An uncommon intestinal manifestation of feline infectious peritonitis: 26 cases (1986-1993)

To provide information on an uncommon intestinal manifestation of feline infectious peritonitis (FIP).

Retrospective case series.

26 cats with FIP that had apparently solitary mural intestinal lesions.

Histologic records of cats for which FIP had been diagnosed by examination of the surgical biopsy specimens were reviewed. Slides of tissue samples from cats identified in the histologic record as having had intestinal lesions were reviewed by the investigators, and records of cats that appeared to have had solitary mural intestinal lesions were included in the study. Information including signalment; history; physical examination findings; results of hematologic, serum biochemical, and serologic analyses; findings at surgery; and results of histologic examination of biopsy specimens were retrieved from these records and supplemented by medical records and additional information obtained from veterinarians submitting the biopsy samples. ABC immunoperoxidase staining was used to detect FIP virus antigen in tissues from cats whose records were selected for inclusion in the study.

26 of 156 cats with a histologic diagnosis of FIP had apparently solitary mural intestinal lesions. Predominant clinical signs were diarrhea and vomiting for 3 months or less before biopsy. All cats had a mass, believed to be a neoplasm, in the colon or ileocecocolic junction. Affected intestine was markedly thickened, nodular, firm, and white, with multifocal pyogranulomas extending throughout the wall of the intestine on histologic examination. Associated lymph nodes were large. Results of immunohistochemical staining were positive for FIP virus. Most cats were euthanatized or died within 9 months of histologic results, many with signs of multisystemic FIP.

The apparent focal nature of intestinal lesions at surgery leads to a different clinical picture than usually seen with FIP, and masses often are believed to be neoplasms. Diagnosis of FIP is important to prevent exposure and infection of other cats. Evaluation of the entire abdominal cavity, biopsy of visible lesions as well as surrounding organs, and postmortem examination are recommended.