Page 709 - Cote clinical veterinary advisor dogs and cats 4th

328 Feline Infectious Peritonitis

because every cat with body cavity effusion DIAGNOSIS Cerebrospinal fluid (CSF) analysis (pp.
also has microgranulomas. A cat with the Diagnostic Overview 1080 and 1323). CAUTION: patient can be
VetBooks.ir • Important to detect effusion for diagnostic Definitive diagnosis is achieved only through herniation.
at increased risk for cerebellar/medullary
dry form will commonly develop effusion
later.
• Can be unremarkable
immunohistochemistry staining of FCoV
purposes. Tests performed on the effusion
markedly higher) and cell count (>5 cells/
much more helpful diagnostically than tests antigen in macrophages of tissues with typical • High protein content (>20 mg/dL, often
histopathologic lesions that have to be obtained
on blood through laparotomy, laparoscopy, or post mcL, often much higher; mononuclear
mortem. Less invasive diagnostic methods with pleocytosis with some neutrophils)
HISTORY, CHIEF COMPLAINT relatively high specificity include polymerase Computed tomography or magnetic reso-
• Commonly nonspecific signs, including chain reaction (PCR) specific for mutations in nance imaging of the brain: hydrocephalus
lethargy, inappetence, and weight loss the spike gene and detection of FCoV antigen common if CNS involvement, multifocal
• Persistent fever, nonresponsive to antibiotics in macrophages by immunofluorescence or granuloma
• Abdominal distention in cats with ascites immunocytology of effusions or other fluids.
• Dyspnea in cats with pleural effusion or In vivo diagnosis for cats without effusion is Advanced or Confirmatory Testing
pulmonary granuloma much more difficult. Immunohistochemistry staining of FCoV
• Other complaints are related to site of antigen in macrophages of tissues with typical
granulomas (e.g., central nervous system Differential Diagnosis histopathologic lesions:
[CNS] signs, icterus diarrhea) • Body cavity effusions: neoplasia, cholangio- • Gold standard of diagnosis
hepatitis, pancreatitis, bacterial peritonitis, • Only way to definitively diagnose FIP
PHYSICAL EXAM FINDINGS pyothorax, chylothorax, diaphragmatic • Requires histopathology of tissue samples
• Abdominal effusion: abdominal distention, hernia, cardiomyopathies obtained through laparotomy, laparoscopy,
sometimes with a palpable fluid wave • Uveitis: toxoplasmosis, FIV infection, or post mortem.
• Pleural effusion: dyspnea, muffled heart and systemic mycoses (p. 1023) Mutation PCR:
lung sounds • Multifocal neurologic lesions: toxoplasmosis, • Most specific noninvasive method for
• Organomegaly or abdominal masses bacterial meningoencephalitis, metabolic, and diagnosis
sometimes palpable (e.g., enlarged mes- toxic CNS diseases • PCR detects specific mutations in the spike
enteric lymph nodes, nodules in other • Hyperglobulinemia: multiple myeloma, protein that leads to FIP-inducing FCoV
organs, intestinal thickening, irregular heartworm disease, FIV infection, severe pathotypes.
kidneys) inflammatory conditions • High specificity (96%) and moderate sensitiv-
• Icterus may be noted due to liver involvement ity (69%) for effusion; not useful for blood
but can also be caused by interference of Initial Database due to very low sensitivity
tumor necrosis factor-alpha with bilirubin Thoracic and abdominal radiographs: Detection of FCoV antigen in macrophages
transport (i.e., icterus with no hemolysis, • Pleural effusion, ascites (in case of by immunofluorescence or immunocytology
biliary obstruction, or increase in liver effusion) staining:
enzymes) Abdominal ultrasound: • Second best method to diagnose FIP
• Encephalitis: ataxia, personality changes, • Ascites, abdominal masses, lymphadenopathy • Can be done on effusion, CSF, aqueous
nystagmus, or seizures CBC (can be normal or nonspecific changes): humor, and lymph node aspirates; not useful
• Uveitis: change in iris color, hyphema, • Lymphopenia, neutrophilia without left shift for blood
aqueous flare, keratic precipitates, vitreous (stress leukogram) • Relatively high specificity (72%) and
clouding, vascular cuffing, manifesting as • Mild nonregenerative anemia of chronic sensitivity (85%) for effusion; some false-
gray lines parallel to retinal vessels inflammation positive test results occur, which limits the
• Unusual presentations include skin fragility Serum biochemistry profile (can be normal): utility.
syndrome and other skin lesions, orchitis, • Hyperglobulinemia (and low albumin/ FCoV antibody detection:
and priapism. globulin ratio) • Very limited usefulness because presence
• Increased bilirubin, often with normal liver of antibodies indicates only exposure to a
Etiology and Pathophysiology enzyme activity coronavirus (including FIP vaccine virus),
• Benign FCoV replicates in enterocytes. If a Serum protein electrophoresis (not necessary not FIP
mutation takes place in the spike protein of if values of albumin and total protein are • Most cats with FCoV antibodies never
the FCoV, virus loses its ability to replicate available): develop FIP.
in enterocytes, making it unlikely that • Polyclonal gammopathy • About 10% of cats with FIP have no serum
mutated virus would be transmitted to Fluid analysis (ascites, pleural effusion, peri- antibodies, especially in terminal stages. A
other cats. cardial effusion): negative antibody test does not rule out FIP.
• The mutated virus is taken up by macro- • Clear, viscous, straw-colored fluid Conventional PCR for detecting any FCoV:
phages and distributed throughout the body. • Analysis (p. 1343): nonseptic exudate with • False-positive results and false-negative results
A second mutation is potentially necessary protein > 3.5 mg/dL (35 g/L) (often much for blood PCR are common because cats
to enable the virus to effectively replicate in higher), total cell count increased but with benign enteric FCoV infection also can
macrophages. relatively mildly (e.g., 2000/mcL) for an have viremia and cats with FIP often lack
○ Replication of the mutated FCoV in exudate (lower than in bacterial serositis), viremia.
macrophages is the key event in the mainly macrophages and nondegenerate • For effusion, PCR more specific and sensitive
pathogenesis of FIP. neutrophils but still not diagnostic for FIP
○ The virus within macrophages initiates the Rivalta test for cats with effusion (addition of
ultimately fatal immune-mediated reaction 1 drop effusion to water-acetic acid mixture, TREATMENT
to virus. watching for coagulation (lava lamp look);
• Signs caused by granulomatous lesions in sensitivity 91%, specificity 65%) (see Video) Treatment Overview
target organs (CNS, eyes, and parenchyma- • If negative, FIP extremely unlikely FIP is an incurable disease. Treatment goals
tous organs) and vasculitis leading to fluid • If positive, FIP likely (but false-positives with are to prolong life and provide comfort and
accumulation in body cavities lymphoma, bacterial serositis) supportive/palliative care.

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