Lymphangiography and Lymphatic Embolization

Fluid seepage through endothelial openings leads (at capillary level) to protein-rich interstitial fluid formation, subsequently termed lymph upon entering lymphatic channels. The lymphatic system, crucial for fluid balance and immune response, comprises initial lymphatics and collecting vessels. Peripheral and central lymphatic system components are examined via pedal lymphangiography and intranodal lymphangiography respectively.

Anatomy:

Cisterna chyli, a sac-like lymphatic channel (at L1-L2 level), receives lumbar trunks and continues as the thoracic duct, although its appearance varies due to complex anastomosis. The thoracic duct, longest in the body, exhibits anatomical variants and diverse termination points in veins, often necessitating procedural adaptations. The majority of the adult thoracic duct’s lower two-thirds form from the embryonic right thoracic duct, while its upper one-third originates from the embryonic left thoracic duct. This configuration represents the prevalent anatomical variation of the thoracic duct. Various authors have categorized multiple variations of the standard thoracic duct configuration. Kausel et al identified five types, including the significant plexiform variant (Type V) that often requires proximal embolization due to challenging catheter advancement. The thoracic duct’s entry into the venous system exhibits diverse locations and duct numbers. Phang et al noted common termination patterns: jugular vein (46%), near jugulovenous angle (32%), subclavian vein (18%), and other veins (4%). These alternative terminations encompass external jugular, vertebral, transverse cervical, brachiocephalic, and suprascapular veins.

Understanding Chylous Fluid:

Daily thoracic duct chyle flow ranges from 2 to 4 L, influenced by dietary habits. Chyle, a mix of lymph and emulsified fat (mainly triglycerides), originates from intestinal lacteals. Chylous leaks (e.g., chylous ascites, chylothorax, chyluria) stem from nontraumatic and traumatic sources (iatrogenic, blunt, penetrating). Iatrogenic chylous ascites links to abdominal surgeries like lymphadenectomy and pancreaticoduodenectomy. Chylothorax results from thoracic surgeries, notably esophagectomy for esophageal carcinoma (incidence: 0.42% for thoracic surgeries, 3.9% for esophagectomy).

Chylous Fluid	Keypoints
Apperance	Milky and Whitish
Labs for Fluid	1. Triglyceride levels > 110 mg/dl 2. Chylomicron > 4% 3. Lymphocytes > 50%
Low-Output	1. < 1000 ml/day 2. Medical management using Octreotide (100-200 umg TDS SC) + Adequate drainage + Fat free diet x 2 weeks
High-Output	1. > 1000 ml /day 2. Lymphatic embolization or Surgical ligation of thoracic duct (also for failed medical management for low-output)

Imaging Techniques for detecting site of Lymphatic leak:

Method	Keypoints
Conventional Lymphangiography	1. Gold standard for imaging lymphatics 2. Lipiodol is preferred choice of contrast agent - Minimal leak of contrast out of vessel lumen due to restricted outward diffusion. - Persist in nodes for months thereby evaluating effect of treatment and progression of disease - Extravasation of lipiodol from leak site causes inflammatory and granulomatous reaction resulting in occlusion of leak site 3. Dose - 1ml/10kg, with upper limit of 10 ml for single limb and 14 ml for both limbs 4. Rate of administration - 4-10 ml/hour (depending on size of lymphatics), excessive rate/ pressure can cause lymph node rupture and spillage of contrast 5. Approach - Intranodal lymphangiography or Pedal Lymphangiography
Magnetic Resonance Lymphangiography	1. Based on heavily T2-weighted sequences provides signal from static or slow moving fluid filled structure. 2. NCMRL (Non-Contrast Magnetic Resonance Lymphangiography) - similar to MRCP and MR urography, non-invasive therefore helpful in pediatric patients and patients with contraindication to use of contrast material. 3. DCEMR (Dynamic contrast material-enhanced magnetic resonance) - Gadolinium based contrast is mixed with saline 1:1 or 1:2 depending on age of patient (dose 0.1 mmol/kg). Route of administration - Intranodal/Pedal
Lymphoscintigraphy	1. Reserved for imaging of extremities 2. Dose 74 to 296 MBq of 99mTc sulfur colloid suspended in 0.1 ml of saline 3. High-resolution collimator is used (at least 300000 counts) 4. Limitations - Poor spatial resolution, exposure to radioactive material

Approaches to Leak site:

Technique	Keypoints
Transabdominal / Translumbar direct puncture	1. Thoracic duct / cisterna chyli are punctured using 21G Chiba needle under fluoroscopic guidance (Right anterior oblique view with caudal angulation)
Retrograde Venous Approach	1. Patients with anatomic variations like left-sided thoracic duct or plexiform variety. 2. Gaining access to thoracic duct through basilic or cephalic vein. 3. Peripheral venous access is secured and using a 5F Simonds type catheter ostial valve at entry of thoracic duct into venous channel is cannulated. Microcatheter over a 0.014 guidewire can be used to advance further into thoracic duct.
Transhepatic approach	1. Hepatic lymphatics are thin and tortuous and therefore limit the used of catheter and guidewire. 2. Direct puncture and embolization using liquid embolic can be performed for patients with heaptic lymphorrhea
Direct puncture of leakage site	Direct puncture of lymphatic at leak site can be performed using USG/CT guidance and embolization can be performed thereafter.
Closest upstream lymph node embolization	1. Lymph node from efferent lymphatic vessel are extravasated on lymphangiography and is labeled as closest upstream lymph node. 2. Direct puncture of lymph node using image guidance and embolization after test dose of lipiodol (confirming leak) can be performed.

Contraindications:

Pulmonary insufficiency
Right to left cardiac shunt
Lymphovenous communication – important when lipiodol administraion reaches more than 20 ml leading to oil embolism and infarction.

References