The kidneys filter our blood every moment of our lives, removing toxins produced as cells normally use the food we eat and the air we breathe to make the energy needed for life. It’s like burning wood creates heat (energy), smoke (carbon dioxide we breathe out), and ash (chemicals that the kidneys deal with). “Renal” is simply Latin for “Kidney”.
Kidneys can stop working for a wide variety of reasons, divided into Acute Kidney Injury (AKI) and Chronic Kidney Disease (CKD) (older terms were Acute or Chronic Renal Failure). When we speak of “failure” or “injury,” we mean conditions affecting both kidneys at the same time. That’s because if someone completely loses one kidney, the other can do all the work the body needs.
See also Diagrams: The Urinary System and The Circulatory System.
Causes of AKI include:
- Anything that cuts down on blood entering the kidneys (blood loss, dehydration, heart failure, etc.)
- Diseases of blood vessels inside the kidney (blood clots, severe hypertension, inflammatory diseases like scleroderma or glomerulonephritis, etc.)
- Damage from medications, chemotherapy, toxins, multiple myeloma (a blood cancer)
- Blockage of urine outflow (kidney stones, large prostate gland)
Causes of CKD include:
- Long-standing Hypertension, Diabetes, Heart Failure
- Inflammatory diseases (Lupus & other rheumatologic diseases like gout, sarcoidosis, etc.)
- Medications
- Uncommon genetic diseases (polycystic kidney, fibromuscular dysplasia, etc. etc.)
If kidneys don’t work well enough, we may simply feel fatigued and simply unwell. A variety of other symptoms may occur as the kidneys get worse. Feet may swell, we may feel short of breath, general nausea, sometimes pain & tingling in the feet. But usually, we just feel bad.
There’s no back pain with kidney failure (now called acute or chronic kidney injury). Back pain happens with Kidney Stone, or with Infection (Pyelonephritis). With those conditions, the kidneys continue to work just fine removing toxins.
We diagnose kidney failure by a blood test for “creatinine.” The lab will calculate a number called “estimated glomerular filtration rate (eGFR)”, which estimates how well the kidneys are filtering. Normal is usually over 90 mL/min for an average-sized person; we don’t diagnose early kidney failure until it falls below 60. Moderate kidney failure is <45, we get patients ready for dialysis if it’s <30, and usually begin dialysis when it’s <15-20.
The worst thing about early kidney failure is that it begins to affect the immune system. Such patients should get vaccines to protect them (before the vaccines don’t work as well), and get tested for Tuberculosis if necessary (with worse kidney failure, the test won’t work well).
The only treatment that really helps Chronic Kidney Failure is dialysis and a kidney transplant.