Don't trust the abstract; read the whole paper

Above are the results and conclusion from an abstract of a paper called "Single-Incision Laparoscopic Cholecystectomy: Will It Succeed as the Future Leading Technique for Gallbladder Removal?" It appears online in the journal Surgical Laparoscopy, Endoscopy & Percutaneous Techniques.

It is another great example of why you need to read the entire paper and not just the abstract.

The methods section says that the study involved 875 patients with prospectively collected data. Don’t be fooled by prospectively collected data. This research is retrospective.

Here are some issues.

Single-incision vs. standard 4-port laparoscopic cholecystectomy: Part 2

Here's another paper that shows why reading only an abstract can sometimes be misleading.

A prospective trial (abstract here) of 49 patients randomized to single-incision laparoscopic cholecystectomy (SILC) vs. 51 who had standard 4-port laparoscopic cholecystectomy (LC) found that average operative times were 63.5 ± 21.0 minutes for the SILC compared to 43.8 ± 24.2 minutes for those who had LC, and hospital charges were also more than $4000 higher for the SILC patients—both significant differences with p values < 0.0001.

Medical and surgical supplies were the major factors contributing to the increased charges for SILC.

Other than a significantly larger number of females in the SILC group, the patients were similar in baseline characteristics.

Other important considerations such as postoperative pain, hospital length of stay (an average of 24 hours or less for both operations), use of analgesics, cosmetic appearance of the wounds, rates of incisional hernia, and quality of life were similar. Average follow-up was 16 months in both groups. The authors concluded that there was no advantage to SILC.

Since this paper supports my bias against single-incision surgery, I was going to tout it as yet another negative paper like a recent meta-analysis (here) from a group in Croatia showing absolutely no advantage for SILC.

But this sentence from the "Methods" section of the paper foiled my plan. "Before partaking in the study, each surgeon developed his or her SILC technical skills in a laboratory setting and demonstrated proficiency during 5 SILCs under the supervision of a surgeon with experience on more than 50 SILC cases."

This was not mentioned in the abstract.

Are you surprised that a surgeon that might take longer to do SILC, an operation done only 5 times before, than LC, which each of the surgeons had probably done hundreds of times? Although the mean operative duration was longer for SILC, it is a "straw man" in statistical parlance. This may not detract from the rest of the results but certainly has to be considered.

As noted by the authors, the study was underpowered (that is, there weren't enough patients) to detect differences in some of the other outcomes due to difficulty recruiting subjects.

Of 946 patients offered enrollment in the study, only 103 consented. Patients declined to participate either because the surgeon explained that he had done more standard LC procedures, or the patients opted for the SILC because of its supposed cosmetic advantage.

The authors, based at Northwestern University Medical School in Chicago, should be commended for their honesty in explaining their inexperience with SILC to potential subjects of the trial and wonder if other surgeons who perform SILC do this.

This paper also highlights the problems associated with attempts to conduct randomized prospective studies involving new surgical procedures.

Bottom line: The extra costs associated with SILC are not worth it.

Part 1 of this 2-part series on SILC appeared on Tuesday, 2/18.

Single-incision vs. standard 4-port laparoscopic cholecystectomy: Part 1 of 2

The saying used to be, "You can get any paper published if you have enough stamps." Now with electronic submission, you don't even need the stamps.

A retrospective study comparing single-incision laparoscopic cholecystectomy (SILC) to standard 4-port laparoscopic cholecystectomy (LC) concluded that "SILC showed no disadvantage concerning risk profiles, operative times or hospital stay."

According to the abstract, 81.7% of the 115 SILC patients had elective surgery vs. 55.5% of the 344 in the LC group. The SILC cohort experienced significantly shorter operative times (70 ± 31 vs. LC: 80 ± 27 minutes) and hospital lengths of stay (3.02 ± 1.4 vs. LC: 4.6 ± 2.8 days), p < 0.001 for both. LC was converted to open surgery in 21 cases vs. none of the SILCs, p= 0.003. Rates of bile leak and incisional hernia did not differ.

Do you see any problems with this study? I do.

The groups were not really comparable because the LC group underwent more emergency operations. That difference is significant with a p value of 0.007—conveniently omitted from the abstract. The preponderance of elective cases likely accounts for the SILC group's shorter operative duration, lower rate of conversion to open, and shorter length of stay. The SILC patients were also a mean of 10 years younger.

The average operative time for the LC patients, 80 minutes, is much longer than the 40 to 45 minutes reported in most other recent series such as this one. In statistical circles, measuring one's pet theory against a false comparator is known as setting up a "straw man." I've written about this before.

This study was done in Germany, where the hospital lengths of stay for both types of surgery are far longer than those seen in the United States where about 90% of patients go home within 24 hours of laparoscopic cholecystectomy.

The authors concluded that "SILC can be regarded as a natural evolution in the era of minimally invasive surgery."

On the other hand "No disadvantage" is another way of saying, "No advantage."

This paper didn't convince me about the value of SILC. How about you?

Part 2 of this 2-part series on SILC appeared on Thursday, 2/20.

Single-incision laparoscopic surgery: What are the indications?

My answer is “None.”

There is no compelling reason to perform single-incision laparoscopic surgery (SILS).

Take cholecystectomy, for example. The three 5 mm incisions in the upper abdomen done for standard laparoscopic cholecystectomy are nearly painless and, after a few months, almost always become invisible. The umbilical incision is larger and does cause pain, but the incision for SILS is generally 50% larger than that of standard laparoscopic cholecystectomy and likely to be just as painful if not more so.

For appendectomy, the same reasoning applies regarding the two 5 mm incisions and the umbilical incision. Not only is the umbilical SILS incision larger, one recent paper reports that it results in more postoperative pain too.

The ergonomics of SILS leave a lot to be desired as well. Since the instruments enter the abdomen so close to each other, it is difficult to triangulate them. Obtaining the critical view of the structures in Calot’s triangle is more difficult. It certainly is hard to imagine that SILS is safer for the patient.

There has not been one study convincingly showing superiority of SILS over conventional surgery for any outcome. It will be a challenge to show that compared with multiple-port surgery, SILS shortens length of stay, decreases pain or even has a better cosmetic result after six months.

Small pilot studies of robotic SILS are surfacing. The robotic method offers the possibility that triangulation is slightly improved. But increased costs and longer operative times negate that minor technical gain. What’s more, triangulation is even better with 4-port surgery.

I propose the following:

If SILS had been invented first, papers extolling the safety, ease and comfort of multiple-port surgery would be appearing and everyone would be jumping on the bandwagon to offer it to patients as a better procedure.

Feel free to comment. And don’t ask me if I’ve done a SILS case. The answer should be obvious.

For a more extensive review of single-port vs.standard laparoscopic cholecystectomy, read this paper. Thanks to @anblog84 for sending it to me via Twitter.

Note: This blog appeared yesterday on General Surgery News.

Read the entire paper not just the abstract

Here is a paper touching on two of my favorite subjects, robotic surgery and misleading abstracts.

It is entitled “Overcoming the challenges of single-incision cholecystectomy with robotic single-site technology” was just published ahead of print in Archives of Surgery. It is a study of 100 robotic single-incision cholecystectomies done by five Italian surgeons.

The conclusion of the abstract:

“Da Vinci single-site cholecystectomy is an easy and safe procedure for expert robotic surgeons. It allows the quick overcoming of the learning curve typical of single-incision laparoscopic surgery and may potentially increase the safety of this approach.”

From the full text of the paper, here is a summary of the results of a survey of the five surgeons who participated in the study.

Rating single port insertion technical issues using a scale of 1 to 5 with 1 being easy and 5 being difficult, one surgeon rated it a 2, two said 3 and two said 4.

Regarding the ergonomics of robotic single-site vs. standard laparoscopic 4-port cholecystectomy, two surgeons rated robotic worse and three said equal.

Comparing robotic to standard laparoscopic 4-port cholecystectomy, all five surgeons said robotic surgery was more difficult.

All five surgeons said the robotic procedure was safe based on their having performed a mean of 18 cases with a range of 12 to 42 cases.

The mean duration of the surgery was 71 minutes, which does not compare favorably to an operative time of 40 minutes from series of 238 single incision non-robotic laparoscopic cholecystectomies reported in the Journal of the American Collegeof Surgeons in 2010.

The authors state, “None of the considered [operative] times (total time and each of its main components) appeared to significantly decrease with the number of patients operated on." How is this statement reconciled with the “quick overcoming of the learning curve typical of single-incision laparoscopic surgery” mentioned in the conclusion of the abstract? No such comparison was included in the paper.

This abstract of this paper, much of which is a survey of only five surgeons with a modest experience in robotic single-incision cholecystectomy, is misleading. The paper itself suggests that compared to standard laparoscopic surgery, robotic single-incision cholecystectomy is less ergonomically comfortable, more difficult and takes longer. To say it is safe based on a series of 100 cases is premature at best.

For previous posts on robotic surgery, see the label to the right of this post.

Here is a previous post on misleading abstracts: "Reading an abstract vs. reading an entire paper."

Single incision laparoscopic surgery for appendicitis may not be better

I don’t usually like to review papers that have only been published in abstract form or orally presented because complete data are not available for analysis. But I’m going to make an exception here because a recent paper presented at the American College of Surgeons annual meeting in October and featured on page 1 of Surgery News supports one of my many biases.

Researchers at the Chinese University of Hong Kong performed a trial involving 200 patients undergoing laparoscopic appendectomy randomized into two groups, conventional 3-port [3P] and laparoscopic single-site access [LESS]. The 3P approach uses 3 small incisions to insert the scope/camera and instruments while the LESS uses a single incision at the umbilicus with the scope/camera and instruments all inserted via the one incision.

Guess what? LESS was not only harder to perform [due to the inability to triangulate the instruments which are too close to each other] but it also caused significantly more postoperative pain.

Although LESS theoretically might result in a better cosmetic result because the only incision is in the umbilicus, the 3P procedure results in one scar in the umbilicus and two 5 mm scars in the lower abdomen. The two 5 mm scars are often invisible several months after surgery.

This study is one of the few large randomized trials on any type of single incision surgery and may be the first to show that LESS is inferior to the current standard. Because of their findings, lead author Dr. Anthony Y. B. Teoh said that his group “reverted to the three-port procedure” for patients presenting with appendicitis.

I previously blogged about a small study extolling the virtues of single-port robotic cholecystectomy, which purported to show [but did not] that it was better than the standard laparoscopic method.

Will there be more disillusionment with single-port surgery as larger and better designed studies emerge?

Robotic Single-Port Cholecystectomy Fails to Convince

I have resisted the urge to blog again about single-port [a.k.a. single-incision] laparoscopic cholecystectomy because I was afraid I would start swearing a lot, but I can contain myself no longer. The stakes have escalated with the appearance of a publish-ahead-of-print paper on robotic single-port laparoscopic cholecystectomy in Archives of Surgery.

One of the co-authors of this paper is the chief medical advisor for the company that makes the robotic surgery device and the other is a consultant. The paper is a pilot study of the feasibility of using the robot to perform single-port laparoscopic cholecystectomy. It attempts to retrospectively compare 10 patients done robotically to 10 patients who had standard, four-port laparoscopic cholecystectomies. Patients with acute cholecystitis were excluded from both groups.

One robotic case had to be converted first to a four-port laparoscopic approach and then to an open cholecystectomy. This patient was excluded from the analysis of the results, a flagrant violation of the “intention to treat” principle which is that all patients should remain in whatever group they originally were assigned to.

The robotic cases [minus, of course, the case that was converted] averaged 105 minutes in duration which was not significantly different than the four-port cases, which averaged 106 minutes. The authors concluded that this showed that the duration of robotic single-port laparoscopic cholecystectomy was equivalent to four-port laparoscopic cholecystectomy. Sounds great, right? Not really. This is a nice example of what is known in the statistics business as a “straw man.” A straw man is defined as establishing a control that is not representative of real life and then comparing the experimental group [favorably] to it. Most four-port laparoscopic cholecystectomies for non-inflamed gallbladders can be done in well under 60 minutes. For example, another recent paper comparing non-robotic single-port laparoscopic cholecystectomy to standard, four-port laparoscopic cholecystectomy noted mean case durations of 88 and 45 minutes respectively.

Of the nine analyzed robotic patients, two suffered urinary retention, one of whom had to be discharged with a catheter. This is a very rare complication of four-port surgery.

The authors state, “This approach [robotic single-port] appears to be safe, even in difficult cases with inflammation, and has a high degree of satisfaction with the patients.” It is difficult to see how they arrived at that conclusion since patients with inflammation were specifically excluded from the study. Patient satisfaction was only briefly discussed and not compared to the standard surgery group.

Not mentioned in the paper is the cost of the robot which is at least $1.3 million plus yearly maintenance fees of hundreds of thousands of dollars. All of this is being advocated without any evidence that the robot is safer or more efficacious for any type of surgery, let alone standard laparoscopic cholecystectomy. And it is being promoted to avoid three 5 mm incisions which in most patients are not painful and barely visible if at all. 

All I can say is "Klaatu barada nikto," which some have interpreted to mean “This escalation is unnecessary.”

The “Straw Man” Is Back

A rather breathless posting on Science Daily today extols the virtues of the “scarless” or single incision laparoscopic cholecystectomy compared to the standard four small incision technique. Single incision, or laparoendoscopic single-site surgery [abbreviated LESS (a catchy acronym is mandatory)], utilizes one incision in the navel through which the entire surgical dissection and removal of the gallbladder are done. LESS cannot usually be done when the surgery is for an acute gallbladder attack or if the patient has had previous upper abdominal surgery. The study was done at Mt. Sinai Hospital in New York.

According to the article “The Mt. Sinai group did find two advantages to the LESS procedure: these patients required less pain medicine after the operation than their counterparts who had the traditional minimally invasive operation; and LESS patients typically reported higher satisfaction scores: —4.7 on a scale of 1 to 5 (5 equals highest score) versus 3.6 for the conventional laparoscopic surgery group.”

Available in the abstract of the paper but not reported by Science Daily were the following: the study was retrospective and involved only 26 LESS patients and 50 conventional laparoscopic cholecystectomy patients; 31% of the LESS patients required additional incisions; the average age of the LESS patients was significantly younger than the conventional group [37 vs. 49 years respectively]; follow-up data were unavailable for over half of the conventional group.

The Science Daily piece quotes one of the authors. "What's really exciting is how these patients would recommend the procedure to a friend or family member," Dr. Chin said. "Seventy-four percent of the patients who had the single-incision operation would strongly recommend the procedure to someone else versus 36 percent of those who had laparoscopic surgery."

Here is where the “straw man” is introduced. A “straw man” is defined [see The Skeptic's Dictionary] as creating a fallacious argument and then refuting it with one’s own position. If you believe this article, only 36% of those who had standard four-incision laparoscopic surgery would recommend it to someone else. However, in the early days of laparoscopic cholecystectomy, papers reported patient satisfaction rates of 94-95% after conventional laparoscopic cholecystectomy.

Patients in both groups had obviously undergone only one of the two procedures making the recommendation data rather difficult to interpret. If 64% of patients who had undergone conventional laparoscopic cholecystectomy would not recommend it to someone else, what then would they recommend? Keep your gallbladder despite the pain? Old fashioned large incision open surgery? Suicide?

The straw man is an old friend. It’s good to see that he is still around.