Nephrogenic Diabetes Insipidus (NDI) is characterised by the inability of the kidneys to concentrate urine in response to arginine vasopressin (AVP). Such patients typically experience polyuria and polydipsia because of this inability to autoregulate their water balance. This provides a perioperative challenge that could lead to a life-threatening situation. This article documents a patient with NDI who underwent an elective bowel re-anastomosis. Two peak serum sodium values were attained. The first when the patient was retaining sodium due to an inappropriate fluid regimen and the second due to hypovolaemia. The literature is reviewed and principles for NDI perioperative management are proposed.