The human body has 78 organs and each one performs a variety of important functions. While it’s possible to live without organs like the appendix, gallbladder, or spleen, several of our organs are considered especially vital for survival. These include the brain, heart, lungs, liver, and kidneys.

Most people are born with two kidneys, but some individuals don’t know what function or purpose they serve. The bean-shaped organs are about the size of a large fist and are located on both sides of the spine, just below the rib cage. Kidneys are important for regulating blood pressure and filtering waste products from the bloodstream; managing urine excretion to prevent dehydration; and regulating levels of electrolytes and nutrients like calcium, potassium, and magnesium – which help with nerve transmission and muscle contraction.

Anything that damages the kidneys can adversely affect any of these important functions and potentially lead to a life-threatening situation.

What is kidney disease?

Kidney disease results from kidney damage and subsequent decline in kidney function, says Dr. Pooja Budhiraja, a nephrologist and hypertension specialist at Mayo Clinic. She explains that there are two main types of kidney disease: short-term (called acute kidney injury or AKI), which is reversible with timely treatment; and long-term (called chronic kidney disease or CKD), which is usually irreversible.

When CKD occurs, the damaged kidneys “gradually lose their ability to filter waste, toxins, and extra water from the blood,” explains Dr. Jason Nagata, a pediatrician at UCSF Benioff Children’s Hospital in San Francisco.

In the early stages of the disease, this can result in mild symptoms such as reduced appetite or feelings of fatigue, but as CKD progresses, “complications like high blood pressure, heart disease, anemia, nerve damage, and fluid retention can arise,” says Nagata. “Without treatment, chronic kidney disease can lead to end-stage kidney failure, which is fatal without dialysis or a kidney transplant.”

In the United States, more than 1 in 7 (about 35.5 million) people have CKD, per the U.S. Centers for Disease Control and Prevention. The chronic disease causes more deaths each year than breast cancer or prostate cancer, according to the National Kidney Foundation.

What causes kidney disease?

The most common causes of CKD are high blood pressure and diabetes, “which damage the small blood vessels and filtering units in the kidneys over time,” says Nagata. Other potential causes he points to include immune system disorders or recurrent kidney infections. “In children, birth defects impacting urinary tract development can also result in kidney disease,” he adds.