Complications of Colonic Resection

Leakage

Leakage at the anastomotic site is the most common complication of colonic resection in the early postoperative period, and the cause of the highest morbidity and mortality. The rate of leakage is highest with low anterior resection, with clinically significant leaks reported in 5 to 10% of cases. A mortality rate of up to 50% may be expected if a leak is not promptly recognized [22]. Leaks usually develop 1 to 2 weeks after surgery but may be clinically silent and not apparent until up to months after surgery [23]. Leaks are often due to devascularization and necrosis of bowel at the anastomotic site. In some cases, plain films may reveal pneumoperitoneum, increasing over time, or obstruction or abscess. There is some evidence to suggest that the development of an anastomotic leak is associated with an increased incidence of tumor recurrence and poorer long-term outcome [24].

Controversy has existed with regard to the performance of a water-soluble enema as a routine procedure after colorectal surgery [1,4,25]. Although some surgeons request water-soluble enemas as a routine study after surgery, most surgeons and radiologists generally feel that since the procedure provides little information of diagnostic value, it should not be routinely performed. Contrast studies in the early postoperative period may demonstrate leaks in a high percentage of patients who are and remain clinically asymptomatic and indeed go on to an uneventful recovery [1]. Leaks may be manifested by extralumi-nal tracts, collections, or free intraperitoneal contrast. Leakage is often posterior in location, and since small leaks may be obscured on antero-posterior and oblique views, it is therefore necessary to obtain good lateral projections in this setting (Fig. 6.24). Postevacuation films should be obtained, since a leak that could not be detected on the filled examination may be identified after evacuation. In patients with low anastomoses, care must be used in rectal tube insertion, to prevent disruption of the anastomosis. A Foley catheter of approximately 16F should be utilized and the balloon should generally not be inflated. Another potential problem is insertion of the catheter through a dehisced anastomosis.

CT imaging may also be useful in the evaluation of postoperative leaks. In addition to demonstration of extraluminal contrast, associated abscesses may be identified. Contrast medium and/or air in the rectum and in a collection posterior to it has been termed the "double-rectum" sign (Fig. 6.25). More precise identification of the site of leakage is generally determined with a water-soluble enema than with CT imaging, however. The retrorectal space typically widens after anterior resection; however, undue widening may suggest an anastomotic leak. In one study, CT images showed the retrorectal space to be 2 cm or more in patients without anastomotic leaks [23]. The same authors reported that the retrorectal space was greater than 5 cm in 70% of cases with acute leaks. Presacral fluid can often be identified normally in the postoperative period and can be distinguished from a leak by the absence

Figure 6.24. Leak after anterior resection; value of the lateral view. (A) Supine view from a water-soluble contrast enema after anterior resection showing no definite leak. (B) Lateral view in the same patient shows extraluminal contrast, due to leakage extending posteriorly from the region of the anastomosis.

Figure 6.25. "Double-rectum" sign due to leak. (A,B) CT scan through the inferior pelvis demonstrates fluid in the rectum and an abscess containing fluid and air posterior to the rectum.

of contrast medium and/or air. In some cases, a collection may be the cause of anastomotic dehiscence rather than its result [1]. The identification of air in the presacral space for longer than 6 months after surgery is also an indication of leak [23].

Anastomotic Stricture

Anastomotic stricture may develop after any bowel anastomosis. If the surgery was performed for malignancy, the differentiation from recurrent tumor is necessary. Benign strictures may be treated by stricturo-plasty or in some cases by endoscopic dilatation. In the colon, enteroliths may develop proximal to a stricture secondary to stasis (Fig. 6.26). Another potential complication is the development of proximal ischemia (Fig. 6.27). The etiology of colonic ischemia proximal to an obstructing lesion is thought to be increased intraluminal pressure, which leads to decreased mucosal perfusion.

Radiografia Nariz Rota

Figure 6.26. Fecaliths proximal to colonic stricture. (A) Plain film of the abdomen shows multiple enteroliths in the colon after a left colectomy with an anastomotic stricture. (B) Coned-down view from a plain film of the abdomen reveals a laminated fecalith. (C) Postevacuation film from a barium enema showed a stricture at the anastomotic site after sigmoid resection with a fecalith proximal to the anastomosis.

Figure 6.26. Fecaliths proximal to colonic stricture. (A) Plain film of the abdomen shows multiple enteroliths in the colon after a left colectomy with an anastomotic stricture. (B) Coned-down view from a plain film of the abdomen reveals a laminated fecalith. (C) Postevacuation film from a barium enema showed a stricture at the anastomotic site after sigmoid resection with a fecalith proximal to the anastomosis.

Figure 6.27. Ischemia proximal to colonic stricture. Film from a barium enema after anterior resection demonstrates a urticarial pattern due to ischemia proximal to a stricture at the anastomotic site.

Recurrent Tumor

Local recurrence after colonic resection for tumor is a catastrophic occurrence with an average survival time of 11 months if untreated [26]. The recurrence rate is related to the tumor stage and the histological grade at the time of diagnosis. The majority of recurrences occur in the first and second years after surgery [27]. Although the prognosis for recurrent disease is poor, early detection of recurrent tumor has been shown to improve the prospect for survival [28]. Postoperative assessment of the colon and abdomen is necessary to evaluate for locally recurrent disease at or near the anastomosis, for the detection of metachronous neoplasm, which occurs in 7 to 10% of patients, and to identify distant metastases, most frequently involving the liver. Local recurrence or metastatic disease develops in up to 40% of patients after curative resection of primary tumors [29]. If the recurrent tumor is localized, curative resection may be performed.

Traditionally, the postoperative evaluation of the colon in the later postoperative period was with barium enema and/or colonoscopy. CT and MR imaging, intrarectal ultrasound, radionuclide-labeled monoclonal antibody studies a carcinoembryonic antigen (CEA) levels, and positron emission tomography (PET) now play contributory roles. The barium enema findings in locally recurrent colorectal carcinoma include anastomotic narrowing (which may be irregular, eccentric, or smooth), mass effect adjacent to or removed from the anastomosis, and obstruction at the anastomotic site. Smooth strictures due to recurrent tumor may be difficult to differentiate from benign strictures on barium enema. The sensitivity of the barium enema in detecting locally recurrent disease is one study was 88% [30]. The CT diagnosis of anas-tomotic recurrence can be made by the identification of a soft tissue mass or obliteration of adjacent fat planes. In one study CT images were less sensitive than barium enema in identifying locally recurrent disease, with a sensitivity of 69% [30]. Overall, CT imaging has been shown to be fairly insensitive and nonspecific in the evaluation of recurrent tumor [31,32]. The barium enema is limited because of its inability to detect pelvic recurrence after AP resection, difficulty in determining the extent of recurrent disease, and inability to assess distant metastases.

In patients with rectal cancer after AP resection it is difficult to differentiate fibrosis from recurrent tumor [27]. If baseline studies have been obtained, an increase in soft tissue in the rectal bed over time would favor recurrent tumor. Nodularity at the anastomotic site, enlarged nodes, and evidence of tumor elsewhere also favor malignancy. Early reports advocated magnetic resonance imaging as a more specific examination than CT in differentiating tumor from fibrosis. Initial reports showed higher signal intensity on T2-weighted images in tumor recurrence than in fibrosis with scar formation [33]. These findings proved to be unreliable, however, in part because tumor with desmoplastic reaction or inflammatory changes, such as those occurring after radiation therapy, may not demonstrate the typical T2 intensity. The use of contrast-enhanced dynamic MRI has been reported to increase accuracy, with malignant lesions showing greater and faster enhancement than benign lesions, although this technique is still of limited diagnostic value in some cases [34]. Recently PET scanning with [18F]fluorescein digalactopyranoside has been employed for the detection of postoperative recurrence of colorectal cancer. Since PET technology relies on the abnormal metabolic activity of tumor cells, it has the potential to identify the presence of tumor before structural changes may be seen on CT or MR imaging. PET scanning also has the capacity to differentiate recurrent tumor from fibrosis on this basis as well. Early experience has demonstrated the superiority of PET over CT and MR scanning in detecting and staging recurrent colorectal carcinoma, except in cases of mucinous adenocarcinoma [35-39].

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