INTRODUCTION: Patients are frequently admitted to hospital on suspicion of dehydration. The diagnosis is widely used for referral to admittance departments. We aimed to prospectively evaluate patients admitted with a diagnosis of dehydration in terms of the accuracy of this diagnosis, to evaluate clinical and biochemical data and to evaluate the outcome and provide a review of the concept of dehydration.

METHODS: Patients who had dehydration as their primary referral diagnosis were prospectively included over a 70-day period. We defined dehydration based on osmolality > 295 mmol/kg. Biochemistry, imaging and outcome were examined.

RESULTS: A total of 128 patients were admitted on suspicion of dehydration, accounting for 7.5% of all patients admitted. In all, 82 of the 128 (64%) were dehydrated. The diagnoses at discharge included infections mainly, but also diagnoses such as cancers and stroke were registered. Mortality during hospitalisation was 9%. Mortality at six months was 27% for the entire group; 37% in the dehydration group versus 11% in the non-dehydration group (p = 0.002). Older age was the strongest predictor of death.

CONCLUSIONS: Suspicion of dehydration is a frequent admittance diagnosis. We suspect that a referral diagnosis of dehydration often reflects an unspecified concern rather than a real suspicion of dehydration. Patients with dehydration had a high in-hospital and six-month mortality, reflecting the severity of this diagnosis.

FUNDING: not relevant.

TRIAL REGISTRATION: The Danish Data Protection Agency, R. no. 05380, BFH-2017-029.