Kidney + Urinary Tract Flashcards
Kidney Functions
- Elimination
- Metabolic waste
- Drugs & toxins - Homeostasis
- Electrolytes, water, pH, blood pressure (renin)
- Bone metabolism
— Vit. D activation
— Ca+2 and PO4
- Bone marrow RBC production (erythropoietin)
Kidney Gross Anatomy
The two kidneys are located in the posterior wall of the abdomen at the level of the 11th and 12th ribs and are wrapped by a protective layer of fat.
The kidney can be divided into the renal cortex (outer region, where most of filtration is) and the medulla (inner region).
The renal columns are connective tissue extensions that radiate downward from the cortex through the medulla to separate the most characteristic features of the medulla: the renal pyramids and renal papillae.
The papillae are bundles of collecting ducts that transport urine made by nephrons to the calyces of the kidney for excretion. The pyramids and renal columns taken together constitute the kidney lobes.
Glomeruli
Nephrons are the “functional units” of the kidney; they cleanse the blood and balance the constituents of the circulation.
The afferent arterioles form high-pressure capillaries called the glomeruli.
The rest of the nephron consists of a tubule whose proximal end surrounds the glomerulus—this is Bowman’s capsule.
The glomerulus and Bowman’s capsule together form the renal corpuscle.
- These glomerular capillaries filter the blood based on particle size.
After passing through the renal corpuscle, the capillaries form a second arteriole, the efferent arteriole.
Filteration of the Bowmans Capsule
One layer of the Bowman’s capsule is composed of uniquely shaped cells (podocytes) with extending finger-like arms to cover the glomerular capillaries. These projections interdigitate to form filtration slits, leaving small gaps between the digits to form a sieve. As blood passes through the glomerulus the plasma filters between these sieve-like fingers to be captured by Bowman’s capsule.
Overall, filtration is regulated by fenestrations in capillary endothelial cells, podocytes with filtration slits, and the basement membrane between capillary cells.
Filtration has:
- endothelial lining with fenestrations
- then, a protein meshwork called glomerular basement membrane. The fluid needs to get through this. It acts as a filter, and has a negative charge. So it is a physical and charge barrier
- then, there are epithelial podocytes with filtration slits
there is protein meshwork between the podocytes too
Structure of the Nephron
After leaving the renal corpuscle, the filtrate passes through the renal tubule in the following order: proximal convoluted tubule (found in the renal cortex), loop of Henle (mostly in the medulla), distal convoluted tubule (found in the renal cortex), collecting tubule (in the medulla), collecting duct (in the medulla).
Function of renal corpuscle
Production of filtrate
Squamous cells
Function of proximal convoluted tubule
Reabsorption of water, ions, and all organic nutrients
Cuboidal cells with abundant microvilli
And mitochondria
Function of distal convoluted tubule
Secretion of ions, acids, drugs, toxins
Variable reabsorption of water, sodium ions, and calcium ions (under hormonal control)
cuboidal cells with few microvilli
Function of nephron loop
Descending thin limb
- further reabsorption of water
- squamous cells
Thick ascending limb
- reabsorption of sodium and chloride ions
- low cuboidal cells
Ascending thin limb
- squamous cells
Function of collecting duct
Variable reabsorption of water and reabsorption or secretion of sodium, potassium, hydrogen, and bicarbonate ions
Function of papillary duct
Delivery of urine to minor calyx
Acute Kidney Injury
- Pre-Renal
- decrease blood flow quickly before the blood goes to kidney
- Shock, dehydration, hemorrhage, trauma, etc.
- often related to the heart and the low cardiac output. - Renal
- directly damages kidney
- Inflammation, infection, ischemia
- Drugs and toxins - Post-Renal
- Acute urinary tract obstruction
- impacts the collecting system
Chronic Kidney Injury
- Pre-Renal
- Hypertension, diabetes - Renal
- Primary glomerulopathies
- Chronic tubulointerstitial diseases - Post-Renal
- Chronic urinary tract obstruction
Acute vs chronic kidney injury
Acute kidney injury
*Acute onset of symptoms
*Potentially reversible
*if treated early enough the damage is not permanent
Chronic kidney injury
*Often asymptomatic at first
*Slowly progressive and irreversible damage
*Loss of glomeruli, chronic inflammation, scarring
Consequences of Kidney Injury
- Loss of water regulation - Edema, often exacerbated by protein loss in the urine.
- Electrolyte disturbances - minerals lost Na+, K+ , Ca2+, PO4
- Lower Blood pH - Acidosis
- Increased Waste products
- Anemia - due to loss of vitamin D.
- Lower bone density- due to loss of vitamin D.
Management of Chronic Renal Failure
- Medication
- Dialysis
- Transplant
Glomerular Diseases
- Primary glomerulopathy:
- Affect kidney primarily or exclusively - Secondary glomerulopathy:
- Systemic diseases that affect multiple organs
- E.g. diabetes, systemic lupus, vasculitis
Glomeruli diseases are associated with several complications
Majority are immune mediated
- Immune Mechanisms underlie Most types of primary glomerular diseases and many of the secondary glomerular diseases. (ex. Poststreptococcal glomerulopathy)
Most damage the glomerular filter in some way
- The deposition of circulating immune complexes in the glomerulus initiates complement and/or Fc receptor-mediated leukocyte activation resulting in glomerular injury.
Investigations for renal disease
Urinalysis:
- Hematuria (blood in urine)
- Proteinuria (protein in urine)
Blood:
- Increased Creatinine and urea (impaired waste elimination)
Kidney biopsy:
- Needed for definitive diagnosis
- Use light microscopy, immunofluorescence and electron microscopy
Kidney biopsy results
Light Microscopy:
* Inflamed, causes more cells than usual
*Thickened matrix, obscured capillaries
* more pink
Immunofluorescence
*Immune complex deposition (IgA)
* can check for diff immune complexes
Electron Microscopy
*Abnormal proteinaceous deposits in the glomerulus
Tubular Diseases
The proximal tubular epithelium is quite sensitive
- it works hard to resorb certain substances and get rid of some substances
- it is sensitive to ischemic insult and toxic insult. you may get death of the tubular epithelium or it may get patchy and parts of it becomes lost
Acute Tubular Necrosis (ATN): Acute tubular injury (ATI/ATN) is a clinicopathologic entity characterized by damage to tubular epithelial cells and an acute decline in renal function.
- ATN is potentially reversible
- Ischemic injury (decreased blood flow to kidney)
Caused by:
- Low cardiac output (heart failure)
- Low blood volume (hemorrhage)
- Vasodilation (sepsis, anaphylaxis) - Nephrotoxic injury
- Exogenous (drugs, toxins)
- Endogenous (muscle injury, transfusion reaction)
Consequences of acute kidney injury, specifically acute tubular necrosis:
- things get clogged up, there is sloughing of dead ep cells
- that causes low urine output (called oliguria)
- thus, there is buildup of back pressure because you are not filtering nor excreting your waste products; this causes high pressure
- there is also decreased blood pH (called metabolic acidosis)
- messing up electrolyte balance (hyperkalemia - increased potassium)
- azotemia is nitrogen containing blood
Kidney Cyst
Cystic diseases of the kidney are a heterogeneous group comprising hereditary, developmental, and acquired disorders.
Acquired
- Simple
- End-stage failure
Genetic
- Polycystic kidney diseases
Neoplastic
- Renal carcinoma variant
Developmental
- Congenital syndromes
Pathogenesis of Kidney Cysts
Altered growth and differentiation of tubular epithelium.
Then there is fluid secretion
And the fluid builds up in the cyst
Acquired Simple Cyst
Simple cysts are generally innocuous lesions that occur as multiple or single cystic spaces of variable size.
Simple cysts are a common postmortem finding that has no clinical significance.
