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  :
Type I – Single-layered omentum
Type II – Double-layered omentum
The image below depicts the omentum being mobilized.
When Casten and Alday introduced omental transposition for treatment of patients with atherosclerosis,  they believed 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.  Babu et al noted revascularization of muscle from omental vessels growing into it in limbs that had been amputated after omental transplantation. 
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. 
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. 
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 2 cases, symptoms did not improve. 
On celiac axis angiography, however, the omental vessels were able to be visualized up to the thigh in only 6 patients and up to the knee in only 4.  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.
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:
Gynecologic – After abdominal hysterectomy (an omental J flap is used to reduce morbidity due to infection), vesicovaginal fistulae, neovaginal reconstruction 
Extra-abdominal settings include the following:
Vascular – Revascularization in peripheral vascular disease
Cardiothoracic – Bronchopleural fistula, poststernotomy mediastinitis, chest wall reconstruction
Urologic – Pyeloureterostomy, pyelovesicostomy, omentovesicopexy for neurogenic bladder
Reconstructive – Pharyngoesophageal reconstruction (eg, with tubed gastro-omental free flaps), filarial lymphedema
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.