Hemodynamic basis for human acute renal failure (vasomotor nephropathy)

Area of Science:

• Nephrology
• Renal Physiology

Background:

• Oliguric acute renal failure (ARF) in humans presents with intense outer cortical vasoconstriction and increased preglomerular resistance.
• The observed fall in renal blood flow suggests a degree of vasoconstriction that should abolish filtration, yet filtration is often maintained.

Purpose of the Study:

• To investigate the vascular resistance changes in the outer cortex during oliguric acute renal failure.
• To determine the relationship between preglomerular and postglomerular resistance and its effect on renal blood flow and filtration.

Main Methods:

• The study analyzes the physiological parameters of vasoconstriction and resistance in the renal cortex.
• It uses mathematical modeling to assess the impact of varying pre- and postglomerular resistance on blood flow and filtration.

Main Results:

• A 50-80% fall in renal blood flow requires significant preglomerular resistance increase, exceeding levels that would abolish filtration.
• Equal increases in pre- and postglomerular resistance could maintain filtration despite ischemia, but this contradicts observed extreme preglomerular attenuation.
• Evidence suggests preglomerular constriction may coincide with postglomerular vascular relaxation.

Conclusions:

• Cortical ischemia in human vasomotor nephropathy is characterized by intense outer cortical vasoconstriction.
• Filtration failure is an inevitable outcome unless there are precisely matched increases in both pre- and postglomerular resistances during cortical ischemia.