Intestinal surgery (part 1) (Proceedings)

Complications associated with intestinal surgical procedures can be reduced by attentiveness to the principles of intestinal surgery and appropriate use of ancillary procedures such as serosal patching.

Surgical principles and technical details of intestinal surgery

The following principles should be followed when performing intestinal surgery: establish an early, accurate diagnosis, isolate the area to be incised, minimize tissue trauma, minimize contamination, preserve the blood supply, maintain an adequate lumen, achieve a secure closure, avoid tension across the suture line, protect the suture line, and accurately assess intestinal viability (see Part II notes).

The more accurately the patient is assessed preoperatively, the better prepared the surgeon will be for the procedure. Also, accurate, efficient operative evaluation of the patient is critical for a successful surgical outcome. Involved segments of the intestinal tract should be exteriorized and isolated from the peritoneal cavity prior to incision. Laparotomy pads or huck towels are used to "pack off" the exteriorized segment to minimize intra-operative contamination and to improve accessibility. All segments except the caudal duodenal flexure and the ileocolic junction are usually readily exteriorized in the dog and cat.

Probably the single most important principle of intestinal surgery is the minimization of tissue trauma. Patient morbidity is reduced whenever tissue trauma is minimized. Factors which are important in minimizing tissue trauma include: atraumatic occlusion of the intestinal lumen, limited manipulation of the intestinal tract, stay suture placement, proper selection and use of instruments, and keeping tissues moist. Atraumatic occlusion of the intestinal lumen is best accomplished by digital occlusion by an assistant, although Doyen intestinal forceps or Penrose drain tubing may be effective alternatives. Minimizing manipulation of the intestine is accomplished by avoiding grasping the intestine with any surgical instruments, including thumb forceps. Instead, the tips of the closed thumb forceps are inserted into the intestinal lumen, the tips are allowed to spring open, and the wound edge is stabilized by the open tips of the thumb forceps. Stay suture placement also reduces the need for manipulating the intestinal tract, especially during resection/anastomosis. Proper selection and use of instruments during intestinal surgery involves the use of scalpel blades to incise rather than scissors, the atraumatic stabilization of the intestine with thumb forceps during suturing, and the use of suture with appropriately-sized swaged taper point or tapered cutting edge needles. If scissors are used on tissue (e. g., excision of everted mucosa), use sharp Metzenbaum scissors. Also, prevent tissue desiccation by regularly using warm, sterile isotonic solution on exposed tissues.

Intra-operative contamination is minimized by the following techniques: exteriorizing and packing off involved segments of the intestinal tract, using stay sutures to assist closure, occluding the intestinal lumen prior to incision, and decompressing affected areas of the intestinal tract prior to incision. Blood supply to the digestive tract is preserved by minimizing tissue trauma, appropriately placing ligatures, and locating incisions properly. Preservation of blood supply is an obvious prerequisite for successful intestinal surgery. Maintenance of an adequate lumen is essential for long-term function of the intestine. Factors which help maintain an adequate lumen include: minimizing tissue trauma, accurate apposition of tissue layers, and using approximating suture patterns rather than inverting, everting, or crushing patterns.

A secure closure of an intestinal incision is achieved by suture incorporation of the submucosa. The only reliable technique for incorporating submucosa is to place full thickness (i.e., lumen-penetrating) sutures. Tension across the suture line, particularly a circumferential suture line, will result in luminal reduction and is to be avoided. Adequate mobilization of tissue is necessary to avoid tension across the incision. Adequate mobilization is particularly important when performing surgery on the relatively fixed portions of the intestine (caudal duodenal flexure and ileocolic junction). More tissue may need to be resected in these areas to minimize tension across the anastomosis. Suture line protection is particularly important in potentially compromised patients. Two techniques are available: greater omental coverage and serosal patch (see below). Greater omental coverage should be provided routinely after closure of an intestinal incision, while a serosal patch is usually reserved for more at risk incisions.

Enterotomy

The most common indications for performing an enterotomy in small animals are removal of foreign bodies, either solitary or linear. Surgical decisions relating to enterotomy for removal of a solitary foreign body include: where (in relation to the foreign body) to position the incision, how to orient the incision, how long to make the incision, how to close the incision, and how to protect the suture line. When removing a foreign object from the small intestine, particularly one large enough to cause partial or complete obstruction, one should not incise directly over the foreign object. Position the enterotomy incision either orad (those cases characterized by segmental intestinal dilatation and larger, more obstructive objects) or just aborad (non-traumatized tissue) to the foreign object. Choose a non-traumatized area of intestine to incise, if possible. Orient the incision longitudinally, and make it long enough to remove the foreign object without further trauma to the intestine. Close the enterotomy longitudinally in a single-layer, appositional, simple interrupted or continuous pattern. Cover the closed incision with greater omentum or serosal patch.

Linear foreign bodies present additional surgical challenges, including the need to determine the proximal fixation point, the location of the distal (aborad) end of the object, the potential for perforation(s) at the mesenteric border, and the potential need for multiple enteric incisions. Avoid the temptation to exteriorize intestinal loops that are plicated due to a linear foreign body. Exteriorization often leads to inadvertent perforation. Once the proximal fixation point of the linear object has been determined, carefully determine the distal extent of the foreign object. Slowly and gently attempt to manipulate (milk) the aborad end of the object towards the stomach. If successful, such manipulation will reduce the tension in the plicated intestine. Next, carefully place stay sutures in the stomach for performing a gastrotomy. Do not attempt to exteriorize the stomach; use laparotomy sponges to help control possible contamination. Release the proximal fixation point of the linear object within the stomach by cutting the proximal aspect of the foreign object. Carefully exteriorize the portion of the intestine containing the linear object. Perform enterotomies at appropriate locations to remove the object in sections.

Serosal patch

Because of its ability to seal visceral perforations, the serosal patch has been described as a surgical parachute. Serosal patching has been found to be effective in many acute and chronic situations. Two primary indications for using a serosal patch are to close intestinal perforations that cannot be closed with sutures and to reinforce a visceral incision line. Serosal patches have advantages compared to greater omentum when used to reinforce incision lines. Serosal patches are stronger, more effective in infected environments or during malnutrition, and more versatile than multiple layers of greater omentum.

Serosal patches are indicated when primary visceral closure is either questionable or not possible or when reinforcement of a visceral wound is deemed appropriate. Specifically, duodenal perforations are candidates for use of a serosal patch, since tension-free primary closure or resection/anastomosis may either be not possible or associated with a higher surgical morbidity. Serosal patching of colonic perforations may also be preferable to attempting primary closure or resection/anastomosis. Reinforcement of visceral incisions (including biopsy sites) is particularly important in septic or malnourished patients. Both conditions can lead to profound hypoalbuminemia and impaired wound healing. The serosal patch will reduce the incidence of visceral wound dehiscence in such cases. Finally, coverage of a suture line in other tissues (e.g., urinary bladder) can be accomplished using a serosal patch.

Placing a serosal patch is technically more challenging than providing greater omental coverage. A portion of intact jejunum is usually employed when placing a serosal patch. Take care to make sure that the jejunal lumen is not compromised when placing the patch. Place one row of interrupted 3-0 or 4-0 sutures of synthetic absorbable (e.g., polydioxanone) or nonabsorbable (e.g., polypropylene) suture material circumferentially between the intact intestine and affected intestine (or other viscus). Place sutures 5 mm away from the edge of the perforation (or visceral incision) and 3 to 4 mm apart. Incorporate the submucosa of both the intact and affected intestine with sutures, but do not penetrate the intestinal lumen. Avoid suturing the patch to the edges of the defect, as this will not provide an effective seal.

Healing of the defect below the serosal patch will ultimately result in full thickness regeneration of the intestinal epithelium. Healing between adjacent serosal surfaces is usually complete at 2 weeks postoperatively in normal dogs. Normal mucosa coverage of smaller intestinal defects (1.5 cm X 3 cm) can be expected within 8 weeks postoperatively in normal dogs. Similar, although slower, healing can be expected in diseased patients.

In summary, the serosal patch has been shown to be beneficial either alone or with primary defect repair when used to cover visceral perforations or incisions. The technique is technically simple, versatile, and relatively efficient. A properly placed serosal patch will often eliminate the need for a second laparotomy in compromised patients.

References & suggested reading

Brown DC. Small intestines. In Slatter D (ed): Textbook of Small Animal Surgery, 3rd ed. W. B. Saunders Co., Philadelphia, 2003, p 644.

Crowe DT. The serosal patch - Clinical use in 12 animals. Vet Surg 1984;13:29-38.