The omentum has proven to be an organ of exceptional versatility. Until the 1800s, its role and function remained a mystery. Its ability to seal perforations, hernias, and fight infections has been demonstrated. It has been used to help achieve hemostasis, neovascularize devitalized structures, and provide lymphatic drainage. It has earned the nickname, deservedly, of the "abdominal policemen". Since the early 1900s, omentum has been used in a variety of surgical situations most notably in gastrointestinal and urogenital operations in people.

Extra abdominal uses of the omentum were first reported in the 1930s. Lengthening procedures helped expand the many uses of omentum. The omental lengthening procedures described by Ross and Pardo in the dog gave new impetus for further exploration into the extraabdominal uses of omentum.

Anatomy and Physiology

The greater omentum varies in size and texture between animals. It originates from the greater curvature of the stomach and extends caudally to the pelvic inlet. It serves a number of important functions but animals can survive without it. It increases serosal surface area for fluid production and absorption. It protects the abdominal viscera and aids in the localization and resolution of peritonitis. It may also prevent the intestines from getting between the stomach and liver.

Clinical Uses of Omentum

The omentum is rich with vascular and lymphatic plexuses and has great mobility. It can adhere to a site of contamination or injury with the peritoneal cavity and help contain infection. It also contributes neovascularization and increases oxygen tension to tissue that may be partially devascularized. The omentum participates directly in bacterial and foreign material absorption and in the transport of phagocytes into the peritoneal cavity.

Over the last 100 years, human surgeons have used omentum in reconstructive surgery in virtually all areas of the body. In the late 19th century, it was used to close perforated gastroduodenal ulcers. Other uses are as follows:

 Intraabdominal:

 Repair of vesicovaginal and vesicocolic fistulas

 Augmentation of bowel anastomoses Augmentation of wound closures involving the urinary bladder

 Repair of defects of the abdominal wall

 Extraabdominal:

 Support of primary suture lines of the esophagus

 Closure of full-thickness defects of the esophagus

 Repair of thoracic wall defects

 Palliation of lymphedema of an extremity

 Revascularization of tissue that is ischemic brain of stroke victims, myocardial ischemia, non-healing wounds of the skin

 Resurface scalp defects

 Reconstruct facial deformities

 Repair of bronchopleural fistulas

Characteristics of Omentum

The unique characteristics of omentum make it useful for reconstructive surgery. Its pliability can allow it to fill deep, irregular, and rigid spaces and be spread and distributed over wide flat defects. It may be lengthened to cover defects. When it is detached from the stomach and based on the right or left gastroepiploic pedicle, it reaches the axillary and inguinal regions in most instances. More specialized lengthening procedures in the dog will allow it to extend to the hock or elbow and possibly further.

Omentum and its use in veterinary surgery

The use of omentum in the dog includes augmentation of an enterotomy or line of anastomosis; repair of thoracic wall defects; treatment of prostatic abscesses; lymphedema; a drainage procedure for chylothorax in dogs and cats.

On occasion, an animal will present with a wound that will not heal in spite of excellent wound management and an attempt at treating an underlying cause. If all causes of impaired wound healing are eliminated but the wound continues to not heal, then a flap of omentum can be mobilized and moved to the site of the wound in an attempt to provide new arterial, venous, and lymphatic communications. This will hopefully alter the milieu of the wound so it can eventually undergo primary healing. In particular, this has been a method used successfully in cats with chronic non-healing wounds.

The omentum can be lengthened by various methods and mobilized to the desired location. It is tunneled subcutaneously to reach these sites.

A cranial ventral abdominal midline incision can be used to gain access to the omentum and its attachments in order to create a pedicle. It is preferable, however, to use a paracostal incision to mobilize and lengthen the omental pedicle. The dorsal leaf of the omentum is freed up from its short epiploic vessels and from a few vascular attachments to the spleen and pancreas. This immediately doubles the length of the omentum that is available. An inverted "L" shaped incision will allow further lengthening of the omentum. The elongated pedicle of omentum is then tunneled subcutaneously to the site of the wound. As the omentum exits a defect left in the abdominal wall, which is sufficient in length not to strangulate the pedicle, it is tacked to the contiguous fascia to keep the omentum from pulling back into the abdominal cavity. The omentum is placed within the wound and gently tacked to the underlying subcutaneous tissue or fascia. The skin adjacent to the wound is now apposed over the omentum. Drains may or may not be used, depending on the discretion of the surgeon. In most cases, a drain is not necessary.

In most cases, it is not necessary to repair the defect left in the abdominal wall unless it is ventral in location. When a paracostal incision is used, it is usually ignored. Although it is not necessary to do a second surgery to amputate the omentum and repair the defect, you can do it for cosmetic purposes. The surgeon should allow at least 4-6 weeks however, before the omentum is separated from its vascular supply provided by the pedicle.

References

1.  Brockman DJ, Pardo, AD et al: Omentum-enhanced reconstruction of chronic nonhealing wounds in cats: techniques and clinical use Vet Surgery 25:99-104, 1996

2.  Roa DM, Bright, RM et al: Microvascular transplantation of a free omental graft to the distal extremity in dogs Vet Surgery 28: 456-465 1999

3.  Lascelles BDX, Davison L: Use of omental pedicle grafts in the management of non-healing axillary wounds in 10 cats Jour of Sm Anim Pract 39:475-480, 1998

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