spacing”), and vomiting.
- Bloody bowel movements suggest strangulation or a diagnosis other than obstruction.
- Abnormal vital signs are generally indicative of hypovolemia (e.g., tachycardia and hypotension).
- Abdominal exam may reveal distension, prior surgical scars, and hernias. Palpation should make note of any masses. Peritoneal signs mandate prompt surgical evaluation and treatment. Digital rectal examination may reveal the presence of an obstructing rectal tumor or impacted stool.
- Laboratory evaluation. In early stages of a small-bowel obstruction, laboratory values may be normal. As the obstruction progresses, lab values reflect dehydration, most commonly demonstrating a contraction alkalosis with hypochloremia and hypokalemia. An elevated white blood cell count (WBC) may suggest strangulation (Am Surg 2004;70:40).
Characteristic findings of SBO on abdominal plain films are dilated loops of small bowel, air-fluid levels, and paucity of colorectal gas. These findings may be absent in early, proximal, and/or closed-loop obstructions. Gas within the bowel wall (pneumatosis intestinalis) or portal vein is suggestive of a strangulated obstruction. Free intra-abdominal air indicates perforation of a hollow viscus. The findings of air in the biliary tree and a radiopaque gallstone in the right lower quadrant are pathognomonic of gallstone ileus. Paralytic ileus appears as gaseous distention uniformly distributed throughout the stomach, small intestine, and colon.
Contrast studies (small-bowel follow-through [SBFT] or enteroclysis) can localize the site of obstruction and suggest an etiology. Barium can be used if subtle mucosal lesions are sought (i.e., lead point in a patient with recurring intussusceptions) but should be avoided in acute obstructions due to the risk of barium impaction. Water-soluble contrast agents are indicated in most instances because they will not worsen the situation and may actually be therapeutic in the case of adhesive partial obstructionfor Small-Bowel Obstruction treatment in Bangalore.
Computed tomography (CT) is an excellent imaging modality for diagnosing small-bowel obstruction. It has the ability to localize and characterize the obstruction as well as give information regarding the cause of obstruction and the presence of other intra-abdominal pathology. Evidence suggests that CT scanning can improve the preoperative diagnosis of strangulation, with negative and positive predictive values above 90% for Small-Bowel Obstruction treatment in Bangalore(J Gastrointest Surg 2005;9:690).
Mesenteric vascular ischemia can produce colicky abdominal pain, especially after meals. Acute occlusion often presents with marked leukocytosis and severe abdominal pain out of proportion to physical findings. Angiography confirms the diagnosis for Small-Bowel Obstruction treatment in Bangalore.
Colonic obstruction can easily be confused with a distal small-bowel obstruction, especially if the ileocecal valve is incompetent. A water-soluble contrast enema can aid in diagnosis. In any event, the initial management and evaluation of large- and small-bowel obstructions are the same.
Paralytic ileus is a common diagnosis in surgical patients. A thorough history, physical exam, and radiologic workup should differentiate ileus from obstruction. Narcotic and psychiatric medications, recent abdominal operations, and electrolyte abnormalities are common causes of ileus.
As in paralytic ileus, radiography of primary hypomotility disorders reveals gas throughout the entire GI tract with particular distention of the small bowel. Treatment for these chronic diseases consists of prokinetic drugs and dietary manipulation.
D. Treatment -Small-Bowel Obstruction treatment in Bangalore
Treatment of SBO has evolved over the last decade and now includes primary prevention at the time of initial laparotomy.
Antiadhesion barriers may be beneficial in reducing the severity of adhesions after surgery. These products are applied to the surface of the bowel at the end of an operation and act as a barrier to adhesion formation between adjacent loops of bowel and between bowel and the parietal peritoneum. Although randomized studies support a reduction in the number and severity of adhesions after major abdominal surgeries, the effect on bowel obstruction is less clear. A multicenter trial of 1,791 patients comparing Seprafil to no treatment (Dis Colon Rectum 2005;49:1) found no difference in the overall rate of SBO (12% in both groups). There was a very modest reduction in the risk of SBO requiring operation over a mean follow-up of 3.5 years (1.8% vs. 3.4%; absolute risk reduction of 1.6%, number needed to treat = 63)for Small-Bowel Obstruction treatment in Bangalore.
Nonstrangulated obstructions can be treated expectantly if the patient is clinically stable. The cornerstone of treating any bowel obstruction is adequate fluid resuscitation to achieve a urine output of at least 0.5 mL/kg/hour. This resuscitation must meet maintenance fluid and electrolyte needs for a nothing-by-mouth (NPO) patient as well as replace prior and ongoing losses from nasogastric (NG) decompression. During any trial of nonoperative management, it is imperative that the patient undergo serial abdominal examinations every 4 to 6 hours. If the patient deteriorates (worsening abdominal exam, peritonitis, shock) or simply fails to improve within a few days, laparotomy is indicated. In patients with a bowel obstruction secondary to an incarcerated hernia, attempts to reduce the hernia can be made with mild sedation and gentle force. After successful reduction, the patient should be monitored carefully for evidence of bowel infarction or perforation. Inability to reduce the hernia requires urgent operation. Other situations that may warrant a trial of nonoperative therapy include early postoperative obstruction, multiple prior episodes of obstruction, a history of multiple previous abdominal operations with extensive adhesions, abdominal irradiation, Crohn disease, and abdominal carcinomatosis.
Strangulated obstructions and those with peritonitis require prompt operative intervention. Mortality associated with gangrenous bowel can approach 30% if operation is delayed beyond 36 hours. Once again, fluid/electrolyte resuscitation and tube decompression are crucial in the preoperative preparation of the patient.
Fluid replacement should begin with an isotonic solution. Serum electrolyte values, hourly urine output, and central venous pressure can be monitored to assess adequacy of resuscitation. Antibiotics should be given only as prophylaxis prior to surgery.
Operative intervention is generally performed via midline incision, but a standard groin incision can be used in the case of an incarcerated inguinal or femoral hernia. During the exploration, all adhesions are lysed, and the source of obstruction is identified. Any gangrenous bowel is resected. The viability of adjacent or compromised bowel must be determined, and a second-look operation within 24 to 48 hours should be planned if any doubt exists. If the obstructing lesion cannot be resected, it may be bypassed. Placement of a gastrostomy tube for postoperative decompression should be considered in select cases for Small-Bowel Obstruction treatment in Bangalore.
The postoperative mortality from nonstrangulating obstruction is very low. Obstructions that are associated with strangulated bowel carry a mortality of 8% if operation is performed within 36 hours of the onset of symptoms. Mortality can approach 30% if operation is delayed beyond 36 hours
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