Albuminuria and its kidney-heart connection

The kidneys and heart are closely related. People with kidney dysfunction are more likely to develop heart complications as well.

The spectrum of disorders involving the heart and kidneys is referred to as cardiorenal syndrome or clinical cardiac syndrome, where an acute or chronic dysfunction in one organ may induce the same in the other. Dr Keshava R, senior director, interventional cardiology, Fortis Hospital, Bengaluru, points out that when the kidney fails, it can lead to heart failure and vice versa. “When the heart functions properly and the blood supply to kidneys is optimal, the kidney function will be normal,” he adds.

One of the determining factors of both kidney and heart health is albuminuria.

What is albuminuria?

Dr Vinod Kumar, consultant, nephrology & renal transplantation, Aster RV Hospital, Bengaluru, explains that albuminuria refers to the presence of abnormal amounts of albumin (a protein found in blood) in the urine. “Normal urinary excretion of protein is approximately around 150 mg per day, of which albumin is the chief component [50 %]. Albuminuria is often the earliest marker of glomerular damage [when protein and sometimes, red blood cells leak into urine] and occurs before the reduction in kidney function,” he says.

Dr Keshava adds that leakage of albumin in the urine means that the microvasculature or micro capillaries in the kidneys are affected. “So, whenever the capillary is affected, we call it a vascular dysfunction. Albuminuria is a marker of vascular health,” he says.

Risk factors for albuminuria

Experts say albuminuria is prevalent in people who suffer from the following conditions:

• Obesity
• Type 2 diabetes mellitus
• Hypertension
• Heart failure

Dr Kumar adds that an elevated urine albumin-creatinine ratio is seen in 25-44 percent of people with heart failure.

Albuminuria and heart failure

Dr Keshava says albuminuria is common among people with congestive heart failure because many of the precursors or predisposing factors for both kidney and heart complications are the same. These factors include diabetes and blood pressure. “Mostly, many people with heart failure will also have a kidney or microvascular dysfunction, causing albuminuria,” he says.

Albuminuria is an indicator of kidney damage and an independent risk factor for heart failure, adds Dr Kumar. “Albuminuria indicates permeability of renal vessels and is a manifestation of general vascular endothelial dysfunction [narrowing of large blood vessels], which is associated with atherosclerosis or plaque formation in the arteries [of the heart],” he says.

Normal range for albuminuria

Albuminuria is measured using the urinary albumin-creatinine ratio (UACR) from a spot urine sample. Normal value for albumin in the urine is less than 30 mg/g, while that for microalbuminuria is 30-300 mg/g and overt albuminuria is more than 300 mg/g.

Dr Kumar says biannual screening for albuminuria is recommended for people at high risk (like diabetics). “Early identification and treatment of albuminuria through certain medications may provide benefits to people with kidney disease and/or heart failure,” he says.

Takeaways

• Albuminuria, which refers to the presence of abnormal amounts of albumin in the urine, is one of the common problems in people with heart failure.
• Obesity, type 2 diabetes and hypertension are risk factors for albuminuria.
• Albuminuria is common among people with heart failure as many predisposing factors for both heart and kidney complications are common.
• Early identification and certain medications may benefit people with kidney disease and/or heart failure.