Chronic kidney disease, or CKD, is a long-term condition characterized by the gradual loss of kidney function over time. Healthy kidneys perform several functions, including filtering waste and excess fluid from the blood to produce urine. They also regulate blood pressure, help produce red blood cells, and maintain a stable balance of electrolytes, such as sodium and potassium.
The development of CKD means the kidneys have become damaged and are less able to perform these duties. Because the decline is often slow and occurs over many years, many individuals are unaware they have CKD until it reaches a more advanced state.
Causes of Chronic Kidney Disease
The two most prevalent causes of chronic kidney disease are diabetes and high blood pressure. In individuals with diabetes, persistently high levels of glucose in the blood can damage the filtering units within the kidneys, known as nephrons. Over years, this damage impairs the kidneys’ ability to filter waste effectively and can lead to a condition called diabetic kidney disease, where proteins may leak into the urine.
High blood pressure, or hypertension, damages the small blood vessels in the kidneys. Elevated pressure can strain and constrict these vessels, reducing blood flow and hampering their function. This reduced filtration capacity means the kidneys are less able to remove waste and excess fluid, and the fluid retention can raise blood pressure further, creating a cycle that accelerates kidney damage.
While diabetes and hypertension are the primary drivers, other conditions can lead to CKD. Glomerulonephritis is a group of diseases that cause inflammation in the kidney’s filtering units. Inherited conditions, like polycystic kidney disease, result in cysts that disrupt kidney structure and function. Other causes include recurrent kidney infections, long-term urinary tract blockages, and extended use of certain medications harmful to the kidneys.
Symptoms of Chronic Kidney Disease
A defining characteristic of chronic kidney disease is its silent progression in the early stages. Many people with mild to moderate CKD experience no symptoms. The body can compensate for a significant reduction in kidney function, allowing the disease to advance for years without detection. The condition is often first discovered through routine blood or urine tests.
As kidney function declines, signs and symptoms may appear, though they are often nonspecific. A common early sign is a persistent feeling of fatigue or weakness, related to the buildup of waste products or anemia, a complication of CKD. Changes in urination, such as needing to urinate more often or noticing foamy urine, can also be indicators.
With more advanced disease, symptoms may develop as waste and fluid accumulate. Swelling, known as edema, may occur in the legs, ankles, and feet due to fluid retention. Other symptoms include a diminished appetite, nausea, dry and itchy skin, muscle cramps, and difficulty concentrating. The appearance of these persistent symptoms should prompt a conversation with a healthcare provider.
How Chronic Kidney Disease is Diagnosed
Diagnosing chronic kidney disease involves laboratory tests that assess kidney filtering performance. The process relies on two main tests: a blood test to estimate the filtration rate and a urine test to check for protein. These tests are performed together, and must show evidence of damage for at least three months to confirm a CKD diagnosis.
The primary blood test measures creatinine, a waste product from muscle metabolism. This creatinine level, along with factors like age and sex, is used in a formula to calculate the estimated Glomerular Filtration Rate (eGFR). The eGFR indicates how many milliliters of blood the kidneys filter per minute, serving as the primary measure of kidney function.
The second diagnostic tool is a urine albumin-to-creatinine ratio (ACR) test, which checks for albumin, a type of protein, in the urine. Healthy kidneys prevent albumin from passing into the urine, so its presence is an early marker of kidney damage. The ACR test is sensitive and can detect small amounts of protein, signaling a problem before significant function is lost.
The Stages of Chronic Kidney Disease
Chronic kidney disease is categorized into five stages based on the estimated Glomerular Filtration Rate (eGFR), which reflects remaining kidney function. This staging system helps healthcare providers understand the disease’s severity and determine the appropriate management. Progression through these stages often happens slowly over several years.
Stage 1 is characterized by an eGFR of 90 or higher, considered normal kidney function, but with other evidence of kidney damage like protein in the urine. Stage 2 indicates a mild decrease in kidney function, with an eGFR between 60 and 89. In both stages, signs of kidney damage must be present for a diagnosis, and symptoms are uncommon.
Stage 3 marks a moderate decline in kidney function and is divided into two sub-stages: Stage 3a (eGFR 45-59) and Stage 3b (eGFR 30-44). At this point, waste products can build up in the blood, leading to complications like high blood pressure or bone disease. Some people may start to notice symptoms like fatigue or swelling, and in Stage 4 (eGFR 15-29), symptoms are more likely.
Stage 5 is the final stage, defined by an eGFR of less than 15. This stage is also referred to as kidney failure or end-stage renal disease (ESRD). At this point, the kidneys have lost most of their ability to filter waste from the blood, leading to a significant buildup of toxins and fluid.
Managing Chronic Kidney Disease
While there is no cure for chronic kidney disease, treatments and lifestyle adjustments can help manage the condition. The primary goals are to slow the rate of kidney damage and address associated complications. The specific treatment plan depends on the stage of the disease and its underlying cause.
Lifestyle modifications are a key component of managing CKD. A kidney-friendly diet is often recommended, which involves limiting sodium, potassium, and phosphorus to reduce the workload on the kidneys. Controlling blood pressure and blood sugar levels is also paramount. Regular physical activity, quitting smoking, and maintaining a healthy weight are additional measures that help slow disease progression.
Medications play a significant role in managing both the causes and complications of CKD. ACE inhibitors and ARBs are blood pressure medications frequently prescribed because they also help protect the kidneys. Other medications may be used to lower cholesterol, treat anemia, manage swelling with diuretics, or protect bones with phosphate binders and vitamin D supplements.
For individuals who progress to Stage 5 kidney failure, advanced treatments are necessary to replace lost kidney function. The two main options are dialysis and kidney transplantation. Dialysis is a procedure that artificially filters waste and excess fluid from the blood, either through hemodialysis (using a machine) or peritoneal dialysis (using the lining of the abdomen). A kidney transplant, which involves surgically placing a healthy kidney from a donor, is the other primary treatment for end-stage renal disease.