Urinary Session 1 Flashcards
Which organ is as metabolically demanding as the kidneys?
Liver
What are the functions of the kidneys?
Regulation of key ECF components
Excretion of waste products
Endocrine synthesis
Metabolism
What hormones does the kidney synthesise?
Renin
Erythropoietin
Prostaglandins
Describe the metabolic function of the kidney.
Activates vitamin D
Catabolism of insulin
PTH
What is osmolality?
Solute per kg of solvent
What is osmolarity?
Number of osmoles of solute per litre
In humans why is osmolality and osmolarity approximately equal?
Constant conditions in the body
Why must the kidney control concentrations of electrolytes?
Variable ingestion and loss of salts and water needs to be balanced so cells don’t shrink or swell and so there aren’t huge changes in BP, tissue fluid or cell function
Why must the kidney control the concentration of bicarbonate in the plasma?
So ECF pH is constant
Why does the glomerular ultra-filtrate have the same osmotic pressure as blood plasma?
Everything but RBCs are removed
Describe the outcomes of blood entry into the vascular pole at the glomerulus.
Fraction enters capillaries to create a constant filtration pressure
Rest moves into glomerular tuft
What determines the GFR?
Afferent arterioles bringing blood into the glomerulus and efferent arterioles bringing blood out
Where is the major site of reabsorption in the nephron?
PCT
How does the organisation of vasculature in relation to the peritubular capillaries aid reabsorption in the PCT?
Efferent blood supply from glomerulus runs around peritubular capillaries for quick reabsorption and to ensure secretions remain go into the tubule
What type of reabsorption occurs in the PCT?
Iso-osmotic
Approximately what percentage of each of the components in the ultrafiltrate is absorbed in the PCT?
Na+: 60-70% Water: 60-70% K+: 80-90% HCO3-: 90% (normally) Glucose and a.a.: 100%
How is an osmotic gradient established in the medulla?
Countercurrent multiplication at the loop of Henle
Which part of the nephron facilitates obligatory reabsorption?
PCT
Which part of the nephron facilitates controlled reabsorption and H+ secretion?
DCT
What is the function of the DCT?
Fine tune components of the filtrate
Where is the major site of variable electrolyte and water reabsorption?
DCT
Describe the filtrate in the DCT.
Hypotonic
What electrolyte movements occur in the DCT?
Sodium and calcium removed
Hydrogen ions actively secreted
Does water always follow electrolyte movement in the DCT?
No
What does the DCT communicate with due to its close proximity?
Glomerulus
Describe the passage of the collecting duct.
From medulla to pelvis through high osmolarity of the medulla
How can the permeability of the collecting duct be altered?
ADH can stimulate insertion/removal of aquaporins in the epithelial cells
Where is the filtrate in the nephron considered to be in relation to the body?
Outside
How does the renin-angiotensin system control ECF volume?
Altering Na+ recovery
How does the ADH system control ECF osmolarity?
Altering water permeability
What is special about the epithelial cells in the nephron?
Have necessary tight gap junctions meaning different transporters can be kept on different sides to allow transport across epithelium (polarised)
In normal water/electrolyte balance what percentage of water, sodium and chloride is recovered?
99%
What percentage of HCO3-, glucose and a.a. Is recovered by the nephron in normal water/electrolyte balance?
100%
At what rate do the kidneys filter blood?
180l per day
What is the first line investigation for imaging the renal tract?
Ultrasound
What are the advantages of using ultrasound to image the renal tract?
Cheap Quick Can differentiate b/w cysts and tumours Identifies fatty tumours Identifies obstructions in collecting ducts Measures blood flow
What are the disadvantages of using ultrasound to image the renal tract?
V. operator dependent
Can’t identify if a tumour is benign
Only able to see arteries in transplant kidneys as these are more superficial
Only see collecting ducts with large fluid load
Do not determine cause of collecting duct obstruction
Describe the 2 methods that can be used to use ultrasound to image the renal tract.
Probe that identifies bloodflow towards and away
Insert probe up rectum for prostate biopsies
What are the clinical implications of horseshoe kidney?
More susceptible to obstruction
May be additional renal arteries from iliac vessels –> complication in surgery
What is crossed renal ectopia?
2 kidneys on one side of the midline
Still have 2 distinct collecting systems and ureters
Do the ureters in crossed renal ectopia usually enter the bladder on the correct sides?
Yes
What does taking a plain radiograph of a pt it the supine position to look at kidneys, ureter and bladder (KUB) identify?
Calcification
What are the problems with using a KUB plain radiograph?
Hard to distinguish between renal fat and calcification
Need more than one film to localise findings
Calcification can be confused with phlebolith of the pelvic vessels
What is phlebolith of the pelvic vessels?
Localised, usually rounded calcification of a vein
Is the tissue which crosses the midline in horseshoe kidney usually functioning?
Yes
What are the advantages of using cT scans to image the renal tract?
No contrast needed (although may enhance image)
Identifies tiny stones
Using iodine and timing can give arterial and venous phases
Staging of cancer - liver metastases identified
Can be taken in any plane
What are the disadvantages of using CT scans to image the renal tract?
Cost
Exposure to radiation
What is pelvic kidney?
Failure of a kidney to ascend from the pelvis during development
How does pelvic kidney present on investigation?
On imaging only one kidney is visible but it has a normal size and renal function so there must be another one somewhere
What is duplex kidney?
Where the superior, middle and inferior poles do not converge causing two ureters which do not join to form
Is duplex kidney pathological?
No, number of calices is normal and most pts are fine but there is an increased tendency for kidney problems
What is MRI of the renal tract particularly good for investigating?
Local staging of bladder and prostate tumours inc. local lymph node involvement
What is the gold standard investigation for renal artery stenosis?
MRI angiography
How is MRI angiography carried out?
Pt given contrast to make bloodflow visible
When might a micturating cystogram be used?
Suspected bladder leak or reflux
How is a micturating cystogram performed?
Catheterise pt and inject dye
Completely fill bladder
Allow to urinate
What iatrogenic cause might lead to bladder leak/reflux?
Damage during surgery, especially if there is lots of inflammation +/- bladder stuck to bowel
When is an ate grade pyelogram carried out therapeutically?
In obstruction of the collecting duct causing impaired kidney function +/- infection
What can be used to look for strictures in the urethra?
Micturating cystogram
Urethrogram
When might arteriography be used?
Therapeutically for artery embolus or renal artery stenosis
How is arteriography carried out when imaging the renal tract?
Dye put into aorta which travels to renal arteries so they can be examined
What is a DMSA scan?
Radionuclide scan that compares function of L+R kidneys
How is a DMSA scan performed?
Radioactive nucleotide marker+chemical with properties that determine kidney uptake –> taken up in kidneys and slowly excreted until steady state reached
What does a missing patch within the outline of a kidney on DMSA scan indicate?
No activity e.g. scar tissue
What does a rounded lesions in DMSA scan indicate?
Lump - needs further investigations to identify
How does a DTPA renogram differ to a DMSA scan?
Series of images and corresponding graph of radioactivity produced over time to give a representation of % activity
Is DTPA renogram or DMSA scan more accurate?
DMSA scan
How can a DTPA renogram be used to investigate suspected kidney obstruction?
Give chemical that stresses kidney to increase urine output
What can kidney obstruction be confused with by using a DTPA renogram?
Collecting system dilation
At what level are the superior poles of the kidneys positioned?
T11/12
What are the approximate dimensions of a normal kidney?
Length: 11-12 cm
Width: 5-7.5 cm
Depth: ~3 cm
Which kidney sits more caudally and why?
Right due to the position of the liver
Describe the path of the ureters.
Run posteriorly down tips of the vertebral transverse processes and then moves anteriorly to pass over pelvic brim
From deep to superficial, what are the surrounding layers of the kidney?
Renal capsule
Perirenal fat
Renal fascia
Pararenal fat
What does the renal fascia enclose?
Kidneys and suprarenal glands
Where does the left renal vein run towards the kidney?
Posterior to the SMA
Why is the right renal vein shorter than the left?
Does not pass over aorta
What are the renal hila?
Entrances to renal sinus where kidney serving structures enter and exit
How does the drainage of the suprarenal and gonadal veins on the right compare to those on the left?
On the right drain directly into IVC, on left drain into left renal vein
Describe the position of renal arteries in relation to renal veins.
Symmetrical and posterior
Where do the renal arteries typically divide?
Close to the hilum
Describe the travel of urine though the kidney.
Renal pyramid –> collected in minor calyx –> minor calices merge to form major calyx –> renal pelvis –> ureter
Approximately how long is the ureter?
25 cm
What make up the renal pyramids?
Medullary rays
What does the parenchyma of the kidney consist of?
Muscle portion = cortex and medulla
Describe the path of filtered arterial blood into and around the kidney.
Abdominal aorta –> renal arteries –> ant and post segmental branches –> interlobar arteries –> arcuate arteries –> interlobular arteries –> afferent arterioles –> capillary network –> efferent arterioles
Where are the interlobar arteries located in the kidney?
Either side of every renal pyramid
How are interlobular arteries arranged in relation to arcuate arteries?
At 90 degrees
When do the interlobular arteries divide into afferent arterioles?
In the cortex
Where can additional aberrant arteries that supply the kidney arise from?
SMA
Suprarenal arteries
Gonadal arteries
Describe the path of the abdominal part of the ureter.
Utero pelvic junction –> anterior surface of psoas major –> cross pelvic brim sacroiliac joint level –> cross bifurcation of common iliac arteries
What gives blood supply to the abdominal part of the ureters?
Renal and gonadal arteries and veins
What provides blood supply to the pelvic part of the ureters?
Superior and inferior vesical arteries and veins
Define the path of the pelvic part of the ureters.
Lateral pelvic walls –> turn anteromedially at ischial spines to move in transverse plane towards bladder –> pierce bladder obliquely on lateral aspect
How does the entrance of the ureters into the bladder allow it to act as a one-way valve?
High intramural pressure collapses the opening
What is the relevance of the phrase ‘water under the bridge’ in hysterectomy?
~2cm superior to the ischial spines the ureters run underneath the uterine artery
Where is ureteric pain referred to?
Dermatomes of T11-L2
When do the ureters run close to the ovaries?
When they cross the pelvic brim
Where is the bladder covered by peritoneum?
Superior aspect
What is the median umbilical ligament a remnant of?
Foetal allantois
How long is the male urethra?
20 cm
What portions is the male urethra split into?
Preprostatic
Prostatic
Spongy
What makes up the neck of the bladder?
Convergence of fundus and 2 inferolateral surfaces
What runs in a circle around the bladder neck to act as an involuntary sphincter?
Detrusor muscle
What is detrusor muscle?
Smooth muscle fibres running in 3 directions to allow stretch
What type of innervation does detrusor muscle have?
Sympathetic and parasympathetic
How long is the female urethra?
4 cm
What is continence mainly controlled by in the female urethra?
Anatomical bend
Who has an internal urethral sphincter?
Males only
What is the purpose of the internal urethral sphincter in males?
Autonomic circle of smooth muscle fibres prevent seminal regurgitation on ejaculation
What is the trigone?
Smooth wall in fundus that cannot distend
Where is the bladder located?
Posterior to pubic bone and pubic symphysis
Why can the bladder not be palpated when empty?
Lies entirely in the true pelvic cavity
How does the shape of the bladder change upon filling?
Empty = tetrahedron Full = spherical
What is the interureteric fold?
Ridge between 2 urethral openings
How is the mucosa in the bladder arranged?
In rugae except for in trigone
What does the external urethral sphincter consist of?
Skeletal muscle under voluntary control
When might mucosa thickness be decreased?
Long term urinary retention
