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Renal artery stenosis
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With renal artery stenosis, ‘stenosis’ means narrowing, which refers to a progressive narrowing of the renal artery, which carries blood to the kidney. This means that the blood downstream of the narrowed spot that goes to the kidney is at lower pressure, which gets sensed by the kidney.
Inside the kidney, there are millions of nephrons, each of which help to filter the blood and then fine-tune the composition of blood by carefully reabsorbing and secreting electrolytes as fluid passes through various parts of the nephron.
Blood approaches the nephron via the afferent arteriole. You can remember it as ‘A’ for approach, and then forms a tangle of capillaries called the glomerulus, before exiting via the efferent arteriole - “e” for exit. That efferent arteriole goes on to split into another set of capillaries - the vasa recta - which surround the nephron, and then blood leaves via the venule.
So there are two capillary beds per nephron, usually we think of it going arteriole - capillary - venule, but in the nephron it goes arteriole - capillary - arteriole - capillary - and finally venule.
So nephrons have the general shape of the letter “U”, with the beginning and end portions getting pretty close to each other.
The reason that this matters, is that over here, lining the inside of the afferent arteriole are endothelial cells.
Renal artery stenosis is a condition that occurs when the artery that carries blood to the kidney becomes more narrow, which reduces the amount of blood that the kidney receives. This can lead to high blood pressure because the kidney senses the low blood pressure due to its impaired blood supply, and responds by releasing the hormone renin which increases blood pressure - ultimately causing systemic hypertension. Renal artery stenosis also leads to reduced kidney function and other serious health complications such as kidney atrophy. Treatment for renal artery stenosis typically involves medications to control blood pressure, lifestyle changes, and procedures to open the narrowed or blocked arteries.
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