Renal artery stenosis
Renal artery stenosis (RAS) is the narrowing of one or both of the renal arteries, most often caused by atherosclerosis or fibromuscular dysplasia. This narrowing of the renal artery can impede blood flow to the target kidney, resulting in renovascular hypertension – a secondary type of high blood pressure. Possible complications of renal artery stenosis are chronic kidney disease and coronary artery disease. Signs and symptoms. Most cases of renal artery stenosis are asymptomatic, and the main problem is high blood pressure that cannot be controlled with medication. Decreased kidney function may develop if both kidneys do  not receive adequate blood flow, furthermore some people with renal artery stenosis present with episodes of flash pulmonary edema. Cause. Renal artery stenosis is most often caused by atherosclerosis which causes the renal arteries to harden and narrow due to the build-up of plaque. This is known as atherosclerotic renovascular disease.This accounts for about 90% of cases with most of the rest due to fibromuscular dysplasia. Fibromuscular dysplasia is the predominant cause in young patients, usually females under 40 years of age. Pathophysiology. The pathophysiology of renal artery stenosis leads to changes in the structure of the kidney  that are most noticeable in the tubular tissue. If the stenosis is longstanding and severe, the glomerular filtration rate in the affected kidneys never recovers and (prerenal) kidney failure is the result. Changes include: Diagnosis. The diagnosis of renal artery stenosis can use many techniques to determine if the condition is present, a clinical prediction rule is available to guide diagnosis. Among the diagnostic techniques are: The specific criteria for renal artery stenosis on Doppler are an acceleration time of greater than 70 milliseconds, an acceleration index of less than 300 cm/sec² and a velocity ratio of the renal  artery to aorta of greater than 3.5. Treatment. Atherosclerotic renal artery stenosis. It is initially treated with medications, including diuretics, and medications for blood pressure control. When high-grade renal artery stenosis is documented and blood pressure cannot be controlled with medication, or if renal function deteriorates, surgery may be resorted to. The most commonly used procedure is a minimally-invasive angioplasty with or without stenting. It is unclear if this approach yields better results than the use of medications alone. It is a relatively safe procedure. If all else fails and the kidney is thought to be worsening  hypertension and revascularization with angioplasty or surgery does not work, then surgical removal of the affected kidney (nephrectomy) may significantly improve high blood pressure. Fibromuscular dysplasia. Angioplasty with or without stenting is the best option for the treatment of renal artery stenosis due to fibromuscular dysplasia.