Introduction
Fecal diversion through formation of a loop ileostomy after low anterior resection (LAR) in rectal cancer patients is a widely used and evidence-based routine to attenuate consequences of a postoperative anastomotic leak (AL) [
1]. Before reversal of the ileostomy, however, clinicians must be sure there is no asymptomatic AL that may become clinically apparent after restoration of intestinal continuity. Although this represents a frequent clinical situation, still no clear consensus exists on how to best assess the integrity of the colorectal anastomosis. Common examination techniques are digital rectal examination (DRE), flexible or rigid endoscopy (FE), and contrast enema radiography (CE) [
2]. However, the routine use of CE for this indication is debatable. While some authors see benefits in its routine performance [
3‐
6], others request limiting its use to selected patients [
7‐
16]. It should be noted that in all studies promoting its routine use, CE was not compared with an endoscopic examination such as flexible endoscopy (FE) or rigid proctoscopy. Studies that routinely performed endoscopic examinations were more critical towards an additional routine CE. These findings could arise from the general need for a diagnostic procedure and a superiority of endoscopy over CE. However, differences in patient cohorts might also have influenced findings. Suggested characteristics of individual patients who could potentially benefit from CE were complications after LAR [
10,
12,
15], abnormal findings in DRE or proctoscopy [
8,
11], and clinical suspicion for a leak [
7,
11,
13,
16]. However, to our knowledge, no current study formally analyzed those criteria.
The primary aim of this study was to investigate if routine CE adds clinically relevant information to a routinely performed FE by analyzing concordance and diagnostic test accuracy. In addition, the influence of a history of clinically apparent AL after LAR on the diagnostic test accuracy of CE and FE was assessed.
Results
Two hundred seven consecutive patients who underwent LAR and had shown no clinical sign of postoperative AL were identified and assigned to group 0, whereas 86 patients had suffered from clinically relevant AL after initial LAR and were assigned to group 1. Median age did not differ significantly between groups 0 and 1 (62 years vs. 61 years,
p = 0.477); however, there were significantly more male patients in group 1 than in group 0 (80% vs. 59%,
p = 0.001) (Table
1). No patient suffered from complications of FE or CE that required medical, interventional, or surgical therapy. In one case of antegrade CE, initial incorrect irrigation of the oral limb was reported; however, no complications resulted from this.
Table 1
Group characteristics
Characteristics | LAR + stoma | No leak after LAR | Anastomotic leak after LAR | |
n | 293 | 207 | 86 | |
Female sex [%] | 34 | 41 | 20 | |
Median age (years) (IQRa) | 62 (54–69) | 62 (54–69) | 61 (54–68) | 0.477 |
Discussion
This study assessed the diagnostic test accuracy of CE and FE for the detection of asymptomatic anastomotic leak. It could be demonstrated that routine CE has no advantage over FE in testing the anastomosis. Even in group 1, with a higher prevalence of asymptomatic AL, CE did not add clinically relevant information to FE. Radiation exposure and discomfort for patients caused by CE are further arguments against this test. Other uses for water-soluble CE such as prediction of fecal incontinence seem to be of little value [
5,
18]. The abolishment of routine CE in favor of endoscopic techniques such as FE appears to be reasonable. In light of the current evidence base, holding on to CE in patients with higher risk for a leak can be arguable for safety reasons. However, the reported high negative predictive value (98.4%) of CE [
2] has only been demonstrated in mixed patient cohorts. In patients who had a complicated postoperative course after LAR, diagnostic accuracy of CE has not been calculated before. This study showed that FE is more sensitive than CE in this important patient cohort. Direct imaging of the anastomosis with the option to clean the anastomotic site of fibrin coating and probing pouches are possible reasons for the superiority of FE over CE. However, FE might not be available to all surgeons. There are no studies formally addressing this problem. Thoroughly executed clinical and imaging examinations are of critical importance in this setting. When opting for CE, the evaluation by the operating surgeon with full knowledge of the postoperative anastomotic anatomy is advisable. Additional clinical investigation of the anastomosis by digital rectal examination has not been part of this investigation. It has been demonstrated that digital rectal examination can compare favorably to CE [
19]. Being a quick to perform clinical test, it should always be included in the decision-making before ileostomy reversal.
We could add new knowledge by demonstrating the relevance of previous AL on test accuracy for AL in asymptomatic patients and AL prevalence. In group 0, there were only 1.4% pathologic anastomoses compared with 25.6% in group 1, and 104 patients in group 0 had to be tested to find one AL. It has previously been shown that routine testing adds no information in patients without postoperative complications [
9,
20], and ileostomies could be safely reversed even in cases of a radiologic leak [
4]. Future investigations are needed to weigh the high effort of routine testing against its gain of information in larger cohorts.
The asymmetrical distribution of gender in the whole study cohort might be attributed to a higher risk for colorectal cancer in men. The higher percentage of men in group 1 compared with group 0 supports a previously reported higher risk for AL in men [
10]. The two groups concur in median age.
Limitations of this study
One limitation of this study is its retrospective design. Also, to increase the sample size in group 1 (leak after rectal resection), the recruiting interval for this group was prolonged in one center; thus, time-related influences in the comparison of the groups cannot be excluded, and a precise leak rate after initial LAR cannot be presented. No standardized test reference (“gold standard”) is available for leakage in the context of ileostomy reversal. Clinical outcome after ileostomy reversal served as clinically and patient-relevant primary reference standard for true or false negative findings. Positive tests being unlikely to be reversed might thus be unrecognized as false positives, potentially overestimating the accuracy of both tests.
Conclusion
Flexible endoscopy is the more accurate diagnostic test for the detection of asymptomatic anastomotic leaks prior to ileostomy reversal. Contrast enema showed no gain of information. In the group without complications after the initial rectal resection, 104 must be tested to find one leak prior to reversal. In those patients, routine diagnostic testing additional to digital rectal examination may be questioned.
Compliance with ethical standards
The Ethics Committees of the University Hospitals Dresden and Mannheim approved the study protocol.
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