Kidney Function, Regulation, and Disease

• The kidneys filter blood, excreting waste such as urea, creatinine, uric acid, and ammonia in urine.
• Electrolyte and acid-base balance and blood pressure are regulated.
• Drug, hormone, and calcium metabolism occur.
• Vitamin D and erythropoietin are secreted.
• Glucose homeostasis and the formation of red blood cells occur.

Epidemiology

• Hypertension and diabetes significantly increase kidney disease risk.
• African Americans have the highest kidney disease incidence and risk.

Basic Concepts of Normal Renal Function

• The kidneys receive 20-25% of cardiac output (5L or 5000 ml/min).
• Approximately 1000-1300 ml of blood is filtered each minute.
• Glomerular filtration rate (GFR) indicates the amount of renal blood filtered per unit of time and kidney function.
• Renal blood is filtered per unit of time.
• Renal perfusion directly impacts GFR; adequate blood flow indicates good kidney function.
• Decreased renal perfusion equates to a decreased GFR and potential dysfunction.
• A normal GFR level is 90-120 ml.
• Aging decreases GFR, potentially leading to the accumulation of excreted substances if kidney function diminishes.
• Blood pressure medicine can accumulate with poor kidney function in the elderly.

Nephron and Excretory Functions

• The nephron is the basic functional unit of the kidney.
• The nephron processes filtered fluid.
• Urine is the end product.
• Glomerular capillaries are specialized capillaries.
• Glomerular capillaries require high hydrostatic pressure to facilitate the blood filtration process.
• The filtrate moves into Bowman's capsule, the initial nephron portion.

Urine Formation

• Things that shouldn't be in urine include sugar, albumin, high potassium.
• Urine formation processes can be tested by doing a urinalysis
• Proximal tubule reabsorbs 60% of water from the filtrate and large amounts of Na+ and K+.
• The loop of Henle controls urine concentration and secretes urea.
• One-fourth of Na+, K+, Cl-, and HCO3 in the filtrate is reabsorbed, along with a small amount of water.
• The distal convoluted tubule is water impermeable.
• Under the influence of aldosterone, RAAS system, absorbs water and sodium.

Understanding Kidney Functions

• Acid-base balance is maintained by excreting and reabsorbing H+ and HCO3 as needed.
• It takes 48-72 hours for the kidneys to begin balancing pH; longer than the lungs.
• Urea, uric acid, creatinine (Cr), and drug metabolites are eliminated as waste.
• Waste that is not excreted becomes toxic.
• The kidneys activate vitamin D; important for calcium absorption.
• The kidneys maintain glucose homeostasis.
• If the renal threshold to reabsorb glucose is exceeded (BG of 180 mg/dL), glucose will leave in the urine, smelling sweet.
• Gluconeogenesis is the making of new glucose/sugar, where the kidneys create glucose from amino acids while responsible for breaking down insulin to regulate blood sugar.
• Kidneys can use this when kidneys are failing
• Kidneys use glucose is kidney failure
• At high risk for kidney injury are patients with defective or low/high function.

Renin-Angiotensin-Aldosterone System (RAAS)

• RAAS contributes to Na+ and water reabsorption in the bloodstream and K+ excretion in renal tubules.
• Renin is secreted from juxtaglomerular cells.
• Renin regulates blood pressure and is released by the kidney in response to decreased blood pressure or volume.
• Renin enters the bloodstream and converts angiotensinogen to angiotensin I.
• Angiotensin I travels to the lung's small blood vessels, where enzymes convert it to angiotensin II.
• Angiotensin II is a potent vasoconstrictor and decreases salt and water excretion.

Consequences of Kidney Dysfunction

• Insufficient filtration results in waste product buildup such as urea/nitrogen leading to a GFR.
• The GFR is up.
• Hemolytic anemia may result from Toxin buildup leading to destruction of blood cells
• Urine is not concentrated.
• Hemolytic anemia is a sign and symptom.
• Confusion, stupor, and encephalopathy may be occur neurologically.
• Excess renin raises blood pressure by activating the sympathetic nervous system.
• Decreased erythropoietin decreases red blood cell production, leading to low oxygen.
• Acid-base balance is not maintained.
• Excess K+ is not secreted.
• Decreased vitamin D and calcium absorption cause renal osteodystrophy.

Etiology of Kidney Dysfunction

• Decreased blood flow and perfusion to the kidneys due to heart failure, cardiac arrest, or hemorrhage can cause Prerenal dysfunction.
• Intrarenal dysfunction is caused by injury, autoimmune diseases such as lupus, or untreated hypertension or uncontrolled diabetes.
• Postrenal dysfunction is when kidney stones, bladder dysfunction, or prostate enlargement obstruct urine flow.
• Acute Tubular Necrosis occurs when no O2 perfusion occurs, thus something starts to die and occurs due to hypozia.

Tests of Renal Function and Diagnosis

• Glomerular Filtration Rate (GFR) should be 90-120 mL/min in a healthy young adult.
• The GFR provides an estimate of properly functioning renal tissue because of directly related renal perfusion.
• Serum Creatinine (Cr) range is 0.5-1.5 mg/dL
• Creatinine is a by-product of creatine metabolism and is filtered by glomerulus without reabsorption.
• Cr reflects the GFR and can be used to estimate kidney function.
• The released amount of creatine reflects function.
• BUN range is 5-20 mg/dL
• BUN is not a very good estimate of kidney function alone, but the BUN ratio tool is a more useful one
• Dehydration can increase blood urea nitrogen (BUN) in the blood/serum.
• Urea is formed in the liver as a byproduct of protein metabolism and is completely eliminated in the kidneys.
• elevated levels indicate albumin and increased protein intake or GI bleed and can inhibit kidney function
• Creatinine Clearance measures blood and urine Cr and 24-hour urine volume.
• Decreased Cr Clearance can indicate less blood is filtered per minute.

Urinalysis

• The normal amount of urine produced daily is 1.5 L.
• A normal urinalysis would be odorless, clear or yellow to amber.
• There should be no glucose in urine.
• Protein, ketones, and blood should not be present
• No bilirubin, nitrates, or leukocyte esterase should be present
• None to very few red blood cells and white blood cells should be detected

Acute Glomerulonephritis

• Acute glomerulonephritis (AGN) is inflammation of the glomerulus, which filters the blood
• Incidence is higher in young (5-15 y.o.) males.
• Onset is sudden
• AGN is most commonly caused by post-streptococcal infection (sexual activity), particularly by group A beta strep.
• Damaged glomeruli capillary walls become impermeable causing large loss of RBC and small loss of albumin.
• Urine output is low due to not filtering properly and urine color is impacted with decrease in GFR.
• Hypertension and edema occur due to the body getting into blood.

Nephrotic Syndrome

• Glomerular damage results in massive proteinuria and edema.
• In many cases diabetes can be a culprit in this syndrome
• African Americans, Native Americans, and Latinos are at a higher risk.
• Proteins are escaping membrane which causes urine to leave, more so then blood.
• Decrease in colloidal pressure because proteins (albumin) go in blood.
• Massive proteinuria, lipiduria, hypoalbuminemia, and hyperlipidemia are findings.

Glomerular Injury

• Systemic diseases that cause glomerular injury include lupus and diabetic nephropathy.
• Lupus may require renal biopsy, testing for hematuria, or proteinuria
• Discussing the relationship of these diseases and their effect on the kidneys, patients may develop microalbuminuria due to the high levels of Glucose, that push albumin into and out of the cell.

Patho Pit Stop

• Massive protein urinary, hyperlipidemia, edema, and hypoalbuminemia are features of nephrotic syndrome.
• Glomerulonephritis is typically acute and due to inflammation, whereas nephrotic syndrome results from glomerular damage that is chronic or autoimmune.

Nephrolithiasis

• Factors increasing kidney stone risk include a supersaturated urine, intestinal absorption issues, calcium, and endocrine imbalances.
• Calcium stones are the most common type
• Struvite stones are related to high levels of calcium and are associated with a UTI
• High purine foods like shrimp, turkey, and sausage can form Uric Acid.

Nephrolithiasis (Renal Calculi) Manifestations

• Manifestations may include colicky and pain in flank.
• Other symptoms may include cool skin, nausea and vomiting
• Diagnostic tests includes. Urinalysis, and Ultrasound
• Non-contrast CT, contrast CT, or enlarged Kidney.

Mechanisms of Renal Damage

• The two most damaging effects of urinary obstruction are static Urine and Hydroephorois
• Static urine builds up and it not being filtered out can cause infections, and kidney stone formation
• Hydronephrosis is when Kidney will swell and have irreversible damage and failure
• Hydronephrosis is when there is a build up outside the Pelvis of the Kidney, causing damage

Pyelonephritis Manifestations

• Acute pyelonephritis often results from infection of renal tubules.
• Common symptoms and UTI
• Pyuria, back pain, fever, chills
• Risk Factors include, not peeing, nursing interventions, foley
• Chronic pyelonephritis can occur from reoccuring UTI's

Neoplasms

• Wilms tumor is a rare embryonal tumor of the kidney, more common in Children, and may show a sign where the baby does not utrine a lot
• Diagnostic tests include Ultrasound
• Renal cell carcinoma- in older males (50-84) are at risk and and bleeding are sings.
• Masses can lead to development

Acute Kidney Injury

• Abrupt injury or decline of the kidney, no normal kidney Functions
• Can be reversed properly and promptly
• Prerenal causes trauma to the heart/ischemic
• Intracranial cause is caused by inflammation or tubular structure issue caused by glomerulonephritis and or pyelonephritis.
• The outside bladder can get effected due to the tumors.

Pre-renal

• Factors that make it diffecult include, cardiac arrest, or a hemorrhage
• In that sense you have cardiac and GFR
• Cardiac arrest, or hemorrhage make it a lot more diffecult to maintain.
• Factors effecting include lower flow and high blood pressure, but it also effects GFR (Glomerular Refiltration Rate).

Intrarenal

• Glomerulonephritis, and Pylonephritis can cause major damage, thus leading to tubular issue
• Acute Tubular necrosis Can occur
• The is tubular injury be can revesable.
• Risk Factors include major surgery and lower function of function.
• Rhabdomyolysis is rapid destruction of skeletal muscle protein.

Acute Tubular Necrosis

• Acute Tubular
• Assessment can be done in nephron,
• If tubules, and GFR decreased then substances are effected, and need more urine is effected
• Issue or problem is with overall vascular volume.

Postrenal

• An acute kidney injury can happen after the Kidney does everything else
• Some reasons why it happens include stones.
• Man with benign prostate hyperplasia

Chronic Kidney Disease

• Results in a gradual loss of functions due to not having enough Nephrons leading to renal Failures
• Decline occurs over a long period of time.
• You get usually no symptoms
• A reduction in GFR because kidney can get reduced.

Diagnostic

• Check for micro Albuin

Classification include

• There can be stages but the stage is to show how to treat it.
• At 4th and 5th stage of having it they cannot reverse