Abstract
Faced with an animal with pyrexia of unknown origin, or ‘PUO’, no doubt every clinician has internally despaired in anticipation of a potentially difficult diagnostic journey ahead. Although pyrexia often proves to be self-limiting or responsive to empirical therapy, some cases require many diagnostic investigations that are costly to the client and may yield little or no useful information, leading to frustration. It was this frustration, as well as the lack of published studies specifically investigating pyrexia in cats, that was the main impetus behind the decision to conduct the study ‘Pyrexia in cats: retrospective analysis of signalment, clinical investigations, diagnosis and influence of prior treatment in 106 referred cases’ published in this issue. 1
The study describes the most common diagnoses seen in a population of UK cats referred with pyrexia, hopefully guiding the clinician in their history taking and first-choice diagnostic tests. Results suggest that test selection, especially diagnostic imaging, should depend on localising signs, avoiding any temptation simply to seek abnormalities without an appropriate focus. Physical examination findings can be instrumental in achieving a diagnosis, but cats tend to give fewer clues than dogs and will often present with non-specific clinical signs such as lethargy and inappetence. Allowing time for new clinical signs or physical examination abnormalities to develop is often worthwhile, and a step-wise approach is recommended. Indeed, the question that the clinician needs to ask themselves at every stage when managing a pyrexic patient is one applicable to many other situations: Do I have justification to perform this diagnostic test and/or give this treatment?
Pyrexic cats will often present with non-specific clinical signs such as lethargy and inappetence. Allowing time for new clinical signs or physical examination abnormalities to develop is often worthwhile, and a step-wise approach is recommended
Our study found that many cats were ultimately diagnosed with relatively common diseases (eg, cellulitis, pancreatitis, lymphoma) but had unusual or early manifestations of these conditions that delayed diagnosis before referral. Furthermore, we suggest that the term ‘PUO’ is somewhat of a misnomer and is probably overused in veterinary medicine, as the number of patients in which a true cause of pyrexia cannot be found was relatively small.
The study data also showed that nearly one-third of cats had received drugs from multiple antimicrobial classes by the time of referral. Although the prevalence of bacterial infections in pyrexic cats in first-opinion practice may be sufficiently high to warrant such treatments, additional studies are needed to support or refute this. We would advocate witholding antimicrobials in stable patients when pyrexia is acute and mild.
On a similar theme, the use of antipyretics, such as non-steroidal anti-inflammatory drugs, remains controversial, as the artificial resolution of pyrexia may improve the patient’s demeanour but is rarely essential and may delay and/or complicate a diagnosis. of course, in some cases, a therapeutic trial may be a viable option, and hopefully such a trial can be used to help obtain a diagnosis (or eliminate a disease category), but multiple treatments should be avoided if possible.
Our hope is that the study findings will inform decision-making when managing pyrexic cats. It will be interesting to see whether similar studies of other feline populations, performed with larger and first-opinion datasets, produce similar findings.