POSTOPERATIVE ADHESIVE INTESTINAL OBSTRUCTION
Ketan R Vagholkar Practising Surgeon; Dr. Vagholkar’s Fracture and Accident Hospital, Thane - 400602
Adhesions have now become the leading cause of intestinal obstruction. The diagnosis though being straight forward, management poses a lot of problems due to the high incidence of recurrence. The advent of laparoscopic surgery may alter the incidence of adhesions. Despite the promise of laparoscopic surgery adhesions still continue to be a major source of concern for surgeons not only because of technical difficulties but also because of the volume of work they generate.
In the absence of any clinically proven means of preventing adhesions from forming, the onus lies with the surgeon to try and reduce their occurrence by improved and meticulous surgical techniques.
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-- ---------------------------------------------------------------------------- INTRODUCTION The clinical presentation of intestinal obstruction is well known to all surgeons when the patient presents with a previous history of abdominal surgery, the most likely diagnosis is adhesions. The incidence of postoperative adhesive intestinal obstruction has been gradually increasing over the last few decades. Vick in 1932 reported that adhesions accounted for 7% of all cases of intestinal obstruction. During the last few decades the leading cause of intestinal obstruction was strangulated external hernia.
The overall incidence of adhesive intestinal obstruction in 30% as shown in the studies conducted by Nemir, Perry, Bevan and Mc Entee.,, Subsequent studies have revealed a steady rise in the incidence of intestinal obstruction to the present day incidence of about 40%.[2
INCIDENCE Various studies have been carried out to assess the severity of problems posed by adhesions. Weibel and Majno carried out a study in a post mortem series to find out the incidence of adhesions.[21,22] In cadavers with no preceding abdominal surgery, adhesions were found in 28% and in those that had minor abdominal surgery 67% had adhesions[21,22] With other abdominal surgery the reported incidence was 50%. If major surgery had been performed adhesions were present in 76% and in cases of multiple abdominal surgery 93% had adhesions.
The incidence of adhesions has also been studied in living subjects. Inflammatory adhesions in patients who has not undergone any preceding abdominal surgery were found to be present in 10%. In patients who had previous abdominal surgery postoperative adhesions were found in 93% and inflammatory adhesions in 20%.
In a review over the last 25 years it has been shown that adhesions accounted for 1% of all surgical admissions and 3% of all laparotomies in a particular surgical unit. It is likely that although the incidence of adhesive obstruction is increasing, it is doing so because more and more patients are being submitted to laparotomies each year.
AETIOPATHOGENESIS OF ADHESIONS Adhesions can be classified as either congenital or acquired. The acquired type is further classified into inflammatory and post surgical. Of all the types described majority of cases are postsurgical. Many studies have been performed to study the time interval from surgery to obstruction. As yet results are not conclusive. The incidence though difficult to be determined is put forward to be 3% of all laparotomies for adhesive obstruction.
All operations which involve handling of the viscera in the infracolic compartment are more likely to produce adhesive intestinal obstruction The possible explanation put forward for them is trauma to the small bowel at the time of surgery. The anatomical distribution of all adhesions have been studied in various studies. The most common site for adhesions were to the undersurface of the abdominal wound which occurred in 84% or to the site of previous surgery in 58%.[14,15,16] The omentum was commonly involved in adhesions to the scar (72%) and to the site of previous surgery (22%). Adhesions from the small bowel to the wound occurred in only 18% of wounds and from the small bowel to the site of surgery in 16%.[14,15,16]
Adhesions which involved the small bowel alone occurred in only 8% of cases. Overall the omentum was involved in 57% of sites for adhesions and the small bowel was involved in 27% of sites. Adhesions between the small bowel and the site of previous surgery caused obstruction in 52%. Adhesions which involved the small bowel alone caused obstruction in 24%.[14,15,16] If the distribution of these obstructing adhesions is compared with that of any adhesions that develops after abdominal surgery, it is clear that although omental adhesions are the most common adhesions to be found they are at low risk of producing intestinal obstruction. Adhesions between small bowel and other viscera or other loops of small intestine occur less frequently but are far more likely to cause adhesive obstruction.
Cont: AETIOPATHOGENESIS OF ADHESIONS The omentum plays a protective role in adhesion formation. Adhesive obstruction after total colectomy is well known. This is because the operation involves, omentectomy and this will remove the organ that forms safe adhesions. As a result it would leave adhesiogenic areas exposed to the small bowel and will result in higher incidence of small bowel adhesions. Another significant factor is a frequent practice to divide any adhesions that are encountered. The division of adhesions which involves the small bowel are at a high risk of later obstruction.
PREVENTION As yet there are no definite methods of completely preventing adhesions. The two commonly used solutions that have anti-adhesive effects in animals povidone iodine and 30% dextran 70. Povidone iodine is used by surgeons more for its antimicrobial action rather than that of its anti adhesive effect. Dextran is a popularly used solution in gynaecologic practice to prevent adhesions in infertility surgery.
The most important way of preventing adhesions is by meticulous technique.
The following are a few operative steps which could be undertaken to reduce the incidence of post operative adhesions.
Careful handling of the bowel to reduce serosal trauma.
Avoid rough unnecessary dissection.
Avoid contact of foreign material from the peritoneum e.g. use of absorbable material as far as possible, avoid excess use of guaze swabs, or wearing starch free gloves.
Adequate excision of ischaemic or infected debris within the peritoneum.
Preserve the omentum as far as possible. Placement of omentum around the site of surgery and run the omentum under the wound to encourage low risk adhesions to form.
Avoid dividing adhesions which do not involve the small intestines.
SURGICAL MANAGEMENT Adhesions producing intestinal obstruction usually require surgical intervention in 30 to 60% of cases.[1,2,3]
Simple adhesiolysis is usually employed in those patients who require surgery for adhesive obstruction. Recurrence rate after adhesiolysis is 11% to 21%. In patients with recurrent obstruction adhesiolysis is combined with a plication procedure or with an insertion of a long intestinal tube. The plication procedures of Noble or Childs and Philips depend upon sutures to hold the small bowel in a specific position so that further adhesive obstruction cannot occur. The long intestinal tube is designed to hold the small bowel in a series of open loops until subsequent adhesions form to maintain the bowel in position and then the tube can be removed. The noble plication has a high incidence of complication hence it is abandoned.[24,26] Although good results have been reported for the long intestinal tubes its use should be confined to patients after division of extensive intraabdominal adhesions.
Cont: SURGICAL MANAGEMENT
If used after division of only a few adhesions when the adhesions reform they may not be extensive enough to hold all the small bowel in an open looped position and therefore will permit movement and twisting of the bowel and allow subsequent adhesive intestinal obstruction to develop.,
RECENT ADVANCES Though there is a better understanding of the mechanisms which lead to adhesion formation, yet there is no pharmacological means of preventing the formation of adhesions. Peritoneal trauma and ischaemia are potent stimuli for adhesion formation. Von Benzer has demonstrated fibrinolytic properties in peritoneum. The fibrinolytic activity is thought to be contained within the mesothelial cell layer.[28,29] The fibrinolytic activity has been identified as plasminogen activation.[30,34] A reduction in this activity is linked to adhesion formation. Changes in plasminogen activator activity levels were shown to be due to stimuli well known to cause adhesions and were particularly marked in the presence of ischaemia. This reduction was not only due to removal of plasminogen activity but also due to the release of plasminogen activator inhibitors present during inflammation and ischaemia.[7,8,12]
This mechanism for adhesion formation supports the use of fibrinolytic agents as anti-adhesion agents.
The commercial production of tissue plasminogen activator rt-PA by recombinant DNA techniques has permitted the study of the use of this agent in adhesion formation.[21,22] It has been used to replace the reduced plasminogen activity of traumatised peritoneum. The effectiveness of rt-PA as an anti adhesive has been confirmed in animal models. Its effectivity in humans has still to be tried out. But it appears to be the most promising agent. Laparoscopic surgery may prove to be the solution to the problem. A study conducted by Luciano demonstrated that when a stimulus is applied at open laparotomy in an animal it produces more adhesions than when the same stimulus is applied through the laparoscope.
CONCLUSION The advent of laparoscopic surgery will undoubtedly alter the incidence of adhesions developing after surgery. The reduced bowel trauma from handling, the absence of large abdominal wounds and the exclusion of foreign material such as starch and guaze from the abdominal cavity will reduce adhesion formation after laparoscopic surgery. It is possible that in the future these problems may be reduced by some form of rt-PA peritoneal lavage after surgery that will prevent adhesion formation or reformation.
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