Proper kidney function is vital to regulating arterial blood pressure and removing waste products and excess fluid from the body. Blood pressure is characterized as the pressure of blood pushing against the walls of your arteries when pumped from the heart. Typically, for a healthy adult, blood pressure rises and falls throughout the day. However, if your blood pressure stays elevated or drops for a period of time, it can result in damage to your heart, kidneys, and other organs.
In the US, uncontrolled high blood pressure is the second leading cause of end-stage renal disease (ESRD). Unmanaged high blood pressure over a period of time can decrease the kidney’s ability to function properly, leading to the development of chronic kidney disease.
- The kidneys play an essential role in the regulation of arterial blood pressure.
- High blood pressure (hypertension) is the second leading cause of kidney failure or end-stage renal disease (ESRD) in the US.
- It is estimated that 1 in 5 adults in the US with hypertension have chronic kidney disease.
Overview of Kidney Function
The kidneys are organs that makeup part of the urinary system, playing an essential role in removing waste from the body. These two bean-shaped organs are located in the back of the abdomen. Each kidney comprises roughly a million nephrons (filtering units), with each nephron containing a tubule and glomerulus. These nephrons function in a two-step process: first, the glomerulus filters the blood, and second, the tubule then removes waste products, returning vital nutrients from the filtered blood back into the bloodstream.
The kidneys remove waste materials from the body by filtering, on average, half a cup of blood every minute. The filtration of blood removes waste and excess water from the body through the production of urine, which is moved into the bladder through the ureters. The kidneys play an essential role in maintaining the balance (homeostasis) of water, salts, and minerals, helping the body’s nerves, tissues, and muscles function properly.
The kidneys also produce hormones that control blood pressure, make red blood cells, and help maintain strong and healthy bones.
Blood flows into the kidneys through a large blood vessel called the renal artery. This blood vessel branches into smaller and smaller blood vessels until they reach the nephrons. Once in the nephron, the blood is filtered by the blood vessels of the glomeruli and then is transported out of the kidney through the renal vein.
Overview of High Blood Pressure
Nearly 45%, or 108 million of the adult population in the US, have high blood pressure. Blood pressure (hypertension) is the force of blood through the blood vessels in the body. If the force against the blood vessels is too high, then it means that the heart is working too hard to pump blood around the body.
When checked, a blood pressure reading of 120/80 mmHg, or 120/80, is considered normal. For example, a reading of 140/90 mmHg or above is considered high blood pressure. The top number in a hypertension measurement is referred to as systolic blood pressure. Systolic pressure measures the force of blood against the walls of the arteries when your heart is pumping. The lower or bottom number of the hypertension reading is called diastolic blood pressure. Diastolic pressure measures the force of the blood when your heart is between beats.
It is vital that both systolic and diastolic pressure is controlled and kept between normal ranges or in the ranges recommended by your healthcare provider.
Over a period of time, high blood pressure can damage the walls of the blood vessels. This can lead to severe and complicated health problems such as chronic kidney disease as well as damage to organs such as the heart, brain, lungs, and eyes. It is estimated that only 1 in 4 or 24-25% of people diagnosed with high blood pressure have their condition under control.
How is Blood Pressure Related to Kidneys?
The kidney and blood pressure are related in two ways:
- Hypertension is a leading cause of the development of chronic kidney disease (CKD). This is due to the damage that high blood pressure causes to the blood vessels throughout the body. The damaged blood vessels can no longer supply adequate blood to organs such as the kidneys. High blood pressure can also cause damage to the glomeruli in the kidneys, resulting in poor waste and extra fluid removal from the blood. The extra fluid in the blood that is not removed can build up and cause a further rise in blood pressure.
- High blood pressure can be a complication of CKD. The kidneys play a crucial role in regulating blood pressure and keeping it in a healthy range. Damaged or diseased kidneys are unable to regulate blood pressure, resulting in hypertension.
Kidneys and High Blood Pressure
It has been established that decreased kidney function can increase blood pressure. Renal hypertension (renovascular hypertension) occurs when the arteries that transport blood to the kidneys constrict, or a partial or total block restricts the amount of blood the kidneys receive. When the kidneys do not get enough blood, they react by producing a hormone that makes blood pressure rise.
When the blood vessels to the kidneys constrict and narrow, the kidneys are not able to excrete the extra fluid and waste products from the body. The extra fluid that is not excreted can, in turn, raise blood pressure, causing more damage to the kidneys.
In the US, approximately 20% or 1 in 5 adults that present with hypertension have CKD. While early-stage CKD patients with hypertension may not experience any physical conditions, if either condition is left untreated, it may result in kidney failure. Thus, CKD patients must regularly get their blood pressure checked, and those with high blood pressure should have their kidney function tested.
Kidneys and Low Blood Pressure
Low blood pressure, or hypotension, is a decrease in systemic blood pressure. Hypotension is generally asymptomatic and only becomes a concern once the pumping pressure is insufficient to supply organs with enough oxygenated blood.
Hypotension leads to decreased blood filtration by the kidneys, resulting in reduced ability for waste products and essential nutrients to be cleared properly. If low blood pressure occurs for a period of time, it can result in acute kidney injury due to decreased blood flow to the kidneys.
Hypotension is common for CKD patients on dialysis, and although not every patient will experience it, blood pressure will be regularly checked and managed.
Kidney Function and Blood Pressure Regulation
The evidence that proves the kidneys play a vital role in blood pressure regulation is seen in chronic conditions of blood pressure control. For example, hypertension generally always begins due to some abnormality of kidney function.
Several connections between the kidney and blood pressure regulation have been identified, such as:
- The kidneys secrete renin, which controls the formation of AII, which acts directly as a vasoconstrictor, on the central nervous system.
- The kidneys produce vasodilator substances that may act on peripheral blood vessels or influence renal excretion of water and sodium.
- It is believed that the kidneys stimulate reflex pathways via afferent nerve fibers, which may, in turn, affect peripheral blood circulation and the heart.
- The kidneys control arterial pressure by regulating the excretion of electrolytes and water. Thus, the kidneys control the body’s extracellular fluid volume (a mechanism referred to as the renal-body fluid feedback system).
Panoramic Health and Your Kidney Care Journey
Panoramic Health provides patients with value-based kidney care to help them in their kidney care journey. We provide a multidisciplinary care team to help slow CKD progression, provide patients with a better quality of life, and help them manage the full spectrum of their health.
If you are a CKD or ESRD patient with a provider partner of Panoramic Health, you can expect holistic care from your nephrologist and assigned care team. Your care team will help you manage any underlying conditions, such as hypertension, giving you the freedom and empowerment to take charge of your health outcomes.