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05 > Renal Physiology > Flashcards

Renal Physiology Flashcards

1
Q

Function of kidneys

A
  • filter blood
  • excrete unwanted waste products (e.g. toxins an metabolic wastes)
  • regulate fluid and electrolyte balance
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2
Q

Urinary System Anatomy

A
  • kidneys
  • ureter - urine transport - kidney to bladder
  • urinary bladder - storage of urin
  • urethra - urine from bladder to external
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3
Q

Renal Anatomy

A
  • located in posterior abdominal wall
  • surrounded by fat around renal capsule
  • right kidney lower then left
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4
Q

Renal blood flow

A

Kidneys filters all contents of blood except protein molecules

Filtration of plasma per unit of time is known as the glomerular filtration rate

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5
Q

Components of the Nephron

A

Glomerulus
- collection of capillaries, with an associated tubule - site of filtration from arterial blood

Bowman’s capsule

  • cup-shaped end of renal tubule that completely surrounds glomerulus
  • recieves fluid from glomerulus

Proximal convoluted tubule

  • recieves fluid from the bowman’s capsule
  • large cuboidal cells with numerous microvilli

Loop of Henle

  • Hairpain-shaped loop of renal tube
  • recovery of water and sodium chloride from urine
  • descending and ascending portion

Distal convoluted tubule

  • cuboidal cells without microvilli - secretion
  • involved with sodium, potassium, and divalent cation homeostasis
  • highly coiled and surrounded by capillaries

Collecting tubule

  • Distal portion of distal convoluted tubule
  • moves it into the renal pelvis and ureters
  • Contiguous with renal pelvis and ureter via collecting duct
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6
Q

Types of Nephrons

A
  • Cortical nephrons - 85% of nephrons; located in the cortex

Juxtamedullary nephrons

  • located at the cortex-medulla junction
  • have loops of henle that deeply invade the meddulla
  • have extensive thin segments
  • are involved in the production of concentrated urine
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7
Q

Urine formation

A

involves 3 major process

  • glomerular filtration
  • tubular reabsorption
  • secretion
  • Blood enters the nephron from the glomerulus via the afferent arteriole arising from the renal artery
  • Glucose, amino acids, Na, Ca, K, Cl are reabsorbed and H2O osmotically in proximal tubule
  • Loop of Henle, distal tubules and collecting ducts, H2O is reabsorbed and solute diffuses out
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8
Q

Urine

A

Urine is 95% water and 5% solutes

  • nitrogenous wastes: urea, uric acid and creatinine
  • solutes include: calcium, magnesium and bicardonate ions

Abnormally high concentrations of any urinary constituents may indicate pathology

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9
Q

Colour, transparency, odour, pH and specific gravity of urine

A
  • clear, pale to deep yellow
  • concentrated urine has a deeper yellow colour
  • drugs, vitamins supplements, and diet can change colour of urine
  • cloudy urine may indicate UTI

Fresh urine is sloghtly aromatic

  • standing urine develops an ammonia odour
  • some drugs and vegetables alter the usual colour

Slightly acidic with range of 4.5 to 8
- diet can altered urine pH

Specific gravity

  • ranges from 1.001 to 1.035
  • dependent on solute concentration
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10
Q

Glucose in urine

A

Glycosuria

  • diabetes mellitus,
  • glomerulonephritis
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11
Q

Proteins in urine

A

proteinuria

  • heart failure, HTN, renal disease
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12
Q

Ketone bodies in urine

A

ketonuria

  • starvation
  • ketoacidosis
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13
Q

Haemoglobin in urine

A

Haemoglobinuria

  • burns, haemolytic anaemia

Pyelonephritis, crash injuries- blood

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14
Q

Bile pigments in urine

A

Bilirubinuria

  • hepatitis, cirrhosis
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15
Q

Erythrocytes

A

Haematuria

  • bleeding due to trauma, kidney stones
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16
Q

Leukocytes

A

Pyuria

  • UTI
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17
Q

Glomerular Filtration Rate

A
  • describes the flow rate of filtered fluid through the kidney per minute
  • creatinine clearance rate helps estimate GFR

Changes in GFR normally result from changes in glomerular BP

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18
Q

Mechanisms that control GFR

A
  • Renal autoregulation (intrinsic system)
    Autoregulation entails two types of control
  • myogenic - responds to changes in pressure in the renal blood vessels
  • flow-dependent feedback - sense changes in the juxtaglomerular apparatus
  • Neural
  • Hormonal mechanism
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19
Q

Creatinine Clearance

A
  • Creatinine is a product of metabolism of creatine and phosphocreatine in skeletal muscle
  • marker of GFR

Reduced CC is an indicator of reduced GFR

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20
Q

Acute vs Chronic Kidney Failure

A

Acute

  • rapid loss of renal function over hours to days
  • failure to regulate fluid, electrolyte and acid-base balance
  • increase in nitrogenous products in blood
  • reversible if underlying cause is treated promptly

Chronic:
- typically refers to GFR status
-

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21
Q

Acute renal failure

A

Defined as a sudden, rapid decline in renal filtration function

clinical indicators:

  • rise in serum creatinine concentration
  • Azotemia (rise in BUN concentration)
  • Disturbances in ECF, electrolyte and acid/base homeostasis
  • Oliguria is a common finding but is not always present
  • May be asymptomatic
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22
Q

Classification of Causes of ARF

A

prerenal ARF - problems with blood supply

Intrinsic - damage to kidney

Postrenal - obstruction in the urinary tract

23
Q

Major causes of prerenal ARF

A

Hypovolaemia e.g. haemorrhage, vomiting

Low CO e.g. pulmonary HTN, disease of the myocardium

Alterations in renal system vascular resistance ratio e.g. renal vasoconstriction

Renal hypoperfusion e.g. ACE inhibitors

Hyperviscosisty syndrome e.f. polycythemia

24
Q

Clinical signs of Prerenal ARF

A
  • Thirst
  • Tachycardia
  • Orthostatic Dizziness
  • Reduced JVP
  • Reduced auxillary sweating
  • Dry mucous membrane
25
Q

Major causes of intrinsic ARF

A

Rena-vascular obstruction e.g. atherosclerosis plaque

Diseases of the glomeruli e.g. glomerulo nephritis

Acute tubular necrosis e.g. ischaemia

Interstitial nephritis e.g. NSIADS, lymphoma

26
Q

Clinical signs of Intrinsic ARF

A
  • Ischaemic and nephritic causes constitute 90% of causes
  • signs are related to the complications associated with renal failure
  • fever, joint pain, flank pain, headache, dizziness, confusion, oliguria, oedema, HTN, HF
27
Q

Major causes of Post Renal ARF

A
  • Obstruction

Examples include:

  • calculi
  • cancer causing obstruction
  • prostatic hypertrophy
  • stricture of the urethra
28
Q

Clinical signs of post renal ARF

A

Suprapubic, Colicky and flank pain

pain over bladder

29
Q

Indicators of ARF

A
  • Intravascular volume overload due to failure of kidney function causing excess fluid in the body
  • Metabolic acidosis as kidney are unable to excess acids
  • hyperkalaemia/phosphatemia
  • anaemia has kidney failure causes decreased production of erythropoietin
30
Q

Complications of ARF

A
  • impairs renal excretion of sodium, potassium and water
  • disturbs cation homeostasis and urinary acidification mechanisms
  • pulmonary oedema due to fluid overload
  • cerebral oedema
  • neurologic abnormalities including seizures
31
Q

Chronic Kidney Disease

A
  • progressive loss of kidney function

Caused by diabetes, HTN, glomerulonephritis

32
Q

Pathophysiology of CRF

A
  • kidneys attempt to compensate for renal damage by hyperfiltration
  • hyperfiltration causes further loss of function
  • chronic loss of function causes generalised wasting and progressive scarring within all parts of the kidneys
  • CRF may not be identified unitl over 70% of the normal combined function of both kidneys is lost
33
Q

Causes of CRF

A
  • Determining the cause of CRF can be difficult

- Most common causes are HTN and diabetes

34
Q

Pre renal CRF

A
  • Poor cardiac function
  • chronic liver failure
  • atherosclerosis of renal arteries
35
Q

Intrinsic renal CRF

A
  • chronic renal failure caused by changes within the kidneys

examples include:

  • diabetic nephropathy
  • chronic glomerular nephritis
  • vasculitis - inflammation of blood vessels
  • polycystic kidney disease
36
Q

Post renal CRF

A
  • obstruction can cause urinary backflow and put pressure on the kidneys

Examples include:

  • kidney stones
  • bladder outlet obstruction
  • retroperitoneal fibrosis
37
Q

Treatment of CRF

A
  • control HTN
  • restrict dietary protein - reduce amino acids
  • manage anaemia

Renal replacement therapy

  • haemodialysis
  • peritoneal dialysis
  • kidney transplant
38
Q

Define the term: urinary tract obstruction.

A

urinary tract obstruction is defined as a blockage of the passage of urine

it can occur at any site along the urinary tract

39
Q

How is the severity of obstructive uropathy classified?

A

it is determined by examining the located of the obstruction, whether the obstruction affects on or both kidneys, the completeness of the blockage, how long the blockage has existed and nature of the obstruction

40
Q

Describe common causes of upper urinary tract obstruction.

A
  • narrowing of a ureter or the urethra
  • compression due to either a congenital defect or physical compression from a blood vessel, scarring, tumour or abdominal inflammation
  • renal calculi
41
Q

What short term effects would this obstruction have on the kidney?

A

depends on the size of obstruction

  • Dilation of the ureter - urine backs up - occurs at the site of the blockage
  • within 14 days, the obstruction will have affects both the proximal and distal part of the nephron
  • in 28 days, backflow of urine will lead to the glomeruli becoming damaged and consequently the renal cortex and medulla will decrease in size
  • total obstruction leads to damage to the renal tubule in 4 hours and is irreversible if not corrected with 4 weeks
42
Q

What effect would an obstruction have on fluid and electrolyte
balance?

A

backflow of urine into the tubules changes pressure gradient and reduces GFR

less blood enters the tubule as filtrate and is retained in the circulation

retention of Na and fluid = increased BP and oedema

Retention of potassium = hyperkalaemia - can affect cardiac function

Retention of H = metabolic acidosis

43
Q

What are kidney stones (renal calculi)?

A

formed in the kidney
- collection of crystals (are calcium oxalate or calcium phosphate), struvite (minerals buildup caused by bacteria) or uric acid

44
Q

What symptoms will a patient with kidney stones exhibit?

A
  • severe pain originating in the flank region and radiating to the groin
  • patient may also experience nausea and vomiting
  • microscopic examination of urine may show the presence of haematuria
45
Q

Describe common causes of lower urinary obstruction.

A

associated with problems of urinary storage in the bladder or problems of urine emptying out of the bladder

result of neurogenic or anatomical alteration

incontinence is the most common symptom observed in these patients

46
Q

Briefly describe the types of urinary tract infections.

A

acute cystitis - infection of the urinary bladder

acute pyelonephritis - infection of the renal pelvis and interstitium

chronic pyelonephritis - persistant infection that leads to scarring of the kidney

47
Q

Compare and contrast acute and chronic glomerulonephritis

A

Acute - inflammation within the glomerulus. the inflammation is often the result of immune reactions following a streptococcal infection

Chronic - inflammation of the glomerulus. however, it is usually due to alterations/diseases, which cause progressive deterioration of glomerular function leading to loss of total renal function

48
Q

What is acute kidney injury and what is the RIFLE staging system?

A

AKI - sudden decline in kidney function and leads to disorders of acid/base, electrolyte and fluid balance

Due to disparity in the literature as to the precise definition of AKI a staging system was required and RIFLE system was developed: Risk - Injury - Failure - Loss of kidney function - End stage renal failure

  • it may be caused by many things including, but not limited to hypovolaemia, acute tubular necrosis, obstructive uropathies
  • clinical progressive of AKI has 3 phases - oliguria, diuresis, recovery
49
Q

Define Acute tubular necrosis

A

death of tubular cells

may result fromL

  • lack of O2
  • exposure to toxic drugs or molecules
50
Q

Why is dialysis often required in acute tubular necrosis?

A

Dialysis is required as waste products can no longer be excreted effectively and electrolyte and fluid reabsorption/excretion is affected

Unlike pre renal ACF, ATN does not improve rapidly after administration of large volume IV fluids because kidneys have lost their ability to handle fluids, therefore administration of fluid can lead to a potential fluid overload

51
Q

What are the clinical manifestations of CKD?

A

accumulation of nitrogenous waste from protein metabolism and toxins in the bloodstream

  • rise in serum creatinine and decreased creatinine clearance rates
  • Na and fluid retention - oedema and HTN
  • if body cant get rid of excess fluid this can lead to hyponatremia
  • hyperkalaemia
  • alterations in Ca and PO4 metabolism leading to hypocalcaemia. renal phsophate excretion decreases which leads to phosphate binding to calcium thus further perpetuating hypocalcaemia
52
Q

Describe the five stages and treatment of chronic kidney disease

A

stage 1 - kidney has the ability to compensate for reduction in nephron function. therefore the patient with stage 1 CKF may not be identified initially, they have a normal GFR (>90mL/min). at this point the BP should be measured, level of proteinuria determined and urinalysis conducts

Stage 2 - patient will exhibit mild kidney damage and will have a mild reduction in GFR (60-89ml/min). urinalysis should be conducted

Stage 3 - moderate kidney damage with a GFR (30-59ml/min), GFR should be monitored every 3 months. nephrotoxins should be avoided and ACE inhibitors may be required

Stage 4 - severe kidney damage with GFR of 15-29ml/min. need treatment from renal specialist and start treatment both physical and psychological to prepare for dialysis and transplant

Stage 5 - end stage kidney disease with GFR < 15ml/min. patient need dialysis and transplant. K and protein need to be carefully monitored

53
Q

Haemodialysis

A

procedure that cleans and filters patient blood, it removes nitrogenous waste, extra salt and fluid and also helps maintain BP and the right balance of K, Na, and Cl

access to the blood stream is provided via a fistula

54
Q

What electrolyte inbalances may occur as a result of kidney disease?

A

Hyperkalaemia - kidney cannot excrete potassium - leads to abdominal cramping, muscle weakness, paralysis and cardiac arrest

Hypernatremia - kidney cannot excrete Na - leads to HTN, muscle weakness and disorientation

Hypermagnesaemia - leads to a decrease in BP, HR, coma and cardiac arrest

Hypercalcaemia - leads to muscle spasms, abnormal heart rhythms

05 (20 decks)

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