Impaired water diuresis in patients with anorexia nervosa

Abstract

Twelve patients with anorexia nervosa and eight control patients with affective disturbance were given a standardised water loading test. Water diuresis was impaired in five of the patients with anorexia nervosa, as evidenced by inability to excrete an appropriately large volume of water, but in none of the control patients. The patients with impaired water diuresis were not always those with oedema. The abnormality, however, varied directly with the duration of the malnutrition, and was not found in patients who had been ill for less than three years. The abnormality was less marked when patients were tested in the recumbent rather than in the erect position. This accounts for nocturnal frequency of urine in some patients with anorexia nervosa. There was no obvious failure of absorption of water from the gastrointestinal tract. The reduction in plasma osmolality after the water load was at least as marked in four patients with anorexia nervosa and impaired diuresis as in four others with a normal response. In one patient a normal absorption of tritiated water was demonstrated by measuring plasma activity at intervals after the water load. There was no evidence of adrenal insufficiency. The patients with anorexia nervosa and impaired diuresis did not differ from those with a normal response in their urinary output of 17-hydroxycorticosteroids or 17-ketosteroids. Prior administration of hydrocortisone did not restore the response to normal. There was no evidence of excessive or inappropriate secretion of antidiuretic hormone. Urinary assays in two patients were normal, and the prior administration of alcohol did not restore the response to normal. There was no evidence of increased secretion of aldosterone. The ability to concentrate urine was normal, and the prior administration of spironolactone did not restore the test to normal. The role of psychological factors is largely discounted by the findings in the control patients who were emotionally disturbed to an approximately equivalent degree. Glomerular filtration rates were reduced in the patients with anorexia nervosa as measured by creatinine clearances in ten patients and inulin clearances in two. A positive correlation was found between the glomerular filtration rate and body weight on the one hand, and the glomerular filtration rate and the diuretic response on the other. Two patients with reduced glomerular filtration rates did, nevertheless, show normal responses to the water loading tests. The normal diuretic response was restored in three of four patients after refeeding and weight gain, but recovery sometimes took several months. Treatment with vitamin B 1 had no effect.