10.1 Pathophysiology of Acute and Chronic Kidney Disease
3 min read•august 9, 2024
Kidney disease can wreak havoc on your body. From filtering blood to balancing electrolytes, your kidneys play a crucial role in keeping you healthy. When they start to fail, it affects everything from your bones to your blood.
happens suddenly, while develops over time. Both can lead to serious complications if left untreated. Understanding the causes, symptoms, and management of kidney disease is key to maintaining your health.
Kidney Function and Structure
Glomerular Filtration and Nephron Structure
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- (GFR) measures kidney function by assessing how much blood passes through glomeruli per minute
- Normal GFR ranges from 90-120 mL/min/1.73 m²
- Nephrons function as the basic structural and functional units of the kidney
- Each kidney contains approximately 1 million nephrons
- Nephron structure includes glomerulus, proximal tubule, loop of Henle, and distal tubule
- Glomerulus filters blood, while tubules reabsorb and secrete substances
Electrolyte Balance and Acid-Base Regulation
- Kidneys maintain electrolyte balance by regulating sodium, potassium, calcium, and phosphate levels
- Sodium regulation influences blood pressure and fluid balance
- Potassium balance affects muscle and nerve function
- Calcium and phosphate homeostasis impacts bone health
- occurs when kidneys fail to excrete sufficient acid or reabsorb enough bicarbonate
- Symptoms of metabolic acidosis include rapid breathing, confusion, and fatigue
- Kidneys compensate for metabolic acidosis by increasing bicarbonate reabsorption and ammonium excretion
Acute and Chronic Kidney Disease
Acute Kidney Injury and Its Causes
- Acute kidney injury (AKI) involves sudden decline in kidney function over hours to days
- AKI classified into prerenal (decreased blood flow), intrinsic (damage to kidney tissue), and postrenal (urinary tract obstruction) causes
- Common causes of AKI include severe dehydration, sepsis, and nephrotoxic medications (NSAIDs, aminoglycosides)
- AKI diagnosis based on elevated serum creatinine, decreased urine output, or both
- Treatment focuses on addressing underlying cause and supporting kidney function
Chronic Kidney Disease Progression and Management
- Chronic kidney disease (CKD) characterized by gradual loss of kidney function over months to years
- CKD stages defined by GFR and presence of kidney damage markers (proteinuria)
- Stage 1: GFR ≥ 90 mL/min/1.73 m² with evidence of kidney damage
- Stage 2: GFR 60-89 mL/min/1.73 m²
- Stage 3: GFR 30-59 mL/min/1.73 m²
- Stage 4: GFR 15-29 mL/min/1.73 m²
- Stage 5: GFR < 15 mL/min/1.73 m² or dialysis (End-stage renal disease)
- End-stage renal disease (ESRD) requires renal replacement therapy (dialysis or kidney transplantation)
- Risk factors for kidney disease include diabetes, hypertension, obesity, and family history
- Management of CKD involves controlling blood pressure, managing diabetes, and dietary modifications
Complications of Kidney Disease
Urinary and Metabolic Abnormalities
- Proteinuria indicates kidney damage and increased risk of CKD progression
- Microalbuminuria (30-300 mg/day) serves as an early marker of kidney disease
- Macroalbuminuria (> 300 mg/day) suggests more advanced kidney damage
- Azotemia refers to elevated (BUN) and creatinine levels
- results from accumulation of waste products in blood due to kidney failure
- Uremic symptoms include nausea, vomiting, fatigue, and altered mental status
Bone and Hematologic Complications
- Renal osteodystrophy encompasses bone disorders associated with CKD
- Altered vitamin D metabolism and secondary hyperparathyroidism contribute to renal osteodystrophy
- Manifestations include osteomalacia, osteitis fibrosa, and adynamic bone disease
- in kidney disease primarily caused by decreased erythropoietin production
- Other factors contributing to anemia include iron deficiency and chronic inflammation
- Treatment of renal anemia involves erythropoiesis-stimulating agents and iron supplementation
Key Terms to Review (18)
Ace inhibitors: ACE inhibitors, or angiotensin-converting enzyme inhibitors, are a class of medications that help relax blood vessels by inhibiting the enzyme responsible for converting angiotensin I to angiotensin II. This action lowers blood pressure and reduces the workload on the heart, making them particularly important in managing conditions like heart failure and kidney disease.
Acute kidney injury: Acute kidney injury (AKI) is a sudden and rapid decline in kidney function, characterized by an increase in serum creatinine levels or a decrease in urine output. This condition can result from various causes, including dehydration, infections, medications, or obstruction of urine flow. AKI is crucial to understand as it can lead to serious complications, including chronic kidney disease if not properly managed and can significantly impact nutrition status.
Anemia: Anemia is a medical condition characterized by a deficiency in the number or quality of red blood cells, which impairs the body's ability to transport oxygen effectively. This condition can be particularly relevant in the context of kidney disease, where reduced erythropoietin production from damaged kidneys can lead to decreased red blood cell formation and contribute to the severity of both acute and chronic kidney disease.
Blood Urea Nitrogen: Blood urea nitrogen (BUN) is a medical test that measures the amount of urea nitrogen in the blood, which is a waste product formed from the breakdown of proteins. BUN levels are important for assessing kidney function, as the kidneys filter urea from the bloodstream and excrete it in urine. Elevated levels can indicate kidney dysfunction, dehydration, or excessive protein intake, making BUN a key marker in various medical evaluations.
Chronic Kidney Disease: Chronic Kidney Disease (CKD) is a progressive condition characterized by the gradual loss of kidney function over time, which can lead to kidney failure if left unmanaged. It affects the kidneys' ability to filter waste products from the blood, regulate electrolyte balance, and maintain overall homeostasis, impacting nutritional status and management in various patient populations.
Creatinine Clearance: Creatinine clearance is a medical test that estimates the kidney's ability to filter creatinine, a waste product from muscle metabolism, from the blood into the urine. This measurement helps assess kidney function and can be crucial in diagnosing and monitoring both acute and chronic kidney disease, as well as informing nutritional strategies for patients with renal issues.
Dialysis diet: A dialysis diet is a specialized nutritional plan designed for individuals undergoing dialysis treatment, focusing on managing fluid, electrolyte, and waste product levels in the body. This diet is essential for maintaining optimal health and preventing complications associated with kidney failure, as it helps to balance nutrient intake while accommodating the limitations imposed by impaired kidney function. The dietary restrictions and recommendations vary based on whether a patient is on hemodialysis or peritoneal dialysis.
Diuretics: Diuretics are medications that promote the excretion of water and electrolytes through urine, primarily affecting the kidneys. They are often used to manage conditions like heart failure and kidney disease by helping to reduce fluid overload and control blood pressure. Understanding how diuretics work is essential for managing electrolyte balance and assessing nutritional needs in patients undergoing treatment with these drugs.
Glomerular filtration rate: Glomerular filtration rate (GFR) is the volume of blood that is filtered by the kidneys per minute, specifically through the glomeruli, which are tiny filtering units within the kidneys. GFR is a critical indicator of kidney function and health, as it reflects the kidneys' ability to filter waste products and maintain fluid and electrolyte balance. Understanding GFR is essential for assessing kidney disease, making nutritional decisions for renal patients, and managing electrolyte and fluid balance in those with renal conditions.
Hyperkalemia: Hyperkalemia is a medical condition characterized by elevated levels of potassium in the blood, typically defined as a serum potassium level greater than 5.0 mmol/L. This condition can arise due to various factors, including kidney dysfunction, which is central to understanding its implications in both acute and chronic kidney disease, as well as the nutritional management of patients undergoing hemodialysis. It is crucial to maintain proper electrolyte balance, as high potassium levels can lead to serious cardiac complications and other health issues.
Metabolic Acidosis: Metabolic acidosis is a medical condition characterized by an excess of acid in the body due to an imbalance in the production and elimination of hydrogen ions or a decrease in bicarbonate levels. This condition often arises in various clinical settings, especially in renal disease, where the kidneys struggle to excrete acid effectively or maintain proper bicarbonate levels. Understanding metabolic acidosis is crucial for recognizing its implications in acute and chronic kidney disease, as these conditions can severely affect acid-base balance in the body.
Nephron function: Nephron function refers to the processes carried out by nephrons, the functional units of the kidneys, responsible for filtering blood, reabsorbing essential substances, and excreting waste products in urine. Understanding nephron function is crucial for grasping how kidney diseases disrupt these processes, leading to a range of health issues in both acute and chronic kidney disease.
Phosphorus: Phosphorus is a vital mineral found in the body, primarily in the form of phosphate, and plays essential roles in bone health, energy production, and cellular function. It is critical for the formation of DNA, RNA, and ATP, which is the energy currency of cells. Imbalances in phosphorus levels can have significant effects on health, especially in individuals with kidney dysfunction or those undergoing dialysis.
Protein restriction: Protein restriction is the dietary practice of limiting protein intake, particularly important for individuals with kidney disease. By reducing protein consumption, this approach aims to decrease the workload on the kidneys, helping to manage symptoms and slow disease progression. In the context of kidney health, appropriate protein restriction is crucial as it helps maintain a balance between necessary nutrient intake and minimizing urea production, which can be toxic in cases of renal dysfunction.
Renal diet: A renal diet is a specialized eating plan designed to support kidney health by managing the intake of nutrients that may be harmful in the presence of kidney disease. This diet emphasizes low protein, controlled sodium, potassium, and phosphorus levels to reduce the burden on the kidneys while ensuring proper nutrition for individuals suffering from acute or chronic kidney conditions.
Sodium control: Sodium control refers to the regulation of sodium intake and balance within the body, especially in individuals with kidney disease. Maintaining appropriate sodium levels is critical because the kidneys play a vital role in filtering excess sodium and managing fluid balance. When the kidneys are impaired, excessive sodium can lead to fluid retention, hypertension, and worsening kidney function.
Uremia: Uremia is a clinical syndrome characterized by the accumulation of waste products in the blood due to kidney failure, affecting multiple body systems. It occurs when the kidneys can no longer effectively filter and eliminate toxins like urea and creatinine, leading to various symptoms such as nausea, fatigue, and confusion. Understanding uremia is crucial for recognizing the severity of kidney dysfunction and guiding treatment decisions in acute and chronic kidney disease.
Vitamin d deficiency: Vitamin D deficiency occurs when the body lacks sufficient vitamin D, which is crucial for maintaining bone health, calcium absorption, and immune function. This deficiency can lead to various health issues, particularly affecting populations with limited sun exposure or malabsorption conditions, significantly influencing the pathophysiology of certain diseases and overall health.