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Lymph nodes (or glands), are small masses of tissue that can be found throughout the body. They play an integral part in the functioning of the dog's immune system, acting as filters for the blood, and as storage places for white blood cells. Consequently, they are often the first indicators of disease in the tissues.
When tissues become inflamed, the regional lymph nodes that these tissues drain into will also become inflamed and swollen in response. This swelling is due to a reactive increase in white blood cells (hyperplasia) due to the localized presence of an infectious agent. This is medically defined as reactive hyperplasia: when white blood cells and plasma cells (antibody secreting cells) multiply in response to a substance that stimulates their production (antigenic stimulation), causing the lymph node to enlarge.
Lymphadenitis is a condition in which the lymphatic glands have become inflamed due to infection. Neutrophils (the most abundant type of white blood cell, and the first to act against infection), activated macrophages (cells which eat bacteria and other infectious agents), and eosinophils (cells which fight parasites and allergy causing agents) will migrate into the lymph node during an episode of lymphadenitis. This convergence of cells results in the swollen feel and appearance of the nodes.
Cancerous cells may also be found in a lymph node biopsy (tissue sample). Cancer cells may be primary, originating in the lymph node (malignant lymphoma), or may be there as a result of the spread of cancer from another location in the body (metastasis).
Lymph nodes can usually be detected by touch, but sometimes there will be no clinical symptoms. Swelling can be felt in the area beneath the jaw (submandibular), or around the shoulder. Swelling in one of the legs is also possible as a result of swollen lymph nodes at the back of the leg (popliteal), or near the joint of the leg (axillary – correlating with the armpit). Swollen nodes in the area near the groin (inguinal) may make defecation difficult for your dog. Your dog may also lose its appetite due to nausea, and have an urge to regurgitate when it does eat. You can also expect your dog to feel a general malaise as its body fights off the infection. If your dog has severely enlarged lymph nodes it may have trouble eating, or have difficulty with breathing.
Something that becomes worse or life threatening as it spreads
General discomfort of the body
A term for a type of neoplasm that is made up of lymphoid tissue; these masses are usually malignant in nature
The growth of pathogens away from the original site of the disease
Underneath the lower part of the jaw
An in-depth examination of the properties of urine; used to determine the presence or absence of illness
Something that is related to the whole body and not just one particular part or organ
Anything pertaining to the blood vessel system in the body
Returning food that has been swallowed into the mouth; often results in vomiting
A medical condition in which the lymph nodes are inflamed
The process of removing tissue to examine it, usually for medical reasons.
The area under the arm; the arm pit.
An allergic disorder that results in difficulty breathing.
The exiting of excrement from the body; bowel movements.
The area between the abdomen and thighs; the inguinal area
Small structures that filter out the lymph and store lymphocytes
An increase in the number of bad white blood cells
A protein in the body that is designed to fight disease; antibodies are brought on by the presence of certain antigens in the system.