Yes, renal failure and kidney failure are the same thing. “Renal” is simply the medical term for “kidney,” derived from Latin. When doctors, lab reports, or medical websites use “renal failure,” they mean exactly what “kidney failure” means in everyday language: the kidneys can no longer filter waste and excess fluid from your blood well enough to keep you healthy.
Why Two Terms Exist
Medicine inherited much of its vocabulary from Latin, which is why you’ll see “renal” on lab results, hospital discharge papers, and insurance documents. Cleveland Clinic notes directly that “renal is another word for kidney.” The same overlap shows up in other areas of medicine: “hepatic” means liver, “pulmonary” means lung, “cardiac” means heart. None of these Latin-rooted words describe a different condition. They’re just the formal version of the same idea.
You might also encounter related terms that sound different but point to the same destination. End-stage renal disease (ESRD), end-stage kidney disease (ESKD), and end-stage renal failure (ESRF) all describe stage 5 chronic kidney disease, the point at which the kidneys have lost nearly all function.
Acute vs. Chronic Kidney Failure
While “renal failure” and “kidney failure” are interchangeable, there is an important distinction within kidney failure itself: whether it happens suddenly or gradually.
Acute kidney injury (previously called acute renal failure) develops over hours or days. It’s typically triggered by a specific event: a serious infection, major blood loss during surgery, severe dehydration, or a reaction to certain medications. The key difference is that acute kidney injury is often reversible. Once the underlying cause is treated, the kidneys can recover some or all of their function.
Chronic kidney disease is the slow version. It usually results from long-term conditions like high blood pressure or diabetes that damage the kidneys gradually over months or years. This type of damage is not reversible, though treatment can slow progression significantly. When chronic kidney disease reaches its most advanced stage, it’s called kidney failure.
How Kidney Failure Is Measured
Doctors track kidney function using a blood test called estimated glomerular filtration rate, or eGFR. This number represents how efficiently your kidneys filter waste. A normal eGFR is 90 or above. Chronic kidney disease is classified into five stages based on this number:
- Stage 1: eGFR 90 or above with signs of kidney damage (such as protein in the urine), but normal filtering ability
- Stage 2: eGFR 60 to 89, mild loss of function
- Stage 3a: eGFR 45 to 59, mild to moderate loss
- Stage 3b: eGFR 30 to 44, moderate to severe loss
- Stage 4: eGFR 15 to 29, severe loss
- Stage 5: eGFR below 15, kidney failure
Stage 5 is the threshold where the term “kidney failure” or “renal failure” formally applies. At this level, the kidneys are filtering less than 15% of what healthy kidneys handle, and waste products build up in the blood faster than the body can manage.
Another common blood test measures blood urea nitrogen (BUN), a waste product that healthy kidneys clear. Normal BUN falls between 6 and 24 mg/dL depending on age and sex. BUN alone doesn’t define kidney failure, but when it rises alongside other markers like creatinine (a waste product from muscle breakdown), it supports the diagnosis.
What Kidney Failure Feels Like
Early kidney disease often produces no symptoms at all, which is why it frequently goes undetected until later stages. As function declines toward failure, waste products accumulate in the bloodstream, a condition called uremia. The first signs people typically notice are nausea and loss of appetite, sometimes starting as mild queasiness in the morning or when smelling food.
As uremia worsens, other symptoms develop: unexplained weight loss, persistent fatigue, shortness of breath, muscle cramps, itchy skin, a metallic taste in the mouth, and difficulty concentrating or remembering things. Swelling in the ankles, hands, or face is common because the kidneys can no longer remove excess fluid.
In severe, untreated cases, the buildup of toxins can cause breath that smells like urine, yellowish-white crystals forming on the skin after sweating, chest pain from inflammation around the heart, seizures, or even coma. These are medical emergencies.
Treatment Options at Stage 5
Once kidneys reach failure, they can no longer sustain life on their own. Treatment at this stage focuses on replacing the work the kidneys used to do. There are three main paths.
Hemodialysis uses a machine to filter your blood, typically three times per week at a dialysis center, though home options exist. Each session lasts several hours. Peritoneal dialysis is a different approach that uses the lining of your abdomen as a natural filter. Fluid is cycled in and out of the abdominal cavity, and many people do this at home, sometimes overnight while sleeping. It can be a good option for people who prefer managing their own treatment schedule.
Kidney transplantation is the third option and, for many people, offers the closest return to normal kidney function. A transplant requires a compatible donor kidney from a living or deceased donor, followed by lifelong medication to prevent the body from rejecting the new organ. Not everyone is a candidate for transplant, and wait times for a deceased donor kidney can be years long.
The decision about when to start dialysis depends on symptoms and lab values, not just the eGFR number alone. Dialysis is generally considered when eGFR drops below 10 to 15 and the body shows signs it can’t compensate, such as dangerous fluid buildup, dangerously high potassium levels, or worsening uremia symptoms that don’t respond to other treatments.