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D i a g n o s t i c T r e e / INTERNAL MEDICINE Fever of Unknown Origin Garret Pachtinger, VMD, and Lesley G. King, MVB, Diplomate ACVECC, ACVIM, & ECVIM (Companion Animal), University of Pennsylvania History • Signalment • Presenting signs • Date when last normal • Progression • Preventatives (heartworm, flea/tick, deworming, vaccines) • Medical & surgical history • Indoor/outdoor (feline) • Toxin exposure? • Travel history • Illness in the household • Systems (vomiting/diarrhea/ coughing/sneezing/urination) • Response to therapy Complete Physical Examination (Repeated at least twice daily while fever persists in hospitalized patients) • Respiratory: Harsh, crackles, wheezes • Abdomen: Pain, organomegaly • Musculoskeletal: Lameness; bone, spinal, or neck pain; joint swelling, redness • Ears/nose/throat: Oral cavity lesions, fundic abnormalities, uveitis • Cardiovascular: Murmur, arrhythmia, heart rate, pulse quality • Integumentary: Redness, erythema, lesions, petechiae, ecchymosis, swelling • Lymph nodes: Lymphadenopathy • Rectal: Prostatomegaly, anal sac abnormalities • Urogenital: Intact vs neutered, pain on palpation of kidneys • Neurologic: Cranial nerve deficits, ataxia Did history or physical examination reveal evidence for disease in a specific body system? Yes No Diagnostic Tests Specific to Body System Initial Diagnostic Tests Examples include: Simple, easy to perform/interpret, readily available, fairly noninvasive, and relatively inexpensive: • Cardiopulmonary: Thoracic radiographs, electrocardiography, echocardiography, electrocardiography • Musculoskeletal: Infectious disease titers, bone/joint radiographs, arthrocentesis • Abdomen: Abdominal radiographs or US • Fundus: CBC, serum biochemical profile, infectious disease titers, radiographs, US • CBC with blood smear evaluation • Serum biochemical profile • FeLV/FIV/thyroxine (cats) • Tick titers (dogs) • Urinalysis + urine culture & sensitivity • Fecal analysis • Radiographs (thoracic & abdominal) • Coagulation testing Did diagnostic tests reveal evidence of specific disease? Yes No Perform further diagnostic testing specific to body system Repeat physical examination Yes Did the repeated physical examination reveal evidence of disease in a specific body system? No 34 ..........................................................................................................................................................................NAVC Clinician’s Brief / March 2010 / Diagnostic Tree Additional Diagnostic Tests • Abdominal US: Organomegaly, abdominal pain, effusion • Arthrocentesis: Joint swelling, pain, redness, lameness • Additional infectious disease titers: Lack of preventive medications, abnormal fundic examination, thrombocytopenia • Skeletal radiographs: Lameness, bone pain • Lymph node aspiration: Lymphadenopathy • Echocardiography: Murmur, arrhythmia • Blood cultures: While fever is peaking • CSF tap: Neck pain, neurologic deficits • Bone marrow aspiration: Abnormal CBC results, smear evaluation Did additional diagnostic tests reveal evidence of disease in a specific body system? No Yes Perform further diagnostic testing specific to body system Repeat physical examination Review patient history Yes Did the repeated physical examination reveal evidence for disease in a specific body system? No Advanced Diagnostic Tests Unfortunately, if physical examination and previous tests have been unrewarding, random use of the tests below without clinical suspicion is also likely to be unrewarding. • Consider repeating Initial and Additional diagnostics to look for changes or trends • Bone marrow evaluation • Echocardiography • CSF & joint fluid analysis Investigation • Bronchoscopy & bronchoalveolar lavage (See Bronchoalveolar Lavage Fluid Collection, page 58) • CT or MRI • Laparoscopy, endoscopy, or exploratory surgery If invasive procedures, such as endoscopy, laparoscopy, or exploratory surgery are performed, it is essential to maximize the yield of these procedures by obtaining biopsy samples for histopathology, cultures, and special stains. Consider therapeutic trial Always consider the risks associated with treatment without a known underlying cause • Antibiotic therapy if bacterial origin is suspected • Doxycycline if tick-borne disease is suspected • Antiinflammatory or immunosuppressive medication (NSAID or corticosteroid) as indicated for suspected inflammatory or immune-mediated disease • Intravenous fluids for hydration Treatment CSF = cerebrospinal fluid; CT = computed tomography; FeLV = feline leukemia; FIV = feline immunodeficiency virus; MRI = magnetic resonance imaging; NSAID = nonsteroidal antiinflammatory drug; US = ultrasound Diagnostic Tree / NAVC Clinician’s Brief / March 2010 ..........................................................................................................................................................................35