Keywords
definition - colorectal - anastomosis - leak - relevance
Definition of Large Bowel Anastomotic Leak
Definition of Large Bowel Anastomotic Leak
Definition
The precise definition of a lower gastrointestinal (GI) anastomotic leak remains nebulous
and ill defined. In a review of 97 studies from 1993 to 1999, the definition of a
lower GI anastomotic leak was described 29 different ways.[1] The lack of a uniform definition makes the true incidence unknown and comparisons
between studies flawed resulting in up to 25% of patients who will be diagnosed with
an anastomotic leak.[2]
[3]
[4] Following a survey of the members of the American Society of Colon and Rectal Surgeons,
a persistent lack of consensus among colorectal surgeons on the definition of an anastomotic
leak despite international guidelines published a decade ago.[5]
In the modern era, the United Kingdom Surgical Infection Study Group was the first
to propose standardized definitions “to allow meaningful comparisons to be made.”[6] In 1991, they defined an anastomotic leak as a “leak of luminal contents from a
surgical joint between two hollow viscera,” and a subclinical leak as “the escape
of luminal contents from the site of the anastomosis into an adjacent localized area,
detected by imaging, in the absence of clinical symptoms.”[6]
In 2010, the International Study Group of Rectal Cancer (ISREC) proposed a definition
and grading system for colorectal anastomotic leaks.[2] The ISREC defined a leak as “a defect of the intestinal wall at the anastomotic
site (including suture and staple lines of neorectal reservoirs) leading to a communication
between the intra- and extraluminal compartments.”[2] This definition was directed at leakage after an anterior rectal resection which
may not be generalizable other GI anastomoses.[7] In addition, the authors did not propose reliable methods of identifying such a
communication in the postoperative period. However, this grading system remains one
of the only standardized definitions for anastomotic leak. The ISREC delineated leaks
by grades A to C based on their clinical management ([Table 1]) which have been validated.[8] There is significant difference in morbidity, length of stay, cost, and mortality
between grade B and C leaks.[7]
[8] For these reasons, some have proposed that grades B and C to be separate entities
due do the magnitude of difference between their management and outcomes.[7]
Table 1
The International Study Group of Rectal Cancer (ISREC) anastomotic leak definition
|
Grade A
|
Results in no change in management
|
|
Grade B
|
Requires active therapeutic intervention short of a laparotomy
|
|
Grade C
|
Requires relaparotomy
|
Further confusion occurs through the creation of additional nomenclature and categories
of leaks. Some authors describe a “symptomatic leak,” that is, grades B and C, as
a clinical leak and an “asymptomatic leak,” that is, grade A, as a subclinical leak.[6]
[9] In 2012, Adams and Papagrigoriadis surveyed colorectal surgeons in the United Kingdom
on a working definition of anastomotic leaks. The authors found a good level of consensus
defining a leak as “extravasation of contrast with an enema” and “fecal matter seen
in the drains or from the wound regardless of management,” 94.2 and 91.8%, respectively.[10] Yet, there was sharp disagreement with “radiological collections treated with antibiotics”
or “… requiring percutaneous drainage.” Half of the respondents did not consider collections
requiring drainage or treated with antibiotics indicative of an anastomotic leak.[10] Of the other half of respondents who agreed drainage constituted a leak, 89% felt
similarly about collections treated with antibiotics. In relation to the ISREC definitions,
there was good consensus for the working definition of grades A and C but disagreement
for grade-B anastomotic leaks. Another study surveyed Dutch and Chinese surgeons on
the definition of anastomotic leaks. Similar to British surgeons, there was a lack
of consensus, except for computer tomography (CT) evidence of extravasation of rectal
contrast.[11]
The Delphi method survey of eight colorectal experts advocated for further refinement
of the anastomotic leak. Using 15 clinical and radiological scenarios of leaks, only
80% of clinical and 30% of radiological scenarios reached consensus.[5] For one particular controversial radiological scenario, when “air bubbles around
the anastomosis” are visualized without other sequelae, there was consensus among
experts that this scenario was indicative of an anastomotic leak. No agreement, however,
was found when a CT scan with oral, intravenous, and rectal contrast demonstrated
a fluid collection near the anastomosis without extravasation of contrast despite
treatment with antibiotics and percutaneous drainage regardless of time frame out
to 35 days.[5] This further demonstrated the controversial nature of the definition of anastomotic
leak.
Categorization
Anastomotic leaks present and are categorized in various ways as follows: (1) simple
fistulas versus large sinuses; (2) intraperitoneal versus extraperitoneal; (3) sepsis-producing
versus asymptomatic; or (4) early versus late. The identification of an anastomotic
leak depends on clinical suspicion and subsequent workup. Anastomotic leaks located
within the peritoneal cavity more often present with diffuse contamination, peritonitis,
and sepsis.[12] Extraperitoneal leaks may present in a less obvious fashion as a fistula, rectal
drainage, pain, or urinary symptoms.[13]
[14] Asymptomatic leaks are usually identified during an evaluation prior to diverting
ileostomy takedown, for example, endoscopy, CT scan with or without contrast ([Fig. 1]), or a lower GI series with contrast enema ([Fig. 2]).[2] In diverted patients, the true incidence of leaks is impacted by the spontaneously
healing of unidentified, asymptomatic leaks.[13]
[15] In a randomized, multicenter trial, patients with a diverting ostomy compared with
those with no diversion were less likely to present with peritonitis and sepsis or
require a laparotomy (10 vs. 28%, respectively, p < 0.001; 8.6 vs 25.4%, p < 0.001).[16] Although asymptomatic leaks were excluded, these data highlight a clear benefit
in the sequelae of symptomatic leaks with proximal diversion.[16] Two other randomized clinical trials have shown similar results with and without
a colonic J-pouch.[17]
[18]
Fig. 1 Sagittal and coronal views of a colorectal anastomotic leak with extraluminal fluid
and gas.
Fig. 2 Rectal contrast enema with posterior colorectal anastomotic leak (arrow) after low
anterior resection.
While proximal diversion offers protection against the clinical consequence of anastomotic
leak, it is not without risks. Loop ileostomy closure has a reported complication
rate of 11 to 18%, including anastomotic leaks, wound complications, dehydration,
and hospital readmission.[19]
[20]
[21]
[22]
[23] Li et al reported 13% readmission rate after diverting loop ileostomy creation with
common reasons including organ space infections, ileus, and dehydration.[22] Other studies have reported readmission rates after ileostomy creation up to 30%.[20]
[21] Using a state surgical quality registry that included 1,737 patients undergoing
a diverting loop ileostomy takedown, 11 and 7.4% of the cohort had a readmission and
reoperation, respectively.[23]
Given the complications associated with not only the presence of ileostomy but also
its subsequent reversal, some surgeons advocate for selective diversion. In a retrospective
review in nonradiated low anterior resection (LAR) anastomoses, there was a 4 and
3.8% clinical leak rate in the diverted and nondiverted patients.[24] These authors advocate for selective diversion in patients who can least withstand
the sequela of a leak, that is, frail, elderly, or those with multiple comorbidities.[24] In a recent administrative claim-based review, Chapman et al reported similar rates
of anastomotic leaks after sphincter-sparing proctectomy with or without a diverting
loop ileostomy, 4.5 versus 4.3%, respectively.[25] The diverted patients had higher rates of interventions, readmissions, and costs.[25] While this study is thought provoking, administrative claims that data do not provide
the granularity for appropriate comparison as these data are collected for billing
purposes and have a reported sensitivity of 29% and positive predictive value of 13%
of detecting anastomotic leaks.[26]
In summary of available studies, there are lower rates of clinically significant anastomotic
leaks with proximal diversion compared with no diversion, and nonoperative management
of leaks is more likely to be successful in diverted patients. However, the morbidity
of a temporary stoma is not trivial and must be considered. Accordingly, selective
diversion has been advocated, yet high-quality studies to support this practice are
lacking.
The Epidemiology of Anastomotic Leak
The Epidemiology of Anastomotic Leak
The anatomic site of the anastomosis remains the most consistent and significant risk
factor for anastomotic leak.[27] The further distal an anastomosis is created, the higher the risk of leak. An ileocolic
anastomosis has a leak rate of 1 to 4% compared with a 0.5 to 18% colorectal or a
5 to 19% leak rate in coloanal anastomoses.[28] In rectal anastomoses, a significant difference can be seen with decreasing distance
from the anal verge,[27] with the highest risk of anastomotic leak at and below 5 cm from the anal verge.[4]
[29]
[30] However, high-volume surgeons have reported leaks rates as low as 1.4% for all types
of lower GI anastomoses.[31]
There are several proposed reasons for the difference in leak rates between proximal
and distal colonic anastomotic locations. First, routine radiologic testing of anastomosis
has been shown to detect 2.4 times more anastomotic leaks than clinical symptoms alone,
and more radiological studies are performed to evaluate distal anastomoses.[4]
[32] Second, the distal colon has an increased amount of intraluminal bacteria, compromised
vascularity, and potentially increased intraluminal pressure compared with the proximal
colon.[33]
[34] In a prospective multicenter French study, Veyrie et al reported a significantly
lower anastomotic leak rates for right-sided compared with left-sided colectomies
for cancer, (1.35 vs. 5.20%, p < 0.0001), with all patients receiving mechanical bowel preparation with parenteral
preoperative antibiotic prophylaxis.[34]
Ileocolic Anastomotic Leak
As previously mentioned, ileocolic anastomoses are considered to have the lowest incidence
of leaks, ranging from 1 to 3%,[4]
[34]
[35] yet when leaks occur, peritonitis and sepsis are more common compared with extraperitoneal
leaks.[12]
Patients with Crohn's disease (CD) are at a higher risk for an anastomotic leak[36] which can have significant impact on disease recurrence.[37] On retrospective review of a national registry, leak rates ranged from 1.6 to 14.3%
by the number of risk factors for ileocolectomy for CD.[38] Emergent surgery, current smoking status, higher wound classifications, weight loss,
and steroid use were strongly associated with anastomotic leaks.[38] In one recent study, there was a 7.4% leak rate in CD patients with ileocolonic
anastomoses which were unassociated with medications.[39] However, steroid use is generally associated with this increased risk of leaks,
while the role of biologic and immunomodulation medications remain debatable.[40]
[41] A recent meta-analysis investigated the risk of leaks with biological medications
for CD and did not find a significant association, however, the authors performed
this meta-analysis without a clear and standardized definition of an anastomotic leak.[42]
Colorectal Anastomotic Leak
Extraperitoneal anastomoses and those under 5 to 8 cm from the anal verge are at a
higher risk of a leak, 5 to 19%, and proximal diversion is generally recommended.[4]
[33]
[43] Diversion has been suggested to decrease the rate of leaks[17]
[38] and significantly improve the morbidity associated with a leak.[17] In a randomized, multicenter trial, Matthiessen et al compared the symptomatic leak
rate for LARs for rectal cancer among diverted versus nondiverted patients. The diverted
group had a significantly lower rate of symptomatic anastomotic leaks compared with
the nondiverted group. The patients in the diverted group were 15% less likely to
present with sepsis or require a laparotomy for management.[16] Historically, diversion has not been considered to impact leak rates.[44] In a large cohort from a single high-volume center, Nisar et al showed no statistical
difference in diverted versus nondiverted patients.[44] In this study, although not compared head-to-head, there was a clinical difference
in anastomotic leaks between patients receiving neoadjuvant radiation who were diverted
versus nondiverted, that is, 7.5 versus 11.6%, respectively.[44]
Briefly, technical considerations that impact anastomotic leak rates include creation
of tension-free and nonischemic anastomoses. Splenic flexure mobilization to relieve
tension is associated with decrease leak rates for left-sided anastomoses.[45] Every rectosigmoid and rectal anastomosis should be tested for a leak during the
initial operation.[46] In a single-center review, anastomotic leaks managed with suture repair alone (n = 41) compared with takedown with repeated anastomosis (n = 14) or proximal diversion (n = 10) had a 12.2 versus 0% postoperative clinical leak rate.[46] The authors therefore advocate for an aggressive approach to redo or divert anastomoses
that have air extravasation on insufflation testing.
Coloanal Anastomotic Leak
Coloanal anastomoses have the highest reported leak rate. LARs for distal tumors may
be performed with a stapled coloanal anastomosis or a hand-sewn coloanal anastomosis
with or without intersphincteric dissection. At experienced centers, a coloanal anastomosis
after neoadjuvant chemoradiation (nCRT) has been shown to be oncologically safe with
a low leak rate.[47]
The variability in reporting, that is, distance from anal verge to tumor versus distance
to anastomosis, complicates comparison of leaks across studies.[29] One series of 329 rectal cancer patients who underwent an ultra-LAR, that is, an
anastomosis below the levator ani muscle, reported a leak rate of 5.5%.[30] The majority of studies, however, reports significantly higher leak rates, albeit
with smaller samples, ranging from 15[48] to 24%.[27]
[49] Significant risk factors include nCRT and male gender, which is presumed to be due
to the technical challenges of working in a narrow pelvis.[29]
[48]
[49] Additionally, documented leaks that healed are at risk for recurrent leaks. Kitaguchi
et al reported recurrent anastomotic leaks after proximal diverting stoma closure
occur 5 and 25% after low anterior and coloanal anastomoses, respectively.[50]
Ileal-Pouch Anal Anastomosis Leak
A leak from an unprotected ileal-pouch anal anastomosis (IPAA) may have devastating
complications, including loss of the pouch. The true incidence of leaks after an IPAA
is unknown. Most publications are retrospective reviews from high-volume single centers
and leaks are generally included under the subheading pelvic sepsis. Reported leak
and fistula rates after IPAA are 3.2 to 19 and 1 to 7%, respectively.[40]
[48]
[51]
[52]
[53] The tip of a J-pouch has a reported leak rate of 0.5%.[54] Anastomotic complications are significantly higher for patients with ulcerative
colitis compared with familial adenomatous polyposis, especially in the setting of
preoperative steroid use.[51]
[55] Late presentations of leaks and fistulas after an IPAA for ulcerative colitis should
prompt a workup for CD.
The Impact of Anastomotic Leak
The Impact of Anastomotic Leak
Short-Term Outcomes
Lack of bowel function beyond the sixth postoperative day is highly predictive of
an anastomotic leak, but the presence of bowel function alone is a poor negative predictor.[56]
[57] Sometimes patients may not display any one sign or symptom, but simply fail to progress,
that is, follow the standard postoperative course. These patients warrant an evaluated
for an anastomotic leak.[12] On average, patients with an anastomotic leak compared with those without a leak
spend almost a week longer in the hospital.[57]
[58] The median time to diagnosis has a reported range between 12 and 17 days from the
time of surgery, at which point patients may have been discharged from the hospital.[59]
[60]
[61] A single-center review reported 32% of leaks are diagnosed over 30 days from the
initial operation.[14] Mortality after a leak can be six-fold higher than patients without a leak, 12%
compared with 1.6%.[62] In one study, patients with grade-B leaks had a mortality of 2.5% and those with
grade C, 5.8%, p = 0.12.[7]
Long-Term Outcomes
Anastomotic leaks can have a significant impact on a patient's bowel function and
quality of life (QOL). Even without complications, colorectal and coloanal anastomoses
have a measurable effect on function and QOL.[63]
[64] An anastomotic leak can lead to pelvic fibrosis which contributes to poor anorectal
function by reduction compliance and capacity of the neorectum.[65]
[66]
[67] The resulting scar may impact pelvic floor and sphincter function, even if the anastomotic
leak completely heals.[13] Ashburn et al compared patients with and without anastomotic leaks after restorative
proctectomy.[67] Individuals with an anastomotic leak were more likely to have frequent day- and
night-time bowel movements and worse control of solid stool compared with patients
without a leak 1-year postproctectomy.[67] QOL scores, also, were significantly lower for individuals with a leak compared
with those without a leak at 1 year.[67] Other studies have reported similar results for symptomatic leaks.[68]
[69]
[70] Inflammatory bowel disease (IBD) patients with an anastomotic leak after an IPAA
have a reported pouch failure of 4.5%.[71]
Hain et al reported higher LAR syndrome (LARS) scores for symptomatic leaks but no
difference on LARS scores for asymptomatic leaks.[70] Recent studies evaluating colon J-pouch compared with side-to-end or end-to-end
colorectal anastomosis report similar functional outcomes.[72]
[73] Although these studies were underpowered to evaluate the impact of an anastomotic
leak on function, there is no evidence to support a superior colorectal anastomotic
technique.[72]
[73] Permanent stoma rates after lower GI anastomotic leaks have been reported up to
50%.[16]
[59]
[74]
Oncologic Outcomes
Studies investigating the association between anastomotic leaks and oncologic outcomes
after colorectal cancer surgery are conflicting. A meta-analysis including 21 studies
and 21,092 patients concluded that anastomotic leaks had a negative prognostic impact
on local recurrence but not distant recurrence.[75]
[76] For stage-III colon cancer patients, another study found leaks were associated with
increased rates of distant recurrence and long-term mortality.[77] Krarup et al reported the leak group had significant delays or cancelation of adjuvant
chemotherapy, which is a strong confounding factor of oncologic outcomes but also
likely the reason for this discrepancy.[77] A recent single-center review of 698 rectal cancer patients who underwent nCRT followed
by a total mesorectal excision reported no association between anastomotic leaks and
oncologic outcome.[78] In more recent years, total neoadjuvant therapy (TNT) for rectal cancer has been
shown to increase treatment adherence with decreased toxicities.[79] TNT may potentially improve oncologic outcomes in patients with anastomotic leaks
by avoiding delays in oncologic treatment.[80]
Costs Associated with Anastomotic Leak
Anastomotic leaks double to triple the costs of medical care.[81]
[82] The reported average incremental costs associated with a leak for each hospitalization
is $24,129.[58] There are few studies reporting the costs of leaks in dollars, however, the costs
can be extrapolated from additional days in the hospital and ICU, as well as the increased
number of treatment procedures.[7] Additionally, complications decrease the profit margin of procedures and in some
cases, may even be net negative.[83] To date, the costs associated with patients' loss of productivity due to anastomotic
leaks have not been evaluated.
Conclusion
An anastomotic leak can result in a wide range of presentations, from an asymptomatic,
clinical insignificant radiologic finding to a septic insult, causing a rapid decline
with multiorgan failure and death. Variability of reported definitions in research
investigations, specifically the underreporting of grade-A leaks, make comparisons
and conclusions difficult to interpret across studies. The goal of this review was
to highlight the need for universal standardization and reporting of anastomotic leaks
and to outline the short- and long-term outcomes associated with anastomotic leaks.
