Lymphaticovenular bypass

Introduction

Historically, the treatment of lymphedema has been focused on ameliorating symptoms and halting the progression of disease. However, with recent advancements in reconstructive microsurgery and supermicrosurgery, lymphedema is now a surgically manageable condition. Operative management of lymphedema can be categorized according to the guiding principles of each operation. Debulking procedures such as liposuction and the Charles procedure effectively remove diseased tissue and skin but do not act upon the lymphatic system itself. Physiologic procedures, including lymphaticovenular bypass (LVB), vascularized lymph node transplant (VLNT), and vascularized lymph vessel transplant (VLVT), aim to restore lymphatic drainage of the affected limb. VLNT and VLVT accomplish this with free tissue transfer of healthy lymphatic structures from an unaffected region of the body. VLVT is a novel procedure in the early stages of adoption. As with any newly described procedures, neologisms abound and while they are meant to be descriptive and clear, they are often confusing. VLVT is an example but it is, in fact, a flap which contains lymphatic channels. Many of the flaps we commonly use have lymphatic channels. Yamamoto has described the lymphatic interpositional flap transfer (LIFT) procedure which utilizes these lymph channels, and his description is extremely clear. While it is highly effective, VLNT carries a small but serious risk of iatrogenic donor site lymphedema. Supermicrosurgical lymphaticovenular bypass (LVB), as its name suggests, re-routes native lymphatic vessels into the venous circulation of the affected extremity. LVB’s minimally invasive nature makes it a particularly appealing procedure to patients, but it has not enjoyed the same level of popularity with surgeons. This may be because of the requirement of supermicrosurgical expertise, uncertain postsurgical outcomes, and lack of consensus on timing, patient selection, and number, location, and configuration of anastomoses. However, with the proper approach to the above elements, outlined in this chapter, LVB is a powerful asset in the treatment of lymphedema.

Background

Microsurgical lymphovenous bypass was first described by Jacobson and Suarez in a canine model in 1962. Sedlacek and colleagues implemented it in humans, but technical immaturity and unsophisticated instrumentation limited their success. Techniques were subsequently refined in animal models until 1977, when O’Brien and colleagues published their series of lymphaticovenous bypass in human proximal upper limbs. However, the technically challenging anastomosis and inability to monitor anastomotic patency with traditional modalities presented barriers to wide adoption. Outcomes remained inconsistent. In retrospect, the unpredictable outcomes were likely due to the limitations of microsurgical anastomosis at this time, which forced surgeons to utilize large veins in the proximal limb. Because the degeneration of lymphatic smooth muscle begins proximally in lymphedema, it was often difficult to find healthy, functionally preserved lymphatics in these regions. Large veins in combination with functionally weak lymphatics resulted in unfavorable pressure gradients, compromising long-term anastomotic patency. The acceptance of LVB was further hindered by the emergence of VLNT. Surgeons’ greater familiarity with the microvascular concepts involved in VLNT helped it gain widespread interest, and LVB fell out of favor with some though many utilized LVB in preference to VLNT because of reports of iatrogenic lymphedema at the donor sites of lymph node flaps.

Interest in lymphovenous shunting stagnated until advances in pre- and intra-operative imaging, operating microscopes, and surgical instruments facilitated the anastomosis of vessels smaller than 0.8 mm in diameter, ushering in the era of supermicrosurgery. First described by Koshima et al ., supermicrosurgical LVB allowed for the anastomosis of smaller lymphatics with venules ranging from 0.1 to 0.6 mm in diameter. The ability to use smaller vessels allowed surgeons to operate in the distal extremity, where lymph vessel function was more likely to be intact, and to select small, low-pressure venules that offered more favorable pressure gradients.

Outcomes of LVB have been difficult to study due to a lack of standardization. There is no consensus on patient selection, timing of surgery, or number, location, or type of anastomoses. Moreover, the literature includes a wide variety of staging systems, tracking modalities, follow-up time, adjunctive postoperative therapy protocols, and patient-related outcomes. While heterogeneous, the available data demonstrate that LVB, in the hands of experienced surgeons, is a highly efficacious treatment for lymphedema. A 2014 meta-analysis demonstrated a 48.9% reduction in limb circumference, with symptomatic improvement in 89.2% of patients and 56.3% able to discontinue compression therapy entirely. Numerous ensuing studies corroborate this while also showing substantial improvements in quality of life, dependence on compressive garments, and episodes of cellulitis. LVB not only improves the clinical features of lymphedema, but also the underlying pathology, including pathologic skin changes, inflammation, and fibrosis. Even in patients who do not experience significant volume or circumference reduction, many exhibit profound symptomatic relief – often within the first postoperative week – and improvement in lymphatic function as seen with indocyanine green (ICG).

Growing experience demonstrates that the efficacy of LVB in severe disease is underestimated. LVB has conventionally been considered most appropriate for early-stage disease, with more advanced patients directed to VLNT or, more recently, VLVT. While the greatest benefit is indeed reported in patients with early (stage 1 or 2) disease, this is likely due to the common use of volumetric reduction as a primary outcome measure, rather than a true lack of efficacy in advanced disease. LVBs been have successfully performed in many patients previously not considered candidates for LVB (i.e., no linear patterns on ICG). While patients with significant lipodystrophy often did not demonstrate remarkable decreases in volume, they experienced sustained improvement in clinical staging, ICG lymphographic staging, and quality of life. This demonstrates the need to replace volume or circumference measurements with more comprehensive outcomes to truly ascertain the efficacy of LVB in these patients.

A number of studies have demonstrated inferior outcomes after LVB for lower extremity versus upper extremity edema. This is thought to be due to the dependent position and higher venous pressure of the legs. Though the outcomes are not quite as impressive, LVB does still have a significant impact on volume, function, symptomatology, and episodes of cellulitis in lower extremity lymphedema and is still a worthwhile intervention to offer these patients.

LVB’s efficacy in primary lymphedema is controversial. The abnormal structure and function of these patients’ lymphatics may theoretically decrease the efficacy of LVB, leading many surgeons to recommend VLNT instead. However, it is not uncommon for patients with primary lymphedema to exhibit impaired lymphatic function on ICG in asymptomatic limbs. Harvesting lymph node flaps from these patients may put them at risk for iatrogenic donor site lymphedema. LVB is a viable, safer alternative following a thorough workup of these patients’ unique anatomy.

LVB is minimally invasive, with small incisions and superficial dissection. It can be performed as an outpatient procedure under general anesthesia or under local anesthesia, depending on patient and physician preference. The rate of complications is low. Reported complications include the need for additional procedures, lymphorrhea, minor wound healing problems, and cellulitis.

Clinical approach

The concepts behind supermicrosurgical LVB are simple. Much discussion in the literature has been devoted to supermicrosurgical technique, but this is only the beginning. Achieving consistently favorable results with LVB requires more than mere proficiency with its technical nuances; success is determined by proper diagnosis, patient selection, intra-operative decision-making on incision placement and choice of anastomotic configuration, and thorough understanding of the underlying pathophysiology. In this section, we detail the approach to diagnostic evaluation, patient selection, and surgical technique. We have refined our particular approach over the course of more than 6000 LVBs. In experienced hands, LVB becomes a powerful procedure.