Lymph Nodes of the Pelvis and Lower Limb
A well-functioning lymphatic system is essential for a healthy human body. It drains the tissue fluid from around our cells and returns it to the vascular system for redistribution. This article will discuss the basics of lymphatic system, the lymphatic drainage of the pelvis and lower limb, along with the anatomy and clinical relevance.
The word ‘lymphatic’ is from the Latin word ‘lymphaticus’ that means related to water. Lymph functions as an immunological defense, while also draining the plasma proteins and cellular debris from the perivascular space. Lymph is a transudative fluid that has a slightly alkaline pH. It is derived from tissue fluid. The word ‘chyle’ simply means lymph from the small intestine.
Superficial lymphatic vessels drain the superficial structures and follow the drainage of the veins. These superficial lymphatic vessels then drain into the deep lymphatic system (that lie near the arteries) and also drain the internal organs.
Both superficial and deep lymphatic vessels traverse through lymph nodes. This is where lymphocytes reside and develop specific antibodies according to the pathogens they are exposed to from the lymphatic vasculature. Afferent vessels bring lymph-to-lymph nodes, and efferents bring lymph away.
The lymphatic trunk is formed by the confluence of many small efferent lymphatic vessels. A lymph duct is a great lymphatic vessel that empties lymph into one of the subclavian veins. There are two lymph ducts in the body—the right lymphatic duct and the thoracic duct. The right lymphatic duct drains the right upper quadrant of the body (the right side of the head, neck, thorax and the whole right upper limb). The duct drains into the right venous angle (angle between the internal jugular and subclavian veins). The thoracic duct drains the remainder of the body, and then drains into the left venous angle.
The cisterna chyli or ‘milk tank’ is a dilated collecting sac that is located retro-peritoneal on the bodies of the first two lumbar vertebrae. It drains the lymph from the intestines and gives rise to the thoracic duct, which then passes through the aortic opening in the diaphragm (at level T12). From here it ascends in the posterior mediastinum, and follows the course of the aortic arch. Next it enters the roots of the neck and travels posterior to the carotid sheath to eventually terminate at the left venous angle and thus rejoin the systemic vascular circulation.
Inguinal Lymph Nodes
These are present in a T shape . There is a horizontal part of the T shape, and a vertical part of the T shape arranged along the greater saphenous vein. The T shape is divided into medial, lateral and vertical groups. They drain back lymph from the following areas:
- below the level of the iliac crest
- the buttock (lateral group)
- the lower abdominal wall
- anal canal
- scrotal skin
- penis (medial group)
- entire lower limb (vertical group)
These lie medial to the femoral vein and drain the following areas:
- glans penis/clitoris
- superficial inguinal nodes mentioned above
- deep lymphatics that follow the femoral vessels
They drain into the external iliac lymph nodes.
Popliteal Lymph Nodes
The popliteal lymph nodes are relatively small in size. They are embedded in the popliteal fat. One lies just deep to the popliteal fascia and drains the saphenous vein territory e.g. the superficial regions of the lateral leg and the sole of the foot. A second node lies near the popliteal artery. This receives lymphatic vessels from the knee joint. The remaining nodes lie at the sides of the popliteal vessels, and receive the lymph from the posterior and anterior tibial vessels.
Cancer and Metastasis
Cancer spreads through the blood and the lymphatic system. Breast cancer particularly spreads via lymphatics (to the axillary lymph nodes and beyond), as does prostate cancer (to the para-aortic lymph nodes). Lymphomas are cancers that originate from lymph nodes, and can be lethal to patients if advanced or if they are of a particularly aggressive subtype.
A tropical parasitic worm (of the filarioidea family) can infect the human body through a mosquito bite. The commonest infecting species is Wuchereria Bancrofti. Many cases have no symptoms, but the parasite can obstruct the lymphatic system and cause lymph build up in the arms, legs or genitals. The skin can sometimes become paler and thicker. This results in a grossly enlarged, oedematous lower limb that is a real cosmetic problem for the patient. Treatment is an antiparasitic drug e.g. albendazole.