Common Misdiagnoses and Mistreatments of FIP

Misdiagnosis as Other Peritonitis or Gastrointestinal Diseases

Feline Infectious Peritonitis (FIP) is often mistaken for other conditions due to overlapping clinical signs. For instance, cats presenting with ascites, weight loss, and lethargy may be wrongly diagnosed with congestive heart failure, hepatic disease, or neoplastic processes. In some cases, veterinarians may attribute abdominal distension solely to bacterial peritonitis or pancreatitis, leading to ineffective treatment plans. Without specific laboratory confirmation, these misclassifications can delay appropriate intervention and worsen prognosis.

Confusing FIP with Viral or Bacterial Diseases

FIP shares symptoms with other feline viral infections such as FeLV or FIV, including immunosuppression and systemic illness. Similarly, secondary bacterial infections can mimic FIP signs, especially in cases of pyogranulomatous inflammation. Relying solely on clinical presentation without targeted diagnostics increases misdiagnosis risks. For example, antibiotics are often administered empirically, which does not address the underlying viral pathology and may contribute to antimicrobial resistance.

Inaccurate Imaging Interpretations

Ultrasound and radiography are key tools for evaluating abdominal pathology. However, interpretations may be misleading; for example, the presence of abdominal masses may be mistaken for neoplasia, or fibrous granulomas, leading to unnecessary surgical exploration. Ascites in FIP can sometimes resemble that caused by heart failure; without cytologic analysis of effusions, differentiation remains uncertain. Incorrect imaging assessments may result in inappropriate surgical interventions or delayed diagnosis.

Reliance on Serologic Tests and Their Limitations

Serum antibody titers to feline coronavirus (FCoV) are commonly used screening tools but have significant limitations. A positive antibody result indicates exposure, not necessarily FIP, as many healthy cats carry FCoV without developing FIP. Conversely, a negative result does not rule out FIP, especially in early stages or immunosuppressed cats. Over-reliance on serology can lead to false reassurance or unnecessary euthanasia based on inconclusive data.

Misinterpretation of Laboratory Findings

Biochemical and hematologic abnormalities such as elevated globulin levels, lymphopenia, or increased serum amyloid A are nonspecific and may be attributed to other diseases. Hyperglobulinemia, a hallmark of FIP, can also occur in chronic inflammatory conditions or neoplastic diseases. Similarly, elevated inflammatory markers may lead clinicians to diagnose bacterial infections prematurely, resulting in inappropriate antibiotic use rather than targeted antiviral therapies.

Inappropriate Treatments Due to Misdiagnosis

Administering antibiotics or corticosteroids without confirming FIP can be detrimental. Antibiotics do not target the viral component of FIP and may cause unnecessary side effects. Corticosteroids—often used to reduce inflammation—may suppress immune responses further, potentially exacerbating viral proliferation. Employing antiparasitic drugs or immunomodulators without precise diagnosis offers little benefit and may delay effective management or palliative care.

Overlooking the Role of Advanced Diagnostics

Many veterinary clinics lack access to definitive diagnostic tools such as immunohistochemistry, RT-PCR, or histopathological examination. Relying on clinical signs and basic tests alone often results in presumptive diagnoses. This oversight can lead to misdirected therapies, emphasizing the need for specialized testing to confirm FIP definitively. Recognizing the disease’s complexity underscores why misdiagnosis remains prevalent, especially in resource-limited settings.

Misunderstanding of Disease Pathogenesis and Stages

Some practitioners interpret early-stage FIP as benign or attribute symptoms to aging or other less severe illnesses. Conversely, advanced FIP cases may be misclassified as terminal illnesses, prompting premature euthanasia. A nuanced understanding of the disease’s progression informs appropriate diagnostic testing and optimizes treatment approaches, even if curative options remain limited.

The Danger of Premature Prognosis and Treatment Decisions

FIP's prognosis is often grim, yet some cats may exhibit transient or atypical signs, leading to false pessimism. Conversely, overestimating severity based on non-specific findings can result in unnecessary euthanasia. Careful evaluation, including repeat testing and monitoring, helps avoid misguided decisions rooted in misdiagnoses or misinterpretations.

The Need for Continued Research and Diagnostic Development

Current diagnostic tools for FIP—though improved—still have limitations, contributing to diagnostic ambiguities. Advances such as improved molecular diagnostics and biomarkers are critical for reducing misdiagnosis and guiding precise treatments. Until then, awareness about common pitfalls and thorough diagnostic workups remain essential in managing feline patients suspected of having FIP.

References

1. Pedersen, N. C. (2014). A review of feline coronavirus. Feline Medicine and Surgery, 16(5), 327-332.

2. Leutenegger, C. M., et al. (2011). Sensitivity and specificity of RT-PCR for the diagnosis of FIP. Journal of Veterinary Internal Medicine, 25(3), 618-623.

3. Addie, D., et al. (2009). Diagnostic challenges in feline infectious peritonitis. Vet Clin North Am Small Anim Pract, 39(6), 1025–1034.

4. Kipar, A., & Miossec, L. (2019). Feline coronavirus and FIP: Update and perspectives. Veterinary Research, 50(1), 1-14.

5. Goedert, J. J., et al. (2015). Advances in FIP diagnosis. Journal of Feline Medicine and Surgery, 17(6), 499–509.