Page 1031 - Cote clinical veterinary advisor dogs and cats 4th

Hyperviscosity Syndrome 509

• Concerns may reflect underlying disorder
(e.g., cough, weight loss, tachypnea)
VetBooks.ir PHYSICAL EXAM FINDINGS Diseases and Disorders
• Swollen, hard extremities (e.g., distal long
bones)
• Occasionally, pitting edema
• Decreased movement in joints secondary to
soft-tissue swelling
• Other findings that suggest underlying
disorder (e.g., palpable abdominal mass,
abnormal lung sounds)
Etiology and Pathophysiology
Cause unknown:
• Autonomic neurovascular reflex increasing
peripheral blood flow and causing periosteal
congestion and new bone formation is
speculated.
• Increased levels of platelet-derived growth HYPERTROPHIC OSTEOPATHY Lateral radiograph of the radius and ulna of a 9-year-old, female, spayed
dachshund dog with pulmonary carcinoma. Note the exuberant periosteal reaction (arrows) typical of hypertrophic
factor (from megakaryocytes diverted osteopathy.
from the pulmonary to the peripheral
circulation) and vascular endothelial PROGNOSIS & OUTCOME
growth factor (often produced by tumors) Advanced or Confirmatory Testing
may stimulate angiogenesis and new bone • Ultrasonography (thorax/abdomen): to • Depends on cause of underlying mass
formation. identify mass in abdominal organ (e.g., • After treatment of the primary disease, bone
intrahepatic mass) or to characterize lung lesions can take months to remodel and are
DIAGNOSIS mass not known to be fully reversible. Clinical
• Biopsy or fine-needle aspiration of lameness often improves.
Diagnostic Overview pulmonary/abdominal lesion for histologic
The combination of a characteristic limb lesion diagnosis (pp. 1112 and 1113) PEARLS & CONSIDERATIONS
and a lung or abdominal mass defines HO.
TREATMENT Comments
Differential Diagnosis Swelling of the distal extremities of an older
Radiographic: Treatment Overview dog with radiographic evidence of characteristic
• Primary or secondary bone neoplasia Treat the underlying thoracic or abdominal palisading periosteal reaction calls for thoracic
• Fungal bone disease disease. and abdominal imaging in search of an underly-
• Panosteitis ing primary lesion.
• Hepatazoon americanum Acute and Chronic Treatment
• Surgical removal of mass lesion; removal of Technician Tips
Initial Database pulmonary metastases can also bring about New lameness or limb swelling in dogs treated
• CBC: neutrophilia, thrombocytosis, or resolution of HO. for malignancy can signal the development of
thrombocytopenia possible • Medical treatment of mass when possible HO. Radiographs (including metacarpus or
• Serum biochemistry profile and urinalysis: (e.g., infectious granuloma) metatarsus) of at least one distal limb can
unremarkable or related to thoracic or • Analgesic therapy if specific treatment is not confirm its presence.
abdominal disease; serum alkaline phos- feasible
phatase elevation is common • Bisphosphonate treatment is helpful in SUGGESTED READING
• Radiographs of extremities: palisades of people; not yet reported for HO in dogs Withers SS, et al: Paraneoplastic hypertrophic osteopa-
periosteal new bone on phalanges, metacarpi, or cats thy in 30 dogs. Vet Comp Oncol 13(3):157-165,
metatarsi progressing to tibia/fibula, radius/ 2015.
ulna Recommended Monitoring
• Thoracic and abdominal radiographs: mass Follow-up radiographs of extremities to evaluate AUTHOR: Nicholas J. Trout, VetMB, MA, MRCVS,
DACVS, DECVS
usually identified in chest or abdomen; lung bone remodeling; monitoring as appropriate EDITOR: Kathleen Linn, DVM, MS, DACVS
metastasis may be recognized for primary disorder

Hyperviscosity Syndrome Client Education
Sheet

BASIC INFORMATION Synonyms Epidemiology
Polycythemia indicates an increased number SPECIES, AGE, SEX
Definition of all cell lines in the circulation; the term Dogs > cats; typically middle-aged to older
An uncommon sequela of diseases that may is often but mistakenly used interchangeably animal
cause elevated blood viscosity; a constellation with erythrocytosis, an increase in circulating
of secondary clinical signs may occur red blood cell mass.

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