Local Complications: Lymphatic

Etiology and Pathogenesis

Lymphedema develops when the rate of production of protein-rich interstitial fluid exceeds the capacity of the lymphatic system to remove the increased lymph volume. When lymphatic transport fails, post-bypass edema occurs. Lymphatic insufficiency has two main causes. First, increased production of interstitial fluid after successful revascularization results in a significant increase in the lymphatic load. Second, the transport capacity of the lymphatic system is reduced because of lymphatic injury and obstruction of deep and superficial lymph channels during dissection in the groin and popliteal space and along the great saphenous vein.

Increased capillary filtration results from elevated arterial pressure after revascularization, alterations in the regulation of microcirculatory flow, and probable endothelial and smooth muscle injury from chronic ischemia. ^, Eickhoff demonstrated that abnormalities in local blood flow regulation normalize approximately within a week after reconstruction, whereas edema persists much longer in these patients. Eickhoff’s experiments support the theory that lymphatic obstruction secondary to surgical injury is the most important cause of post-bypass edema.

If the number of functioning major lymph channels decreases to a critical level, lymphedema develops. In patients studied with lymphangiography after infrainguinal bypass, the average number of patent superficial lymph vessels visualized was reduced to 1.7 per patient compared with the normal average of 9.5. In a similar series of 37 patients, edema was not significant when more than three intact superficial lymph vessels were visualized on the postoperative lymphangiogram. AbuRahma et al. examined the involvement of the lymphatic system in the pathophysiology of edema formation in patients who underwent femoropopliteal bypass grafting. Edema developed in 29 of the 72 patients (40%). Leg swelling occurred in 85% (17 of 20) of the patients treated by conventional dissection of the femoropopliteal arteries. When careful dissection preserving lymphatics was performed, edema developed in only 2 of 20 patients (10%). Postoperative lymphangiography showed normal anatomy in six of the eight patients without edema, but markedly abnormal anatomy was in all eight patients with edema.

Persson et al. found less edema in patients who needed less dissection; that is, less edema in patients with prosthetic grafts compared to those with vein grafts and less edema in patients with above-knee grafts compared to below-knee bypasses. Studies using albumin clearance in patients with edema after revascularization also supported the idea that edema is mainly lymphatic in origin. A reduction in the plasma albumin level with a concomitant increase in albumin content in the extremity was noted after infrainguinal bypass. The increase in albumin content was three times greater in limbs revascularized by femoropopliteal bypass than in those revascularized with aortoiliac grafts. These data correspond to the clinical observation that edema is less likely after aortofemoral revascularization.

Lymphedema with lymphocele has also been reported following varicose vein surgery. There is an association of lymphatic dysfunction in patients with incompetent varicose veins, and therefore one must take the same care to protect lymphatics during open vein surgery. ^,

Although venous thrombosis has been proposed as a cause of postoperative leg edema, ^, studies have demonstrated a low incidence of deep venous thrombosis in patients with post-bypass edema. ^, In one series, normal venous hemodynamics and morphology were confirmed in 41 of 45 patients with leg edema after arterial bypass. The incidence of deep venous thrombosis after femoropopliteal bypass was found to be similar in patients who had edema (7%) and in those who did not (10%). Deep venous thrombosis therefore seems to play a minor role in post-bypass edema in most patients. ^{, ,}

Diagnosis

Mild, partially pitting ankle edema appears on the second or third postoperative day and resolves almost completely with leg elevation and bed rest. Lymphedema is frequently unilateral and involves the dorsum of the foot (“buffalo hump”) and the toes (“squaring”). The differential diagnosis of postoperative limb swelling includes deep venous thrombosis, infection with cellulitis, and compartment syndrome. The history and physical examination can aid in identifying cellulitis or compartment syndrome, and duplex scanning can diagnose deep venous thrombosis. If the cause of the edema is still in question, lymphoscintigraphy can confirm the presence of lymphedema ( Fig. 54.1 ).

Management

Postoperatively, mild edema of the extremity should be treated by frequent elevation of the limb. Some surgeons advocate for strict bedrest. Cardiac failure should be treated promptly to help preserve the normal pressure gradient and allow venous return and lymph flow toward the heart. Moderate to severe post-bypass edema is treated with compression wrapping until the incisions have healed, followed by calf-length, 30- to 40-mm Hg compression stockings. For patients with a below-knee, in situ bypass or any bypass to the distal tibial or pedal arteries, management is individualized to avoid direct compression of a subcutaneous vein graft. Attempts to prevent or limit post-bypass edema pharmacologically with steroids, mannitol, terbutaline, or furosemide have not proved effective and are not recommended.

Prevention

Meticulous, lymph-preserving surgical dissection is needed to minimize post-bypass edema. ^, For infrainguinal bypass, a vertical groin incision slightly lateral to the femoral pulse should be made in an attempt to preserve the patency and integrity of the lymph nodes. The inguinal lymphatics should be retracted medially, and a vertical incision should be made in the femoral sheath to dissect the femoral arteries. Loupe magnification facilitates identification of the lymph nodes and lymph vessels. The lymphatics should be carefully preserved; if they must be divided, they should be ligated to avoid leakage of lymph. Attempts should be made to preserve as much lymphatic tissue as possible between the saphenofemoral junction and the femoral artery.

Multiple short skin incisions to harvest the saphenous vein may disrupt fewer superficial lymphatics. In theory, endoscopic video-assisted vein harvest may also cause less lymphatic injury and decrease wound-healing problems without compromising vein conduit quality. In a series of 68 lower extremity bypass procedures, only one bleeding complication was related to the video-assisted harvest, and two seromas developed at the arterial dissection sites. The benefit of endoscopic versus open vein harvesting in terms of a reduced rate of lymphatic complications was confirmed in prospective randomized studies, ^, and such harvesting can result in a reduction in postoperative wound infections. ^, Dissection around the popliteal artery should be performed with the same care to avoid lymphatic disruption. The vascular sheath should be opened longitudinally without dissection of the popliteal vein or the posterior tibial nerve in the neurovascular bundle. Fibroadipose tissue, which contains the deep lymphatics in the popliteal fossa, should be left intact. Obara et al. reviewed 1580 open and endovascular surgery procedures and concluded that significant reductions in lymphatic complications occur with planned procedure, and endovascular procedures, as well as using minimal incision techniques for femoral artery exposures when possible. More recently, Dessalvi et al. described the prophylactic use of lymphoscintigraphy and blue dye with or without lymphovenous anastomoses eliminated the risk of lymphatic complications associated with open venous surgery.

Etiology

Important factors that contribute to lymphatic leakage are failure to ligate or cauterize divided lymphatics and failure to approximate the tissue layers properly at closure. Lymphatic leakage occurs more frequently in older diabetic patients with poor wound healing. Excessive early limb motion, infection of the operated leg or foot, reoperation, and placement of a prosthetic graft to the groin are other possible causes.