Omentoplasty

Omentoplasty is a surgical procedure in which part of the greater omentum is used to cover or fill a defect, augment arterial or portal venous circulation, absorb effusions, or increase lymphatic drainage. The omentum has been described as the "policeman of the abdomen," in that it wraps around abdominal structures such as the gallbladder and appendix and can revascularize them when they are deprived of their blood supply. Omentoplasty may be classified into the following two types[1] :

• Type I – Single-layered omentum
• Type II – Double-layered omentum

When Casten and Alday introduced omental transposition for treatment of patients with atherosclerosis,[2] they believed that it worked by supplying extra blood to the ischemic limb. However, this explanation is implausible because the diameter of the omental vessels is roughly one tenth that of the popliteal artery. Later studies demonstrated that an increase in local collateral circulation (rather than any significant increase in blood flow) was the likely mechanism of action for omental transfer.[3, 4, 5, 6, 7]

Goldsmith et al showed that the omentum contains a lipid fraction that promotes neovascularization; thus, a local effect on limb musculature with increased local collateral circulation may be a possible mode of action.[8, 9]

Omentum is known to adhere to surrounding structures and develop connections with them. Hoshino et al observed vascular connections between the omentum and the limb vasculature in limbs that had been amputated after omental transplantation.[1] Babu et al noted revascularization of muscle from omental vessels growing into it in limbs that had been amputated after omental transplantation.[10]

Agarwal et al performed postoperative angiography in 50 patients who underwent omental grafting; they observed a greater number of collateral vessels at the graft site, with filling of vessels distal to the block in the limbs.[11]

In an extension of the same study, 20 dogs underwent allograft omental transfer in limbs after ligation of the femoral artery. In 10 cases, exploration of the graft site after 3 weeks revealed an increased number of collateral vessels at the graft site, with filling of vessels distal to the site of the block. The authors' conclusion stated that even an omental graft that is mismatched with respect to blood group and human leukocyte antigen (HLA) is taken up and revascularizes the ischemic limb.[11]

Subodh et al used postoperative Doppler studies and selective celiac axis angiography to study the circulation in the omental graft and found that in 18 of 20 cases, the arterial pulsations were heard up to the knee on Doppler study; in the other two cases, symptoms did not improve.[12]  On celiac axis angiography, however, the omental vessels could be visualized up to the thigh in only six patients and up to the knee in only four. The authors concluded that omental transposition probably works by promoting local collateralization; similar conclusions were drawn in another study comparing free omental grafts to pedicled omental grafts.

Three randomized controlled trials involving a total of 2296 participants concluded that omentoplasty for esophagogastrostomy after esophagectomy in patients with esophageal cancer may decrease anastomotic leakage without affecting the rate of other complications.[13, 14, 15, 16, 17, 18]

Omentoplasty has been used in various settings involving both intra-abdominal and extra-abdominal conditions. Intra-abdominal settings in which omentoplasty is indicated include the following:

• Gastrointestinal – Hydatid disease of the liver, ^{[19, 20]} perforated peptic ulcer (Graham patch), ^[21] colorectal anastomosis, ^{[22, 17, 18]} surgically treatable pancreatic conditions ( pseudocyst, chronic pancreatitis)
• Gynecologic – After abdominal hysterectomy (an omental J flap is used to reduce morbidity due to infection), vesicovaginal fistulae, neovaginal reconstruction ^{[23, 24]}

Extra-abdominal settings include the following:

• Vascular – Revascularization in peripheral vascular disease
• Cardiothoracic – Bronchopleural fistula, poststernotomy mediastinitis, ^[25] chest-wall reconstruction
• Urologic – Pyeloureterostomy, pyelovesicostomy, omentovesicopexy for neurogenic bladder
• Reconstructive – Pharyngoesophageal reconstruction (eg, with tubed gastro-omental free flaps), filarial lymphedema ^[13]

The presence of advanced intra-abdominal malignancies is the only absolute contraindication for omentoplasty.

Omentoplasty has two main relative contraindications. One is unavailability of a sufficient length of omentum for the procedure being planned; this may occur as a consequence of prior intra-abdominal infections or previous surgical procedures. The other relative contraindication is unavailability of acceptable-quality blood vessels; this may occur secondary to atherosclerosis.

Infection and subsequent graft extrusion are the most common complications. Prevention requires thorough preoperative preparation, administration of antibiotics prophylaxis before the procedure, and strict maintenance of intraoperative sterility.

The standard laparotomy set is required for omentoplasty; it includes the following:

• Scalpel with No. 11 and No. 15 blades
• Curved and straight artery forceps
• A pair of toothed thumb forceps
• A pair of nontoothed forceps
• Allis forceps
• Noncrushing intestinal clamps
• Surgical cautery
• Hemostatic clips or ligatures
• Handheld ultrasonic dissector (if available)
• Abdominal wall retractors or self-retaining retractors
• Atraumatic visceral retractors
• Suture materials (absorbable and nonabsorbable)
• Anastomotic staplers

General anesthesia is preferred for this procedure. An epidural block may be added for postoperative pain management. After anesthesia induction, a 16- or 18-French Ryle tube is passed and kept on continuous drainage. The patient is then catheterized with a 14-French Foley catheter so that intraoperative and postoperative urine output can be monitored.

The patient is placed in a supine position, and preparation should include the whole of the abdomen, as well as the affected limb in which the omental transplant is planned.

Patients are assessed 7 days, 1 month, and 3 months after undergoing omentoplasty. The success of the procedure is evaluated both subjectively and objectively. The primary subjective criterion is symptomatic improvement. The main objective criteria include the following:

• Improvement in the local skin temperature
• Healing of ulcers and the amputation site
• Improved oxygen saturation values on pulse oximetry

In this procedure, the transverse colon and stomach are delivered out of the abdomen. The greater omentum is then detached from the transverse colon. The omental apron is lifted upward, and the lesser sac is approached via the posterior part of the greater omentum. Dissection is carried out in the avascular plane between the antimesenteric border of the transverse colon and the posterior layer of the greater omentum.

The arterial pattern of the omental vessels (see the image below) is carefully studied. It is of particular importance to note the sizes of the right and left gastroepiploic arteries. Either of these vessels may be selected as a feeding vessel on which a pedicled graft is to be constructed.

Omentoplasty. Omentum being mobilized.

The greater omentum is then detached from the greater curvature of thw stomach. The gastroepiploic arterial arch is retained in the omental pedicle graft. The vessels between the stomach and the arch are individually ligated and carefully divided. Strict hemostasis is maintained throughout. The omental pedicle must not be subjected to tension and must be kept moist during the procedure.

Once the omentum has been fully mobilized, the clinician should make the decision regarding which gastroepiploic artery should be divided in the creation of the omental pedicle. The omentum is then lengthened by dividing it according to the anatomic pattern of the vessels. The omental pedicle is converted into a ribbon form in this fashion. The distal end is tied with a thread to facilitate tunneling down the lower limbs. Again, strict hemostasis should be maintained throughout this procedure.

A suprainguinal incision about 3-4 cm in length is made on the affected side, and the omental pedicle is withdrawn from the abdomen, with care taken to ensure that it is not twisted or subjected to tension. Arterial pulsation should be readily palpable. The abdomen is closed in layers.

A horizontal subcutaneous incision about 4 cm in length is then made over the upper third of the thigh. Between this upper-thigh incision and the previously placed suprainguinal incision, a subcutaneous tunnel is made with the help of blunt dissection and an arterial forceps. The omental pedicle is advanced through this tunnel and brought out through the lower incision.

The omental pedicle is then placed over the leg, and its length is marked on the skin of the limb (see the first image below). A series of transverse incisions (typically three or four) are made over the medial aspect of the thigh and leg (see the second image below). The clinician should make a subfascial tunnel connecting these incisions, and the omental pedicle is advanced along this tunnel and delivered out of the last incision. The thread marker is removed, and the distal end of the pedicle is fixed to the gastrocnemius with atraumatic 2-0 chromic catgut.

Omentoplasty. Omentum being mobilized to reach below knee.

Omentoplasty. Skin incisions made on limb for subcutaneous tunneling of omentum.

The final step of the procedure is surgical wound closure. In the suprainguinal incision, the peritoneum is closed at the lateral ends so that the pedicle is not constricted. At all of the incision sites, the skin is sutured with nonabsorbable suture material; care must be taken not to include the omentum. After all of the wounds have been cleaned with an antiseptic solution, sterile dressings are applied.

Complications of pedicled omentoplasty include the following:

• Ileus
• Infection
• Abscess formation
• Intestinal obstruction
• Total necrosis of the omental flap

Performance of a pedicled omentoplasty with special attention to transposing techniques may minimize the complications attached to it.

One unusual complication involves herniation occurring through the tunnel created to bring the omentum into the thigh. Boiskin et al observed herniation of the transverse colon into the transposed omentum that was used for chest reconstruction after sternectomy.[26]

The purpose of pharmacotherapy is to induce anesthesia.

Class Summary

General anesthesia is preferred for this procedure. After anesthesia is induced, a 16-French or 18-French Ryle tube is passed and kept on continuous drainage. The patient is then catheterized with a 14-French Foley catheter to monitor intraoperative and postoperative urine output.

Propofol (Diprivan)

Propofol is a phenolic compound unrelated to other types of anticonvulsants. It has general anesthetic properties when administered intravenously. Propofol IV produces rapid hypnosis, usually within 40 seconds. The effects are reversed within 30 minutes, following the discontinuation of infusion. Propofol has also been shown to have anticonvulsant properties.

Etomidate (Amidate)

Etomidate is a nonbarbiturate imidazole compound with sedative properties. It is short acting and has a rapid onset of action; the duration of action is dose dependent (15-30 min). Its most useful feature as an induction agent is that it produces deep sedation while causing minimal cardiovascular effects.

The major application of etomidate is induction for endotracheal intubation, particularly in patients with, or at risk for, hemodynamic compromise. Etomidate has been shown to depress adrenal cortical function; however, this effect is not significant clinically during short-term administration. Since the drug is mixed in propylene glycol, continuous infusion is not recommended.

Thiopental

Thiopental is a short-acting barbiturate sedative-hypnotic with rapid onset and a duration of action of 5-20 minutes. Like methohexital, it is most commonly used as an induction agent for intubation. To use thiopental as a sedative, titrate in dosage increments of 25 mg (adjust to lower dose in children).