Herniation at the site of cannula insertion after la pa roscop ic c holecystectomy
Letter 1 Sir I read with interest the Case Report by Messrs McMillan and Watt (Br J Surg 1993; 80: 915) concerning the herniation of small intestine through the site of insertion of a 10-mm cannula after laparoscopic cholecystectomy. Unfortunately this is not the first report of this acute complication, which has been recorded at least twice previously'**. There have also been letters published casting doubt on their conclusion that fascial closure of the unextended 10-mm defect is required to prevent this occurrence334.
All three of these patients were symptomatic within 3 days, and I have not yet seen a report of a similar herniation of small intestine at a later stage after laparoscopic operation. Thus it appears that the cause of herniation is likely to be perioperative and, as I have written previously3, probably related to the method of cannula removal.
Messrs McMillan and Watt state that they expelled all the carbon dioxide before extraction of the subumbilical cannula, a practice that is normal at present in laparoscopic cholecystectomy. However, when this manoeuvre is performed there is a pressure gradient between the gas in the peritoneal cavity and the atmosphere, allowing small bowel or omentum to become attached to the end of the cannula and then held there by the pressure differential. The act of withdrawing the cannula will pull the attached bowel into the wound and cause the hernia.
In addition, the defect in the anterior abdominal wall fascia is produced by the dilating effect of the 10-mm trocar and this is then held open by the cannula. The removal of this cannula allows the defect to close suddenly, reducing the size of this small hole and causing it to act as a sphincter, holding any misplaced bowel within the wound. Obviously, if bowel or omentum is pulled far enough through the abdominal wall it will be seen and replaced immediately. It is when the viscus is trapped only within the deeper layers of fascia, where it cannot be seen, that the danger arises. Therefore in laparoscopic trocar wounds up to 10 mm that have not been extended, I suggest that careful digital examination of all the cannulation sites at the end of the operation is more likely to avoid this complication than attempted fascial repair of these very small defects.