Kidney damage can increase your risk of heart disease

The kidneys are the body’s waste filtration system. They remove any excess byproducts from the blood and make sure it leaves the body.

Sometimes the kidneys can become damaged or blood flow to the kidneys becomes compromised. When this happens, a person may eventually develop chronic kidney disease.

The main risk factors for developing chronic kidney disease include:

• diabetes
• high blood pressure and/or heart disease
• obesity
• age — it is more common in people aged 65 or older
• genetics
• previous kidney damage

Chronic kidney disease normally progresses slowly and in stages.

A doctor uses a test called glomerular filtration rate to determine if a person has chronic kidney disease and what stage they are in. They will also use urine tests, kidney scans, and biopsies to make a diagnosis.

Symptoms of chronic kidney disease may include:

• high blood pressure
• swollen feet, ankles, and/or hands
• fatigue
• anemia
• inability to urinate or more frequent urination
• bloody and/or dark urine
• loss of appetite
• itchy skin

According to Dr. Leo F. Buckley, a researcher in the Department of Pharmacy at Brigham and Women’s Hospital and lead author of this study, people with chronic kidney disease often have diabetes, high blood pressure, and obesity, which are well-known risk factors for heart disease.

“There may be other reasons specific to chronic kidney disease, like (a) build-up of toxins that would normally be cleared by the kidneys,” he told Medical News Today.

Past studies have shown chronic kidney disease to be a risk factor for a number of cardiovascular issues, including coronary artery disease, atrial fibrillation, heart attack, heart failure, and stroke.

For this study, Buckley and his team used kidney tissue collected during clinically indicated biopsies from about 600 adults from the Boston Kidney Biopsy Cohort. All study participants had no history of heart disease.

Scientists looked specifically for kidney lesions on the tissue samples.

“Kidney disease lesions are abnormalities in the kidney tissue itself,” Buckley explained. “A very small sample of kidney tissue is removed through a needle. A pathologist then identifies different abnormalities in the kidney tissue sample. Most other research on kidney and heart disease uses blood biomarkers, but we were able to look directly at the kidney itself.”

Researchers discovered that over a median of 5.5 years of follow-up, major cardiovascular events — including heart failure, stroke, heart attack, and death — occurred in 126 study participants.

Upon further investigation, scientists found two specific types of kidney damage were associated with an increased risk of heart disease.

The first was mesangial expansion, which is an extra build-up of waste in the kidney’s filtration system.

The second, arteriolar sclerosis, occurs when the walls of the small blood vessels in the kidney thicken and blood cannot flow freely.

“Arteriolar sclerosis confirms our initial suspicions — blood vessel damage can lead to heart disease,” Buckley said. “Mesangial expansion is related to diabetes, so that may explain why mesangial expansion was a primary finding.”

Additionally, the research team found study participants with diagnoses of vascular kidney disease, diabetic kidney disease, or who had greater severity of chronic kidney lesions were also at an increased risk for heart disease.

“The vascular kidney disease and diabetic kidney disease findings were expected because people with chronic kidney disease have blood vessel disease and diabetes — two risk factors for heart disease,” Buckley said. “Previous studies on these relationships categorized people into each diagnostic category using medical history and examination, whereas our study was able to directly assess the kidney tissue itself.”

After reviewing this research, Dr. Maria Lourdes Gonzalez Suarez, a nephrologist at the Mayo Clinic in Rochester, Minnesota, told Medical News Today she thought it was an interesting study that makes a connection between microscopic injuries in the kidney tissue and the risk of developing cardiovascular disease.

“It is known that chronic kidney disease is associated with (a) higher risk of cardiovascular problems; this study helps to confirm that microscopic changes in the kidney tissue are also associated with an increased risk of developing heart disease, including coronary artery disease, heart failure, stroke, and death,” she continued.

“The study also suggests chronic changes associated with fibrosis of the kidney tissue and atherosclerosis in the tiny vessels that provide blood supply to the kidneys are more likely to cause cardiovascular disease and death than the acute inflammatory changes in the kidneys associated with autoimmune diseases, such as lupus nephritis and IgA nephropathy, in patients that did not have any prior history of heart disease,” Gonzalez added. “This study emphasizes that the cause of chronic kidney disease matters in terms of increasing the risk of cardiovascular disease.”

Gonzalez said doctors know once chronic changes are found in a biopsy, they are usually nonreversible and they will remain present over time.

“It would be interesting to determine if lifestyle modifications such as a low-salt diet, increased exercise activity, lowering cholesterol, and controlling blood pressure are also associated with a limited progression of the chronic changes seen in the initial kidney biopsies,” she said.

Medical News Today also spoke with Dr. Naitik Sheth, a nephrologist at Hackensack Primary Nephrology in Teaneck, New Jersey, about the study.

“Patients with [chronic kidney disease] are at an increased level of cardiac events and (is) the number one cause of mortality in the population,” he said. “(The) study looks at (the) biopsy level to answer some of the questions we have always thought about. It is interesting to know that even patients who did not have diabetes mellitus and hypertension, still with similar lesions on biopsy, were at increased risk of cardiac events.”

Sheth said these findings can help doctors better educate patients about disease processes.

“We can prognosticate risk to patients better based on biopsy findings,” he added.