What precisely is autoregulation in the kidney? Is it solely the ability to vary the diameters of the afferent and efferent arterioles? If so how is this controlled?

Autoregulation is the ability of any vascular bed to maintain its capillary blood supply/perfusion pressure fairly constant despite changes in mean (systemic) arterial pressure. Autoregulatory control must be mediated locally as autoregulation is an effect that’s intrinsic to a particular organ (i.e. it occurs independently of nervous or endocrine input).The mechanism usually involves changes in diameter of the arterioles supplying the capillary bed to the organ/structure in response to changes in mean arterial pressure. Unlike other organs, the kidney has the additional option of changing the diameter of the efferent, as well as the afferent, arterioles. There are a number of possible mechanisms that could bring about renal autoregulation: stretch-mediated vasoconstriction of the afferent arteriole may occur when renal arterial pressure increases; and/or changes in afferent and efferent arteriolar diameter may be triggered by changes in the rate of delivery of sodium to the macula densa.