Tuesday, March 8, 2016

An intraoperative leak test should not be done; or should it?

Here is an abstract recently published ahead of print in the American Journal of Surgery. Please read it because a one-question test follows.

Introduction: Staple line leak after sleeve gastrectomy (SG) is a rare but dreaded complication with a reported incidence of 0-8%. Many surgeons routinely test the staple line with an intraoperative leak test, but there is little evidence to validate this practice. In fact, there is a theoretical concern that the leak test may weaken the staple line and increase the risk of a postop leak.

Methods: Retrospective review of all SG performed over a 7-year period. Cases were grouped by whether an intraoperative leak test (IOLT) was performed, and compared for the incidence of postop staple line leaks. The ability of the IOLT for identifying a staple line defect and for predicting a postoperative leak was analyzed.

Results: 542 SG were performed between 2007-2014. 13 patients (2.4%) developed a postop staple line leak. The majority of patients (N=494, 91%) received an IOLT, including all 13 patients (100%) who developed a subsequent clinical leak. There were no (0%) positive IOLTs and no additional interventions were performed based on the IOLT. The IOLT sensitivity and positive predictive value were both 0%. There was a trend, although not significant, to increased leak rates when a routine IOLT was performed versus no routine IOLT (2.6% vs. 0%, p=0.6).

Conclusions: The performance of routine IOLT after sleeve gastrectomy provided no actionable information, and was negative in all patients who developed a postoperative leak. The routine use of an IOLT did not reduce the incidence of postop leak, and in fact was associated with a higher leak rate after SG.


Do you agree with the authors that the routine use of the IOLT was associated with a higher leak rate after sleeve gastrectomy?

I don't, and here's why.

As I tend to do whenever I criticize a paper, I begin with a confession that I have written a lot of marginal papers in my time. It's one of the reasons I maintain my anonymity.

A "trend" has no scientific validity. A comparison is either statistically significant or it is not. Many scientists and statisticians have rightfully criticized our blind faith in p values, but they remain a standard way of comparing research results. That discussion is for another time. Let’s face it—p values will be around for a long time.

The claim that there was a trend toward an increased leak rate with IOLT was based on a difference of 2.6% among 542 subjects. Even if one believed in trends, the p value of 0.6 clearly indicates that there is no difference between the two percentages. Many authors get away with stating that trends exist when p values are 0.051 or 0.06. That's still debatable, but at least close to the magic p of < 0.05.

I was never a big fan of intraoperative leak testing and agree with the authors' finding that postoperative leaks can occur when the IOLT was negative. As they mention in their discussion, leaks often present long after the date of the operation and may be caused by ischemia, cautery injury, or other factors not readily identifiable by an IOLT.

Because the authors didn't find a single leak by doing the IOLT in 494 cases, they suggest that an IOLT is not necessary. But what if they had found one leak and fixed it. Would that have changed their conclusion?

I wonder if everyone at their institution has stopped doing IOLTs.

PS: Don’t just read the abstract; read the whole paper.

8 comments:

Anonymous said...

Random thought from a non-surgeon: Is it possible that tension induced by the IOLT could affect healing at the suture line?

Their "trend" is just wishful thinking IMO.

Skeptical Scalpel said...

Yes, it is possible that distending the stomach with air could be detrimental to a fresh staple line. However, postop distension with air can occur with gastric atony or ileus. That sort of distension doesn't seem to cause leaks.

William Reichert said...

The test is pretty insensitive. How disastrous is it to miss a leak
and have to repair it later on.? How did the 13 patient with leaks fare?
Does the leak test pose a risk to the patient such that the overall
length of stay, or wound infection rate or other complication rate was higher than the outcomes in the group of 48 that did not have the test?
Can an experienced surgeon use the leak test in cases that
might be expected to have a leak and avoid it in more straight forward cases where he is certain that there is no leak clinically?

Skeptical Scalpel said...

Good questions.

How disastrous is it to miss a leak
and have to repair it later on.? It can be very bad, in fact life-threatening if not diagnosed and treated promptly.

How did the 13 patient with leaks fare? There were no deaths. From the paper: "Postoperative leaks were managed with re-operation and primary repair (46%), operative washout and drain placement (31%), primary percutaneous drainage (8%), or endoscopic
treatment utilizing stents, clips, and fibrin glue (15%). Following primary operative repair additional procedures were required in 50% of patients. These included repeat operations,
endoscopic treatments, or percutaneous drainage of abscesses. Among patients in whom leaks were managed with either endoscopic treatments or with drainage procedures, the average time to leak resolution was 8 weeks (range 2-20 weeks). The mean length of hospital stay for patients following a leak was 23 days."

Does the leak test pose a risk to the patient such that the overall length of stay, or wound infection rate or other complication rate was higher than the outcomes in the group of 48 that did not have the test? No.

Can an experienced surgeon use the leak test in cases that might be expected to have a leak and avoid it in more straight forward cases where he is certain that there is no leak clinically? Possibly one could tell that in the OR, but as the paper pointed out, all patients who leaked had negative OR leak tests.

Strode said...

Honestly, this paper is stupid and I know some of the authors personally. Omitting a simple step that costs nothing to avoid a large fixable problem makes no sense. Leaks happen after several days in most cases.. That's weLL known but if you have a leak leaving the operating room, you have a whole different issue.

Skeptical Scalpel said...

Strode, thanks for commenting. I agree with you. I've always felt that a negative leak test was no guarantee that an anastomosis wouldn't leak later. That's about the only thing this study proves.

Anonymous said...

It's like saying that retained sponges always occur with a correct count. So people will say they are useless. Well I've pulled a few lap sponges out of very obese people after hearing count was incorrect. Saved me a lot of misery.

Skeptical Scalpel said...

A correct count is not useless, but it's also not foolproof. I don't know that anyone is saying not to count sponges and instruments. An incorrect count ALWAYS requires a search for the missing object including an x-ray if necessary.

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