Key gastrointestinal surgeries: Omentalization

OMENTALIZATION, THE PLACEMENT of omentum around organs or within cavities to improve vascularization or drainage, has been used in a variety of abdominal, thoracic, oncologic, and reconstructive surgical procedures.1-3 The omentum has an extensive supply of blood and lymphatic vessels, providing a rich source of inflammatory and immunogenic cells—including neutrophils, T and B lymphocytes, mast cells, and macrophages—that stimulate healing and help prevent and resolve infection.2 The omentum's large surface area also aids in lymphatic drainage and bacteria and particulate matter absorption.3 Additionally, angiogenic factors released from the omentum encourage neovascularization and activation of macrophages, mast cells, and lymphocytes from local tissues.2,4-6

INDICATIONS

Omentalization is most commonly used to seal intestinal anastomotic sites (see the intestinal anastomosis article).4 Wrapping suture lines with omentum reduces the risk of leakage after end-to-end anastomoses. By adhering to the surgical site, omentum rapidly seals the incision, fills dead space, and provides an environment conducive to healing.6,7 For these reasons, omentalization is also useful for covering enterotomy, gastrotomy, and cystotomy incisions, particularly when the blood supply or tissue health is questionable, and for sealing around feeding tubes exiting the gastrointestinal (GI) tract.

The omentum can be used as a physiologic drain for prostatic, paranephric, pancreatic, and hepatic cysts; prostatic and uterine stump abscesses; and necrotic neoplastic sublumbar lymph nodes.2,4,5,8,9 In refractory cases of chylothorax or pleuritis, an omental flap can be brought through a diaphragmatic incision and sutured to the mediastinum to increase absorption of effusion.1,10

Using omental pedicle grafts to aid in the reconstruction of delayed or infected skin wounds is ideal because of the omentum's many functional characteristics that promote healing. Nonhealing axillary wounds in cats can be covered with a subcutaneously tunneled, extended omental graft and then closed with skin flaps.6 Additionally, a mesh skin graft can be placed directly over a subcutaneous bed lined with an omental flap to provide the graft with a novel blood supply and to encourage its survival.11

TECHNIQUE FOR OMENTALIZATION OF GI SURGERY SITES

An omental patch can be applied to any portion of the GI tract. Distal regions, such as the lower descending colon or rectum, may be reached by developing an omental pedicle extension.4,12 For general perioperative considerations when performing this procedure, including diagnostic testing, patient monitoring, and postoperative support, please see the symposium introduction.

Figures 1,2,3,4

To create an omental patch, tack the omentum over the GI incision site by using multiple simple interrupted sutures of rapidly absorbable monofilament suture. For end-to-end anastomotic sites, suture two portions of the caudal omental fold (the junction of the ventral and dorsal leaves) or the distal edge of an extended flap to either side of the incision line so that each covers half of the circumference of the anastomosis site (Figures 1-4).

To create an omental pedicle extension, exteriorize the omentum and spleen from the abdomen. Retract the dorsal leaf13 of the omentum cranially to expose its pancreatic attachments, and sharply transect them. Ligate or cauterize vessels as they are encountered. Then extend the dorsal leaf caudally, unfolding the omentum and doubling its length. This length is usually sufficient for all abdominal procedures. To achieve full extension, incise the flap in an inverted L-shape on its left side, just caudal to the gastrosplenic ligament.12 The incision should extend one-half to two-thirds the length of the omental width. Continue the incision caudally alongside the omental vessels for up to two-thirds of its length.

COMPLICATIONS

Complications arising from omental patch placement or omental pedicle grafting are rare and fairly inconsequential. The most common complication is partial necrosis of the omentum, which is usually the result of excessive tension or strangulation of a pedicle.2,4 Excessive or improper handling of the omentum during surgery may also lead to desiccation. Desiccation can be prevented by frequently moistening the omentum during the procedure or by keeping it wrapped in saline-soaked laparotomy pads. Intestinal entrapment by omental adhesions or tears can cause strangulation or torsion of the bowel in animals that have not undergone omentalization; a similar problem could occur after omental patch placement.14,15 We know of two animals that developed intestinal obstruction after omentum, which had been wrapped 360 degrees around their intestines, hypertrophied. Consequently, encircling the intestines with a single flap of omentum is not recommended.

Erik Anderson, BS

Karen M. Tobias, DVM, MS, DACVS

Department of Small Animal Clinical Sciences

College of Veterinary Medicine

The University of Tennessee

Knoxville, TN 37996-4544

REFERENCES

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2. Hosgood G. The omentum—the forgotten organ: physiology and potential surgical applications in dogs and cats. Comp Contin Educ Pract Vet 1990;12:45-51.

3. Kirby BM. Peritoneum and peritoneal cavity. In: Slatter D, ed. Textbook of small animal surgery. 3rd ed. Philadelphia, Pa: WB Saunders Co, 2003;414-445.

4. Heller J, Hunt GB. Clinical applications of the omentum in dogs and cats. Aust Vet Practit 2002;32:66-73.

5. White RA, Williams JM. Intracapsular prostatic omentalization: a new technique for management of prostatic abscesses in dogs. Vet Surg 1995;24:390-395.

6. Lascelles BD, White RA. Combined omental pedicle grafts and thoracodorsal axial pattern flaps for the reconstruction of chronic, nonhealing axillary wounds in cats. Vet Surg 2001;30:380-385.

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8. Campbell BG. Omentalization of a nonresectable uterine stump abscess in a dog. J Am Vet Med Assoc 2004;224:1799-1803.

9. Hoelzler MG, Bellah JR, Donofro MC. Omentalization of cystic sublumbar lymph node metastases for long-term palliation of tenesmus and dysuria in a dog with anal sac adenocarcinoma. J Am Vet Med Assoc 2001;219:1729-1731.

10. LaFond E, Weirich WE, Salisbury SK. Omentalization of the thorax for treatment of idiopathic chylothorax with constrictive pleuritis in a cat. J Am Anim Hosp Assoc 2002;38:74-78.

11. Smith BA, Hosgood G, Hedlund CS. Omental pedicle used to manage a large dorsal wound in a dog. J Small Anim Pract 1995;36:267-270.

12. Ross WE, Pardo AD. Evaluation of an omental pedicle extension technique in the dog. Vet Surg 1993;22:37-43.

13. Evans HE, deLahunta A, Miller ME. Guide to the dissection of the dog. 5th ed. Philadelphia, Pa: WB Saunders Co, 2000;201-202.

14. Rawlings CA. When and how to quickly use the omentum in surgery, in Proceedings. North Am Vet Conf Small Anim Exotics Ed 2004;18;1190-1191.

15. Hosgood G, Bunge M, Dorfman M. Jejunal incarceration by an omental tear in a dog. J Am Vet Med Assoc 1992;200:947-950.