Your Complete CKD Glossary

Thankfully, some of the confusing terminology is being changed so patients can better understand, says Mohamed Atta, M.D., professor of medicine in the division of nephrology at the Johns Hopkins University School of Medicine in Baltimore. “I think as we move to more precision medicine, you’ll find these changes will make it much easier,” says Dr. Atta. Here, Dr. Atta and James Simon, M.D., a nephrologist at Cleveland Clinic’s Glickman Urological & Kidney Institute explain some of the common CKD terms and why they’re important for you to know.

“Renal just means ‘of the kidney,’ like cardiac means ‘of the heart,’” says Dr. Simon. But expect this term to become a thing of the past, he says. “A lot of the scientific community is trying to get people away from those terms, so they’re replacing ‘renal’ with ‘kidney’ now, even when we talk to each other.” This is changing even in the scientific literature that physicians read, Dr. Atta says. “We’re moving from ‘renal’ to ‘kidney’ across the board.”

Your kidneys perform many important functions. One of their main function is to filter waste and extra fluid out of your blood, which then comes out in your urine. Glomerular filtration rate (GFR) is the number that shows how well they’re working. For example, if your GFR is 100, you have about 100% kidney function; if it’s 65, you have 65% kidney function, says Dr. Atta. “When we’re talking about empowering patients to understand their disease, if they need to know one thing, it’s what their GFR is,” says Dr. Simon. GFR is calculated using a blood test that measures how much creatinine—a waste product—is in your blood.

To be diagnosed with chronic kidney disease, there must be evidence of either kidney damage OR decreased kidney function AND it must last for three months or more. Dr. Atta says that kidney damage can be found during an ultrasound, as in the case of a genetic disease called polycystic kidney disease, or when you have blood or protein in your urine. You have decreased kidney function when you have a blood creatinine test that shows a GFR of less than 60 for three or more months. CKD has five stages, but most people are diagnosed in Stage 3 or beyond.

When your kidney function suddenly drops, this is called acute kidney injury, says Dr. Simon. It’s usually temporary, but some people’s kidneys only recover partially, and they end up with CKD. There are lots of reasons acute kidney injury can happen, but in most cases, it’s because something else in the body is going wrong, like a drug reaction, severe infection, low blood pressure, surgery complications, heart or liver failure. “People with CKD can be more susceptible to developing acute kidney injury because their kidneys don’t work as well,” Dr. Simon says.

Dr. Atta says that The National Kidney Foundation developed the five CKD stages because doctors were all using different terms to explain kidney disease, so the five stages got everyone on the same page. It has also helped researchers do more targeted studies on CKD. One of the problems with the staging system, he says, is that it doesn’t tell you what caused the kidney disease. Dr. Atta says there’s movement away from the term “chronic” to the terms “mild,” “moderate,” and “severe” to describe CKD stages, along with a description of the cause: for example, “mild diabetic kidney disease.”

Nephros is the Greek word for “kidney,” explains Dr. Simon, so “nephrology” is the science of the kidneys. Your nephrologist is, in simpler terms, a kidney specialist. That said, Dr. Simon says nephrologists don’t just deal with kidneys—they also treat high blood pressure, kidney stones, potassium and electrolyte problems, and more. “The kidneys are so intertwined with regulating a lot of that,” he says. Nephrologists work on the medical side of things, unlike urologists who are surgeons that operate on anything from the kidneys to the urethra.

Dialysis is a treatment that cleans your blood when your kidneys can’t. People in Stage 4 and Stage 5 who aren’t on dialysis yet are considered “pre-dialysis,” says Dr. Atta. If you’re in either of these stages, your nephrologist will talk to you about a potential future plan for dialysis. Dr. Simon says that getting people to start preparing for dialysis can be a challenge, but he believes it’s empowering to understand and accept your situation. It’s important to note that not everyone who has CKD will need dialysis, which is why it’s so important to diagnose CKD early.

“End-stage” was one of the terms that patients in the study felt caused fear and a sense that death is right around the corner. But in this case, end-stage means the end of your kidneys, not your life—there’s still dialysis and/or kidney transplant. Dr. Simon says that there’s a difference between Stage 5 and ESKD—in ESKD, you’re on dialysis or you’ve had a kidney transplant, but in Stage 5, you’re not quite there. Transplant is the goal, if possible, though if needed, you can live on dialysis for years.

Albumin is a protein in your blood. Normally, your kidneys will make sure the albumin stays there, but if they’re damaged, you can leak protein into your urine, a condition called albuminuria. If there’s a lot of protein in your urine, you may notice that you have puffy eyelids, swelling in your ankles or legs, and frothy urine, says Dr. Atta. Albuminuria impacts both your kidneys and your heart, so it’s important to have this level checked if you’re at high risk for kidney disease or you’ve been diagnosed with CKD.