Unusual circadian hypertension associated with polydipsia

A 76 year old female patient with chronic polydipsia and abnormal circadian blood pressure oscillations with periodic daily hypertension in the afternoon despite antihypertensive treatment is described. The abnormal diurnal blood pressure rise spontaneously disappeared when her daily drinking volume was reduced to normal. She began voluntary polydipsia after an episode of painful urolithiasis 12 years ago when she was advised to maintain a high daily fluid intake to prevent a relapse. During clinical workup, no other etiologic factor could be detected to explain the high diurnal blood pressure changes. Four years earlier, she had suffered an ischemic stroke in the vertebrobasilar territory caused by cerebral microangiopathy. She showed mild renal insufficiency, a residual neurologic syndrome after stroke and hypertensive heart disease with normal left ventricular ejection fraction. Plasma Na and other electrolytes were normal. A renal ultrasound exam was unremarkable and excluded renal artery stenosis. Extended laboratory investigations including plasma and urinary glucocorticoids, mineralocorticoids, metanephrins, thyroid function tests and the plasma aldosterone/renin ratio were also normal. We discuss abnormal control of volume homeostasis by hormonal and renal mechanisms and abnormal central blood pressure regulation following brain stem infarction as potential causal mechanisms to explain the association of polydipsia with the recurrent diurnal hypertension in our patient. Although chronic polydipsia may be rare, it may occasionally be a modifiable cause contributing to blood pressure elevations and treatment resistance of hypertension particularly when volume handling is impaired by concomitant disease.