Acute haemorrhagic diarrhoea syndrome (AHDS) in dogs is often treated with antibiotics due to the potential risk of bacterial translocation from the gastrointestinal tract to the blood stream. However, recent studies indicate that antibiotics are not always necessary. According to the Danish antibiotic use guidelines for companion animals 2012, antibiotics are not recommended for routine treatment of AHDS but only indicated in hospitalized dogs with severely affected overall condition and signs of systemic inflammation (SIRS)/sepsis. The aim of this study was to evaluate severity of disease and outcome in hospitalized dogs with acute haemorrhagic diarrhoea that did not receive antibiotics.

The study was performed as a retrospective, observational study based on information from medical records for dogs with acute haemorrhagic diarrhoea of unknown aetiology, hospitalized at the University Hospital for Companion Animals during the period 25/2‐2014 to 9/10‐2018. Signalments, concurrent diseases, clinical disease at the time of hospitalization and during each consecutive day, treatment prior to and during hospitalization, days of hospitalization/euthanasia and laboratory results were registered for each patient. Clinical disease was scored according to the AHDS‐scoring system from 0‐18 and the number of SIRS criteria (tachycardia (HR > 120), tachypnea (RR > 40), hyper or hypothermia (T > 39.0°C or < 37.5°C), leucocytosis (WBC > 18*109/L), leukopenia (WBC < 5*109/L, band neutrophilia and/or hypoglycaemia [glucose <4 mmol/L]) were recorded.

One‐hundred and seventy‐two dogs were excluded from the analysis due to suspected drug induced disease (vaccination(s) (N = 4), anaesthetics (N = 5), corticosteroids or NSAIDs (N = 81)), alimentary foreign body (N = 5) or treatment with antibiotics during hospitalization (N = 128). Of the 128 dogs, where an obvious cause for the diarrhoea were not found and that only received supportive treatment (intravenous fluid therapy N = 128; antiemetics N = 98; gastroprotectants N = 107), 98% survived to discharge (125/128 dogs). Two dogs were euthanized due to financial constraints and reluctance from the owner to proceed with further treatment due to advanced age and one brachycephalic dog suffered a respiratory crisis with respiratory arrest non‐responsive to resuscitation. The surviving 125 dogs were hospitalized for an average of 1.7 days (range 1‐4 days) with a mean AHDS‐score of 12 at hospitalization (range 4‐16). The mean AHDS‐score after 24 hours of hospitalization was 5.5 (range 0‐14). 29% (37/128) of the dogs met ≥2 SIRS criteria during hospitalization. None of the 128 dogs had a degenerative left‐shift.

These results suggest that antimicrobial therapy in dogs with acute haemorrhagic diarrhoea may not always be necessary in dogs even when 2 or more SIRS‐criteria are met. Disclosures No disclosures to report.