Your circulatory system and the kidneys highly depend on each other to maintain good health. The kidneys use many blood vessels to filter extra fluids and waste present in the blood. When the vessels are damaged, the nephrons responsible for filtering blood do not receive enough nutrients and oxygen to function well. This explains why high blood pressure, or hypertension, is the second leading cause of kidney failure after diabetes. In fact, more than half of the patients with chronic kidney disease have high blood pressure.
What is Blood Pressure?
This is the force of blood that pushes against the walls of the blood vessels when the heart pumps out blood. High blood pressure occurs when there is an increase in the force exerted against the walls of the blood vessels. Narrow, stiff, or clogged blood vessels and high blood volume resulting from extra fluid in the blood are the most common culprits for this increased force. Blood pressure is expressed in 2 numbers, separated with a slash. The top number is known as the systolic pressure, and the bottom is referred to as the diastolic pressure. If your blood pressure stays below 120/80, you are considered healthy.
What the Kidneys do
Located just below the rib cage, kidneys are the size of the fist, and the two are bean-shaped. They are responsible for filtering between 120 to 150 quarts of blood to produce urine. Urine is a composition of extra fluids and waste. It flows from the kidneys to the bladder through the ureters. Once the bladder empties, the urine is excreted from the body through the urethra. Each of the kidneys is composed of about a million nephrons (filtering units) responsible for filtering small amounts of blood.
Each kidney has a filter called glomerulus, which lets waste products and fluids out, preventing the large molecules, especially proteins and blood cells from passing through. It then sends the filtered content to the second filter known as the tubule. Here, the needed minerals are sent back to the bloodstream, while the rest are excreted as waste. This is what forms urine.
How Blood Pressure Affects the Kidneys
How healthy your blood pressure is can affect the functioning of your kidneys and vice versa. It means that if your kidneys are not healthy, then your blood pressure is likely to be affected. High blood pressure can damage the blood vessels and reduce the ability of the kidneys to work properly. The blood vessels stretch to allow blood to flow easily. When the force is high, the stretching and the force exerted eventually weaken and scar all blood vessels in the body, including those in the kidneys. Should the vessels in the kidneys be damaged, they end up hurting the process of removing waste and extra fluid from the body.
The extra fluid left in the blood vessels raises the blood pressure even more. The biggest health risk for individuals with kidney disease is not just kidney failure. These patients are at a greater risk of developing stroke and heart disease. Complications develop slowly, over a long stretch of time, often without notable symptoms. With time, kidney disease may cause your kidneys to fail, requiring dialysis or a kidney transplant. If you or a loved one suffer from kidney disease, work to keep the blood pressure healthy, and seek treatment to delay these complications.
Telling Symptoms of Kidney Disease
Kidney disease has 5 stages. Your doctor should determine the stage you are at, based on the extent of damage to the kidneys and your glomerular filtration rate (GFR). GFR is the level of kidney function. In the early stages, kidney disease may not present with obvious signs, making it difficult to detect. Once it advances, you may notice the following:
- Itchy skin
- Color and smell changes in urine
- Swelling of the hands, face, and the legs
- Persistent thirst
- Tiredness and feeling ill
- Loss of appetite
- Sleep problems
- Trouble concentrating
- Dry skin
- Darkened skin
- Chest pain
- Muscle cramps
- Weight loss
How should I know my Blood Pressure is too High?
High blood pressure is a silent disease that cannot be easily detected. This is why it is known as a silent killer. Rarely will symptoms such as blurred vision, shortness of breath, headaches, and nose bleeds show. The only reliable way is to have it measured. A single reading should not confirm you have high blood pressure. It should be done on a different follow-up session with your doctor. If you have been diagnosed with high blood pressure in the past, the following signs may mean you are dealing with secondary high blood pressure. This is blood pressure triggered by another medical condition such as kidney disease:
- Extreme high blood pressure with a systolic reading of 180 millimeters of mercury (mm Hg) and a diastolic pressure of 120 mm Hg.
- High blood pressure that fails to respond to blood pressure medications even those previously used to control it.
- Sudden onset of high blood pressure before the age of 30 or after the age of 55
- Absence of high blood pressure history in your family
Because patients with high blood pressure are at a higher risk of developing kidney disease, the following tests should be done:
- A urine test for protein: If the protein in the urine is persistent, it could mean you have kidney disease. It could also mean that your kidney disease may get worse and cause heart disease.
- A blood test for creatinine: The readings should be used to calculate the glomerular filtration rate. If the readings are too low, it could mean that your kidneys are not able to excrete enough waste and extra fluids from the blood.
- A urine test to check white and red blood cells.
How to Prevent Kidney Disease Caused by Hypertension
High blood pressure can take some time before it causes damage to your kidneys. Several steps can be taken to control blood pressure. If you are already struggling with kidney disease, control your blood pressure to prevent more damage to your kidneys. Here is what you should do to prevent kidney disease from getting worse:
- Follow a heart-healthy diet
- Limit alcohol
- Control your blood sugar if you have diabetes
- Maintain a healthy weight
- Quit smoking or using tobacco
- Exercise more: At least 30 minutes. Moderate activities include dancing, brisk walking, riding a bike, cleaning the house, or bowling.
- Manage stress
What Does a Heart-Healthy Diet Look Like?
Foods that are low in fat and salt can keep your blood pressure at a healthy range. Here is a simple guide:
- Do not add salt to cooked food. Cook with lemon juice, fresh herbs, or spices.
- Buy items labeled “low-sodium” or “reduced-sodium.” Ensure that the products do not contain a salt-substitute and potassium.
- Limit salty snacks and fast food
- Limit preserved or pickled foods
- Choose frozen or fresh vegetables over canned. If you have canned, rinse them thoroughly to get rid of extra salt.
- Choose fish and lean meats. Trim the fat off and remove the skin before cooking
- Use low or fat-free products. Choose fat-free mayonnaise, and salad dressing
- Use canola or olive instead of vegetable oil
- Grill, boil or bake food instead of frying
- Eat egg whites instead of whole eggs
A dietician should help in figuring out other ways of limiting fat and salt in your diet. On top of that, you can also try tea to lower your blood pressure. Your doctor may also advise you to monitor your blood pressure at home using a digital blood pressure monitor.
How are Kidney Disease and Blood Pressure Diagnosed?
High blood pressure is diagnosed when multiple readings show a systolic pressure above 130 and a diastolic pressure above 80 according to the new guidelines. Kidney disease is diagnosed after blood and urine tests.
Dipsticks are used to detect the presence of albumin (protein) in the urine. The protein is present in the blood and can get into the urine when the kidneys are damaged.
This test determines the amount of blood filtered by the kidneys every minute. This is what is referred to as the estimated glomerular filtration rate (eGFR). Here is a breakdown of the eGFR readings.
- Normal range – 60 or above
- Kidney damage – below 60
- Kidney failure – 15 or below
Should the tests detect kidney damage, your doctor may suggest an ultrasound scan of the kidneys to reveal where the damage is and its extent. When detected early, kidney disease can be treated to prevent or delay serious complications. If you have high blood pressure, you are advised to have regular screenings, including urine albumin, blood pressure test, and eGFR. Even if blood pressure is not responsible for causing kidney disease, it can increase the damages. With kidney disease, ensure your blood pressure levels remain below 130/80.
How Is Kidney Disease Treated?
In the early stages, your kidneys may require little to no treatment. Because kidney disease raises the risk of heart conditions, your doctor will want to be sure that the risk is as low as possible. The most important step to controlling kidney disease and reducing the risk of stroke and heart disease is managing blood pressure. Your doctor will work with you to ensure it is below 130/80 mm Hg. If lifestyle changes fail to control your blood pressure, medication may be used.
The top choices of blood pressure medications for patients with kidney disease include angiotensin receptor blockers (ARBs) and ACE inhibitors. These are known to protect the kidneys against further damage. Diuretics (water pill) such as bendroflumethiazide may also be recommended to help the body get rid of extra fluids. They act on the kidneys to help in the elimination of sodium and water to reduce blood volume. The buildup of extra fluids in the blood can heighten blood pressure levels.
If the medication does not bring the blood pressure numbers down, other forms of treatment may be adopted. If you also suffer from diabetes, blood pressure levels must be brought to a comfortable low to prevent the development of serious damage to the kidneys. With many treatment options available, the chances are; an effective drug combination will be found to control your blood pressure without unmanageable side effects.
Adults with high blood pressure, diabetes, or both are at a greater risk of developing kidney disease than those without. As such, you are advised to keep your blood pressure and blood sugar levels controlled.