Polyuria and polydipsia — OSCE

Candidate brief

You are the paediatric registrar. The patient is a 4-month-old boy admitted with poor weight gain, irritability and hypernatraemic dehydration. Investigations have confirmed congenital nephrogenic diabetes insipidus: his blood glucose is normal, his serum sodium was 158 mmol per litre, his urine osmolality was maximally dilute, and he did not respond to desmopressin. The consultant has asked you to explain to his parents what the diagnosis means, why the usual hormone tablet will not work for him, what the daily care involves, and how to keep him safe. The parents are frightened that his kidneys are failing and that he will not grow. Explain clearly, check their understanding, and agree a plan. ^[9]