Reviewing Causes, Treatment Of Feline Lymphadenopathy - DVM360

Q: Please review the various causes of abdominal lymphadenopathy in cats.

A: Dr. John R. August gave an excellent lecture entitled "Abdominal Lymphadenopathy in Cats: A Diagnostic Challenge" at the 2008 American College of Veterinary Internal Medicine Forum in San Antonio.

Here are some relevant points from his lecture:

Abdominal lymphadenopathy, or masses that may be confused with enlarged lymph nodes, are common clinical findings in sick cats, either on physical examination or via ultrasonography. Many inflammatory, infectious and neoplastic diseases can cause enlargement of regional lymph nodes in the abdomen. Assessment of lymph-node size and cytologic or histopathologic characteristics may provide important information when more invasive diagnostic methods are not available. As with all sick cats, the history and physical examination are necessary to identify additional clinical abnormalities that may clarify the cause of the lymphadenopathy.

Causes of lymphadenopathy

Lymph nodes that are palpable in healthy cats and dogs include the mandibular, superficial cervical, axillary, superficial inguinal and popliteal nodes. Lymphadenopathy is defined as enlargement of a solitary node, a regional group of nodes or of all lymph nodes. Causes of lymph-node enlargement in cats include:

• REACTIVE HYPERPLASIA, resulting from proliferation of lymphocytes and plasma cells from antigenic stimulation

• LYMPHADENITIS, resulting from an influx of inflammatory cells due to local infection

• NEOPLASTIC INFILTRATION, either from primary lymphoid neoplasia or from infiltration from metastatic neoplastic disease.

Differential diagnosis

Abdominal lymphadenopathy in cats may represent a response to a local disease process within the abdominal cavity or may be a component of a systemic disease accompanied by generalized lymph-node enlargement.

Organomegaly, most often associated with small-intestinal masses, but also due to splenomegaly or hepatomegaly, may accompany abdominal lymph-node enlargement, complicating the accurate identification of lymphadenomegaly on palpation.

Reactive mesenteric lymph-node hyperplasia is a common ultrasonographic abnormality, but less common physical finding, in cats with inflammatory bowel disease. The degree of thickening of the small intestine and the degree of lymphadenomegaly correlate well with the severity of the disease. Clinical signs include vomiting, diarrhea, weight loss, reduced appetite and poor body condition and haircoat.

Intestinal tumors occur commonly in cats, accounting for 35 percent of all feline tumors. Approximately 74 percent of all feline intestinal tumors are the result of lymphoma, with intestinal adenocarcinomas being the cause of an additional 17 percent of intestinal neoplasia.

An abdominal mass is detected by palpation in 86 percent of cats with intestinal lymphoma, with lymphoblastic lymphoma being more likely to induce discrete masses. The small intestine is the most common site of lymphoma in cats, followed by the stomach, ileocolic junction and lastly the colon.

Diffuse intestinal thickening is more common in low-grade lymphocytic lymphoma. Concurrent mesenteric lymphadenopathy is noted ultrasonographically in 33 percent to 50 percent of cats with alimentary lymphoma, intestinal masses or thickening in about 40 percent of affected cats, and splenomegaly, hepatomegaly or abdominal effusion in a smaller number of cats.