Page 1438 - Small Animal Internal Medicine, 6th Edition

1410 PART XIII Hematology

TABLE 88.2
VetBooks.ir Correlation Between Clinical Presentation and Cause in
Dogs and Cats With Lymphadenopathy*
SOLITARY OR REGIONAL
GENERALIZED SUPERFICIAL INTRACAVITARY

Lymphoma Abscess Histoplasmosis (A, T)
Histoplasmosis Periodontal Blastomycosis (T)
Blastomycosis disease Apocrine gland
Postvaccinal Paronychia adenocarcinoma (A)
Anaplasmosis Deep Primary lung tumors (T)
Ehrlichiosis pyoderma Lymphoma (A, T)
Leukemias Demodicosis Mast cell tumor (A)
Malignant Mast cell Prostatic
histiocytosis tumor adenocarcinoma (A)
Systemic lupus Malignant Malignant histiocytosis
FIG 88.2 erythematosus melanoma (A, T)
Anatomic distribution of clinically relevant lymph nodes in a Other Eosinophilic Lymphomatoid
dog. The nodes are in the same general location in cats. granuloma granulomatosis (T)
The lymph nodes depicted by the darkened circles include, complex Tuberculosis (A, T)
from cranial to caudal, the mandibular, prescapular, Lymphoma
axillary, superficial inguinal, and popliteal lymph nodes.
The lymph nodes depicted by the open circles include, from
cranial to caudal, the facial, retropharyngeal, and iliac or A, Abdomen; T, thorax.
*In the midwestern United States (in relative order of importance).
sublumbar lymph nodes. (From Couto CG: Diseases of the
lymph nodes and spleen. In Ettinger SJ, editor: Textbook of
veterinary internal medicine—diseases of the dog and cat,
ed 3, Philadelphia, 1989, WB Saunders.) neoplasia (less commonly), whereas most cases of deep
(e.g., intraabdominal, intrathoracic) solitary or regional
lymphadenopathy result from metastatic neoplasia or sys-
mycoses, salmon poisoning, Rocky Mountain spotted fever temic infectious diseases (e.g., systemic mycoses). Recently,
(RMSF), anaplasmosis, ehrlichiosis, bartonellosis, leishman- cyst-like lesions of intraabdominal lymph nodes in patients
iasis, or acute leukemia, and in some dogs and cats with with both nonneoplastic (70%) or neoplastic (30%) lesions
immune-mediated diseases. Clinical signs are rare or can be were described (Liotta et al., 2017). Idiopathic mesenteric
absent in dogs and cats with chronic lymphocytic leukemia, purulent lymphadenopathy was also recently described in
anaplasmosis, most lymphomas, and reactive lymphadenop- dogs (Salavati Schmitz, 2016). Most cases of generalized
athies occurring after vaccination; cats with idiopathic reac- lymphadenopathy are caused by systemic fungal or bacte-
tive lymphadenopathy (see later) are usually asymptomatic. rial infections (dogs), nonspecific hyperplasia (mainly cats),
Clinical signs in dogs and cats with lymphadenopathy or lymphoma (dogs; Table 88.2).
or splenomegaly are vague and nonspecific and are usually The characteristics of the lymph nodes on palpation are
related to the primary disease rather than the organ en- also important. In most dogs and cats with lymphadenopathy,
largement. They include anorexia, weight loss, weakness, ab- regardless of the distribution, the lymph nodes are firm,
dominal distention, vomiting, diarrhea, polyuria-polydipsia irregular, and painless; their temperature is normal to the
(PU-PD; in dogs with lymphoma-associated hypercalcemia), touch (cold lymphadenopathies); and they do not adhere to
or a combination of these. Enlarged lymph nodes can oc- the surrounding structures. However, in patients with lym-
casionally result in obstructive or compressive signs (e.g., phadenitis, the lymph nodes may be softer than usual and
dysphagia resulting from enlarged retropharyngeal nodes, more tender and warmer than normal; they may also adhere
coughing resulting from enlarged tracheobronchial nodes; to surrounding structures (fixed lymphadenopathy). Fixed
see Fig. 79.7). lymphadenopathies may also be the presenting feature in
The distribution of the lymphadenopathy is also of dogs and cats with metastatic lesions, lymphomas with
diagnostic relevance. In patients with solitary or regional extracapsular invasion, or certain infectious diseases (e.g.,
lymphadenopathy, the area drained by the lymph node(s) mycobacteriosis).
should be examined meticulously because the primary The size of the affected lymph nodes is also important.
lesion is generally found there. As discussed earlier, Suami Massive lymphadenopathy—lymph node size 5 to 10 times
et al. recently published an excellent review of lymphatic normal—occurs almost exclusively in dogs with lymphoma,
territories. Most cases of superficial solitary or regional malignant histiocytosis (Fig. 88.3), or infectious lym-
lymphadenopathy in dogs and cats result from localized phadenitis (lymph node abscess formation; hilar lymph-
inflammatory or infectious processes or from metastatic adenopathy in dogs with histoplasmosis). In cats, the