Treatment of Lymphedema: Vascularized Omental Lymphatic Transfer

Key Points

Intraoperative mapping of the right gastroepiploic lymphosome is valuable to identify critical flap components.
No-touch flap elevation will prevent damage to the flap lymphatics and microvasculature.
Harvesting additional capillary networks can minimize venous congestion.
Additional vascular anastomoses may be required to mitigate venous congestion.

Introduction

Although lymphatic surgery has been practiced for over 100 years, advances in lymphatic comprehension, instrumentation, and imaging have resulted in a rebirth of this field. Similarly, advances in techniques and anatomic knowledge have resulted in the renewed interest in the omental flap for reconstruction and lymphatic surgery.

The omentum has been called the “policeman of the abdomen” due to its immunogenic and angiogenic properties. It contains high concentrations of critical factors, including immunoglobulin M and vascular endothelial growth factor protein. Vascularized omental lymphatic transfer not only provides gastroepiploic lymph nodes but also contains critical lymphatic structures, including the omentum-associated lymphoid tissue (OALT) (“milky spots”), which initiate absorption from the peritoneum. With these characteristics, the omentum has become a versatile flap option for reconstructive and lymphatic surgery.

Initial applications of the omentum for the treatment of lymphedema did not gain wide acceptance. Limitations of early approaches included the need for a celiotomy and its use as a pedicled flap, incurring the risk for hernia, bowel infarction, flap ischemia, and loss of the critical flap structures along the arc of rotation. The application of free tissue transplantation and minimally invasive flap harvest reduces donor site morbidity and pedicled flap complications. This chapter will detail the surgical considerations to improve successful outcomes with the vascularized omental lymphatic transfer.

Concepts

This flap has been described as a large, flattened-out lymph node. With meticulous techniques and comprehension of the flap anatomy, the omental lymphatic flap can remain well vascularized and retain its physiologic lymphatic architecture.

Regional Anatomy

Understanding the flap anatomy and extensive variability is critical to successful flap harvest and outcomes. The arterial blood supply to the omentum can come from two dominant pedicles, the right and left gastroepiploic arteries, which run along the greater curvature of the stomach. The right gastroepiploic artery is the largest branch of the gastroduodenal artery off of the celiac trunk. Although this usually arises near the pylorus, the origin may emanate anywhere along the greater curvature of the stomach to the mid-body.

At their origins, the right gastroepiploic artery diameter is usually greater than 2.5 mm, with the vein usually being larger than 3 mm. Although these relatively larger diameters compared to other lymph node transfers may be appealing, it is important to remember that the numerous small branches must be controlled to avoid postoperative complications, such as hematoma. Additionally, like other intestinal flaps, these vessels are superficial, have thinner walls, and are more fragile than non-intestinal flaps, making them more susceptible to devascularization, kinks, twists, and compression, especially as the flap does not have the benefit of a skin paddle to support its inset.

The branching and connections of the omentum vary significantly. The anastomosis between the left and right gastroepiploic vessels is weak in 60% and absent in over 20% of patients. Identifying this relationship is essential when harvesting a larger flap or splitting a flap. Several branches will perfuse into the omentum, including the right, middle, and left omental branches. If a trans-omental arch is present and contiguous with the major omental branches, including it within the flap is valuable to improve the capillary network.

The omental lymphatic flap includes a complete organ of lymphatic structures within its lymphosome. The commonly named gastroepiploic lymph nodes include lymph node stations 6 (subpyloric) and 4d (right gastroepiploic). These lymph nodes can vary in size and may not be present or visible on radiologic imaging. Although utilizing the gastroepiploic lymph nodes alone may be performed, incorporating the entire lymphosome does not require a significant amount of extra work and can help the patient only by providing additional lymphatic tissue and capillary beds to reduce venous congestion. The OALTs are essentially lymph nodes without capsules. They initiate absorption into the peritoneal cavity and may be more effective than the gastroepiploic lymph nodes. These are generally smaller than the gastric lymph nodes and present variably along the apron of the omentum, making the inclusion of these structures in intraoperative localizing imaging important. The efferent lymphatics from the OALTs can be easily damaged as they are friable and superficially coalesce toward large efferent lymphatics alongside the right gastroepiploic vessels.

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