Ischemia, endometriosis, rare entities
Symptoms of LBO depend on a number of factors, in particular the etiology, the degree of obstruction (partial or total), and how it presents (acute or chronic, closed or open loop, with a competent or incompetent ileocecal valve). Symptoms may occur suddenly, suggesting an acute obstruction, such as that which occurs in sigmoid or cecal volvulus, or they may be progressive, making colorectal cancer a more plausible cause. The most frequent clinical presentation may include a change in bowel habits, constipation, colicky abdominal pain and distension, nausea, and vomiting. Severe, continuous abdominal pain, especially in the right iliac fossa, increases the suspicion of gangrene, with imminent perforation.
Systemic symptoms may be present but are usually less serious than those of small-bowel obstruction; these include weight loss, fatigue, anorexia, and anemia – suggesting a neoplastic lesion – or fever, chills, and an unwell feeling, which are associated with an inflammatory disorder such as subacute diverticulitis or colitis. A history of chronic constipation, straining to defecate, pneumaturia, or fecaluria could reveal diverticulitis or carcinoma, and a change in stool caliber is indicative of the latter. In the case of colonic ischemia, signs and symptoms of acute toxicity may be found, and septic shock is possible.
The initial physical examination must evaluate the severity of the patient’s condition. Careful and comprehensive history-taking is required, along with a complete physical examination assessing vital signs, general physical appearance, and mental status.
A focused abdominal examination is required. Significant abdominal distention is found in the vast majority of patients. Colonic distension may be extremely large, as in the case of a closed-loop obstruction or with a competent ileocecal valve, in which the risk of ischemia or perforation (mainly cecal) is higher. Hyper-resonance is noted upon percussion. Palpation reveals tenderness; rebound tenderness in the right lower quadrant suggests ischemia or perforation of the cecum, which needs urgent surgical treatment. Perforation can also occur at the site of obstruction (tumors or diverticulitis). Eventually, a mass evoking a carcinoma or diverticulitis, or a markedly dilated caecum, can also be palpated. At auscultation, during the initial phase, bowel sounds may be hyperactive or normal, becoming diminished or absent in cases of long-standing obstruction, colonic ischemia, or colonic pseudo-obstruction. Digital rectal examination should always be performed to identify a rectal or lower pelvic mass and in some cases an impacted foreign body. The presence of blood suggests a carcinoma.
Routine laboratory studies are necessary to evaluate fluid and electrolyte imbalances, chronic blood loss, and/or sepsis, including blood for a complete blood count, prothrombin time, crossmatch, electrolyte concentrations, creatinine, and liver function tests. Arterial blood gas should also be determined. An elevated white blood cell count suggests bowel ischemia/necrosis or diverticulitis.
Computed tomography (CT), which is used expeditiously today, has progressively become the gold standard for the diagnosis of LBO; it is useful for a complete, one-venue assessment of a patient’s condition, providing detailed information about the etiology and severity of an obstruction as well as complications such as perforation. If the cecal diameter is larger than 12 cm, there is a risk of rupture, and urgent surgery is indicated. CT can also be used as part of a therapeutic procedure (Fig. 33.1). When CT is unavailable, a plain abdominal series (flat and upright or left lateral decubitus films) may be used. This distinguishes small- from large-bowel obstruction, confirming the diagnosis in 60–80 % of cases. An erect chest radiograph or an upright abdominal film may reveal free air if a perforation has occurred. If the diagnosis – whether a mechanical or nonmechanical obstruction – or the site of obstruction is in doubt, in the absence of signs of peritoneal irritation, a water-soluble contrast enema should be carried out. Ultrasound plays a limited role; it has low accuracy because of the presence of major gaseous distention.
Large-bowel obstruction (colon cancer)
Colonoscopy may help determine a diagnosis in this setting and also has a therapeutic role in reducing a sigmoid volvulus or in decompressing the colon in O’Gilvie syndrome. It has to be done carefully because of the risk of perforation.
33.5 General Management
A patient’s resuscitation must begin immediately. This includes volume resuscitation, correction of electrolyte imbalances, and transfusion, if necessary. Because intravascular volume is usually depleted, early intravenous crystalloid fluid rehydration is required (isotonic saline or Ringer lactate solution), sometimes by means of a central venous catheter. A urethral catheter is inserted to monitor urinary output.
When bowel obstruction is partial, these measures should precede or accompany intestinal decompression efforts, which can be attempted by inserting a transanal large-bowel tube or by means of retrograde enemas. A nasogastric tube is also necessary if the patient is vomiting, in some cases revealing fecal content. Prophylactic antibiotics should be considered.
Appropriated treatment depends on the etiology of the colonic/rectal obstruction (Table 33.1). Each situation, including its prognosis, is described below.
Laparoscopic treatment of LBO is feasible and safe in the hands of highly experienced laparoscopic teams, who report results similar to those of elective colonic laparoscopic resection. Except in these situations, however, the abdominal approach continues to use an open approach .
A patient’s informed consent about management options should be obtained whenever possible. In the case of potential stoma formation, patient consent should be obtained and the possible site marked before surgery (Fig. 33.2).
Management of colorectal (large-bowel) obstruction
33.6 Neoplastic Colorectal Obstruction
Colorectal carcinoma is responsible for approximately one-third (in the United Kingdom) to one-half (in the United States) of all cases of colorectal obstruction. About 15 % of all patients with colorectal carcinoma present with obstruction. Most patients are older than 70 years. The risk of obstruction is greater in the left colon, most often in the sigmoid segment or at the splenic flexure, whereas rectal carcinomas are less prone to obstruction than other carcinomas. Cancers found with LBO are usually at an advanced stage of disease: 25 % are already metastatic when the diagnosis is made .
The onset of symptoms caused by an obstructive tumor may be insidious or acute. Most patients report symptoms evolving over a 3 to 6-month period, whereas acute obstruction occurs as the first symptom in 15–20 % of carcinomas of the left colon. Symptoms are actually nonspecific and often ignored until complete obstruction occurs. They include an inability to pass gas and feces, colicky abdominal pain and abdominal distension, anorexia, asthenia, bloody stool and rectal bleeding, changes in bowels habits and the diameter of feces, tenesmus, abdominal mass and/or marked weight loss, jaundice, ascites, and cough raising suspicion of a metastatic disease.
Whether the tumor is located in the right or left colon can also affect the clinical picture. The former presents with obstruction of the small bowel and the latter with obstruction of the large bowel.
The stepped procedures mentioned above for a general diagnosis should be followed. A patient’s history usually reveals a drawn-out evolution, with changes in bowel habits over several months. Results of the physical examination depend mainly on the tumor stage and duration of symptoms: signs of cachexia, malnutrition, and dehydration can be found, or, on the contrary, the patient’s general health status may be preserved. Prompt resuscitation could be necessary.
Abdominal distension is usually present with loud borborygmus. In some cases a mass can be palpated, corresponding to the site of the tumor. Rebound tenderness in the right lower quadrant can be caused by a pre-perforated cecum or local gangrene. A digital rectal examination may identify and characterize the tumor.
Laboratory studies (including carcinoembryonic antigen) should be requested. CT is the most useful tool in the case of a large-bowel obstruction caused by a colorectal cancer (especially using triple contrast: intravenous, oral, and rectal), helping in the clinical staging or the differential diagnosis with diverticulitis  (Fig. 33.3). A water-soluble contrast enema could be considered if CT is not available or in cases of a dubious diagnosis. Flexible endoscopy may be useful if the colon distal to the obstruction can be prepped with enemas. It allows for biopsies.
Large-bowel obstruction (local recurrence of rectal cancer)
In the case of a partial colonic/rectal obstruction caused by colorectal cancer, patients can be initially managed conservatively, with appropriate reanimation and bowel preparation, allowing an elective surgical procedure. Complete obstruction requiring early and urgent treatment has a higher morbidity and mortality and worse survival rates than partial obstruction . Surgical procedures are mostly used, but nonsurgical procedures such as endoscopic stenting (introduced in the early 1990s) are also useful to relieve obstruction. Stent placement before elective surgery as a bridge to surgery is an alternative to emergent surgery in patients with acute left-sided malignant colonic obstruction. However, because its benefits are uncertain, there is no consensus about the most appropriate therapeutic options to select . Several options are currently available to permit a one-stage procedure, avoiding the inconvenience directly related to multistaged procedures performed in the past, requiring at least one temporary stoma. These procedures are, however, far from being abandoned.
184.108.40.206 Conservative Treatment
To minimize the risks associated with surgical treatment of patients with LBO, there has been a trend toward decompressing the colon before surgery, allowing an emergency situation in an unstable patient to be converted into an elective one, and in the mean time avoiding the need for a stoma. This can be accomplished by laser tumor ablation or by endoscopic stent placement to canalize a neoplastic obstruction.
Stent insertion is today the most commonly used nonsurgical endoluminal technique ; the need for repeated treatment sessions and the risk of complications have limited the widespread acceptance of laser dilatation. Stents have been increasingly applied since their introduction in the early 1990s, bridging patients from emergency to elective surgery  by reestablishing the intestinal lumen and allowing thorough bowel preparation before surgery. Bowel function is restored immediately after the stent is inserted. Despite its efficacy in resolving distal LBO (technical and clinical success rates of stent placement are around 70 %), the results of different randomized controlled trials, multicenter studies, meta-analyses, and systematic reviews comparing stent insertion and emergent surgery are conflicting [7, 10–15]. No firm conclusions can be drawn concerning morbidity, mortality, need for stomas, primary anastomosis, complications, oncological outcomes, and technical and clinical success rates. Further evaluation and studies are needed to elucidate which group of patients could benefit most from stent insertion or emergency surgery, since high-grade evidence is currently sparse . As a whole, however, this technique seems to compare favorably with surgery . Colonic stents are also used as a palliative and definitive treatment in patients in whom surgery should be avoided because of significant comorbidities, incurable malignancy, or nonresectable cancer. Although debatable, endoluminal stent insertion seems to be a cost-effective technology, especially when skills to implement this approach are present, with a high rate of successfully relieving obstruction in the vast majority of patients .