Urinary Flashcards
What is the overall structure of the urinary system?
Each kidney connects to the bladder via a ureter. The bladder then empties via the urethra
What are the main functions of the kidney?
Regulation, excretion, endocrine and metabolism
Where are the kidneys located?
Between T12 and L3
Right kidney is slightly more caudal
What part of the trilaminar disc is the kidney derived from?
Intermediate mesoderm
What part of the kidney forms first, when and what does it do?
Pronephros - week 4 - it has no function as a kidney but extends the pronephric duct which drives the later stages
What is the second part of the kidney that forms, when and what does it do?
Mesonephros - end of week 4 - acts as an embryonic kidney and sprouts the ureteric bud for the definitive kidney. No part of the mesonephros becomes the definitive kidney
What is the third part of the kidney that forms, when and what does it do?
Metanephros - week 5 - becomes the final kidney. The collecting system is derived from the ureteric bud and the excretory system is formed from the mesoderm under the influence of the ureteric bud
Describe the ascent of the kidneys
Undergoes an apparent caudal to cranial shift as the embryo moves but the kidney does not. Laterally displaced and rotated 90 degrees
What is renal agenesis and how might it occur?
Failure of the renal system to develop. Due to the ureteric bud failing to interact with intermediate mesoderm
What are some potential problems with the migration of the kidneys?
May not cross the arterial fork and stay lower down
The kidneys ascend close together and may fuse to make a horseshoe kidney
What is the pathology behind an ectopic ureter?
Ureteric bud splits. Opening could be elsewhere
What are the types of cystic kidney disease?
Multicystic - ureter atresia
Polycystic - poor prognosis
How might abnormal renal vessels form and why are they problematic?
As the kidney ascends it creates new blood supply and destroys the old ones. Sometimes they aren’t lost however. Problematic because they are an end artery and the area they supply isn’t reached my the main renal artery
What does the urogenital sinus become?
Upper - bladder
Lower - pelvic and phallic
What is the difference between the male and female urogenital sinus?
Male gets independent openings from the ureteric bud and the mesonephric ducts. Female just gets the opening from the ureteric bud as the mesonephric duct regresses
What are the parts of the male urethra?
Preprostatic
Prostatic
Membranous
Spongy
Explain exstrophy of the bladder
Bladder is outside the abdominal wall
What is hypospadias
The urethra opens on the ventral wall of the penis not at the end of the glans
What is the excretory portion and the collecting portion of the kidney?
Excretory - nephron
Collecting - collecting duct, pelvis, ureter, bladder and urethra
What is the epithelium in the PCT, thin and thick limb of the loop of Henle, DCT, ureter and bladder
Simple cuboidal with brush border Simple squamous Simple cuboidal - no brush border Simple cuboidal - no brush border Transitional Transitional
How does the concentration of various substances in the ultrafiltrate compare to the plasma?
They’re the same except the ultrafiltrate has no large proteins and cells
What forces contribute to filtration?
Hydrostatic pressure in capillary
Hydrostatic pressure in Bowmans capsule
Osmotic pressure difference between capillary and tubular lumen
How is filtration auto regulated?
Myogenic response - BP increase causes afferent arteriole constriction and vice versa
Tubular glomerular feedback - if GFR increases Na+/Cl- increases in the DCT, detected by macula densa cells which release adenosine causing constriction. If it falls the prostaglandins are released causing dilation
What is the physiological range for GFR in men and women?
Men: 115-125
Women: 90-100
Define clearance
Volume of plasma from which any substance is completely removed by the kidney in a given time
What is GFR
The glomerular filtration rate is the amount of plasma the kidney filters. It is estimated using creatinine clearance rate as creatinine is neither reabsorbed or secreted
What happens if a clearance rate is over 125ml/min? Or under?
Over means its being secreted
Under means its being reabsorbed
What is transport maximum?
The maximum transport capacity. Anything over this is not reabsorbed and excreted in the urine
From deep to superficial what are the layers of tissue that surround the kidney?
Renal capsule
Peri renal fat
Renal fascia
Pararenal fat
Outline the passage urine takes within the kidney
Renal pyramid/minor calyx/major calyx/pelvis/ureter
Describe the locations of the kidneys vasculature
Right renal artery is longer and posterior to IVC. Distal to superior mesenteric
Left renal vein is longer and anterior to AA
Where do the ureters turn anteromedially?
Ischial spine
Where are ureteric narrowings?
Uretopelvic junction
Pelvic brim
Ureters entrance to bladder
Why are ureters vulnerable during an ovarectomy and hysterectomy?
Pass close to ovaries and posterior to uterine artery
What defines the trigone?
Two ureters and urethra
Smooth wall
How is Na+ taken in and removed?
Food
Sweat, faeces, urine
What are the percentages of Na+ reabsorbed in the various parts of the nephron?
PCT - 67
LoH - 25
DCT - 5
CD - 3
What is Na+ reabsorbed along with in the PCT?
Glucose, amino acids, H+, phosphates, water and chloride
What drives water reabsorption?
Osmosis, hydrostatic forces and oncotic forces
How are salts and water reabsorbed in the loop of henle?
Descending limb - just water
Ascending - salts via NaKCC2 channels
What channels facilitate Na+ reabsorption in the DCT and the CD?
NCC
ENaC
What four neurohormonal ways does the body control blood volume over long time periods?
Renin angiotensin aldosterone system
Sympathetic nervous system
Anti diuretic hormone
Atrial natriuretic peptide - opposes the other 3
Outline the RAAS pathway
Renin converts angiotensinogen into angiotensin I which is converted to angiotensin II by ACE
What are the effects of angiotensin II? And the other effect of ACE?
Vasoconstrict, increase aldosterone production, increase Na+ reabsorption in the kidney! increase thirst
Breakdown bradykinin thereby causing further vasoconstriction
How does the sympathetic nervous system affect blood volume?
Decreases blood flow and therefore Na+ excretion
Increase NHE and Na pumps
Increase renin production
How does ADH affect blood volume?
Increase Na+ and water retention
How does ANP affect blood volume?
Dilate afferent arteriole this increasing GFR
Inhibit Na+ reabsorption
What do prostaglandins do and what are they affected by?
Clinical use as vasodilators
NSAIDS stop there formation
What are the two types of hypertension?
Essential - unknown cause - 95%
Secondary - as a result of a primary condition - 5%
Explain how renal artery stenosis can cause secondary hypertension
Narrowing of the artery reduces perfusion and therefore increases the RAAS system
What are some adrenal causes of hypertension?
Conn’s syndrome
Cushings
Pheochromocytoma
How do you treat hypertension?
ACE inhibitors Diuretics Vasodilators Beta blockers Exercise, diet, reduce Na+ and alcohol intake
What happens to plasma osmolarity if water intake < excretion
Increases
What senses plasma osmolarity?
Hypothalamic osmoreceptors
Where is ADH released from, what stimulates it and what is its effect?
Posterior pituitary
An increase in osmolarity
Increase water reabsorption and slightly increases salt reabsorption
What is the ADH mechanism of action?
ADH–>G protein–>ATP->cAMP–>PKA–>insert aquaporin into apical membrane
What is SIADH
Syndrome of inappropriate ADH secretion
ADH isn’t inhibited by low osmolarity so excess water is retained causing hyponatremia
Outline the basis of the corticocapillary osmotic gradient
Filtrate enters the descending limb
Water moves out and into the vasa recta which remove it. This concentrates the filtrate
Ascending limb pumps out salts creating a gradient for water
What are some causes of hypercalcaemia and symptoms? How is it treated?
Primary hyperparathyroidism, (non)haematological malignancies, PTHrP
Stones, depression, constipation
Increase hydration and diuretics to increase excretion
Bisphosphatase stop inhibit bone breakdown
What is the effect on the body of alkalaemia?
Parasthesia and tetany
What is the effect on the body of acidaemia?
Affect muscle contractility, glycolysis and hepatic function
How does the kidney respond to acidaemia?
Recover all HCO3- and make more using the CO2 produced by the kidney. The H+ is excreted in urine
How is acid secretion in the urine kept safe?
Buffered by phosphate
Attached to ammonia
Explain the anion gap
If HCO3- is replaced but not by Cl-
It increases if metabolic acid is produced
What is the kidneys response to alkalosis and why might this not always be possible
Excrete HCO3-
Because if there is volume depletion HCO3- is recovered along with Na+
What is the function of ICF potassium?
Maintain volume, regulate pH, control enzymes, DNA/protein synthesis, cell growth
What is the effect on the cell membrane if ECF K+ increases?
Depolarise the membrane as it’s less negative inside
Where in the nephron is the controllable portion of K+ secretion?
Principal cells
What factors increase K+ excretion and how?
Aldosterone - increase Na pumps and ENaCh
Hyperkalaemia - increase aldosterone
Alkalaemia
What increases K+ movement from ECF to ICF?
High concentration, insulin, Catecholamines, aldosterone, alkalosis
What is the effect of hyper and hypokalaemia on the heart?
Hypo - hyperpolarise cell making more excitable
Hyper - depolarise cell making less excitable as fewer Na+ channels open
What factors increase chance of a UTI?
Shorter urethra - females
Obstruction - prostate, pregnant, stone, tumours
Neurological - incomplete emptying
Ureteric reflux - ascending infection
What factors enable bacteria to infect? What is the usual bacteria?
Fimbriae to attach
Urease break down urea for favourable environment
Capsule
Coliforms like E. coli gram -ve
What are symptoms of UTIs?
Lower - fever, dysuria, frequency, urgency
Upper - fever, loin pain
What investigations do you do for a UTI?
Uncomplicated - don’t culture
Complicated (male, child, recurrent, pregnant) - mid stream urine sample/collection bag/catheter - urine dipstick and cultures
When is it not useful to use dipstick tests?
Acute uncomplicated women
Men with severe
Catheters
Older
How are UTIs treated?
Fluids
Treat underlying disorder
3-5 day course of trimethoprim
Pyelonephritis - 14 days co amoxiclav
How and when should UTIs be prevented?
3+/year and no treatable cause
Trimethoprim prophylactic
Why might you have sterile pyuria?
Can’t culture UTI due to antibiotics, chlamydia, TB, appendicitis
Define dieresis and when are diuretics used?
Increased formation of urine by kidney
When water and Na+ retention causes ECF expansion
What are the main types of diuretic, where do they work and on what channel?
Loop diuretics - loop of Henle - NaKCC
Thiazides - early DCT - NaCl
Spironolactone - CD/late DCT - inhibit aldosterone
Amiloride - CD/late DCT - ENaC
When might loop diuretics be used?
Heart failure, nephrotic syndrome, renal failure, hypercalcaemia
Very potent
When might thiazides be used?
Hypertension
Less potent
When are K+ sparing diuretics used?
Hyperaldosteronism, cirrhosis
Explain how congestive heart failure causes oedema
Increase venous pressure –> oedema
Decrease CO –> RAAS –> fluid retention –> oedema
Explain how nephrotic syndrome and cirrhosis lead to oedema
Decrease protein –> decrease oncotic pressure –> oedema
Explain the mechanism behind loop diuretics causing hypokalaemia
Increase Na+ and H2O excretion means a faster flow and more K+ washed away. Blocking NaKCC means less K+ reabsorbed
What else has diuretic effects and why?
Alcohol - decrease ADH
Coffee - increase GFR and decrease Na+ reabsorption
Diabetes
What are the three layers of the Detrusor muscle and the function of this arrangement?
Inner longitudinal
Middle circular
Outer longitudinal
Strength in all directions
What are the internal and external urethral sphincter made of?
Smooth muscle - physiological sphincter and main continence muscle
Pelvic floor muscles - anatomical sphincter under somatic control
What is the innervation to the Detrusor muscle and the urethral sphincters?
Detrusor - parasympathetic - pelvic nerve - contract
Sympathetic - hypogastric nerve - relax
Internal urethral sphincter - sympathetic - hypogastric - contract
External urethral sphincter - somatic - pudendal - contract
Outline the voiding reflex pathway
Brain micturition centres –> spinal micturition centres –> parasympathetic neurones –> Detrusor contracts –> cerebral cortex stimulates external urethral sphincter to relax
Outline how the bladder stores urine
Distend so pressure doesn’t increase
Sympathetic via hypo gastric cause the Detrusor to relax and internal urethral sphincter to contract
Pudendal nerve contracts external urethral
Explain the main types of incontinence
Stress urinary incontinence - leakage on exertion (sneezing)
Urge urinary incontinence - urge to urinate
Mixed urinary incontinence
Overflow urinary incontinence - bladder struggles to empty so overflow causes a leak
What are risk factors for incontinence?
Weak pelvic floor muscles - childbirth
How is urinary incontinence managed?
Modify fluids, stop smoking, lose weight, reduce caffeine
Pelvic floor muscle training
Bladder training
Anticholine and botulinum to reduce Detrusor contraction
Women - vaginal tape
Men - artificial sphincter
What is acute kidney injury?
An abrupt decline in GFR
<0.5ml urine 6 hours
What are the causes of acute kidney injury?
Pre renal
Intrinsic renal
Post renal
Explain pre renal causes of AKI
Reduced perfusion - hypovolaemia, systemic vasodilation, cardiac failure
Compensation overwhelmed - NSAIDS constrict afferent arteriole, ACE inhibitors dilate
Explain acute tubular necrosis
Ischaemia, nephrotixins, sepsis cause
Cells can’t reabsorb salts and water so fluid resuscitation can overload
Contrast pre-renal and ATN when diagnosing
In pre-renal Na+ is actively reabsorbed so low urinary Na+
ATN it is higher >20mmol
Name some nephrotoxins
Myoglobin, bilirubin
ACEi, amino glycosides, NSAIDS, gentamicin
What is rhabdomyolysis?
Muscle necrosis releasing myoglobin. A crush injury
Elderly people, unconscious drug users, wars
Explain post renal failure
An obstruction such as stones, tumour, prostate, stricture
What are some risk factors for AKI?
Old Female Heart/liver disease Diabetes Sepsis Ill Trauma
How is AKI treated?
Treat underlying cause Reduce Na+ and water Ca2+ gluconate and reduce K+ Sodium bicarbonate Dialysis
What is nephrotic syndrome?
A non specific disorder that damages the kidneys and leak protein
Proteinuria, hypoalbuminaemia, oedema
What is nephritic syndrome?
Collection of signs associated with disorders affecting the kidneys - small pores in podocytes allowing protein and RBCs to enter
Differentiate between nephrotic and nephritic syndrome
Nephritic - abrupt onset, raised blood pressure, red cell cast
Nephrotic - more oedema and proteinuria than nephritic. Low BP
What are some risk factors for prostate cancer?
Age, family history, ethnicity (black>white>Asians)
What are some problems due to screening?
Overdiagnosis and treatment
Reduced quality of life due to treatment
Costs
Other causes for positive test - infection, inflammation and large prostate all cause raised PSA
How might a patient with prostate cancer present?
Asymptomatic
Urinary symptoms
Bone pain
Haematuria
What investigations are done if prostate cancer is suspected?
Digital rectal exam, serum PSA
How is prostate cancer treated?
Prostatectomy, surveillance, radiotherapy, hormones
Suggest some causes for haematuria
Cancer - renal/transitional/bladder/prostate
Stones, infection, inflammation, prostate hyperplasia
Define chronic kidney disease
Irreversible, sometimes progressive loss of renal function over a period of months/years
What are some causes of chronic kidney disease?
Glomerulonephritis, pyelonephritis, polycystic kidney disease, hypertension, diabetes
What are the pros and cons of haemodialysis?
Effective, 4/7 days free, less responsibility
Fluid/diet restriction, limit holiday, access problems, CVS instability
What are the pros and cons of peritoneal dialysis?
Done at home, done by self, mobility, less food/fluid restriction
Frequent 4x a day, peritonitis, responsibility
What are the pros and cons of a renal transplant?
Restore renal function and improved survival
Limited supply, operation risk, immunosuppresion
