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598 Lymphadenopathy

• In dogs that are treated, Quant C6 or PEARLS & CONSIDERATIONS 6 months because of the short duration of
immunity.
OspF antibody testing is recommended at Comments • Lyme disease vaccines are controversial
VetBooks.ir comparison if signs recur. High pre-treatment In humans, one day’s dose of doxycycline taken because the most serious forms of Lyme
0 and 3-6 months; the new baseline is for
titers usually drop by at least 50%; lower
disease in dogs have an immune-mediated
within 72 hours of detaching an engorged Ixodes
titers may not. Qualitative C6 (SNAP 4Dx
paramount.
Plus) often remains positive after treatment. tick in Lyme-endemic areas helps prevent pathogenesis; adequate tick control is
Lyme disease. The human Borrelia vaccine
• For Lyme nephritis: monitoring initially q was removed from the market because of poor
1-4 weeks for hematocrit, serum creatinine, sales due to concern about possible immune- Technician Tips
blood urea nitrogen (BUN), albumin, urine mediated sequelae in genetically predisposed All seropositive dogs need screening for
protein/creatinine ratio, and blood pressure individuals. proteinuria and better tick control.
measurement, decreasing to q 3-6 months
if clinically stable Prevention Client Education
• Tick prevention and control are paramount Proper tick removal, tick surveillance; prophy-
PROGNOSIS & OUTCOME whether using vaccines or not. New tick laxis for ectoparasites is lifesaving
control methods to prevent attachment
• Prognosis is good for Lyme arthritis. or cause a fast kill of ticks include collars, SUGGESTED READING
Most dogs respond immediately without topicals, and new oral isoxazolines. Littman MP, et al: ACVIM consensus update on
recurrence. • Available Lyme vaccines include bivalent Lyme borreliosis in dogs and cats. J Vet Intern
• Prognosis is guarded to poor for Lyme bacterins (which induce OspA and OspC Med 32: 887-903, 2018.
nephritis, especially in hypoalbuminemic, antibodies), recombinant subunit OspA, and AUTHOR: Meryl P. Littman, VMD, DACVIM
dehydrated, azotemic cases; life expectancy a new chimeric recombinant OspA with 7 EDITOR: Joseph Taboada, DVM, DACVIM
may be days to weeks. strains of OspC. Boosters may be needed q

Lymphadenopathy Client Education
Sheet

Clinical Presentation
BASIC INFORMATION • Evaluate for apparent inciting cause in region
HISTORY, CHIEF COMPLAINT of affected node.
Definition Clinical signs generally reflect the underly- ○ Example: if a single popliteal node is
Enlargement of a solitary, a regional group of, ing disorder and are not caused by the enlarged, evaluate for lesions of the foot
or all lymph nodes lymphadenopathy. (dermatosis, foreign body, neoplasm).
• Exception: mechanical obstruction due
Synonym to marked lymph node enlargement may Etiology and Pathophysiology
Lymphadenomegaly cause dysphagia, respiratory stridor, cough, • Lymph nodes enlarge as a result of prolifera-
regurgitation, cranial vena cava syndrome, tion of normal cells within them or due to
Epidemiology swollen limb(s), or dyschezia. infiltration with normal or abnormal cells.
SPECIES, AGE, SEX • Reactive hyperplasia
Dogs and cats, any age, either sex PHYSICAL EXAM FINDINGS ○ Proliferation of lymphocytes and plasma
• Evaluate all accessible lymph nodes during cells in response to antigens arriving
GENETICS, BREED PREDISPOSITION physical exam; the following nodes are through afferent lymphatics
Lymphoma (p. 609) palpable in dogs and cats: ○ Occurs mostly in response to inflammation
○ Mandibular, prescapular (superficial in the tissues drained by the lymph node
RISK FACTORS cervical), and popliteal ○ After vaccination
Infectious diseases: exposure to arthropod ○ Axillary and inguinal nodes are palpable ○ Immune-mediated diseases
vectors if enlarged. • Lymphadenitis
○ Enlarged sublumbar node may be palpable ○ Migration of inflammatory cells into the
CONTAGION AND ZOONOSIS on rectal exam if enlarged. node, usually caused by infection (bacte-
• Few infectious causes of lymphadenopathy ○ Fat surrounding lymph nodes can be an rial, rickettsial, fungal, parasitic, viral)
may be direct zoonosis (e.g., Yersinia imposter for lymphadenopathy; consider • Neoplasia
pestis). body condition. ○ Primary: lymphoma
• Exercise caution when aspirating lymph • Node pain, erythema, heat, and adher- ○ Secondary: carcinomas, melanomas,
nodes from animals with suspected infec- ence of node to underlying tissue suggest sarcomas, mast cell tumors
tious diseases (zoonosis by needlestick lymphadenitis. • Extramedullary hematopoiesis (rare)
injury). • Patient may show vague signs of systemic • Vascular changes: edema, congestion (rare)
illness from underlying disease (e.g., fever,
GEOGRAPHY AND SEASONALITY anorexia, weight loss). DIAGNOSIS
Tick vectors are more prevalent in summer. • Patients with chronic leukemias, post-
Fleas and tick vectors are more prevalent in vaccinal lymphadenopathies, and early Diagnostic Overview
the tropics and subtropics. Many infectious lymphoma generally show subtle signs Fine-needle aspiration of the lymph node for
agents (e.g., systemic mycosis) have specific or no clinical signs other than node cytologic exam to classify the disease process is
geographic areas of prevalence. enlargement. the first step. CBC, serum biochemistry profile,

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