Abdominal ultrasonographic findings of cats with feline infectious peritonitis: an update

Abstract

Objectives: The aim of this study was to describe the abdominal ultrasonographic findings in cats with confirmed or presumed feline infectious peritonitis (FIP).

Methods: This was a retrospective study performed in an academic veterinary hospital. The diagnosis of FIP was reached on review of history, signalment, clinical presentation, complete blood count, biochemistry panel, peritoneal fluid analysis, cytology and/or histopathology results from abnormal organs, and/or molecular testing (immunohistochemical or FIP coronavirus [FCoV] RT-PCR). Cats with confirmed FIP by molecular testing or with a highly suspicious diagnosis of FIP were included. Abdominal ultrasound examination findings were reviewed.

Results: In total, 25 cats were included. Common clinical signs/pathology findings included hyperglobulinemia (96%), anorexia/hyporexia (80%) and lethargy (56%). Abdominal ultrasound findings included effusion in 88% and lymphadenopathy in 80%. Hepatic changes were noted in 80%, the most common being hepatomegaly (58%) and a hypoechoic liver (48%). Intestinal changes were noted in 68% of cats, characterized by asymmetric wall thickening and/or loss of wall layering, with 52% being ileocecocolic junction and/or colonic in location. Splenic changes were present in 36% of cats, including splenomegaly, mottled parenchyma and hypoechoic nodules. Renal changes were present in 32%, encompassing a hypoechoic subcapsular rim and/or cortical nodules. Mesenteric and peritoneal abnormalities were seen in 28% and 16% of cats, respectively. Most cats (92%) had two or more locations of abdominal abnormalities on ultrasound.

Conclusions and relevance: The present study documents a wider range and distribution of ultrasonographic lesions in cats with FIP than previously reported. The presence of effusion and lymph node, hepatic and/or gastrointestinal tract changes were the most common findings, and most of the cats had a combination of two or more abdominal abnormalities.

Keywords: Ultrasound; abdomen; feline infectious peritonitis; viral diseases.

Figure 1

Longitudinal ultrasonographic (US) image of the abdomen in a 12-year-old female cat with feline infectious peritoniris (case 9). (a) Part of the moderately thickened parietal peritoneum is seen between the calipers (2.6 mm). (b) The hyperechoic mesentery appears nodular (between the calipers: 1.2 cm) and irregular. Anechoic peritoneal effusion (asterisk) was also present.

Figure 2

Jejunal suppurative lymphadenitis in a 7-month-old female cat (case 21). Longitudinal ultrasound image of the enlarged jejunal lymph nodes. Note the cranial mesenteric vein (asterisk). The most dorsally located jejunal lymph node is markedly enlarged, hypoechoic, with an ill-defined anechoic cranial pole (white arrow) and slightly lobulated. Regional perinodal fat is hyperechoic, supportive of steatitis (white arrowhead)

Figure 3

Longitudinal ultrasound image of the liver in an 8-year-old male neutered cat with feline infectious peritonitis (case 14). A 2.4 mm ellipsoid hyperechoic nodule (cursors) is noted within the periphery of the liver, bulging along the hepatic capsule. Serosal granuloma was diagnosed by histopathology. Slightly echogenic peritoneal effusion is also noted (asterisk)

Figure 4

Transverse ultrasound image of (a) the ascending colon and (b) ileocolic junction in a 3-year-old female cat with feline infectious peritonitis (case 10). (a) The ascending colon is thickened with lost wall layering (between the calipers: 8.5 mm). (b) An ileocecocolic junction-centered colonic wall thickening with loss of wall layering (between the calipers: 8 mm). The ileum is also seen (asterisk)

Figure 5

(a) Parasagittal ultrasound image of the right kidney in an 8-month-old cat with feline infectious peritonitis (case 19) showing a 1 cm hyperechoic cortical nodule (cursors). There is concurrent retroperitoneal anechoic effusion (asterisks). (b) Pyogranulomatous nephritis in a 1-year-old cat with feline infectious peritonitis (case 18). Longitudinal ultrasound image of the enlarged (4.7 cm long) right kidney with heterogeneous parenchyma and slightly irregular margination. A thin hypoechoic rim is also noted at the outer cortical (white arrow). The perirenal fat is hyperechoic. The asterisk indicates a scant amount of urine in the renal pelvis. Pyogranulomatous nephritis was diagnosed on necropsy