Urine as an Indicator of Disease Flashcards
What are the 3 aspects of urine that you can investigate?
gross appearance
microscopy
biochemistry
What are the advantages of urine analysis?
- non-invasive diagnosis
- easily obtained - feasible in local GP practice
- normal composition normally know
- for pre-renal or renal disease
- changes in levels of what should be present or appearance of material that should be ‘absent’
What are the normal levels of the following substances in the urine?
- uric acid
- bicarbonate ions
- creatinine
- potassium ions
- sodium ions
- chloride ions
- ureas
- uric acid = 0.6g
- bicarbonate ions = 1.2g
- creatinine = 3.2g
- potassium ions = 3.2g
- sodium ions = 4.1g
- chloride ions = 6.6g
- ureas = 25g
Why is a 24h urine sample the most useful?
most representative as levels of substances change over the course of a day
Describe appropriate collection of urine
- clean/sterile container
- random samples, clean catch midstream specimen
- timing depends on test required
- test as soon as possible
- 24 hour specimen, with empty bladder at hour 0
What is a typical volume of urine in 24 hours?
0.8-2L
What should the gross appearance of urine be?
- pale yellow and clear
Blood in different sections of urine indication blood from where
early = urethra throughout = bladder end = prostate
What is pseudohaematuria caused by?
- free Hb, myoglobin, porphoryins, drugs
What does red/brown urine indicate?
- conjugated bilrubin
What does black urine indicate?
- melanin e..g in disseminated melanoma
What does foamy urine indicate?
proteinuria
What does cloudy urine indicate?
- protein, oxalates, cells, phosphates, platelets
Why does normal urine darken on standing?
completion of oxidation
What does dramatic darkening on standing indicate?
- haematuria in case of sever P.falciparum malaria
What four things can be found on microscopic examination and how?
Centifuge urine sampel, examine sediment for:
- bacteria
- cells
- casts
- crystals
How many RBC’s and WBC’s are normal in the urine?
RBC >1 is abnormal
WBC >10 is abnormal
What do casts indicate?
What do redcell casts indicate?
Casts e.g. hyaline. composed for primary mucoprotein secreted by tubules or fine granular
- normal finding post exercise
- larger coarse casts are abnormal
- red cell cast = kidney damage
What 4 kinds of crystals can be present in urine?
- oxalate crustals
- crusting
- triple phosphate
- amorphous crystals
What is a normal pH range for urine?
4.5-8
What factors in diet lead to acidic urine?
What factors in diet lead to alkaline urine?
acidic = meat alkaline = citrus fruit and veg
What diseases cause extremely acidic urine?
- uncontrolled diabetes, starvation, respiratory disorders
What diseases cause extremely alkaline urine?
- UT obstruciton, some repistoraty disorders e.g. alkalosis
What can cause variation in excreted creatinine?
- increased = excessive meat diet
- decrease = wasting disease, malnutrition, poor renal blood blood or function
Which two kinds of disorder cause abnormal solute excretion?
pre-renal and renal
Describe pre-renal cause of abnormally high/low solute excretion
- kidney function is normal
Overspill: - increased solute filtration –> increased production in body
- abnormal metabolite so no suitable transporter for reabsorption
Decreased solute filtration - decreased production in body
- decreased delivery e.g. cardiac failure, haemorrhage, burns
Describe renal causes of abnormal solute excretion
- kidney is abnormal
Glomerular malfunction - infection, autoimmune disease, inflammation –> leakage
Tubular malfunction - infection, autoimmune disease, inflammation, necrosis, drugs, toxins
- defective reabsorption e.g. glucose
- defective secretion e.g. H+
What is urea?
the non-toxic end-product of nitrogen metabolism
What factors increase urea excretion?
- excess protein intake
- protein energy malnutrition
- uncontrolled DM1
- infections, burns, wasting diseases, trauma
What factors decrease urea excretion?
- low protein diet, severe liver disease/genetic defects
- glomerular nephritis, acute tubular necrosis
- poor renal bloody supply or renal obstruction
What are the outcomes of decreased urea excretion?
- hyperammonaemia, NH4+ crosses BBB –> lethargy, irratibilty, finally coma
What are the casues of glycosuria? x3 categories
Metabolic hyperglycaemia - diabetes mellitus type 1 - anxiety, stress - phaechromocytoma Reduced renal threshold - pregnancy or renal glycosuria (genetic) Tubular malfunction - generalised tubular damage secondary to other damage - fanconi syndrome
What are the characteristics of pheochromocytoma? What is it? What are the symptoms? How is it diagnosed? What is the treatment?
- a pre renal disorder –> increased end-product excretion
- secreting adrenal medullary tumour
- ocassinoaly ectopic
- excessive secretion of adrenaline causes hypertension, headaches, sweating, anxiety, palpitation, tachycardia, anorexia, hyperglycaemia, high plasma FFAs
- diagnosed by excessive adrenaline breakdown products in ruine - metaneprhones and VMA
- therapy by surgery and blockers
What sugars are abnormally excreted in urine?
When might they be present?
- galactose = enzyme deficieny
- fructose = fructose intolerance, essential fructosuria
- lactose = lactation, lactase deficient, coeliac
- pentoses = essential pentosuria
When may ketones be present in the urine?
- unctornled type 1 diabetes
- starvation
When might amino acids be present in the urine?
- generalised tubular damage
- specific transporter defects (e.g. cystinuria and Hartnup’s)
- raised plasma AA’s e.g. PKU, cystinosis
When might conjugated bilibruin be present in the urine?
- liver damage
- obstructed bile ducts
What is the definiciton of proteinuria?
What does it indicate?
- > 200mg/24h of proteins
- nephrotic syndrome
What is orthostatic proteinuria?
- usualyl a benign condition affecting children
- protein isnot detectable in morning
- delvops only after standing uprights
- insignificant if proteinuria is detected only in somme of the urine samples
What are the mechanisms of proteinuria?
Pre renal problem (overflow) e.g. Bence Jones proteins
Renal problem
- glomerular e.g increased permeability to albumin
- tubular e.g. impaired of saturated respiration
- secreted e.g. due to secretion by kidneys or epithelium of urinary tract
Protein size indicates pre-renal vs renal problem.
Explain
Low MWt –> kidney is topically normal e.g. myoglobin
High MWt –> damaged kidney e.g. albumin
What is the deficiency in PKU?
What does it lead to in the urine?
What are the consequences
- genetic deficieny of Phe hydroxylase
- excess excretion of phenylpyruvate
- accumulation of hydrophobic Phe which affects the brain
- build up of transmission byproducts
