EPIDEMIOLOGY
Regarding the incidence of peripheral lymphatic lesions, after every major open or closed trauma, different levels of involvement of the lymphatic structures can be observed, from their capillary components (initial lymphatics), or in the most proximal sectors (lymphatic pre-collectors and collectors), with differing clinical pictures, depending on lesion severity.
Duct lesions are most frequently iatrogenic (>50%), or correlated to surgery (0.2-0.5% of chest-heart surgeries, 3% of endoscopic esophagectomies). Even during other cervical, supraclavicular, and thoracic surgeries (e.g. lymphadenectomies, retroclavicular goitre resection, resection of the first rib or clavicle, correction of subclavian aneurysm, scalenotomy, etc.), iatrogenic lesions of the thoracic duct may occur. In case of severe traumas (such as in the case of victims of several traumas), thoracic duct lesions may occur in 15-25% of cases, following falls from height, spine compression, in cases of broken vertebrae or ribs, following sudden spine hyperextension, as well as in penetrating wounds.
PATHOGENESIS
Every wound, especially if associated with a more or less significant loss of surface tissues, involves the most peripheral lymphatic branches (initial lymphatics). When lymphatic drainage of the affected area (for example upper or lower extremity) is normal, lymphorrhagia is minimal and stops spontaneously, since the lymph during inflammation can clot. Conversely, in limbs with chronic output failure (e.g. lymphedemas or flebolymphedemas), lymphorrhoea, persists due to the high pressure inside the lymphatic system. In addition, this condition favors infections (lymphangitis), since the lymph is an excellent pabulum for bacterial proliferation, and the wound is an entry gate, in particular for saprophytic germs (gram- positive cocci).
In closed traumas, collections of lymphatic fluid – mostly suprafascial serum-lymphatic (seromas, lymphoceles), or haemolymphatic collections – can occur. They are generally self-contained, due to the compression from adjacent areas, and they are usually found in association with contusion edema of the cutaneous and subcutaneous tissues. The course of these collections of lymphatic fluid depends on their extension: they can disappear spontaneously, with complete seroma absorption; they may become infected, or even turn into abscesses, following contamination, that may be triggered by repeated exploration punctures for fluid aspiration.
Surgeries – e.g. lymphadenectomy, especially if performed for oncological reasons, but also only as a biopsy, venous surgery, inguinal or crural hernioplasty, resection of protrusions (for example lipomas) in critical sites (armpits, groin) – are another pathogenetic mechanism of lymphatic lesions. After these surgeries, in particular on naturally prone patients (e.g. with latent lymphatic output failure), complications may occur, such as lymphangitis, lymphorrhoea, lymphocele, infection of surgical wounds, which may also promote the onset of secondary lymphedema of the corresponding extremity.
PATHOLOGIC ANATOMY CLASSIFICATION AND STAGING
Traumatic lesions of lymph vessels can be classified into traumas of peripheral lymphatics and traumas of the thoracic duct (including the receptaculum chyli of Pecquet and pre-cisterna chyli chylipherous vessels). Traumas, in turn, can be distinguished into open or closed traumas.
Open traumas of peripheral lymphatics are further classified into traumas of healthy or lymphedematous limbs. Therefore, lesions can occur that will spontaneously heal, as well as lesions that tend to become chronic (lymphorrhoea), with superimposed infections (lymphangitis).
Closed traumas of peripheral lymphatics are classified according to the type of fluid collection they trigger: serous fluid collection (fluid exudate), lymphocele (lymph), and haemolymphatic effusion. These collections are further classified depending on whether they tend to be fully reabsorbed, or persist with likely suppuration.
Open traumas of the thoracic duct (penetrating lesions, accidental lesions during surgery, broken vertebras or ribs) are classified according to the cervical or thoracic segment involved and the relevant clinical picture (lymphatic fistulas, chylocele, chylothorax, chylomediastinum, chylous ascites).
Closed traumas of the thoracic duct are correlated with an indirect mechanism and include traumas of cervical-dorsal spine hyperextension, obstetric traumas, thoracic traumas causing a sudden compression or traction of the duct (“bursting” of the duct, particularly during repletion, or caused by endoductal hypertension).
Traumatic lesions of the thoracic duct (and ensuing chylothorax) can be classified into three stages that take account of prevailing symptoms following trauma: initial stage (post-traumatic shock) – shock symptoms prevail, caused by thoracic contusion trauma, and often in association with other traumatic lesions (for example, in multiple trauma patients); intermediate stage (free interval) – symptoms improve; third stage (chylothorax) – characterized by dyspnea and circulation failure (caused by chylous effusion stimulating the pleura). This three-stage mechanism means that the pleura, which is initially sound, breaks down after a few days or weeks since beginning of chylous effusion in the mediastinum, with subsequent chylothorax.
GALLERY
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Following figures: Clinical, radiological (lymphangio-CT, retrograde ductography), surgical picture (needle placed in orifice corresponding to the chylous fistula and chylocele capsule), and long-term follow-up of a traumatic lesion of the thoracic duct.
PHYSIOPATHOLOGY AND CLINICAL ASPECTS
The clinical picture varies depending on physiopathological mechanisms through which either peripheral and/or central lymphatics are damaged by trauma, on the site of the lesion, and whether an underlying lymphatic disease is also present. In peripheral traumatic lesions of the limbs, with disruption in the lymphatic continuity, serum-lymph collections may form (post-traumatic lymphocele), featuring floating swellings, most commonly presenting a well known dermato-lymphangitis of the overlying skin region, and associated with distal edema (lymphedema). Sometimes, in congenitally predisposed extremities, a traumatic event associated with lymphangitis may trigger persisting edema (post-traumatic, post-lymphangitis lymphedema). In these cases, a differential diagnosis must be made with superficial thrombophlebitis, which differs from lymphangitis, being the latter condition characterized by a diffuse erythematous and edematous region, clear-cut margins, and without the typical painful and tender cord, which corresponds to the vein involved by the phlebo-thrombotic process. Traumatic lesions involving some solution of continuity of more superficial tissues do not cause lymphorrhagia, unless they involve limbs with lymphatic output failure. As a matter of fact, in this latter case, lymphorrhoea may develop, which can also be difficult to stop and needs proper specialist treatment. Infections are more common, leading to more persisting and larger lesions.
Clinical pictures of thoracic duct traumas may include chylomediastinum, which, initially, can be asymptomatic, until it turns into a chylothorax. The right side is the worst affected, due to the connections between the duct and right and left mediastinal pleuras: lower down, the duct has a closer connection with the right pleura, whereas at the top, it has direct connections with the left pleura. There are, however, many anatomic variations, which, in practice, do not allow the setting of any fixed rules. Chylous ascites or chyloperitoneum are less common events in the case of a lesion of the initial duct portion or of the receptaculum chyli of Pecquet, with chyle effusion into the peritoneal cavity. However, chyle can collect only in the retroperitoneal space, with no risk of continuity with the chylomediastinum. In the cervical portion, lymphatic fistulas can form, with development of a supraclavicular chylocele or cutaneous lymphatic fistula, which is often difficult to treat without surgery.
Le manifestazioni cliniche dei traumi del dotto toracico sono rappresentate dal chilomediastino, che all’inizio può essere del tutto asintomatico, sino a sfociare in un chilotorace. Il lato più colpito è il destro, in relazione ai particolari rapporti che il dotto presenta con le pleure mediastiche destra e sinistra: in basso, il dotto ha più stretta connessione con la pleura destra mentre, in alto, assume rapporti diretti con la pleura sinistra. Esistono, tuttavia, numerose varianti anatomiche che in realtà non permettono regole sicure. Più raramente si può determinare un’ascite chilosa o chiloperitoneo in relazione a una lesione del tratto iniziale del dotto o della cisterna di Pecquet, con versamento di chilo nel cavo peritoneale. Il chilo può, tuttavia, raccogliersi solamente nello spazio retroperitoneale e rimanere in continuità con il chilomediastino. Nel tratto cervicale, si possono verificare delle fistole linfatiche, con la formazione di un chilocele sovraclaveare o di una fistola linfatica cutanea, di difficile trattamento e che spesso richiede una soluzione chirurgica.
DIAGNOSIS
In traumas of the peripheral lymphatics, the most important instrumental investigations include ultrasonography, to determine the site and nature of collection, color-Doppler ultrasounds, which give information on whether venous blood circulation is also involved, and lymphoscintigraphy, for an accurate assessment of superficial and deep lymphatic drainage of the affected extremity versus the contralateral one.
Lesions of the thoracic duct and of the chylous cyst and related clinical pictures are investigated by chest X-Ray (which confirms whether a thoracic effusion is present), thoracentesis (to assess the nature of effusion, which will be milky in appearance, if formed by chyle), ultrasonography (for supraclavicular lesions and to detect any endoperitoneal effusion), spiral CT (especially for the thoracic segment of the duct), coupled with lymphography (lymphangio-CT), performed through bilateral intermalleolar incannulation of a lymphatic collector, with liposoluble ultrafluid contrast medium (“Lipiodol”). Lymphography gives accurate information about the site and extent of lesions. In case of more cranial lesions, the duct can be incannulated also from its proximal portion (retrograde ductography). MRI can also provide useful information, especially for more cranial lesions of the duct, in particular if it is performed according to a specific fatty tissue subtraction technique (lymphangio-MRI).
GALLERY
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Figure 1,A-F: Clinical, radiological (lymphangio-CT, retrograde ductography), surgical picture (needle placed in orifice corresponding to the chylous fistula and chylocele capsule) and long-term follow-up of a traumatic lesion of the thoracic duct.
THERAPY
Traumas of peripheral lymphatics with persisting lymphorrhoea and concurrent lymphangitis are mostly treated on an outpatient basis, by means of multilayer functional medicated paste bandages containing zinc oxide; rest with limb elevation; and broad-spectrum antibiotics. In case of lymphocele, the fluid collection is aspirated and compression medication applied. In cases of relapsing lymphocele, repeated aspirations are not advisable, to avoid the fluid collection from getting infected and suppurating. Conversely, lymphocele must be surgically drained by resection of the capsule and placement of aspiration drainage, to be removed as soon as lymphorrhoea subsides.
Thoracic duct lesions are initially treated with medical therapy aimed at reaching an adequate metabolic balance, in particular by TPN (Total Parenteral Nutrition), which aims at reducing the lymphatic-chylous capacity inside the duct-chylous cyst system. In case of traumatic fistula of the duct in supraclavicular region with secondary chylocele, the surgical technique features the removal of the chylocele, and repair of the fistula by microsurgery. In the thoracic portion, the duct is repaired by direct suture or by fashioning a duct-venous shunt, using the azygos and hemiazigos or collateral veins (duct-azigos anastomosis). Closures of the duct have also been reported as a treatment in case of traumatic lesions, but complications are likely to occur, such as lymphatic-chylous hypertension upstream to the surgical closure, with worsening chylothorax and chyloperitoneum development, as well as with mesenteric-intestinal repercussions (malabsorption, chylous cysts, and chylous peritonitis).
In some cases of minor traumatic lesions, TPN and simple effusion drainage (chylomediastinum, chylothorax, chyloperitoneum) have proved to be enough for a chylous-lymphatic fistula to close spontaneously, without the need of surgery. This proves how important it is to start a conservative treatment in every case, before resorting to any type of surgical treatment.