Podcast
Questions and Answers
Which of the following is NOT considered a common etiology of Chronic Kidney Disease?
What clinical manifestation is associated with Chronic Kidney Disease?
Which of the following complications can arise from Chronic Kidney Disease?
Which diagnostic test can specifically help distinguish pre-renal causes from intrinsic causes in Chronic Kidney Disease?
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What is a typical management strategy for Chronic Kidney Disease?
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Which of the following is NOT a clinical manifestation of Chronic Kidney Disease?
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Which imaging study is particularly useful for identifying post-renal causes of kidney problems?
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What essential lab test is generally used to assess kidney function in cases of Chronic Kidney Disease?
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What role does the Juxtaglomerular apparatus (JGA) play in kidney function?
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Which of the following substances can easily cross the glomerular capillaries?
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What is the primary method for assessing kidney function?
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What condition is indicated by a decrease in urine output and an increase in serum creatinine?
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What type of shock is associated with impaired blood flow to the kidneys?
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Which of the following complications is NOT associated with acute kidney failure?
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Which imaging test is utilized for visualizing kidney structure abnormalities?
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What does the term AKI replace in clinical terminology?
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Which type of medication is typically not used for treating acute kidney injury?
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What is one of the first signs of acute kidney injury?
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Which of the following is a post-renal cause of kidney failure?
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In which stage of acute kidney injury is urine output typically reduced?
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What does serum creatinine indicate in relation to kidney function?
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What is a common cause of acute kidney injury (AKI)?
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Which hormone produced by the kidneys stimulates erythropoiesis?
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What is the primary function of the nephron?
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What structure is responsible for transporting urine from the kidneys to the bladder?
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Which part of the nephron is primarily responsible for the reabsorption of glucose?
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What is the typical urinary output for an adult per day?
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What condition is indicated by proteinuria?
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Which anatomical feature increases filtration pressure in the glomerulus?
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What is the role of the juxtaglomerular apparatus?
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How many nephrons are typically found in one kidney?
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What allows the bladder to expand and store urine?
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What is azotemia?
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What is the main function of the renal pelvis?
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In addition to filtering blood, what is a secondary function of the nephron?
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What is the main function of the descending limb of Henle's loop?
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Which characteristic is true for the ascending limb of Henle's loop?
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What regulates the permeability of the distal convoluted tubule to water?
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Which substance is primarily reabsorbed from the collecting ducts into the interstitial spaces?
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What is the main waste product filtered by the kidneys during urine formation?
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What is the osmolarity of the fluid in the collecting ducts under normal conditions?
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Which part of the nephron is responsible for the majority of nutrient reabsorption?
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What process primarily occurs in the glomerulus of each nephron?
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Which statement accurately describes an effect of diuretics?
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What is the primary function of the nephron?
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In what condition would you expect oliguria to occur?
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Which of the following best describes the composition of normal urine?
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Why is the structure of the nephron considered efficient for filtration?
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What happens in the peritubular capillaries after filtration at the glomerulus?
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What is the main purpose of urine analysis in the context of kidney injury?
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What is a necessary measure to ensure proper management of a patient with acute kidney injury (AKI)?
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Which electrolyte imbalances are particularly important to monitor in patients with acute kidney injury?
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In the progression of chronic kidney disease (CKD), what is the likelihood of developing end-stage renal disease?
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What is one significant outcome for patients who have experienced acute kidney injury?
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What characterizes the early stages (1-3) of chronic kidney disease (CKD)?
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What is the primary treatment focus for chronic kidney disease (CKD)?
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Which imaging study is most effective for identifying post-renal causes of kidney injury, such as hydronephrosis?
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Study Notes
Renal and Urology System
- The renal system works closely with the lungs, skin, and intestines to maintain homeostasis and keep the body's chemical and water balance in check.
- The renal/urinary system consists of 2 kidneys, 2 ureters, 1 bladder, and 1 urethra.
- Urinary tract infections (UTIs) can occur if urine becomes stagnant or backflows.
Kidneys
- The kidneys are purplish-brown, bean-shaped organs found high in the back of the abdominal cavity, below the rib cage.
- The right kidney is slightly lower than the left due to the position of the liver.
- Adult kidneys measure 10-12 cm in length and 5-7 cm in width and weigh approximately 150g.
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Primary kidney functions include:
- Removing excess water, urea, creatinine, and wastes from the blood
- Forming urine from water, urea, creatinine, uric acid, and other wastes
- Maintaining homeostasis by stabilizing substances in the blood
- Generating erythropoietin (EPO) for erythropoiesis
- Activating vitamin D
- Regulating blood pressure
Ureters
- Each kidney has one narrow tube called a ureter which carries urine from the kidney to the bladder.
- Muscles in the ureter walls contract and relax to force urine down towards the bladder and away from the kidneys.
- Urine is emptied into the bladder from the ureters approximately every 10-15 seconds.
Bladder
- The bladder is a triangle-shaped, hollow organ located in the pelvic cavity.
- A healthy adult bladder can store 400-500mls of urine.
- During urination, the bladder muscles squeeze and two sphincters (valves) open to allow urine to flow out.
- The urethra is longer in males (8 inches - 20 cm) than females (1.5 inches - 4 cm) because it passes through the penis.
Urethra
- The urethra is a tube that allows urine to be excreted outside of the body.
- Sphincter muscles relax to let urine exit the bladder through the urethra.
- The female urethra is shorter (≈ 4 cm) than the male urethra (≈ 15-20 cm) making them** more susceptible to UTIs**.
Kidney Structures
- Kidneys are found below and posterior to the liver in the peritoneal cavity.
- Adrenal glands (suprarenal glands) sit on top of each kidney.
- Kidneys filter blood and purify it ("clean" it).
- The blood in the human body is filtered 40 times a day by the kidneys.
- Filtration requires 25% of cardiac output (1,250 mils/minute) and 25% of the total oxygen from the lungs.
- The filtrate coming out of the kidneys is called urine.
External Structures of the Kidney
- The kidneys are surrounded by three layers:
- Renal fascia (outermost layer, tough connective tissue)
- Perirenal fat capsule (second layer, helps anchor the kidneys in place)
- Renal capsule (innermost layer)
Internal Structures of the Kidney
- The kidneys have three regions:
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Renal Cortex (outer):
- Contains the nephron, the functional unit of the kidney
- Filtration takes place here
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Renal Medulla (middle):
- Contains renal pyramids (8 in each kidney)
- Each pyramid has a column through which blood vessels pass
- The tips of the pyramids (renal papillae) point toward the renal pelvis.
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Renal Pelvis (inner):
- Contains the hilum of the kidney, where blood vessels and nerves enter and exit
- The ureters exit and empty into the bladder at the hilum.
- The renal pelvis branches into major calyces, which further branch into minor calyces.
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Renal Cortex (outer):
Nephron
- The nephron is the functional unit of the kidney, responsible for cleansing the blood and maintaining homeostasis in the circulation.
- Each kidney contains over 1 million nephrons in the renal cortex.
- The nephron has three main functions:**
- Filtration: filtering waste products from the blood
- Reabsorption: returning essential substances back to the blood
- Secretion: removing additional waste products from the blood
- Secondary Nephron functions include:
- Blood pressure control
- Synthesizing Renin
- Erythropoiesis
- Synthesizing erythropoietin
- Calcium absorption
- Generating vitamin D
Nephron Structure
- Each nephron consists of:
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Renal corpuscle:
- Glomerulus: a tuft of capillaries located within the Bowman’s capsule
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Proximal convoluted tubule:
- Located in the renal cortex
- Located proximal to the glomerulus
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Loop of Henle:
- Forms a loop with descending and ascending parts
- Passes through the renal medulla
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Distal convoluted tubule:
- Located in the renal cortex
- Connects to the collecting ducts in the medullary pyramids
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Renal corpuscle:
Bowman's Capsule
- The Bowman's capsule is only one cell thick and surrounds the glomerulus.
- High blood pressure in the glomerulus is due to the efferent arteriole being narrower than the afferent arteriole, creating a high filtration pressure.
- The filtration at the glomerular capillaries is known as ultrafiltration.
- Approximately 180 liters of glomerular filtrate are formed every 24 hours.
Proximal Convoluted Tubule (PCT)
- The PCT functions primarily in reabsorption.
- All glucose and amino acids are reabsorbed in the PCT.
- Four-fifths of ion salts and water are reabsorbed.
- Glucose, amino acids, and salts are reabsorbed by active transport.
- Water is reabsorbed by osmosis.
- The cells lining the PCT are rich in mitochondria, which supply the ATP for active transport.
- These cells are located in the renal medulla.
Loop of Henle
- The Loop of Henle is U-shaped and located in the renal medulla.
- The descending limb of the loop is highly permeable to water and impermeable to ions, resulting in a large amount of water reabsorption and an increased osmolarity of 1200 mOSm/L.
- The ascending limb is impermeable to water but highly permeable to ions, causing a large drop in osmolarity of fluid passing through the loop to 100 mOSm/L.
- The countercurrent mechanism is generated by the fluid flow in opposite directions in the descending and ascending limbs.
Distal Convoluted Tubule (DCT)
- The DCT and collecting duct are the final site of reabsorption in the nephron.
- Water permeability in the DCT and collecting duct is variable and dependent on a hormonal stimulus (ADH).
- This variability allows for complex regulation of blood osmolarity, volume, pressure, potassium, sodium, calcium, and pH.
Collecting Ducts
- The collecting ducts are a continuation of the nephron but not technically part of it.
- Each duct collects filtrate from several nephrons.
- The collecting ducts are lined with simple squamous epithelium with receptors for ADH, allowing water to pass from the duct lumen through the cells and into the interstitial spaces to be recovered by the vasa recta.
- This process allows for the recovery of large amounts of water from the filtrate back into the blood.
Nephron Summary
- The nephron functions in excretion, osmoregulation, and homeostasis.
Urine / Filtrate Characteristics
- Normal Characteristics:
- Color: Pale yellow to deep amber
- Odor: Odorless
- Volume: 750-2000 mL/24 hour
- pH: 4.5-8.0
- Specific gravity: 1.003-1.032
- Osmolarity: 40-1350 mOsmol/kg
- Urobilinogen: 0.2-1.0 mg/100 mL
- White blood cells: None
- Leukocyte esterase: None
- Protein: None or trace
- Bilirubin: None
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Abnormal Characteristics:
- Polyuria: excessive urine production (excess caffeine or alcohol; kidney disease; diuretics; sickle cell anemia; excessive water intake)
- Oliguria: diminished urine production (dehydration; blood loss; diarrhea; cardiogenic shock; kidney disease)
- Anuria: absent urine production (kidney failure; obstruction, kidney stone or tumor; enlarged prostate)
Nephron Blood Supply
- Each renal artery enters at the renal hilum
- The renal artery branches into smaller arterioles until reaching the afferent arteriole of each nephron and each glomerulus.
- Filtered blood exits the glomerulus via the efferent arteriole, moves through the peritubular capillaries, and vasa recta.
- Filtered blood leaves the kidneys through the interlobar renal vein, then renal vein to return to systemic circulation.
Renal Anatomy
- The kidneys are located in the retroperitoneal space, receiving approximately 20% of the total resting cardiac output.
- The cortex is the outer layer of the kidney, with nephrons consisting of glomerulus and tubules.
- The renal artery branch entering the glomerulus is the afferent arteriole, with Juxtaglomerular apparatus (JGA) cells.
- The JGA secretes renin, an enzyme crucial for blood volume regulation.
- Glomerular capillaries are fenestrated, allowing substances less than 8 nm to cross, including water, glucose, urea, and ions like sodium.
- Red blood cells (RBCs) and proteins, like albumins are too large to pass through glomerular fenestrations.
Renal Assessment and Diagnostics
- Urine output measurements, including 24-hour collections provide insight into kidney function.
- Urinalysis may reveal abnormalities suggestive of kidney failure.
- Renal stone analysis helps in understanding the underlying cause of kidney stones.
- Blood tests such as serum urea and creatinine levels are vital for evaluating kidney function.
- Imaging tests, including renal scan, cystoscopy, ultrasound, CT scan, MRI, MAG3 scan, and retrograde pyelogram are used to visualize the kidneys and urinary tract.
- Biopsy offers information on kidney tissue condition by retrieving a small sample for analysis.
Normal Renal Function Tests
- Measurements such as serum creatinine, BUN, electrolytes, and urine output are used to assess kidney function.
Generic Renal Medication Regimes
- Treatment approaches for kidney disorders are tailored to the root cause, categorized into three types:
- Pre-renal: Issues before the kidney, such as hypotension.
- Intra-renal: Problems within the kidney, such as glomerulonephritis.
- Post-renal: Conditions after the kidney, like urethral obstruction.
- Specific treatments include:
- Analgesia for kidney stones.
- Antibiotics for hydronephrosis (mild cases).
- Anticoagulants for thrombosis risk.
- Antihypertensives for secondary hypertension.
- ACE inhibitors or ARB blockers for blood pressure management.
- Calcium, glucose, or insulin for hyperkalemia.
- Calcium and vitamin D supplements for hypocalcemia.
- Corticosteroids for nephrotic syndrome.
- Diuretics for fluid overload.
- Erythropoietin and iron for anemia.
- Statins to lower LDL cholesterol levels.
Acute Kidney Injury (AKI)
- AKI is characterized by a sudden reduction in kidney function, evident within 48 hours, with an elevation in serum creatinine, decreased urine output, or need for dialysis.
- AKI is classified into three stages: pre-renal, intra-renal, and post-renal failure.
- The term AKI replaces previously used terms like acute renal failure and acute renal insufficiency.
Acute Renal Failure Classifications
-
Pre-renal: Impaired blood flow to the kidneys.
- Etiology: Hypovolemic shock, hemorrhagic shock, cardiogenic shock, septic shock, anaphylactic shock, cardiovascular medications, acute coronary syndromes, heart disease/failure, severe infections, liver failure, NSAIDs, severe burns, severe dehydration.
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Intrinsic-renal: Damage to the kidneys.
- Etiology: Thrombosis, atherosclerosis, glomerulonephritis, hemolytic uremic syndrome, severe infections, lupus, chemotherapy drugs, antibiotics, imaging dyes, scleroderma, thrombotic thrombocytopenic purpura, alcohol, heavy metals, cocaine, rhabdomyolysis, and tumor lysis syndrome.
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Post-renal: Obstruction to urine flow from the kidneys.
- Etiology: Kidney stones, urinary tract thrombosis, bladder nerve damage, enlarged prostate (BPH), bladder cancer, prostate cancer, cervical cancer, and colon cancer.
Acute Kidney Failure Manifestations
- Neurological: Anxiety, confusion, fatigue, weakness, seizures, and coma in severe cases.
- Cardiovascular: Peripheral edema, shortness of breath, pulmonary edema, cardiac dysrhythmias, chest pain, and angina.
- Renal: Oliguria.
Acute Kidney Failure Complications
- Respiratory: Acute pulmonary edema/effusion, pericarditis.
- Metabolic: Muscle fatigue, uremia syndrome, leading to heart failure, myocardial infarction, seizures, and decreased level of consciousness (LOC).
- Neurological: Uremic encephalopathy.
- Renal: Permanent kidney damage, end-stage renal disease, and death.
Acute Kidney Failure Assessment and Diagnostics
- Laboratory Tests: Serum creatinine to differentiate acute from chronic kidney damage, complete blood count to identify AKI, hemolytic uremic syndrome, or thrombotic thrombocytopenic purpura, and urinalysis to determine baseline values.
- Imaging Tests: Renal ultrasonography to detect post-renal issues, tumors, hydronephrosis, BPH, and CT or MRI imaging.
- Biopsy: Used when pre-renal and post-renal causes have been ruled out and the cause of intrinsic renal injury is unclear.
Acute Kidney Failure Management
- Hospitalization is necessary to ensure adequate renal perfusion, maintain haemodynamic stability, and prevent hypovolemia.
- Maintaining arterial pressure above 65 mm Hg is crucial, and cardiac function can be optimized with positive inotropes or afterload and preload reduction.
- Address and manage electrolyte imbalances, including hyperkalemia, hyperphosphatemia, hypermagnesemia, hyponatremia, hypernatremia, and metabolic acidosis.
- Diuretics generally do not improve morbidity, mortality, or renal outcomes and should not be used unless volume overload is present.
- Renal replacement therapy (dialysis) should be considered in cases like refractory hyperkalemia, volume overload resistant to conventional therapies, uremic pericarditis, uremic encephalopathy, and intractable acidosis.
Acute Kidney Failure Prognosis
- Patients with AKI have an increased risk of developing chronic kidney disease in the future.
- They have a greater risk of end-stage renal disease and premature death.
- Consistent monitoring is vital for individuals with AKI to identify and manage developing or worsening chronic kidney disease.
Chronic Kidney Disease (CKD)
- CKD is a gradual and progressive loss of kidney function, with minimal clinical manifestations in the earlier stages.
- CKD progresses with time, eventually leading to end-stage renal disease which is fatal without dialysis or kidney transplantation.
- Management of CKD primarily aims to slow down the progression of kidney damage, primarily by controlling contributing factors like diabetes mellitus and hypertension.
Chronic Kidney Disease Stages
- Stage 1: Normal GFR: 90-120 ml/min/1.73 m2.
- Stage 2: Mildly reduced CKD: 60-89 ml/min/1.73 m2.
- Stage 3: Moderately reduced CKD: 30-59 ml/min/1.73 m2.
- Stage 4: Severely reduced CKD: 15-29 ml/min/1.73 m2.
- Stage 5: Kidney failure: GFR less than 15 ml/min/1.73 m2 or on dialysis.
Chronic Kidney Disease Etiology
- Diabetes mellitus
- Hypertension
- Glomerulonephritis
- Interstitial nephritis
- Polycystic kidney disease
- Inherited kidney diseases
- Enlarged prostate
- Kidney stones
- Cancer
- Vesicoureteral reflux
- Pyelonephritis
Chronic Kidney Disease Clinical Manifestations
- Metabolic: Nausea, vomiting, anorexia, and muscle cramps.
- Gastrointestinal: Fatigue and weakness.
- Neurological: Sleep problems, decreased mentation, seizures.
- Cardiovascular: Peripheral edema, pulmonary edema, pericarditis, and uncontrolled hypertension.
- Renal: Polyuria, oliguria, and anuria.
- Skin: Pruritis.
Chronic Kidney Disease Complications
- Cardiovascular: Right and left heart failure, cor pulmonale, and pulmonary edema.
- Electrolyte imbalances: Hyperkalemia.
- Metabolic: Anemia, osteoporosis, decreased libido, erectile dysfunction, and reduced fertility.
- Neurological: Mentation disruptions.
- Immunological: Decreased immune response.
- Pregnancy: Pregnancy complications.
- Renal: End-stage renal disease.
Chronic Kidney Disease Assessment and Diagnostics
- Laboratory Tests: Serum creatinine, complete blood count, urinalysis, and urine electrolytes.
- Imaging Tests: Renal ultrasonography, CT scan, and MRI.
- Biopsy: Used when pre-renal and post-renal causes have been ruled out and the cause of intrinsic renal injury is unclear.
Chronic Kidney Disease Management
-
Treating complications:
- Antihypertensive medications
- Diuretics
- iron supplements
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