High Blood Pressure and Kidneys

When considering the relationship between high blood pressure and the kidneys, the kidneys are often both the cause and the victim. This means they can both cause high blood pressure and be the victims of high blood pressure, which is much more common. As a result of damage caused by high blood pressure, the kidneys often become accomplices in the process.

The Kidney as a Cause

Why kidney diseases can lead to high blood pressure is not yet definitively clarified and is still being researched. It is certain that certain kidney diseases trigger high blood pressure. For example, a one-sided or bilateral narrowing of the renal arteries or a bilateral inflammation of the kidneys can quickly lead to high blood pressure. People with a unilaterally reduced kidney or polycystic kidneys often also suffer from high blood pressure. If the kidneys are damaged by long-standing diabetes, this often also leads to high blood pressure.

The cause could be a disturbed hormonal balance due to kidney damage. The kidneys regulate not only neural (via nerves) but also hormonal feedback loops that influence blood pressure. As kidney function declines, more blood pressure-increasing hormones are released. These, in turn, prompt the nerves to constrict blood vessels, leading to an increase in blood pressure.
However, the significantly impaired excretion of water and salt in cases of reduced kidney function can also play a role, which is why high blood pressure is caused by the kidneys.

To determine whether the kidneys are the cause of high blood pressure, an ultrasound examination of the kidneys, certain blood values, and a urine test for protein and blood components provide insights.

The Kidney as a Victim

However, much more frequently than being the cause, the kidney is the victim of excessively high blood pressure values. The damage caused by high blood pressure in the vessels often also affects the vessels in the kidneys. If the vessels of the kidneys are narrowed due to arteriosclerosis, which can be triggered by permanently high pressure conditions, or due to inflammation, clots, or the aforementioned nerve-induced constriction, a higher blood pressure is required to ensure adequate blood flow to the kidneys. The smallest blood vessels, which are part of the kidney's filtration system, particularly suffer. They harden, become porous, and can increasingly fail to perform their filtering function. However, the larger renal arteries can also calcify, restricting blood flow. This paves the way for chronic kidney insufficiency.

Since the kidneys are directly involved in regulating blood pressure (see above), a vicious cycle arises. High blood pressure damages the kidneys, which in turn strive to maintain sufficient blood flow to ensure adequate filtering function and therefore release more hormones that further increase blood pressure.

Since kidney damage - like high blood pressure - does not cause symptoms in the early stages, it often goes undetected or is only discovered at a point when there has already been significant damage to the organ.
Therefore, high blood pressure patients are considered the kidney patients of tomorrow and should always have their kidney function checked. Conversely, it is also important for kidney patients to monitor their blood pressure.

Comprehensive information on chronic kidney insufficiency, including stages and a calculator, can be found at https://nierenrechner.de/

Further information on the topic of kidneys can be found at the Federal Association of Kidneys e.V. - http://www.bnev.de/ - or PKD Familial Cystic Kidneys e.V. - http://www.pkdcure.de/.

Renal Denervation (RDN)

In the treatment of severe high blood pressure that cannot be adequately controlled with medication, there is the possibility of providing relief through a minimally invasive procedure. This relatively new treatment method is called renal denervation or denervation (RDN). In this procedure, specific points in the renal artery are ablated using a catheter introduced through the groin artery, similar to a heart catheter examination. The vicious cycle caused by reduced kidney blood flow, which leads to constant peripheral activation of the sympathetic tone and thus high blood pressure values, is interrupted by the targeted disruption of nerve conduction.

The procedure itself is not new. Until the 1950s, complete transection of the sympathetic nerve below the diaphragm was performed as a last resort for treating high blood pressure. Although this relatively large and complicated procedure usually led to the desired reduction in blood pressure, it also brought many side effects, unlike the new method.

A study published in April 2022 demonstrated a good reduction in blood pressure through renal denervation in conjunction with antihypertensive medication therapy.

Sources:

By Sabine Croci. This article is medically reviewed. Last updated (01/2024).
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High Blood Pressure and Kidneys

The Kidney as a Cause

The Kidney as a Victim

Renal Denervation (RDN)

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