Anatomy, Abdomen and Pelvis: Inguinal Lymph Node

Structure and Function

Lymph nodes are small, round kidney-shaped structures that run with the lymphatic system. Lymph nodes play a vital role in the body’s ability to fight off infection. A tough fibrous connective tissue capsule encapsulates lymph nodes. The fibrous capsule extends into the lymph node to form trabeculae and divide each node into lobules. Different lymph node size has a different number of lobules. Each lobule divides into separate compartments; cortex, paracortex, and medulla—the cortex houses primary follicles, which are dormant B- cell lymphocytes. The paracortex houses T-cell lymphocytes. The medulla contains reticular cells and macrophages and communicates with efferent lymphatic vessels.[1] 

Lymph node has afferent vessels that carry lymphatic fluid to the lymph node. As the fluid travels through the lymph node, immune cells within the node filter for harmful substances such as bacteria, viruses, parasites, and other foreign material. If there is a presence of an antigen, B-cell lymphocyte in the follicles create antibodies that are specific to the antigen. Activated primary follicles form into secondary follicles called germinal centers and indicate the proliferation of B-lymphocytes and the production of antibodies. The antibodies tagged the antigen for destruction by other immune cells. T-cell lymphocytes are responsible for cell-mediated immunity. Macrophages phagocytize pathogens such as bacteria and viruses and destroy them.

Lymph nodes are located throughout the body and can be found deep within tissues and superficially and drain specific areas of the body. The inguinal lymph nodes are in the groin area and classify as superficial and deep. The superficial inguinal lymph nodes reside below the inguinal ligament and subdivide into the inferior, superolateral, and superomedial nodes. The superficial inguinal lymph nodes drain the anal canal(below the pectinate line), the skin below the umbilicus, lower extremity, scrotum, and vulva. The deep inguinal lymph nodes are within the femoral sheath medial to the femoral vein. The deep nodes receive drainage from the glans penis or clitoris, as well as the superficial lymph nodes. The superficial and deep inguinal lymph nodes both drain into the external iliac lymph nodes.

Embryology

The lymph node development starts from the 11 weeks of gestation as a mesenchymal condensation giving rise to the lymph node capsule and connective tissue. The T-cell lymphocytic region begins development during the 13 weeks. The B-cell lymphocytic region begins during the 14 weeks. From week 13 onward, monocytes and macrophages can be present with the lymph sac. During the 20 weeks, the follicle, paracortex, and medulla are discernable and continue to develop throughout gestation and after birth.[2][3]

The lymphatic system derives from the mesodermal embryological sheet.

Blood Supply and Lymphatics

Artery enter from the hilum, a depression on the concave side of the lymph node, on the concave side of the kidney-shaped structure. The artery passes through the medulla and into the cortex. Once in the cortex, the artery branches into arterioles and capillaries. The vein exits the lymph node from the hilum as well. The afferent lymphatic vessel enters the lymph node on the convex side of the node. The afferent vessels carry lymph through one-way valves and into the node where it is circulated through the sinuses. After the lymph fluid is filtered, it exits through the efferent lymphatic vessels from the hilum. The efferent vessels also have one-way valves to prevent the backflow of lymph fluids.[4] 

Nerves

The femoral nerve is in the Scarpa triangle or femoral triangle. Swollen lymph nodes can compress the nerve and cause a femoral neuropathy.

Surgical Considerations

The inguinal lymph node resides within the femoral triangle. The femoral triangle is bounded by the inguinal ligament, adductor longus muscle, and sartorius muscle. The fascia lata forms the roof of the femoral triangle. The floor of the femoral triangle forms from the iliopsoas and pectineus muscles. On surgery day, technetium-99m radiolabelled nano colloid is injected into the primary site of cancer. The location of the sentinel node is located using a handheld gamma camera. Blue dye is also often injected in the primary site of cancer to assist with visualization of the sentinel node after making the incision.[5] The incision is made parallel to the inguinal ligament, and the deep inguinal lymph node can be found medial to the femoral vein. 

A surgical approach in this area can give several adverse symptoms for the patient:

• Lymphocele
• Wound dehiscence
• Skin necrosis
• Seroma
• Ventral inguinal hernia

Clinical Significance

Lymphadenopathy

Swollen lymph nodes usually indicate infection from bacteria or viruses. Swollen inguinal lymph nodes could indicate an infection of areas of the lower body. One of the more concerning causes of inguinal lymphadenopathy is sexually transmitted infections. Sexually transmitted infections that commonly presents with inguinal lymphadenopathy are lymphogranuloma venereum, secondary syphilis, and chancroid caused by Chlamydia trachomatis(L1-L3), Treponema pallidum, and Haemophilus ducreyi, respectively.  

Lymphogranuloma venereum

Lymphogranuloma venereum is a disease of the genital area caused by the gram-negative bacteria Chlamydia trachomatis (serovars L1, L2, and L3). Lymphogranuloma venereum primarily affects the lymphatic system and has three stages. The secondary stage of lymphogranuloma venereum can present with unilateral or bilateral tender inguinal lymphadenopathy.[6] 

Syphilis

Syphilis is a bacterial infection caused by the spirochete Treponema pallidum. Clinical presentation of secondary syphilis can present with diffuse lymphadenopathy along with fever, skin rashes, and condylomata lata.[7] 

Chancroid

Chancroid is a rare sexually transmitted disease caused by a small gram-negative rod, Haemophilus ducreyi. Fifty percent of infected individuals present with tender inguinal lymphadenopathy along with ulcers with exudate.[8]

Lymphedema

Lymphedema is the swelling that typically occurs in the arm or leg due to the lymph vessels unable to drain lymph fluid sufficiently. Damage to the inguinal lymph node can present with lymphedema of the lower limb. Infection-related lymphedema is more common in developing countries in tropical and subtropical regions. Wuchereria bancrofti is a nematode known to commonly cause lymphedema of the leg. Transmitted by mosquito bites, Wuchereria bancrofti invade lymph nodes and causes inflammation and damage to the lymph node and lymphatic system.[9]     

In developed countries, lymphedema causes are commonly due to malignancy or treatment of malignancy. Treatment includes the excision of malignant lymph nodes for diagnosis and radiation treatment.[10]   

Cancer Diagnosis

Cancer can appear in the lymph node as the primary site of cancer or can spread there from another primary site. Cancer cells are able to migrate through the lymphatic system and end up in a lymph node that is draining the primary site. For carcinomas that disseminate through the lymphatic system, they commonly spread to the regional node before spreading to the next tier of nodes. These immediate regional nodes are called the sentinel lymph nodes. If the clinician suspects an individual of having cancer, a biopsy or dissection of the sentinel lymph node that is draining the site of interest can help to determine if cancer has metastasized. Upon finding a cancerous cell in the sentinel lymph node, this information can assist with staging cancer and direct mode of therapy.[11][12][13]

Common tumors that metastasize to the inguinal lymph node include squamous carcinoma of the vulva, penis, and anus.

Vulvar Cancer

The vulva is the area of skin surrounding the urethra and vagina. Vulvar cancer is more common in postmenopausal women and can present with lumps or bumps and itching. Other symptoms include tenderness, bleeding, and skin changes. The precise etiology of vulvar cancer is unknown, but some factors increase the risk of someone getting vulvar cancer. These risk factors include older age, exposure of human papillomavirus, smoking, a weakened immune system, and a skin condition involving the vulva.[14]  

Penile Cancer

Penile cancer is most common in Asia, Africa, South America. Penile cancer begins as a small lesion on the glans that varies on appearance. The lesion can appear as masses growing from skin or white or reddish-colored mass. Risk factors include uncircumcised and human papillomavirus infection. Other risk factors include a history of phimosis, balanitis, chronic inflammation, tobacco use, lichen sclerosis, and poor hygiene.[15] 

Anal Cancer

Anal cancer is cancer that occurs in the anal canal. Patients can present with anal bleeding, weight loss, a sensation of a mass, tenderness, and itching. Risk factors include older age and human papillomavirus infection.[16]  

Other Issues

Digeorge syndrome is due to a small deletion on chromosome 22, resulting in poor development in several organ systems. One of the problems commonly present in someone with DiGeorge is thymus gland dysfunction. The thymus gland is where T cells mature and help fight infection; thus, thymus gland dysfunction will result in T-cell deficiency. T-cell deficiency will result in the paracortex of lymph nodes not being well developed.[17]