Position-related renal perfusion disturbances as a possible underestimated mechanism in patients with resistant hypertension: a case vignette.

PURPOSE: In patients with resistant hypertension and large blood pressure fluctuations, the role of orthostatic hypertension, associated with position-dependent renal perfusion disturbances, has not been investigated in detail yet.

METHODS

In this regard, four patients from our outpatient clinic were investigated by the use of 24-h ambulatory blood pressure monitoring (ABPM), active standing test, renal duplex sonography and Tc99m-mercaptoacetyltriglycine [MAG3] renal scintigraphy in supine and upright position.

RESULTS

Four patients (three males and one female; 51-79 years) with a mean of 4.25 antihypertensive drugs including a diuretic were evaluated. The recorded blood pressure fluctuations were up to 89/58-198/121 mmHg. Three patients exhibited an extreme and one a normal dipping pattern in the 24-h ABPM. Three patients demonstrated a hypertensive orthostatic reaction in the active standing test. By duplex sonography, a bilateral decrease in the overall intrarenal resistive indices was shown in two patients, a unilateral overall decrease in one patient and a localized decrease in the last patient. From a morphological standpoint of view, all patients had a normal anatomical position and a physiologic descent of both kidneys. But the normalized tubular extraction rate was pathologic in all patients in the upright body position and normalized when lying down in three patients.

CONCLUSIONS

Position-dependent renal perfusion should be considered in patients with large blood pressure fluctuations and extreme dipping. If morphological imaging shows no abnormalities, functional imaging provides additional information. Further investigation is needed, foremost if nephropexy could improve blood pressure control in some of these patients.