Kidney disease typically progresses silently. In many cases, renal disease destroys a substantial amount of kidney function long before causing any symptoms. Kidney disease can progress to renal failure that requires dialysis and kidney transplant. Left untreated, kidney disease and renal failure can lead to death.
The kidneys filter about 180 liters of fluid each day, removing waste and excess water to create 800 to 2000 milliliters per day, with a normal fluid intake of about 2 liters per day. This means the kidneys filter the entire plasma volume of the body, which is about 3 liters, 60 times each day.
Shaped like a bean and about the size of a fist, the kidneys perform four essential functions: filtration, reabsorption, secretion and excretion. Filtration involves the transfer of water and waste from the blood into the glomerulus, a small cluster of capillaries in the kidneys. Glomeruli filter waste from the blood.
The filtration process creates glomerular filtrate, a fluid that contains a significant amount of water but also contains important molecules like proteins, glucose, salts and the excretory material, urea. Reabsorption is the absorption of important molecules, ions, and water from the glomerular filtrate back into the body. Secretion is, in essence, the opposite of reabsorption as the kidneys secrete the water and the waste into the kidney tubules. The kidneys then excrete the waste products and water to the bladder for excretion to the outside through urine.
About Kidney Diseases
Kidney disease includes chronic kidney disease (CKD), diabetic kidney disease, acute kidney injury, simple kidney cysts and polycystic kidney disease, kidney stones, and pyelonephritis.
The two leading causes of kidney failure include diabetes and hypertension, with diabetes causing 44 percent of new cases of kidney failure in 2012 and high blood pressure responsible for 28.4 of all new cases that year. Glomerulonephritis, cystic/hereditary congenital diseases, and urological diseases all contributed to kidney failure.
An estimated 15 percent of people in the United States have CKD, according to the Centers for Disease Control and Prevention (CDC); most of the people with CKD do not know they have the condition. CKD is more common in people aged 65 and older, females, non-Hispanic blacks, and Hispanics. Risk factors for CKD include diabetes, hypertension, heart disease, obesity, a family history of chronic kidney disease, past damage to the kidneys, and older age.
Understanding the risk factors and causes of kidney diseases can help practitioners detect kidney diseases in the early stages, when treatment can lead to more optimal outcomes.
Kidney disease stages
Chronic kidney disease is a progressive condition. Tissue damage causes increasing kidney dysfunction that eventually leads to kidney failure. The National Kidney Foundation’s guidelines describe five stages of CKD. The stages range in severity from mild kidney dysfunction. Diagnosticians assess kidney function and perform CKD staging with the help of a glomerular filtration rate (GFR) blood test, which provides an estimate of the volume of blood passing through the glomeruli each minute.
Stage 1: The kidneys are still functioning normally but urine test results suggest kidney disease, with GFR levels at 90 and higher
Stage 2: Slightly reduce kidney function with GFR rates between 60 and 89
Stage 3: Reduced kidney function with GFR rates dropping to 30 to 59
Stage 4: Severely reduced kidney function with jaundice; GFR rates are 15 to 29
Stage 5: The patient is on dialysis and awaiting renal transplant; without dialysis, GFR rates drop to less than 15
Early Detection Tools
Blood, urine and imaging tests can help clinicians detect and diagnose kidney disease. Blood tests include creatinine measurement. Creatinine is a chemical waste product of creatine, a chemical the body makes to supply energy to muscles and other body tissues. Laboratory specialists combine creatinine levels with other factors, such as age, ethnicity, gender, height and weight, to determine the patient’s GFR.
Urine tests include an albumin to creatinine ratio (ACR). Albumin is a type of protein commonly found in blood but not in urine. The presence of albumin in the urine suggests that the kidneys are doing a poor job of filtering and reabsorption. Blood in the urine is also a sign of poor kidney function.
Imaging and biopsies can help doctors detect kidney disease in its early stages, and to determine the underlying cause of the disease.
Medical care can cure some types of kidney diseases, such as kidney infections and cysts. Acute kidney failure is usually, but not always, permanent. While there is no cure for chronic kidney disease aside from kidney transplant, treatment can slow the progression of kidney damage and dysfunction. Dialysis can filter waste and excess fluids from the body until a transplant donor can be found.