UCF Professor Ferdowsi Pathophysiology 1 - Exam 4

The kidneys are responsible for:

Maintaining fluid and electrolyte homeostasis

Riding the body of water-soluble wastes

Describe the function of nephrons (functional unit)

Removal of 50% of a person's nephrons → no significant impairment of renal function

75% and 90% of the total nephrons have been damaged → serious renal impairment

What structures make up the urinary system?

Kidneys, ureters, urinary bladder, urethra

Where are the kidneys located?

Retroperitoneal space under the diaphragm

Which kidney is slightly lower than the other?

Right kidney

What external landmark is useful for locating the kidneys?

Costovertebral angle (CVA)

What enters and exits the kidney through the hilum?

Lymphatic vessels, blood vessels, and nerves

Describe the three main areas the renal parenchyma is divided into:

Pelvis: composed of urinary collecting structures (calyces)

Medulla: middle portion containing renal pyramids

Cortex: outer portion containing glomeruli and nephron tubules

Nephron

Structural and functional unit of the kidney

What are the three major functions of the nephron?

Filters water-soluble substances from blood

Reabsorbs filtered nutrients, water, electrolytes

Secretes wastes/excess substances into the filtrate

Describe the composition of the nephron:

Glomerulus: capillary tuft and Bowman capsule

Tubule: proximal convoluted tubule, Loop of Henle, distal convoluted tubule

Proximal convoluted tubule

Made up of cuboidal epithelium

Reabsorbs 2/3 of filtered water/electrolytes (passively), all of the glucose, amino acids, proteins, and vitamins

Loop of Henle

Thin descending limb: receives filtrate and delivers to ascending limb (permeable to water)

Thick ascending limb: powerful Na+, K+, and 2Cl- cotransporters (impermeable to water)

Distal convoluted tubule

Further reabsorption

Aldosterone and angiotensin II stimulate cells to reabsorb sodium and water

Atrial natriuretic peptide and urodilatin > inhibit reabsorption

Collecting duct of the nephron

Form medullary pyramids

Two cell types:

-Principal (P) cells

-Intercalated (I) cells

What determines the glomerular filtration rate (GFR)?

Filtration pressure in the glomeruli

Permeable surface of the glomerular membrane

Capillary hydrostatic pressure

Bowman capsule oncotic pressure

Plasma/capillary oncotic pressure

Bowman capsule hydrostatic pressure

What factors affect filtration pressure?

Blood volume

Pressure within Bowman capsule

Specialized mesangial cells in the glomerulus

Describe what happens to fluid when GFR increases and decreases

Increases: blood volume increases, extra fluid excreted

Decreases: blood volume decreases. fluid conserved

What controls each nephron regulating its own GFR?

Juxtaglomerular apparatus

Describe the effects of glucose and amino acids on the regulation of GFR

Increased tubular glucose and amino acids -> increased amount of sodium reabsorbed by the proximal tubule

Describe the function of specialized juxtaglomerular cells

Produce/release renin

What two routes is reabsorption and secretion accomplished by in renal tubules?

Transcellular: move substances between tubular filtrate and interstitial fluid

Paracellular: moves substrates from tight junctions that hold tubular epithelial cells together (passive)

Where is all filtered glucose normally reabsorbed?

Proximal tubule sodium-dependent cotransporter (SGLT2)

What can cause glycosuria?

Excessive tubular loads of glucose

What is the renal threshold?

Point of which glucose begins to spill into the urine

Describe the regulation of acid-base balance in the renal tubules

Kidneys excrete H+ and regulate concentration of bicarbonate

What affects the secretion of potassium?

Activity of the K+-H+ exchanger

Plasma K+ concentration

How to the kidneys regulate blood volume and osmolality?

Altering GFR

Reabsorption from the urinary filtrate

Antidiuretic hormone is also called:

Vasopressin

Antidiuretic hormone increases the permeability of the:

Collecting tubule to water leading to increased reabsorption and reduced blood osmolality

What hormones alter blood volume without affecting blood osmolality?

Aldosterone

Angiotensin II

Natriuretic peptides

Urodilatin

Uroguanylin

Guanylin

What hormones increase sodium and water reabsorption? What inhibits reabsorption?

Increase: aldosterone and angiotensin II

Inhibit: natriuretic peptides and urodilatin

Describe the function of diuretic agents

Drugs that alter the osmolality of the urinary filtrate and oppose the reabsorption of water, resulting in an increase in urine volume

What is the function of osmotic diuretics?

Increase osmolality of the filtrate causing more water to remain in the tubule, which is excreted

The kidneys secrete:

Erythropoietin: growth factor for red cells and increased release with hypoxia and decreased circulating red cell mass

What is the necessary cofactor for calcium reabsorption from the intestine?

Active vitamin D

In chronic renal failure, impaired production of what hormones result?

Erythropoietin and Vitamin D

Intrarenal disorders occur primarily within the _________ and have the potential to result in renal insufficiency or failure

Kidney

Categories of intrarenal disorders

-Congenital

-Neoplastic

-Infectious

-Obstructive

-Glomerular

What term refers to kidney and renal pain?

Nephralgia

Where is nephralgia usually felt? What would it be recorded as?

Costovertebral angle recorded as CVA tenderness (flank pain)

Pain transmitted to T10 and L1 by:

Sympathetic afferent neurons (may be felt through dermatomes)

What provides clues to intrarenal pathologies?

Dipstick

Microscopic urinalysis

Color

What would dark colored, strong-smelling urine indicate?

Decreased renal function

What would cloudy pungent urine indicate?

Infectious process

What does KUB identify?

Gross abnormalities related to size, position, and shape (may show renal calculi)

What does a renogram/renal scan show?

Renal vasculature

Tumors

Ultrasonography

Imaging of urinary tract structures using high-frequency sound waves

CT/MRI

Provides detailed info about vasculature and tissue

What are the pathologic conditions of the kidney?

Glomerulopathies

Tubular Disease

Urinary Tract Infection

Urinary Tract Obstruction

Renal Failure

Glomerular disorders are also called?

Glomerulopathies

What do glomerular disorders alter?

Glomerular capillary structure/function

Damage from glomerular disorders is mediated by?

Immune process

Inflammatory process

What factors can cause glomerular disorders?

Hereditary and environmental

-metabolic

-infectious

-hemodynamic

-toxic

-genetic

-injuries

What combinations can be seen with glomerular disorders?

Hematuria

Proteinuria

Abnormal casts

Decreased GFR

Edema

Hypertension

Primary classification of glomerular disorders

Only one kidney involved

Secondary classification of glomerular disorders

Results from other diseases, etc.

Ex: Goodpasture syndrome, Systemic lupus erythematosus, Diabetic nephropathy

Glomerular disorder classification: Diffuse

All glomeruli

Glomerular disorder classification: Focal

Some but not all glomeruli

Glomerular disorder classification: Global

Affecting all parts of the glomerulus

Glomerular disorder classification: Segmental

Only specific parts/patches of glomerulus

Glomerular disorder classification: Membranous

Thickening of glomerular capillary walls

Glomerular disorder classification: Sclerotic

Scarring

Acute Glomerulonephritis

Acute inflammation of the glomeruli

Clinical manifestations of acute glomerulonephritis

Increased blood urea nitrogen (BUN) and serum creatinine

Decreased GFR

Proteinuria -> foamy urine

RB cell casts in urine

Oliguria

Edema

Hypertension

Describe treatment and diagnosis of acute glomerulonephritis

Dietary /fluid management

Management of systemic/renal hypertension

ESRD (End Stage Renal Disease)

-dialysis

-kidney transplantation

Describe postinfectious acute glomerulonephritis

Follows skin (impetigo) and throat infections

Common in children

Smoky/coffee colored urine

Describe IgA nephropathy:

Common in adults

Hematuria presents in 1-2 days

Prognosis: variable, may progress to end-stage renal disease

What was crescentic GN previously called?

Rapidly progressive glomerulonephritis (RPGN)

What is the shape of the lesions from crescentic GN?

Crescent shaped

Describe the etiology and clinical manifestations of crescentic GN

Etiology: primary disorder, caused by acute/subacute infection, multisystem disease, drug exposure

Clinical manifestations: acute onset, hematuria, proteinuria, red cell casts, renal function decline

What is Goodpasture syndrome a combination of?

Glomerulonephritis

Alveolar hemorrhage

What are the symptoms of Goodpasture syndrome?

Hematuria

Hemoptysis

Kidney failure

Describe the pathogenesis of Nephrotic Syndrome

Increased glomerular permeability to proteins

Urinary loss 3-3.5g of protein/day

Hypoalbuminemia

Generalized edema (most common finding)

How is nephrotic syndrome treated?

Conservative symptom management

Lipid-lowering agents

Steroids

Antihypertensives

Prognosis of nephrotic syndrome

May resolve spontaneously

Progress to end-stage renal disease

Kidney failure results in retention of:

Salt and water

Urea

Metabolic acids

Acute Kidney Injury (AKI)

a.k.a. Acute Renal Failure

Sudden Reduction of kidney function causes:

Disruption in fluid/electrolyte/acid-base balances

Retention of nitrogenous waste

Increased serum creatinine

Decreased glomerular filtration rate

What is AKI characterized by?

An abrupt deterioration in renal function

Is AKI reversible?

Yes, if caught early enough

What is the time period that AKI occurs over?

Hours to weeks

How is renal function monitored in AKI?

Serum creatinine

Creatinine clearance

What are risk factors for AKI?

Aging

Associated comorbidities

Insults to the kidney

Describe the three sites of disruption for AKI

Renal perfusion

Urine flow distal to the kidney

Circumstances within the kidney

(Distinction between the sites helps determine appropriate therapy)

What conditions diminish perfusion of the kidney?

Prerenal kidney injury

What is prerenal kidney injury characterized by?

Low GFR

Oliguria

High urine specific gravity, and osmolality

Prolonged prerenal ARF ->

Leads to acute tubular necrosis (intrinsic)

What does obstruction of normal outflow of urine from kidneys lead to?

Increased pressure in Bowman capsule

Decreased GRF

What are the clinical findings of postrenal kidney injury based on?

Duration of the obstruction of normal outflow of urine from kidneys

Intrinsic/intrarenal kidney injury

Primary dysfunction of the nephrons and the kidney

Etiology of intrinsic/intrarenal kidney injury

Renal tubules

Glomerular

Vascular

Interstitial

Pathophysiologic processes of AKI

Vascular: renal blood flow decreased (hypoxia, vasoconstriction)

Tubular: inflammation and reperfusion injury (causes casts)

What occurs if the acute kidney injury is sustained?

Leads to end-stage renal disease (ESRD)

Prodromal phase

Time of mild signs or symptoms

Oliguric phase

-Urine output decreases

-UO of 100-400 mL/24 hours

-This client is in fluid volume excess

-The potassium will be increased!

Postoliguric phase

-fluid volume deficit

-labs begin to normalize

What other comorbidities are linked to chronic kidney disease?

Hypertension

Diabetes Mellitus

Chronic kidney disease is the result of ________ and _______ loss of nephrons

Progressive and irreversible

What is the final outcome of chronic kidney disease?

End-Stage Renal Disease