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Deliberate salt poisoning is a serious cause of hypernatraemia in children and represents a diagnostic challenge for the treating physician. The most important aspect is to actually consider this diagnosis, given its rarity and the severe medical and social consequences associated with it, since parents and carers suddenly become suspects to be confronted with the possibility of having deliberately harmed their child. Wrongfully accusing carers may have serious repercussions and the paediatrician has to have good evidence before raising the diagnosis.1 Moreover, salt poisoning is exceedingly rare. While the true incidence is unknown, as the diagnosis is likely missed in some cases, the annual incidence of recognised non-accidental salt poisoning in the UK in one study was approximately 1 in 10 000 000 children aged under 16 years.2 Thus, most paediatricians will never encounter such a case in their professional life. Yet, considering this diagnosis is key to preventing the potentially fatal consequences. Here, we will review clinical and especially diagnostic aspects of salt poisoning. Due to its rarity, evidence-based guidelines are difficult to establish. Thus, the initial diagnosis has to rely mainly on our understanding of physiology and is ideally subsequently confirmed by forensic investigations.
Hypernatraemia and salt poisoning
A previous expert consensus statement made recommendations for the approach to the patient with suspected salt poisoning, emphasising the importance of weight measurements and paired plasma/urine biochemistries with calculation of the fractional excretion of sodium (FENa) to distinguish from the much more common hypernatraemic dehydration.3 The emphasis on FENa, rather than absolute urine sodium concentrations is to account for the approximately 20-fold variability in urine concentration (50–1000 mOsm/kg), which makes absolute solute concentrations difficult to interpret.4 Urine sodium concentrations as high as 152 mmol/L have been reported in hypernatraemic dehydration.5 This is similar to those reported in salt poisoning, although most cases reported had …