Renal Denervation. 
Sympathetic nervous system over-activity is closely linked with elevation of systemic blood pressure.  Both animal and human studies suggest renal sympathetic nerves play an important role in this respect.  Historically, modulation of sympathetic activity has been used to treat hypertension.  More recently, catheter based renal sympathetic denervation was introduced for the management of treatment resistant hypertension.  Sound physiological principles and surgical precedent underpin renal denervation as a therapy for treatment of resistant hypertension.  Encouraging results of early studies led to a widespread adoption of the procedure for management of this condition.  Subsequently a sham controlled randomised controlled study failed to confirm the benefit of renal denervation leading to a halt in its use in most countries in the world.  However, critical analysis of the sham-controlled study indicates a number of flaws.  A number of lessons have been learnt from this and other studies which need to be applied in future trials to ascertain the actual role of renal denervation in the management of treatment resistant hypertension before further implementation.  This chapter deals with all these issues in detail.