Sympathetic overactivityplays a crucial pathogeneticrole in the genesis of hypertension in Autosomal Dominant Polycystic Kidney Disease (ADPKD) Gabow PA, 1984 . Although the use of multi-drug therapy in ADPKD, successful control of blood pressure (BP) occurs in less than 30% of patients Gabow PA, 1990 . Renal denervation has been shown to be effective and safe in reducing BP in patients with treatment-resistant hypertension, even with chronic kidney disease (CKD) Hering D, 2012  (full text). However, there are no cases in hypertensive patients with ADPKD or with single-kidney. We report the exceptional case of a single-kidney woman with stage 4 CKD secondary to ADPKD and uncontrolled treatment-resistant hypertension.
Our patient, a 50-year-old woman with stage 4 CKD secondary to ADPKD, showed a severe resistant hypertension (BP> 200/110 mmHg), The finding of hypokalemia and metabolic alkalosis, unusual for a stage 4 CKD patient, suggested a diagnosis ofhyperaldosteronism, that was then investigated. Although the laboratory-tests performed were not consistent with renal artery stenosis, a renalscintigraphy with assessment of individual renal function was performed and showed a good perfusion of the right kidney with a preserved function of 93%, and the left kidney with poor perfusion and excretion, and a relative function of 7%. A magnetic resonance (MR) angiography showed a stenosis on the proximal two-thirds of the left renal artery. Finally, a renal arteriography, performed to confirm the diagnosis of left renal artery stenosis and in order to perform a renal angioplasty, showed ahypoplasicleft renal artery. Because of the BP values constantly elevated, the impossibility to perform an angioplasty for the anatomical anomaly of the left renal artery, the reduction of left kidney functional capacity to less than 10% of total function, and the absence of evidence for significantly accelerated progression of renal failure when uninephrectomized patients were compared with matched non-uninephrectomized ADPKD patients, removal of left kidney was performed, without complications or worsening of renal function. However, three months after the nephrectomy, the patient showed a progressive worsening of hypertension (BP>180/100 mmHg).Because of the ineffectiveness of all pharmacological and surgical therapeutic strategies, renal denervation by radiofrequency ablation of the right renal artery was finally performed (Fig. 1-2).
The patient decreased the requirement of antihypertensive medication and the BP showed a remarkable reduction, that resulted stable 12 months after the procedure. We did not observe any uncontrollable adverse event during the procedure or during the short-term follow-up of 12 months.
Our patient did not experience a significant deterioration of renal function despite nephrectomy and renal denervation, in according to the findings in a rat model of ADPKD, in which bilateral kidney denervation resulted in normalization of the blood pressure and in slowing renal disease progression both structurally and functionally, likely through the modulation of renal renin release and angiotensin II activity Gattone VH, 2008 . Possible explanations for the limitated deterioration of the renal function in denervated rats may result from the lower blood pressure and from an improvement of the renal flow. Moreover, another possible mechanism could be that the reduction of the sympathetic activity ameliorate the cyst enlargement, because the angiotensin II is a known renal epithelial cell mitogen Terada Y, 1995 . In according to these observations, our patient did not experience a significant worsening of renal function despite renal denervation. This is the first case showing the safety and feasibility of a catheter-based renal denervation approach, in a single-kidney CKD patient with resistant hypertension and ADPKD.