“Renal” means something related to the kidneys. Healthcare professionals use the terms “renal failure” and “kidney failure” interchangeably. But there are other common terms you may also hear them use.

Your kidneys are two bean-shaped organs that act like your body’s filtration system. They filter fluid and blood, pulling out wastes that leave your body via your urine.

If you experience kidney failure, your kidneys aren’t working as well as they once did. If your kidneys aren’t working at all, the results could be deadly if you don’t get treatment.

Healthcare professionals may use a lot of different terms for kidney failure. Keep reading to learn more about these and what they mean for your health.

Kidney failure means your kidneys don’t filter as well as they once did. Healthcare professionals may also call this “renal” failure. Renal is a Latin word that means “of the kidneys.”

As you get older, doctors expect your kidneys won’t work as effectively as they once did. But if you experience changes in your kidney function that are outside the norm for your age, your doctor may say you’re in kidney failure.

There is no one specific test that a healthcare professional uses to say you definitely have kidney failure or you don’t. They may take into account several blood tests, urine tests, and your medical history.

Kidney failure can be acute or chronic, each of which has different potential causes and changes to kidney function.

Kidney disease is the preferred term for medical conditions where your kidneys don’t work as well as they should.

Healthcare professionals used to use chronic renal failure and chronic kidney disease to speak about the same thing. But renal failure can sound misleading because the term sounds like your kidneys don’t work at all.

When your kidneys work at a very low level, healthcare professionals call this end-stage renal disease or ESRD.

If you have ESRD, you require dialysis or a kidney transplant. But it’s possible to have kidney disease for some time without requiring dialysis to treat your condition.

Acute renal failure (aka acute kidney injury) is when you experience a sudden change in how well your kidneys work. The condition isn’t progressive. It’s fast, usually occurring in hours to a few days.

Acute renal failure is common in the hospital because you may be very sick, dehydrated, or have another medical condition that affects blood and fluid flow to your kidneys.

Some medications you receive in the hospital may also contribute to renal failure.

You don’t always experience symptoms from acute renal failure. If you do, you may produce less urine, experience swelling in your legs and ankles, or feel more fatigued than usual.

If you’re already sick, it can be easy to relate these symptoms to your other medical condition.

The good news is that acute renal failure is often treatable. While you may need dialysis to act as an artificial kidney for a short time, with treatment, healthcare professionals can usually help reverse acute renal failure.

But this isn’t usually the case for chronic renal failure.

Chronic renal failure or chronic kidney disease (CKD) occurs when you have a significant loss of kidney function for 3 months or more. Healthcare professionals assess your kidney function through blood tests and urine tests.

One blood test, called the glomerular filtration rate (GFR) test, measures how well your kidneys are functioning. If your GFR is less than 60 for 3 months, a healthcare professional will likely diagnose you with CKD.

Your kidneys may still work if you have CKD. But they don’t work as well as they once did. CKD also tends to be progressive, meaning one day, your kidneys may not work, and you could require dialysis.

Condition TypeAcute Kidney InjuryChronic Kidney Disease
Onset• sudden, usually over several hours or days• over 3 months (or longer)
Causes • infection
• dehydration
• severe blood loss
• other causes
• progressive condition that often occurs with hypertension and diabetes mellitus
Outlook • usually reversible
• may require dialysis treatments
• usually progressive
• may treat in earlier stages with diet changes and medications
• may require dialysis or kidney transplant in late stages

Kidney failure and renal failure mean the same thing. You may hear healthcare professionals use the terms kidney injury or kidney disease to refer to the same thing.

Whether acute or chronic, kidney failure can be a serious medical condition.

If your kidneys don’t work properly, wastes build up in your body, which can make you feel very sick. But you don’t usually start experiencing symptoms from kidney disease until your kidneys are functioning at about 20% or less of their previous levels.