Lymphadenopathy

Introduction

• Enlargement of lymph nodes is a common clinical finding in dogs with a wide range of underlying disease states, but may sometimes be the primary presenting complaint.
• Technically, the term lymphadenomegaly is the correct description for lymph node enlargement, but lymphadenopathy (lymph node pathology) is generally used synonymously.
• Lymphadenopathy may involve peripheral (palpable) lymph nodes and/or internal visceral lymph nodes (as determined by imaging examination). Lymphadenopathy may be localized (solitary or regional) or generalized in distribution. The differential diagnosis of lymphadenopathy is important not all lymph node enlargement is attributed to neoplastic change, and there are numerous causes of relatively benign lymphadenopathy. Finally, there are some exceptions to these general comments:
  • Lymphadenopathy might also encompass situations where lymph nodes are reduced in size, for example in senility, cachexia or with viral infection or immunosuppression that depletes lymphoid tissue. Further, lymph nodes might display pathological change (eg the presence of metastatic tumor) without necessarily being enlarged.

Diagnosis

Clinical signs

• By definition a dog with lymphadenopathy will have enlargement of one or more lymph nodes.
• External nodes should be palpably enlarged, and internal lymph node enlargement will be visualized by imaging examination ) or identified on laparotomy/laparoscopy. Palpation of most enlarged lymph nodes reveals them to be firm to touch, mobile within surrounding tissues, painless and of normal temperature.
• The exception to this rule is dogs with lymphadenitis where the nodes are more likely to be soft, warm and tender.
• Lymph nodes affected by lymphadenitis, or where neoplastic cells infiltrate through the node capsule, are more likely to be adherent to surrounding tissue than mobile within it.
• The size of the enlarged lymph nodes might also be informative. Extreme enlargement (five to ten times greater than normal) is more likely to occur with lymphoma, metastatic neoplasia or lymphadenitis, than a benign reactive process.

• Dogs presenting with lymphadenopathy as a primary clinical problem will often display a range of non-specific clinical signs such as pyrexia, inappetence/anorexia, malaise.
• The effect of gross lymphadenomegaly will be compromise of adjacent structures, eg enlargement of retropharyngeal nodes might lead to dysphagia, or of cervical/bronchial nodes might cause dyspnea.
• Lymphadenopathy which disrupts the flow of afferent lymph from tissues will be associated with edema of that tissue site.

Diagnosis

Differential diagnosis

• The main differential diagnoses for canine lymphadenopathy are described above.

Sources

Publications

Refereed papers

• Ruiz de Gopegui R, Penalba B & Espada Y (2004) Causes of lymphadenopathy in the dog and cat. Vet Rec 155 , 23-24.
• Dobson J (2004) Classification of canine lymphoma: a step forward. Vet J 167 (2), 125-126.
• Fan T M (2003) Lymphoma updates. Vet Clin North Am Small Anim Pract 33 (3), 455-471 Pub Med.
• Miniscalco B, Guglielmino R, Morello E, Tarducci A & Geuna M (2003) Clinical usefulness of peripheral blood lymphocyte subsets in canine lymphoma. Vet Res Commun 27 (Suppl 1), 407-409.
• Ponce F, Mangol J P, Marchal T, Chabanne L, Ledieu D, Bonnefont C, Felman P, Fournel-Fleury C (2003) High-grade canine T-cell lyphoma/leukemia with plasmacytoid morphology: a clinical pahtologoical study of nine cases. J Vet Diag Invest 15 (4), 330-337 PubMed.
• Day M J & Whitbread T J (1995) A review of pathological diagnoses in dogs with lymph node enlargement. Vet Rec 136 , 72-73.
• Day M J, Pearson G R, Lucke V M, Lane S J &Sparks R S J (1996) Lesions associated with mineral deposition in the lymph node and lung of the dog. Vet Pathol 33 , 29-42 PubMed.
• Day M J (1996) Expression of interleukin-1b, interleukin-6 and tumour necrosis factor-a by macrophages in canine lymph nodes with mineral-associated lymphadenopathy, granulomatous lymphadenitis or reactive hyperplasia. J Comp Pathol 114 , 31-42 PubMed.
• Rogers K S, Barton C L & Landis M (1993) Canine and feline lymph nodes. Part I. Anatomy and function. Comp Contin Educ Pract Vet 15 , 397-409.
• Rogers K S, Barton C L & Landis M (1993) Canine and feline lymph nodes. Part II. Diagnostic evaluation of lymphadenopathy. Comp Contin Educ Pract Vet 15 ,1493-1503.

Other sources of information

• Day M J (1999) Diseases of lymphoid tissue. In: M J Day. Clinical Immunology of the Dog and Cat. Manson Publishing, London. pp. 250-265.