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28 Cards in this Set
- Front
- Back
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What is the Primary Function of the Kidneys? |
1. Regulation of plasma ionic composition, volume and osmolarity 2. Regulation of acid - base composition 3. Removal of metabolic waste products & foreign substances from plasma 4. Compensation mechanism in acid-base disorders |
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What is the Main Function of the Kidneys? |
Homeostasis of cortisol and blood pressure |
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What is the Secondary Function of the Kidneys? |
1. Gluconeogenesis: Metabolic process of glucose production for catabolic reactions from non-carbohydrate precursors . Endocrine: EPO, Renin and Vitamin D3 activation |
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Summarise Urine Formation |
In the proximal tubules - many substances are reabsorbed and some are secreted The loop of henle is concerned with maintaining osmotic gradient in the renal medulla 20% of plasma is filtered into bowman's capsule |
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What % of urine is reabsorbed? |
- Over 24 hours kidneys produce 200L filtrate - Only 1% remains as urine and the rest is reabsorbed - In prox tubules 65% water is reabsorbed - In collection ducts a change in water movement is dependant on the hormones present |
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What are the Three Classifications of Renal Disease? |
1) Pre Renal: Decrease in renal functioning / perfusion caused by something affecting the kidneys blood supply 2) Post renal: Obsruction at some site of the urinary tract (kidney stones / cancer) 3) Intrinsic renal: Caused by glomerula / vascular / tubulointerstitial disorders |
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What are the Goals of Laboratory Investigation of Renal Disease? |
1) Establishing the correct diagnosis: History, physical exam and urinalysis 2) Assessing the severity: Serial monitoring of protein concentration and CK levels |
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How is Glomerula Filtration Measured? |
- Cannot be measured directly
- Estimated by measuring the rate of clearance of a substance which is freely filtered but then neither absorbed or secreted by the renal tubules e.g. Inulin and cfreatinine |
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What Compounds are Used to Measure Glomerula Filtration? |
1) Inulin: However the clearance is 125 ml/min in adults which is inconvenient for clinical practise 2) Creatinine: Used as an alternative in current practise |
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What is the equation for creatinine clearance? |
(U x V) / P ml/min Where U = Creatinine concentration in the urinie (Umol/L) P= Plasma creatinine |
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What is the normal clearance rate of creatinine? |
120 ml / min |
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What are Some Useful Indicators of Impaired Renal Functioning? |
1. Colour, Odour, Volume of Urine 2. Proteins in urine 5. Cellular material 7. Billiruben and urobilliogen |
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What is Urinalysis? |
- Performed on a fresh specimen within 30-60 minutes of voiding - the first part of analysis involves visual observation: Normal urine is clear, pale to dark yellow / amber. - Turbidity may indicate cellular material in urine or precipitation of salts at room temp |
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What is Urine Dipstick Chemical Analysis? |
- Semiquantitative method - Most effective device used to screen urine - Relies on the ability to immobilise chemical reagents on a paper strip - Detects the presence of ketones, glucose, nitrites, haem, proteins and a change in PH |
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What May the Presence of the Following Indicate in Urine: Glucose, Ketones, PH, Nitrites, Haem and Proteins? |
Glucose: Indicative of diabetes or proximal tubule damage Ketones: Ketoacidosis in diabetes mellitus PH: Alone indicative of nothing, acidic suggests UTI with urea splitting organism Nitrites: UTI Haem: Kidney injury releasing RBC Proteins |
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What is Urinary Protein? |
- 7-10 g protein filtered every hour - >98% reabsorbed in proximal tubules - < 150 mg released in urine every 24 hours - Proteins not normally found in urine, increase in proteins indicative of proteinurea 50% Tamm Horsfall protein |
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What are the Causes of Proteinurea? |
1) Glomerula: Increased permeability of the glomerula cappillary wall allows for abnormal protein filtration - larger proteins excreted in urine 2) Tubular: Low MW proteins usually reabsorbed however tubulointerstitial disease interferes with this reabsorption leading to protein excretion 3) Multiple Myeloma: Can cause proteinurea overflow |
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What Protein Found in Urine May Indicate Multiple Myeloma? |
Bence Jones Protein: - Part of the light chain of immunoglobulin - When there is an increase in the number of antibodies produced in response to cancer, there is also an increase in the presence of light chains - Bence Jones is filtered in the kidneys, however with increased levels there is some spill over into the urine |
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What is the Urine Sulfosalycyclic Test? |
- 3% sulfosalicyclic acid reagent added to clear and equal volumes of urine - Acidification causes precipitation of proteins in the sample causing increased turbidity graded on a semiquantitative scale from trace - +4 - Measure of turbidity shows increased levels of proteins -Used to detect globulin, albumin and bence-jones protein |
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Why is Microalbuminurea measured? |
- Dipstick analysis is insensitive to initial increase in glomerula permeability - By this time in DM advanced glomerula injury has already occured -Direct measurement of albumin excretion allows much earlier detection of glomerula injury - Albumin persistently >30 mg/day is indicative of neuropathy especially in diabetes - Albumin can be measured in diabetics before symptoms are present |
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Why do we use Microscopic Analysis of Urine? |
- Must be standardises
- Used to measure the number of cells per field of view - Under normal circumstances little cellular material should be present thus increase in the number of WBC, RBC, endothelial cells etc is indicative of an issue |
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What do RBC found in Urine Indicate? |
Haematourea: May be caused by glomerula damage, tumours, kindney trauma / stones, renal infections, tubular necrosis and nephrotoxins. |
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What do White Blood Cells in the Urine Indicate? |
WBC have a lobed nuclei and refractive cytoplasmic granules thus are easy to identify. When found in the urine they are indicative of infection e.g. UTI or inflammation |
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What are Epithelial Cells in the Urine Indicative of? |
Damage / tumour of the kidneys |
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How are Renal Casts Formed? |
Under low PH / high salt concentrations / decreased flow rate protein precipitation is favoured. These proteins precipitate around the tubules forming a cast. Casts are useful in diagnosis as things can get trapped in them e
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What are RBC Casts Indicative of? |
- Glomerula / tubular injury
- RBC found in casts is indicative of kidney damage |
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What are WBC Casts Indicative of? |
Infection |
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What is a Hyaline Cast Indicative of? |
In small numbers indicative of nothing, however in larger numbers they are indicative of a decreased flow rate e.g. In the case of kidney malfunction |
