INCIDENCE AND PREVENTION OF POSTOPERATIVE ADHESIONS

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Incidence of Postoperative Adhesions
The frequency of peritoneal adhesion formation after abdominal surgery is difficult to assess due to the lack of studies with a high-level of evidence on this subject.

Frequency of post-operative adhesions after upper abdominal surgery
According to available data, peritoneal adhesions form in 93-100% of cases after laparotomy for upper abdominal surgery in adults [10-11]. The laparoscopic approach would seem to decrease the risk to 45% [11]. The frequency of surgical re-intervention for adhesion-related symptoms varies with the type of initial procedure but, in all cases, remains below 10% in adult patients [10] between 6.4 and 10% [22-24]. The greater omentum is the organ most typically involved by adhesion formation [10].

Frequency of symptomatic post-operative adhesions after lower abdominal surgery
An analysis of the frequency of symptomatic adhesions is not possible at present except by analysis of long-term postlaparotomy complications.

Surgery by open laparotomy
After lower abdominal open surgery, 67-93% of patientsdevelop adhesions [10,25], but only 5-18% of these casesbecome symptomatic (bowel obstructions). The rate ofsymptomatic complications varies depending on the type ofinitial operation and the duration of post operative follow-up.The rate of complications directly related to adhesionsresulting in one or more hospitalizations is 3.8% [25-33].The most common site of adhesion formation is betweenthe greater omentum and the midline closure, but theseadhesions rarely result in bowel obstruction unless the bowelwall itself is involved [10]. Risk factors for the developmentof symptomatic adhesions include the number of previousinterventions, a history of peritonitis, and age less than 60years [26].

Laparoscopic surgery
No data with high-level evidence are available in this context. The frequency of symptomatic adhesions requiring re-intervention after lower abdominal laparoscopic surgery has been evaluated at 2% after colorectal surgery (whether for benign or for malignant disease) at 2.8% after rectal surgery (benign or malignant), and at 0.76% after appendectomy [34-37]. The long-term incidence of adhesion-related post-operative obstruction has been measured in two randomized prospective studies comparing laparoscopy versus laparotomy for colorectal surgery. These studies showed no statistically significant difference in the rate of postoperative obstruction: 5.1% versus 6.5% in the study by Scholin et al., and 2.5% versus 3.1% in the study by Taylor et al. The highest rate of post-operative obstruction was seen in the group of patients who required conversion from laparoscopy to laparotomy (6%) [38].

Medical and surgical consequences of peritoneal adhesions
Adhesions are responsible for direct complications (acute intestinal obstruction, chronic abdominal pain, infertility) and for indirect complications encountered at surgical re-interventions (difficult dissection, prolonged operative time, intra- and post-operative complications).

Direct consequences
There are multiple direct of adhesions with serious potential complications.

Acute intestinal obstruction
Peritoneal adhesions are the underlying cause of 32% of acute intestinal obstructions and of 65%-75% of small bowel obstructions. (SBO) This complication accounts for 2.6-3.3% of all indications for laparotomy [10,30-47]. The number of previous abdominal surgeries increased the development of peritoneal adhesions. The interval between the initial abdominal surgery and the first episode of acute small bowel obstruction varies enormously from eight days to 60 years with a mean interval of 3.7-8.9 years [10,30-47]. The need to resect intestine during re-intervention for small bowel obstruction varies from 5.7-23.2% [39]. The greatest risk of this complication seems to occur after previous colorectal surgery, which is fraught with risks of more complex adhesion formation. Recurrent complications of adhesions occur frequently after surgery for acute bowel obstruction (12-19%). The identified risk factors for acute intestinal obstruction were: age under 40 years, a complicated post-operative course, the type of adhesions (complex), multiple (>3) previous abdominal surgeries, and conservative treatment of a previous acute small bowel obstruction [41]. It seems that the first episode of acute small bowel obstruction occurs in 3/4 cases after one or two abdominal surgery [41]. However, the increase of peritoneal adhesions based on the number of surgical procedures, does not correlate in proportion to the risk of bowel obstruction. The post-operative mortality related to surgery to relieve adhesion-related acute small bowel obstruction was estimated at less than 10%. The pre- and post-operative risk factors for mortality included: ASA score greater or equal to 3, age above 75 years, the presence of dyspnea at rest, renal insufficiency, hemoconcentration/dehydration, the type of obstruction (mechanical + strangulation), intraoperative complications (intestinal spillage with peritoneal contamination), and post-operative medical complications. Surprisingly, the need for intestinal resection did not appear as a risk factor for mortality [47,48]. The post-operative morbidity for adhesion-related acute SBO is estimated at 13—47%. Risk factors for morbidity include: ASA greater or equal to 3, age above 80 years, poor general condition for independent living, past history of cardiac insufficiency, previous stroke with neurological deficit, chronic obstructive pulmonary disease (COPD), leukopenia (WBC <4500/mm3), creatinine more than 1.2 mg/dL, the type of previous surgery (intestinal resection vs. adhesiolysis), infected or contaminated operative field, more than ten adhesions, and failure to perform enterectomy after a bowel injury [47,48]. The most frequent complications were: pneumonia/atelectasis (17%), prolonged ileus more than seven days (16%), inability to wean from ventilator within 48 hours (13%), need for endotracheal re-intubation (9%), wound infection (9%), abdominal wall abscess and/or evisceration (more common after enterectomy) [47,48].

Post-operative chronic abdominal pain
Post-operative pain due to adhesions is a controversial entity; its definition remains imprecise and is often not specified in the numerous studies on this subject. Its actual incidence is therefore unknown. Laparoscopy has both a diagnostic and therapeutic role since it permits recognition and simultaneous treatment of the cause of pain, although adhesiolysis may result in renewed adhesion formation. In any case, the benefit of extensive adhesiolysis in the treatment of patients with chronic abdominal pain and diffuse adhesions has not been proved, and this procedure has its own significant morbidity (enterotomy) [49]. On the other hand, chronic abdominal pain frequently recurs, even after an initial period of improvement.

Indirect consequences of intestinal adhesions during surgical re-interventions
The presence of abdominal adhesions increases operative time, particularly when the operative site of interest has already been dissected. Adhesions lead to increased intra-operative morbidity due mainly to intestinal wounds. Intestinal injuries occur in from 0.06% to 19% of cases and are the cause of increased post-operative morbidity (fistula, intestinal obstruction, wound abscess, respiratory complications) [50,51]. The number of previous laparotomies, and obesity (BMI > 25 kg/m2) were risk factors for intestinal injury. The laparoscopic approach seems to be associated with a delay in recognition of intestinal perforation [52-57]. The laparoscopic approach to adhesiolysis also seems to directly increase the incidence of this complication, particularly due to accidents of trocar placement that are responsible for 40% of such injuries. If bowel injury is recognized intra-operatively, conversion to laparotomy is often necessary. The risks related to conversion are highly variable depending on the type of procedure performed (3.3-100%). There are few reports of hemorrhagic complications due to adhesiolysis. The need for post-operative transfusion is higher in patients who have had previous laparotomy [58]; they are considerably higher if the surgery addresses an abdominal site that had been previously dissected. For all these reasons, it is important that patients be informed of an increased risk of surgical complications associated with previous surgery and postoperative adhesions.

Prevention
In view of the magnitude of the medical problems and financial burden related to adhesions, prevention or reduction of postoperative adhesions in an important priority. Some groups have recognized the importance of the problem and have attempted to educate physicians on this issue. Numerous articles on adhesion barriers have been published but several controversies such as the effectiveness of available agents and their indication in general surgical patients still exist. Most of the available literature is based on gynecologic patients. For general surgical patients no recommendations or guidelines exist. Any prevention strategy should be safe, effective, practical, and cost effective. A combination of prevention strategies might be more effective but our knowledge on this topic is fairly limited. The prevention strategies can be grouped into 4 categories: general principles, surgical techniques, mechanical barriers, and chemical agents.

Adhesion control
Clinically, there is no means of completely preventing adhesion formation. Two commonly used solutions in clinical practice that have some anti-adhesion effect in the laboratory animal are povidone-iodine [59] and 32% dextran 70 [60]. Povidone-iodine is popular among some general surgeons as a peritoneal lavage, more for the antimicrobial effect than the anti-adhesion properties. Dextran is often used by gynaecological surgeons for adhesion prevention in infertility surgery and there is some clinical evidence that it has some effect in these cases [61]. Independent of adjuvant therapy for the prevention of adhesion formation, there are several operative steps that can be taken to reduce the extent of adhesion formation and to minimise the chances of subsequent adhesive obstruction:
1.      Handle the bowel carefully to reduce serosal trauma.
2.      Avoid unnecessary dissection.
3.      Exclude foreign material from the peritoneum, e.g. use absorbable ligatures and sutures where possible, preferably those that are hydrolysed rather than phagocytosed. If non absorbable material is to be used then keep the cut ends as short as possible. Avoid excessive use of gauze swabs. Wear starch free gloves.
4.      Adequately excise ischaemic or infected debris within the peritoneum.
5.      Preserve the omentum, if possible. Place the omentum around the site of surgery and run the omentum under the wound to encourage low-risk adhesions to form.
6.      Avoid the division of adhesions that do not involve the small bowel.

By what means we can prevent post-operative adhesions?
Technical means

Any surgical technique that can reduce visceral and peritoneal traumatic injury is considered a priori potentially beneficial in the prevention of adhesions.

Two methods devolving from this principle are:
·         Surgery should be performed with the most atraumatic technique possible [62,63]. The measures which seem most useful to prevent the risk of adhesions include: gentle manipulation of tissue, meticulous hemostasis, the choice of small caliber sutures of inert composition, frequent irrigation of the area of dissection to prevent the formation of fibrinous deposits, minimal use of monopolar electrocautery to prevent diffuse thermal injury, maximal resection of devitalized tissues, removal of fibrinous residues and blood clot prior to peritoneal closure;

·         Laparoscopy: the theoretic advantages of this approach include: minimal incision of the parietal peritoneum, a maximal reduction of microscopic foreign bodies, preservation of the moist closed intraperitoneal environment, decreased bleeding and more precise dissection (particularly for pelvic and rectal surgery), and the absence or minimization of manipulation beyond the operative zone; these advantages have been highlighted in several retrospective studies comparing laparotomy and laparoscopy [63-65], but the level of evidence is low in these studies. The theoretical advantages have not been shown to translate into a decreased risk of bowel obstruction in two randomized prospective studies comparing the long-term risk of bowel obstruction after colorectal surgery by the laparotomy or laparoscopic approach [38,66]. These contradictory results suggest that a decrease in abdominal adhesions does not necessarily result in a decrease in the rate of post-operative obstruction.

Commercial products and devices to prevent adhesion formation
The mechanisms of action of anti-adhesion products are based on two principles: hydroflotation and the barrier phenomenon.

Hydroflotation
It is the mechanism of action of products instilled into the peritoneal cavity. These are fluids such as a 4% solution of Icodextrin. Their principal theoretical advantage is that the product is applied to the entire peritoneal surface and is easy to use in the laparoscopic setting.  Disadvantages include: the kinetics of peritoneal reabsorption are variable from patient to patient, but reabsorption is often complete within one to two days while the histopathologic process of adhesion formation continues throughout the first postoperative week, and the fluid tends to accumulate in the pelvis and pouch of Douglas as the patient changes position [62]. At this time, these products do not have marketing approval in France for gastrointestinal surgery indications.

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