What is Chronic Kidney Disease (Longterm abnormal Kidney Function)?
Chronic kidney disease, or CKD for short, is a condition where the kidneys gradually lose their function over a period of more than three months. This can happen due to kidney damage or because the kidneys are not filtering waste and excess fluid as effectively as they should (a metric called the glomerular filtration rate or eGFR being less than 60 ml/min/1.73 mt2). Kidney damage might be obvious through scanning methods or a kidney biopsy, or detected by abnormalities in the urine, like a high amount of a protein called albumin.
CKD severity is measured using a 2012 classification system called KDIGO. This system puts CKD into six stages based on how well your kidneys are working (G1 to G5, also splitting G3 into G3a and G3b). It also uses three stages based on the amount of albumin in the urine (A1, A2, and A3). For instance, G1 is when the kidney function is as good as or better than 90 ml/min per 1.73 m2, and G5 when they function so poorly that the individual has to undergo dialysis.
In terms of albuminurea stages, A1 indicates a relatively low amount of albumin in the urine, an ACR less than 30 mg/gm (less than 3.4 mg/mmol). On the opposite end, A3 means an ACR greater than 300 mg/gm (greater than 34 mg/mmol).
While this classification system helps in better understanding the prognosis of patients with CKD, it also poses a risk of overdiagnosing CKD, especially in elderly people.
What Causes Chronic Kidney Disease (Longterm abnormal Kidney Function)?
Chronic Kidney Disease (CKD) has many different causes around the world, which eventually lead to severe kidney disease, also known as end-stage renal disease (ESRD). The primary diseases causing CKD are Diabetes Type 2 (30% to 50% cases), Diabetes Type 1 (3.9% cases), High Blood Pressure (27.2% cases), Primary Kidney Inflammation (8.2% cases), Chronic Tubulointerstitial Nephritis (3.6% cases), Hereditary or cystic diseases (3.1% cases), Secondary Kidney Inflammation or Blood Vessel Inflammation (2.1% cases), and Plasma Cell Disorders or Tumors (2.1% cases). Sickle Cell Nephropathy, which causes less than 1% of ESRD cases in the U.S, is also a cause.
CKD can result from problems in three main areas: prerenal (low blood flow to the kidneys), intrinsic renal (damages to the blood vessels, filtering units, or tubules within the kidneys), or postrenal (blockages after urine is produced).
Prerenal Disease is a long-term condition that can occur in patients with chronic heart failure or liver disease. These conditions result in consistently low blood flow to the kidneys, which may cause kidney injury, such as acute tubular necrosis (ATN), and progressive loss of kidney function over time.
Intrinsic Renal Vascular Disease, like nephrosclerosis, causes long-term damage to blood vessels, filtering units, and tubules in the kidneys. Other vascular diseases include renal artery stenosis from hardening of the arteries or fibro-muscular abnormalities, leading to a condition called ischemic nephropathy.
Intrinsic Glomerular Disease is indicated by abnormal urine test results. It might show red blood cell casts, odd shaped red cells, white blood cells, and variable levels of protein. Common causes include post-streptococcal GN, infective endocarditis, shunt nephritis, IgA nephropathy, lupus nephritis, Goodpasture syndrome, and vasculitis.
Intrinsic Tubular and Interstitial Disease is most often caused by polycystic kidney disease (PKD). Other causes include nephrocalcinosis (usually due to high calcium levels), sarcoidosis, Sjogren syndrome, and reflux nephropathy in children and young adults.
There’s an increased recognition of the CKD of unknown cause, prevalently found among farmworkers from Central America and parts of Southeast Asia.
Lastly, Postrenal or Obstructive Nephropathy is a condition often caused by chronic obstructions due to prostate disease, kidney stones, or pelvic tumors. Retroperitoneal fibrosis, though rare, is another cause of chronic ureteral obstruction.
Risk Factors and Frequency for Chronic Kidney Disease (Longterm abnormal Kidney Function)
Chronic kidney disease (CKD) is a condition that is difficult to accurately measure in the population. This is due to the fact that in the early to moderate stages of the disease, there are often no symptoms. Around 10% to 14% of the general population suffers from this disease. Furthermore, 7% of people suffer from albuminuria (or A2) and between 3% to 5% have a Glomerular Filtration Rate (GFR), which measures kidney function, less than 60. In 2012, CKD was responsible for 2,968,600 (or 1%) of years of healthy life lost due to disability and between 1% to 3% of years of life lost.
The protocol for diagnosing CKD requires patients to undergo testing on three occasions over the span of three months. Out of these three tests, at least two results need to be consistently positive to confirm a CKD diagnosis.
CKD behaves differently in different segments of the population. In the general population, CKD is mostly seen in older people. These individuals have been exposed to cardiovascular risk factors, hypertension, and diabetes for years, which can also negatively impact the kidneys. In this group, the kidney function typically decreases at a rate of 0.75 to 1 ml/min/year after the age of 40 to 50 years. CKD detected in the general population usually does not require renal replacement therapy, but it does lead to a number of deaths from cardiovascular disease.
On the other hand, those with CKD who are referred to kidney specialists usually display early symptoms. The cause can be hereditary, such as autosomal dominant polycystic kidney disease (ADPKD), or acquired, such as glomerulonephritis, diabetic nephropathy, or tubulointerstitial disease. This group typically shows a more rapid decline in kidney function.
There are several risk factors that contribute to the progression of CKD. These can be divided into non-modifiable and modifiable risk factors.
- Non-Modifiable CKD Risk Factors: These include older age, male gender and non-white ethnicity. Genetic factors have also been found to influence CKD progression.
- Modifiable CKD Risk Factors: Factors such as systemic hypertension, proteinuria, and metabolic disorders can cause CKD. Other factors include obesity and smoking, as well as insulin resistance, dyslipidemia, and hyperuricemia.
There are specific guidelines for screening people for CKD. This typically targets individuals who are at high risk, such as those with hypertension, diabetes, or above 65 years of age. The screening process includes a urinalysis, measurement of serum creatinine and estimation of GFR. It has been found to be cost-effective and there is no evidence to justify screening asymptomatic individuals in the general population for CKD.
Signs and Symptoms of Chronic Kidney Disease (Longterm abnormal Kidney Function)
Chronic Kidney Disease typically doesn’t show any signs or symptoms until it has progressed to the stages 4 or 5. It’s often picked up during routine blood or urine tests. Once symptoms do begin to appear, they might include things like:
- Nausea
- Vomiting
- Loss of appetite
- Feeling tired and weak
- Having difficulty sleeping
- Producing less urine than normal
- Feeling mentally slow or foggy
- Experiencing muscle twitches and cramps
- Swelling in your feet and ankles
- Constant itching
- Chest pain, which can be a sign of inflammation of the heart lining
- Shortness of breath from fluid build-up in the lungs
- High blood pressure that is hard to control
To the naked eye, there aren’t many obvious signs of this disease. But a doctor might notice:
- Changes in skin color
- Scratch marks from constant itching
- A rubbing sound in the heart due to inflammation of the heart lining
- Crystalline residue on the skin (uremic frost) from high levels of a waste product called blood urea nitrogen
A medical expert might also see changes in the back of the eye related to long-term high blood pressure.
Testing for Chronic Kidney Disease (Longterm abnormal Kidney Function)
If a person’s kidney function test (specifically, their eGFR value) falls below a certain threshold, doctors must examine prior blood and urine tests, along with the person’s medical history, to figure out whether this is due to sudden or chronic kidney disease. Certain signals can help with this analysis, including a history of hypertension, skin pigmentation changes, and test results for various other health conditions.
Interestingly, people who seem in good health but show significantly high levels of certain substances in their blood and urine are more likely to have chronic kidney disease than acute kidney disease.
If it’s not clear whether a patient is dealing with acute or chronic kidney issues, doctors may repeat the kidney function tests after two weeks. If previous tests or a retest over three months confirm the low eGFR, it’s a clear sign of chronic kidney disease. In cases where the eGFR measure might not be entirely precise, other markers can be explored.
To check for protein in the urine (aka proteinuria), doctors might take an early morning urine sample and assess the albumin-creatinine ratio. Sometimes there might be other proteins present in the urine, and testing for these could provide additional insights.
Imaging techniques can be useful too. For example, ultrasound imagery can indicate if kidneys are smaller than usual or if there are other signs of longstanding disease. A kind of imaging test called renal angiography can also be helpful to diagnose specific conditions. Different kinds of scan techniques are used depending on the situation, such as CT scans for diagnosing kidney stone disease, or renal scans mostly for children due to lower radiation exposure.
Finding the precise cause of chronic kidney disease is crucial, as different underlying conditions need different treatments. Sometimes a kidney biopsy is needed to identify the cause of the issue and assess the level of kidney damage.
Treatment Options for Chronic Kidney Disease (Longterm abnormal Kidney Function)
General treatment for kidney disease often involves adjusting medication dosages based on a patient’s estimated glomerular filtration rate (GFR), a test that measures how well the kidneys are filtering waste from the blood. Sometimes, when the disease progresses to the point that the kidneys can no longer function properly, a patient may need to prepare for a dialysis treatment, which could involve placing something called an arteriovenous fistula or graft.
In cases of acute kidney injury, where the kidneys suddenly stop working, it’s crucial to identify and address potentially reversible causes. These can include infections, drugs that interfere with normal kidney function, low blood pressure, or instances that cause a loss of body fluids, like vomiting and diarrhea.
People with chronic kidney disease (CKD) should be very cautious about undergoing imaging studies that involve intravenous contrast dyes, as such procedures can be harmful to the kidneys. Alternatives should be considered. It’s also advisable to avoid certain drugs that may harm the kidneys, including a category of antibiotics known as aminoglycosides and non-steroidal anti-inflammatory drugs (NSAIDs).
Managing the factors that accelerate the progression of CKD, like high blood pressure, excessive protein in the urine, metabolic acidosis, and high cholesterol levels, can also help slow down the disease. Quitting smoking, carefully managing protein intake, and supplementation of bicarbonate to treat chronic metabolic acidosis have all been shown to decelerate CKD progression.
When CKD advances, different renal replacement therapy options can be considered. These include hemodialysis (carried out at home or in a clinic), peritoneal dialysis, and kidney transplantation. Hemodialysis is performed after a stable vascular access pathway is established in an arm, which lets blood flow out and back into the body. Another option, peritoneal dialysis, is performed after a catheter has been inserted into the abdominal cavity.
In kidney transplantation, the preferred treatment for end-stage kidney disease, a new kidney replaces the function of the existing failed kidneys. Patients who do not want any type of renal replacement therapy should have information about conservative and palliative care management.
Renal replacement therapy might be necessary in an array of circumstances, like persistent nausea and vomiting, uncontrollable hypertension, fluid overload, and a range of metabolic imbalances. It’s essential to consult a healthcare provider to discuss the best options.
Unfortunately, not all patients can or want to undergo dialysis or transplantation; they might potentially opt for conservative management of their condition. This approach includes managing the symptoms, advance-care planning, and providing appropriate palliative care. Such a course of action can be particularly suitable for extremely frail individuals with a poor overall health status and multiple existing health issues.
Generally, a person with CKD should be referred to a kidney specialist, or nephrologist, when the estimated GFR drops below 30 ml/min/1.73 mt2. At this stage, the different options of renal replacement therapies could be discussed with the specialist.
What else can Chronic Kidney Disease (Longterm abnormal Kidney Function) be?
These are some of the kidney-related conditions that doctors need to consider:
- Sudden kidney damage or failure
- Alport syndrome (a genetic condition leading to kidney disease, hearing loss, and eye abnormalities)
- Disease that attacks the tiny filters in your kidneys
- Long-term inflammation and damage to the kidneys’ filtering units
- Kidney damage resulting from high blood sugar related to diabetes
- A cancer of plasma cells that can damage the kidneys
- Formation of hard deposits, known as kidney stones
- Hardening or thickening of the kidneys due to high blood pressure or aging
- A rare kidney disorder that causes rapid loss of kidney function
- Narrowing of the arteries that carry blood to the kidneys
Remember, it’s important that anyone experiencing kidney-related symptoms should see a doctor who can conduct appropriate tests to figure out the correct diagnosis.
What to expect with Chronic Kidney Disease (Longterm abnormal Kidney Function)
The rates of end-stage renal disease (ESRD) significantly vary between different racial and ethnic groups. The highest rate is found in African Americans, followed by American Indians and Alaska Natives, Asian Americans, Native Hawaiians, and other Pacific Islanders, with whites having the lowest incidence. Furthermore, Hispanics have higher rates of ESRD than non-Hispanics.
Early-stage chronic kidney disease (CKD) and ESRD are linked to increased sickness and higher usage of healthcare services. According to a review of the 2009 annual data report from the United States Renal Data System (USRDS), the number of hospitalizations for ESRD patients is approximately 1.9% per patient per year.
A study also found that people with CKD, including cardiovascular, cerebrovascular and peripheral vascular diseases, have health conditions comparable to those in the US dialysis population. The same study observed that CKD patients had triple the rates of hospitalization and hospital days spent per patient per year compared to the general US population. This means those with CKD have a higher likelihood of being hospitalized and getting heart diseases, a risk that increases as kidney function (GFR) continues to decrease.
Those with CKD, and specifically ESRD, are at an increased risk of death, especially from heart-related diseases. Reviewing the USRDS 2009 data suggests that the chance of a person on dialysis surviving beyond five years is only around 34%.
Possible Complications When Diagnosed with Chronic Kidney Disease (Longterm abnormal Kidney Function)
Chronic Kidney Disease (CKD) can bring about several complications. Patients at stages IV and V can find it hard to maintain fluid balance after excessive sodium intake. The best way to manage this is by reducing their sodium intake to less than 2 grams per day and using a loop diuretic, as recommended by the 2012 KDIGO guidelines.
Sometimes, CKD patients face a condition called Hyperkalemia, where the potassium levels in the blood are higher than usual. This could occur especially in patients with less urine output and those with reduced aldosterone secretion. Other causes can include potassium-rich diet, cellular breakdown, hypoaldosteronism, and certain medications like ACE inhibitors and nonselective beta-blockers.
Chronic Metabolic acidosis is another complication common in CKD patients due to the kidney’s tendency to retain hydrogen. This could potentially lead to osteopenia, more protein breakdown, and secondary hyperparathyroidism. Therefore, patients should take bicarbonate supplements to achieve a target serum bicarbonate of 23.
CKD significantly increases the risk for Cardiovascular Diseases (CVD), and this risk multiplies with the severity of CKD. A thorough assessment of Epicardial adipose tissue (EAT), a fat layer around the heart, can help predict the cardiovascular risk in CKD patients.
Bone and mineral disorders are also associated with CKD.
- Hyperphosphatemia: it’s a condition of high phosphorus levels in the blood, common in CKD patients due to decreased filtering of phosphorous by kidneys. This condition leads to excessive secretion of Parathyroid hormone (PTH), causing secondary hyperparathyroidism and bone issues – a condition called renal osteodystrophy. The condition is often managed with phosphorus binders and dietary restriction on phosphorus.
- Hypertension: High blood pressure is a common symptom of CKD, often a result of increased fluid volume in the body. Patients should be given a loop diuretic for effective blood pressure control.
Anemia is also common in CKD patients, usually characterized by standard size and color of red blood cells. This is due to lower levels of erythropoietin, a hormone that stimulates red blood cell production, and reduced red cell survival. Hemoglobin levels should be checked regularly, and Erythropoietin stimulating agents (ESA) should be considered if hemoglobin is less than 10.
For End Stage Renal Disease (ESRD) patients, malnutrition and uremic bleeding are frequent complications. A diet providing minimum 30-35 kcal/kg per day is suggested for ESRD patients. Uremic bleeding can result from poor platelet function, leading to increased bleeding time. It’s usually not treated unless there is active bleeding or in pre-surgery scenarios.
Renal transplantation can also have diverse complications related to cardiovascular, renal, neurological, and gastrointestinal systems, such as hypertension, dyslipidemia, coronary artery disease, arrhythmias, heart failure, stroke, infections, neuromuscular disease, seizures, cancer and digestive disorders.
Preventing Chronic Kidney Disease (Longterm abnormal Kidney Function)
People who are at a high risk of developing kidney disease, such as those with diabetes or high blood pressure, should not only be screened for Chronic Kidney Disease (CKD), but they should also be informed about the symptoms and signs of CKD. Those diagnosed with CKD should be educated on ways to manage the disease at home.
Most patients (80% to 85%) with CKD also have high blood pressure. They should be guided to check their blood pressure every day, keep records of daily blood pressure readings and body weight. It would generally be recommended to include a type of medicine called a diuretic as part of their treatment to control high blood pressure.
Patients with severe CKD should learn how to administer a specific type of medicine known as erythropoietin stimulating agents at home. These are injected under the skin to help the body produce more red blood cells.
For diet, patients should discuss with nutritionists or doctors about eating low protein diets and managing foods rich in potassium. This might help slow down the progress of CKD.
Those with severe CKD should be educated on the importance of controlling their phosphorus levels. They could do this by taking medication that binds to phosphate (phosphorus in your body) during meals, which can help lower phosphorus levels in the blood.
Pregnant women with CKD should be made aware that pregnancy might make their kidney disease worse. They should also understand how decreased kidney function could negatively affect the health of their pregnancy.
