How Uncontrolled Blood Pressure Affects Kidneys: Warning Signs To Note

Various functions of different organs in the body are interconnected. Your chest pain could be associated with your digestive system, difficulty in walking and maintaining balance could be a neurological problem, and surprisingly, uncontrolled blood pressure can also lead to kidney issues. But how is that possible?

In an interaction with the OnlyMyHealth team, Dr Atul Ingale, Director-Nephrology and Consultant Transplant Physician, Fortis Hiranandani Hospital, Vashi, sheds light on the association between uncontrolled blood pressure and kidney disease; how the two are related and what can be done to manage it. 

Also Read: Understanding Hypertensive Crisis: A Critical Health Concern

What It Means To Have Uncontrolled Blood Pressure?

Uncontrolled blood pressure, often referred to as hypertension, is a condition where your blood pressure consistently exceeds normal range, which is considered to be around 120/80 mm Hg, where the first number (systolic pressure) measures the pressure in your arteries when your heart beats, and the second number (diastolic pressure) measures the pressure when your heart is at rest between beats.

"By scientific definition, when BP is not under control despite three BP medicines, it’s called ‘uncontrolled hypertension’ or ‘resistant hypertension’," explains Dr Ingale. 

If left unmanaged, it can lead to problems like heart disease, stroke, kidney disease, and other cardiovascular issues.

How Uncontrolled Blood Pressure Affects Kidneys

According to the American Heart Association (AHA), kidneys and the circulatory system depend on each other for good health. With the help of the blood vessels, the kidneys help filter wastes and extra fluids from blood. However, if the blood vessels get damaged, the nephrons that filter your blood won't get the oxygen and nutrients they need to function well. This is why high blood pressure is the second leading cause of kidney failure, as per the health body. 

Dr Ingale says, “Kidneys are made of 20-24 lakh filtering units known as nephrons and the part of nephron glomerulus is made of small blood vessels (arteriole), which facilitate high volumes of blood to flow through them.”

The AHA explains, over the course of time, uncontrolled high blood pressure can narrow down, weaken, and harden arterioles, which when damaged are unable to deliver enough oxygen- and nutrient-rich blood to nephrons, making the kidneys lose their ability to filter blood and maintain proper fluid levels, hormones, acids, and salts in the body.  

Adding to it, Dr Ingale says that when the nephrons fail to receive enough blood, it can result in the fall of Glomerular Filtration Rate (GFR), an estimate of how much blood passes through the glomeruli each minute. As GFR falls, hormone renin, which controls the production of aldosterone, a hormone made by your adrenal glands,  is secreted, which constricts blood vessels, in turn causing elevation of BP.

Therefore, uncontrolled blood pressure and kidney problems create a dangerous spiral effect, where each condition exacerbates the other. 

High blood pressure can damage the delicate blood vessels in the kidneys, reducing their ability to function correctly. As kidney function declines, the body retains more sodium and water, leading to further blood pressure elevation. This relentless cycle can progress to chronic kidney disease (CKD), where the kidneys struggle to filter waste and excess fluid. Ultimately, both conditions significantly increase the risk of heart disease and stroke, making it crucial to manage blood pressure and kidney health to break this harmful spiral. Regular medical monitoring and lifestyle adjustments are therefore vital to disrupt this damaging cycle.

Also Read: Kidney Disease: Expert Explains Stages Of Kidney Disease And How To Prevent It

Warning Signs To Note

Here are some common signs of kidney issues include:

• High or worsening blood pressure
• Decrease in amount of urine or difficulty urinating
• Oedema (fluid retention), especially in the lower legs

How To Keep Blood Pressure Levels In Check?

Dr Ingale says, “For patients who have high blood pressure and kidney disease, the most important treatment is to control their blood pressure through lifestyle changes.” These include:

• Salt intake should be < 3 gm/day
• Control alcohol consumption
• Quit smoking
• Reduce weight
• Regular exercise

Also, drugs can lower blood pressure and protect the kidneys from further damage, according to the doctor. He adds, treatment needs to be individualised and target BP should be around 130/80.