[Extreme neutrophilia in cats - aetiology and prognosis]

The aim of this retrospective study was to evaluate the aetiology and prognostic factors of extreme neutrophilia in cats.

Patient data over a 5-year period (January 2008  -  December 2013) were reviewed. Cats with a neutrophil count > 40 x 10⁹/l were included. They were further assigned to four groups: "inflammation", "neoplasia", "immune-mediated diseases", "unknown aetiology". Clinical signs, rectal temperature, hospitalisation, duration of hospitalisation, survival, left-shift and toxicity of neutrophils were evaluated.

In total, 28/5185 cats (0.5%) displayed extreme neutrophilia with a mean neutrophil count of 48.5 x 10⁹/l (40.0-76.0 x 10⁹/l). The most common aetiology was a severe inflammation, as seen in 16/28 cats (57%), whereby peritonitis (5/15 cats, 31%) predominated. In cats with neoplastic diseases (9/28 cats, 32%), intestinal neoplasia with subsequent peritonitis was the most common diagnosis (4/9 cats, 44%). Diseases of unknown aetiology (2/28 cats, 7%) and immune-mediated diseases (1/28, 3.6%) were rare. The most common clinical indications included lethargy, anorexia, fever, and gastrointestinal signs. Rectal temperature ranged between 33.9  °C and 40.2   °C, whereby in 2/24 cats (8%) hyperthermia (> 39.3°C) and in 5/24 cats (21%) hypothermia (< 38.0°C) was observed. Hospitalisation occurred in 21/28 cats (75%) with a median duration of 5.5 days (1-30 days). In 24/28 cats, a manual differential count was performed. A left-shift and toxicity of neutrophils were seen in 23/24 cats (96%) and 21/24 cats (88%), respectively. The overall median survival rate was 50%, whereby the survival rate was significantly lower in cats with neoplasia than in those with inflammatory diseases (22% vs. 56%, p < 0.0001).

An extreme neutrophilia is rare. It is commonly caused by peritonitis due to foreign bodies or ruptured intestinal tumours (in particular, intestinal lymphomas) and is characterised by a high mortality.