High blood pressure may be caused by kidney disease!

Author: Zuo Li, Chief Physician, Peking University People's Hospital

Chairman of Blood Purification Branch of Chinese Society of Research Hospitals

Reviewer: Li Mingxi, Chief Physician, Peking Union Medical College Hospital

Member of the Medical Science Branch of the Chinese Medical Association

Hypertension is often believed to be caused by factors such as the heart, blood vessels, and emotions, but there is another possibility - it is caused by kidney disease.

1. Can kidney disease also cause high blood pressure?

The formation of blood pressure depends on three factors.

The first is the strength of the heart. When people are angry, quarreling, nervous, excited, or emotionally agitated on a first date, vasoactive substances are activated and the heart's contractile force is enhanced.

The second is the tension of blood vessels. In certain exciting situations, blood vessels will also contract, causing increased blood vessel tension.

The third is the capacity within the blood vessels.

Any increase or enhancement of any of these three factors will cause high blood pressure.

Figure 1 Original copyright image, no permission to reprint

When you have kidney disease, it generally does not affect the heart's contractile strength, so the first factor is relatively stable.

However, kidney disease can activate vasoactive substances, causing blood vessels to constrict, leading to increased blood pressure; at the same time, kidney disease can also increase the volume in blood vessels, thereby causing increased blood pressure.

Therefore, kidney disease can cause high blood pressure. In clinical practice, it is very common for kidney disease to cause high blood pressure.

For example, most cases of chronic nephritis are accompanied by hypertension, and when renal insufficiency reaches a certain degree, most people also have hypertension.

2. What should you pay attention to when choosing antihypertensive drugs for hypertension caused by kidney disease?

When choosing antihypertensive drugs, it is important to distinguish which disease and mechanism causes the hypertension.

If it is because the heart is too strong, targeted drugs can be used to slow down the heart's contraction;

If there is too much volume in the blood vessels, you need to find ways to control the volume, such as eating a lighter diet, and the volume in the blood vessels will gradually decrease. However, if the blood pressure is too high, you need to use some diuretics to discharge the volume in the blood vessels and control the blood pressure;

In cases where vascular tension is increased, medication is needed to reduce vascular tension and lower blood pressure.

When choosing medication for hypertension caused by kidney disease, you need to pay attention to the following matters.

When kidney function is not very good and blood creatinine rises above 300μmol/L, some antihypertensive drugs are not suitable for use because they may bring other side effects, such as accelerating the progression of kidney disease or increasing blood potassium levels.

The same is true for diuretics. Some diuretics can cause elevated blood potassium. Some diuretics, if used excessively, can lead to a decrease in blood volume, especially in patients with nephrotic syndrome, who already have low blood volume, which may increase the risk of thrombosis.

Some antihypertensive drugs are relatively safe, but their protective effect on the kidneys is slightly poor, especially for chronic nephritis, which can lead to the inability to recover. At this time, certain antihypertensive drugs with special effects are needed to protect the kidneys.

Therefore, when choosing a drug, it is necessary to make a specific judgment based on the patient's specific situation and comprehensive consideration of all aspects.

3. Are renal hypertension and hypertensive nephropathy the same?

Renal hypertension is high blood pressure caused by kidney disease. It is caused by excessive volume in blood vessels, hardening of blood vessels, or increased vascular tension, which leads to increased blood pressure.

Hypertensive nephropathy is caused by long-term high blood pressure, which weakens the kidney's self-regulation function. The kidney pressure is directly transmitted to the glomerulus, increasing the renal perfusion pressure. The glomerulus hardens under the long-term high pressure impact, thus leading to kidney disease. Simply put, hypertensive nephropathy is the direct effect of high blood pressure on the kidney, causing the kidney to gradually harden and atrophy.

Therefore, renal hypertension and hypertensive nephropathy are different.

4. How to distinguish renal hypertension from hypertensive nephropathy?

It is usually easier to diagnose kidney disease in its early stages. The most important differentiation point is to look at the time sequence of hypertension and kidney disease. Some patients have a clear time relationship with their illnesses: nephritis first, then hypertension, or hypertension first, and kidney damage occurs after a few years or decades. Therefore, the time of disease onset is a particularly important basis for differential diagnosis.

For some early-stage kidney diseases, if the patient is relatively young and has nephritis and hypertension but no family history of hypertension, it can be determined that the hypertension is caused by kidney disease.

In addition, another basis for differential diagnosis is proteinuria and hematuria. When blood pressure is well controlled in kidney disease caused by hypertension, the amount of proteinuria is not large and there is generally no hematuria. However, hypertension caused by kidney disease, such as hypertension caused by glomerular disease, generally has a large amount of proteinuria and hematuria.

If kidney disease has reached an advanced stage and creatinine has reached 200 or 300, it will be difficult to determine whether kidney disease causes high blood pressure or high blood pressure causes kidney disease.

Figure 2 Original copyright image, no permission to reprint

For example, when a patient comes to see a doctor, his past medical history is unclear, but his creatinine is as high as 500-600, which is about ten times higher than that of a normal person. There are also cases of renal insufficiency, proteinuria, and hypertension. At this time, it is often necessary to combine some special examinations to make a judgment.

Sometimes, some details of the patient's complaint may help the doctor's judgment. For example, when the patient first develops the disease, he does not have symptoms such as hematuria and edema, but he gets up at night. If young people in their 40s and 50s start to get up at night, and get up several times a night, it means that the patient may have renal tubular damage. Kidney damage caused by hypertension first damages the renal tubules, so at this time it can be roughly determined that the patient may have kidney disease caused by hypertension. But in general, some situations are still difficult to judge.