Week 5 Flashcards
1
Q
What are some roles of the kidney
A
Excretion of waste products
Control of body fluid volume & composition of this fluid
Regulation of body fluid osmolality & electrolyte concentrations
Regulation of acid-base
Regulation of arterial pressure
Erythropoietin
Regulation of 1,25-Dihydroxyvitamin D3 production
Gluconeogenesis
2
Q
describe the location of the kidneys
A
3
Q
Label
A
4
Q
Label
A
5
Q
Describe urine flow in kidney in cattle, pigs & primates
A
urine drains from tip of pyramids into minor calyx
2-3 minor calices then drain into a major calyx
major calices then drain into renal pelvis
renal pelvis drains into ureter
6
Q
Describe urine flow in kidney in dogs, cats, sheep & horses
A
Medullary pyramids are fused and form renal crest
no calices
renal crest drains into renal pelvis
renal pelvis is located within renal sinus
7
Q
Describe renal pelvis differences across species
A
8
Q
Describe dog, cat, sheep & goat kidneys
A
kidney bean shaped
9
Q
Describe equine kidneys
A
10
Q
Describe porcine kidneys
A
long and flat
11
Q
Describe bovine kidneys
A
oval & irregular shape
obvious lobes = reniculate
12
Q
Describe these parts of the kidney
A
13
Q
Describe unilobar kidneys
A
rodents & lagomorphs
single renal lobe
single pyramid
single papilla
- may extend through hilus in desert-adapted species
14
Q
Describe cow, elephant, bear & aquatic animal multilobular kidney
A
15
Q
Describe pig & primate multilobular kidney
A
16
Q
Describe dog, cat, sheep & horse multilobular kidney
A
17
Q
Fill in the kidney table
A
18
Q
Give an overview of renal blood flow
A
Kidney receives 25% of cardiac output
basic flow is from hilus to cortex, then cortex to medulla
venous drainage is from medulla to cortex to join cortical venous drainage
outflow via hilus
19
Q
Describe blockage in arcuate vs interlobulary arteries
A
doesn’t matter if an arcuate vessel gets blocked because they are anastomotic so blood can flow via different vessel
interlobulary arteries are end arteries so blockage causes infarcts and sections of kidney will die
20
Q
Describe the renal blood flow circuit
A
21
Q
Describe the capillary networks in the kidney
A
22
Q
Describe the arterial portal system in kidneys
A
23
Q
Describe blood flow in juxta-medullary nephrons
A
24
Q
Describe the extra cortical venous drainage in carnivore kidneys
A
25
Describe what the ureter wall is made of
26
Describe how the ureter enters the bladder
27
Describe bladder anatomy
28
Describe bladder appearance when empty vs distended
29
label
30
Label the bladder ligaments
31
Describe the female urethra
32
Describe the general male urethra
33
Compare male urethra in different species
34
Label
35
Label
36
What supplies the renal pelvis, proximal ureter & distal ureter
37
What is the blood supply to the bladder and urethra
38
What is the lymphatic drainage of the kidney, ureter and bladder
39
Describe the kidney innervation
40
describe the bladder innervation
41
Describe the layers in the renal filter (glomerular capillary)
1. Endothelial cells of the glomerulus
- large fenestrations which allow many products to pass through
- a lot of material that makes up pores is negatively charged & so there is charge-barrier as well as physical space restriction when passing through
- Blood cells and most proteins are too large to pass
2. Glomerular Basement Membrane (GBM)
- Main filtration barrier to cells & large molecules
- It is also negatively charged
3. Podocytes of the visceral layer of Bowman’s capsule
- Podocyte projections don’t completely cover GBM as there are some gaps
- They therefore make a discontinuous layer on urinary space side of the GBM
- Spaces between foot projections are called filtration slits
- Filtration of smaller molecules is blocked by presence of thin negatively charged membrane within filtration slits
42
Label the glomerulus
43
Describe the juxtaglomerular apparatus
Region at vascular pole of the glomerulus. It is made up of 3 types of cells:
1. Juxtaglomerular cells
- modified smooth muscle cells in wall of afferent arterioles
- contain renin
2. Macula densa cells
- specialised epithelial cells in wall of TAL of Loop of Henle &/or distal tubule
- detect changes in luminal sodium chloride (NaCl) concentration
- can signal changes in arteriolar resistance & so affect blood flow to glomerulus
- signals release of renin
3. Extraglomerular mesangial cells
- bridge afferent & efferent arterioles & MD cells & help coordinate messages & effects of JGA
44
Describe the proximal convoluted tubule
This area of nephron is very coiled & these segments make up much of renal cortex
site where most solute reabsorption occurs
Cells here have a number of features that are suited to these roles:
- Cuboidal epithelial cells
- Apical intercellular tight junctions (try to stop “leakage” of molecules between cells but allow easy movement of water & some small ions)
- Intercellular gap junctions
- Layer of microvilli (brush border) – modification to increase surface area for absorption & intracellular transport of luminal material
- Basolateral intercellular interdigitations: increase surface area between cells to maximise transcellular transport of materials
- Lots of mitochondria
45
Describe the Loop of Henle
This part of tubule descends into medulla & then ascends back into cortex
It has several parts:
1. The thick descending Limb
- active in reabsorption
- Simple cuboidal cells
2. The thin descending and thin ascending limbs
- Changes abruptly to flatter cells: simple squamous epithelium
- No brush border or lateral interdigitations
- Few organelles
- important role in concentrating urine
3. The thick ascending limb
- Thicker again: simple cuboidal epithelium
- Rises up towards cortex & ends up next to glomerulus & macula densa
46
Describe blood vessels associated with the Loop of Henle
Efferent arterioles in cortical nephrons go on to form peritubular capillaries – which surround rest of tubular system
Efferent arterioles from juxtamedullary nephrons:
- first form vascular bundles which give rise to peritubular capillaries & straight vessels that form vasa recta
Vasa recta are sole blood supply to medulla & are very important in creating concentration gradient
47
What are cortical vs juxtamedullary nephrons
Nephrons can be classified by location of their glomeruli. In cortex as superficial (near capsule), cortical, or juxtamedullary (near medulla)
Juxtamedullary nephrons are long & adapted to resorb lots of water back into blood
Useful in animals that need to minimise amount of water they lose in urine
- eg desert animals
Ability to produce very concentrated urine is associated with greater percentage of juxtamedullary nephrons
48
Describe the distal convoluted tubule
This part of the nephron is after the macula densa
It is shorter in length & has less developed microvilli than PCT
However, it has lots of basolateral interdigitations & even more mitochondria than PCT
49
describe the collecting ducts
This has 3 sections according to their depth in the kidney:
- Cortical collecting duct
- Outer medullary collecting duct
- Inner medullary collecting duct
Several nephrons join same collecting duct & several collecting ducts join to form papillary duct
50
Describe filtration process in the kidney
1. blood carried to glomeruli is filtered
2. ultrafiltrate is funnelled to PCT where glucose, amino acids, small proteins, vitamins, sodium & water are reabsorbed
3. tubular fluid leaves cortex & enters descending loop of Henle where water is passively removed
4. in the ascending LoH Na+ & Cl- are actively removed
5. tubular fluid leaves medulla & enters DCT in cortex where salt & water balance between urine & blood is adjusted by juxtaglomerular apparatus & RAAS
6. urine leaves nephron & enters collecting ducts that pass back through medulla
51
Label
52
Describe the function of the glomerulus
Selective filtration barrier that acts like sieve to filter blood based on size & charge of particles
No blood cells pass
Very little protein passes (albumin does)
Has a charge
Creation of an ULTRAFILTRATE:
- Water
- Electrolytes
- Glucose
- No cells, no/little protein
53
What is Glomerular Filtration Rate (GFR)
amount of fluid filtered from glomerular capillaries into Bowman’s Capsule per minute (across all nephrons)
GFR = Kf x net filtration pressure
- Kf is filtration coefficient – represents permeability of membranes
54
Why is GFR important
GFR is cumulative over all functional nephrons
Renal function is directly related to number of functional nephrons
so acts as an indirect measure of renal function
55
What GFR forces can be regulated and what cant be
Some forces can’t be regulated:
- Hydrostatic pressure in Bowman’s capsule
- The filtration coefficient
But some can:
- Hydrostatic pressure in the glomerular capillaries
- Renal blood flow
56
What factors can affect arterial blood pressure in afferent & efferent vessels
Autoregulation
- Stretch receptors
- Macula Densa
Angiotensin II
- Via renin release from JGA
Neural regulation
- SNS and PSNS
57
Define renal clearance
volume of plasma cleared of substance in unit of time
58
What substances are good candidates for measuring GFR
Urea
- From protein catabolism, easy to measure in blood
- Variable (protein meals (raw fed dog), GI bleeding, catabolic states)
Creatinine
- From muscle (& food) breakdown, easy to measure in blood
- Steady rate
- Affected by age, muscle mass
- Not very sensitive
Inulin
- Gold standard in human medicine
- Has to be administered & then measured (not practical in animals)
Cystatin-C
- Produced by all tissues
- Freely filtered, resorbed (PCT) and destroyed
- Good indicator of PCT damage
SDMA
- Produced by all cells
- More sensitive measure of GFR than creatinine
FGF-23
59
How can urinalysis be used to assess renal system function
We can use urinalysis to assess renal system function by knowing:
- What concentration “normal” urine should be
- What it should, and should not, normally contain
* blood, haemoglobin, glucose, ketones, protein, Crystals (can occur if sample is old), casts, other cells
- Other parameters
* PH
* Colour, turbidity, smell
60
What is nephrotic syndrome
Glomerulonephritis --> widespread inflammation, lots of causes
Glomerular disease often causes proteinuria
rare complication = nephrotic syndrome can result from extreme urinary protein loss
Nephrotic syndrome is defined as combination of significant protein loss in urine, high serum cholesterol & low serum albumin
Tissue oedema forms as a consequence of the low protein
61
What do these cause
62
Why is renal blood flow high?
Haemodynamic factors:
- lots of ‘push power’ to get blood to be adequately filtered
High resistance of afferent and efferent arterioles means the hydrostatic pressure beyond them is relatively low - helps promote resorption
63
Describe countercurrent exchange mechanism in kidney
Vasa recta amplifies concentrating ability of nephron
In the ascending limb:
- ions are pumped out of LoH
- water cannot follow
- makes interstitium salty
In the descending limb:
- water moves out
- concentrating tubular fluid
64
What is the vasa recta
Blood vessels that follow the LoH
Important in urine concentration
65
Which of these adaptations might desert mammals have to help them to live in such a water-depleted environment?
Ability to hyper-concentrate urine
Longer Loop of Henle
Proportionally more juxtamedullary nephrons
Reduced RBF so not as much water gets filtered or lost in urine
Ability to hyper-concentrate urine ✅
Longer Loop of Henle ✅
Proportionally more juxtamedullary nephrons ✅
66
Describe the autoregulation of renal blood flow
Myogenic reflex:
- high BP => stretches BV => reflex vasoconstriction and reduced blood flow
Tubuloglomerular feedback:
- Rise in glomerular pressure => increased GFR => increased tubular flow rate => less time for Na and Cl reabsorption => macula densa detects higher Na/Cl => JGA releases adenosis => afferent arteriolar vasoconstriction => reduces blood flow and GFR
67
What factors affect renal blood flow
Autoregulation
RAAS system
Vasoactive peptides
68
what are some vasoactive peptides that control renal blood flow?
Bradykinin
Natriuretic peptides (ANP, BNP and CNP)
Endothelin
Vasopressin
Adrenomedullin
69
What does myoglobin in urine indicate
muscle damage
70
What substances can be found in urine that indicate disease
Crystals (urolithiasis)
Myoglobin
Bilirubin
RBCs
Haemoglobin
WBCs
71
Describe the use of the gross appearance of urine in urinalysis
Colour:
- should be pale yellow-amber
- abnormal colour can be caused by diet, meds, environment or illness
Turbidity:
- should be clear
- cloudiness caused by suspended material e.g., bacteria
Smell:
- should be relatively odourless
- strong ammonia smell suggests infection
72
How is protein measured in urinalysis & what does it indicate
Dipstick
Should have no proteins in urine
Proteins present suggests poor filtration in glomerulus and/or poor reabsorption in the proximal tubules
73
How is urine pH used in urinalysis
Normal = 6-7.5
Increased pH may results from UTI
decreased pH may be due to diets high in animal protein or milk
74
How is glucose used in urinalysis
Glucose not normally present in detectable quantities on dipstick
Glucosuria occurs due to high blood glucose levels e.g., diabetes mellitus
If blood glucose is normal with glucosuria = renal tubular dysfunction
75
Describe urine ketones in urinalysis
Usually undetectable in urine
may suggest ketosis secondary to diabetes mellitus or starvation
76
How is occult blood used in urinalysis
Detects haem-containing substances e.g., haemoglobin
Red cells in sediment indicates haematuria is causing occult blood
77
Describe bilirubin in urinalysis
Should not be present (except small amount in healthy dogs)
Renal threshold for bilirubin is low in most animals
78
Describe what RBC, WBC & epithelial cells may suggest in urinalysis
79
What can casts suggest in urinalysis
can indicate:
renal disease
UTI
Dehydration
Neoplasia
& more
80
Define azotaemia
81
Why is azotaemia a useful marker in clinical practice and what are its limits
82
What are the types of azotaemia
Pre-renal azotaemia = azotaemia occurs because of systemic factors that result in inadequate renal perfusion
Renal azotaemia = due to reduced function of the kidneys
Post-renal azotaemia = caused by a problem after the kidneys (ureters, bladder or urethra)
83
What are the clinical signs of pre-renal azotaemia
Concentrated urine - high USG as kidneys working to reduce fluid loss
Azotaemia
Clinical signs of hypovolaemia and dehydration
84
What are the clinical signs of renal azotaemia
85
What are the clinical signs of post-renal azotaemia
86
What are the possible causes of renal azotaemia
87
What are the possible causes of pre-renal azotaemia
88
What are the possible causes of post-renal azotaemia
89
What is the result of failed excretion of waste products
90
What is the result of failed control of body fluid volume & composition
91
What is the result of failed regulation of acid-base
92
What is the result of failed erythropoietin
93
What urine sampling methods an be done at home?
Floor sampling
Litter tray sampling
Free catch
94
What are the pros and cons of free catch urine sampling
95
What are the pros and cons of litter tray sampling
96
What are the pros and cons of floor sampling (urine)
97
What urine sampling techniques can be done in practice
Expressed sample
Catheterised sample
Blind cystocentesis
Ultrasound guided cystocentesis
98
What are the pros and cons of expressed sampling (urine)
99
describe how to collect a catheterised urine sample from males
100
What are the pros and cons of catheterised sampling
101
Describe how to perform a blind cystocentesis
102
What are the pros and cons of blind cystocentesis
103
Describe how to perform an ultrasound guided cystocentesis
104
What are the pros and cons of ultrasound guided cystocentesis
105
Why should you not use cystocentesis on animals with a bladder mass?
Most common bladder neoplasia = transitional cell carcinoma (TCC)
Can ‘seed’ into abdomen if transabdominal needle sampling
106
What are the appropriate tubes for a urine sample?
Plain tube for biochemical and sediment analysis/imminent culture
EDTA - prevents degradation of cellular components
Boric acid - hold bacterial population and cellular components statis for 4 days
107
What levels are measured with a dipstick in urine?
Blood
Bilirubin
Ketones
Glucose
Protein
pH
108
What USG is normal
109
What might be seen in urine microscopy
Haematuria - blood cells
Transitional cells
Renal tubular cells
Squamous cells
Moulds of renal tubules
mucoproteins
Lipid droplets
Sperm
Pathogens
Contaminants
110
In what situations might you find crystals in urine
Normal urine
Artefact from storage
Altered pH (UTI)
Liver disease
toxins or drugs
111
What is this
Hyaline cast
112
What is this
cellular cast
113
What is this and when might we see it?
struvite crystal
e.g. in altered pH (UTI)
114
What is this and when might we see it?
calcium oxalate dihydrate crystal
e.g. normal urine or artefact-storage
115
What is this and when might we see it?
calcium oxalate monohydrate crystal
e.g. toxins or drugs
116
What is this and when might we see it?
ammonium biurate crystal
e.g. liver disease
117
What is this and when might we see it?
bilirubin crystal
e.g. liver disease
118
What views can be used for urinary tract radiography
ventrodorsal and both laterals
119
describe collimation & centring of VD radiography of urinary tract
120
describe collimation & centring of lateral radiography of urinary tract
121
Put the uroliths struvite, cystine, ammonium urate and calcium oxalate in order from least to most radiodense
122
Label the kidneys and bladder
123
What are the options of retrograde cystograms in contrast radiography of the lower urinary tract?
Pneumocystogram
Positive contrast cystogram
Double contrast cystogram
124
What is the contrast used in a pneumocystogram and what are the possible uses?
Contrast = air
Use = assess bladder wall thickness
125
What is the contrast used in a Positive contrast cystogram and what are the possible uses?
Contrast = dilute iodine
Used = bladder rupture
126
What is the contrast used in a double contrast cystogram and what are the possible uses?
Contrast = air and dilute iodine
uses = improved detail of bladder wall, filling defects
127
What is a retrograde vaginourethrogram
128
What is a retrograde urethrogram
129
What is this pointing at
130
What is this pointing at
131
Label this frontal/dorsal view of kidney
132
label this sagittal view of the kidney
133
What is the direction of a frontal view
lateral to medial
134
What is the direction of a sagittal view
central to dorsal
135
label the transverse view
136
Label the bladder wall layers
137
Label the bladder
138
What is the technique for bladder endoscopy
139
Label
140
Label and what is abnormal?
Uterus contains fluid = pyometra
141
What condition is present in this ultrasound of cat
142
based on the mineralisation present radiographically, can you estimate how long this patient has been pregnant
143
Label
144
What conditions can cause an enlarged prostate
Benign prostatic hypertrophy
Prostatitis
Neoplasia
Abcesses
Paraprostatic cysts
145
Label the male radiograph showing Benign prostatic hypertrophy
146
What conditions cause urethral obstruction
Urolithiasis
Urethral spasm
Urethral plugs
Urethral inflammation
Neoplasia
147
Identify the uroliths
148
Identify the urolith and the organ is it in in this ultrasound of a dog
149
Label the ultrasound
150
Is this a transitional cell carcinoma or cystitis? why?
151
Is this a transitional cell carcinoma or cystitis? why?
152
Label the kidneys. what is abnormal?
153
What pathology is present in this kidney
154
What pathology is present in this kidney
155
What is osmolarity
Conc of solute particles
Na+ extracellular
K+ intracellular
Water will move towards areas of high solute conc
156
What are the components of extracellular fluid
Protein
Na+
Cl-
HCO3-
Capillary membrane freely permeable to water and electrolytes
157
What are the components of intracellular fluid
K+
Cell membrane freely permeable to water only
158
What are Starling's forces
Hydrostatic pressure
Oncotic pressure
Osmotic pull
Permeability
159
Define osmotic pull/force
Water diffuses from area of highest conc of water to area of lowest conc of water
160
define hydrostatic pressire
161
Define oncotic pressure
162
define permeability
163
Describe the balance of forces that balances water movement in and out of capillaries
164
Define tonicity
osmotic pressure of solution relative to the plasma
isotonic = same osmotic pressure as plasma
165
Define osmolarity
conc of particles dissolved in a fluid per L
166
Define osmolality
Conc of particles dissolved in a fluid per kg
167
into plasma
168
What is a hypertonic solution
solution that is more concentrated than plasma
169
Give an example of a isotonic, hypertonic and hypotonic solution
170
What is an effective osmole and an ineffective osmole
effective osmole:
a solute that does not freely cross the membrane, e.g., Na+, K+
ineffective osmole:
a solute that freely crosses the membrane e.g., glucose, urea
171
What is the formula for blood pressure
blood pressure = Heart rate x stroke volume x systemic vascular resistance
172
What is pressure natriuresis
If perfusion to the kidneys is increased => more fluid is ‘pushed’ through the kidney => more excretion of sodium and water => lowers BP
Works with RAAS to maintain BP
173
Normal dog blood pressure
Systolic = 110-160
Diastolic = 60-90
174
Normal cat blood pressure
Systolic = 120-180
Diastolic = 70-90
175
What is target organ damage
176
What are the general treatment guidelines for hypertension
177
List some drug groups that might be effective to manage hypertension
Angiotensin converting enzyme inhibitor (e.g. benazepril)
Angiotensin receptor blocker (e.g. telmisartan)
Calcium channel blocker (e.g. amlodipine)
A1 blocker (e.g. prazosin)
Direct vasodilator (e.g. hydralazine)
Aldosterone antagonist (e.g. spironolactone)
B blocker (e.g. propranolol)
Thiazide diuretic (e.g. hydrochlorothiazide)
Loop diuretic (e.g. furosemide)
178
Where is erythropoietin produced
interstitial fibroblasts in renal cortex and outer medulla of kidney
179
What is the function of erythropoietin
Stimulates production of RBCs in bone marrow when kidneys detect hypoxia
Binds to receptors on erythroid progenitor cells in bone marrow => proliferation and differentiation into mature RBCs
180
181
Why is Angiotensin converting enzyme inhibitor (drug) effective at managing hypertension
blocks conversion of angiotensin I to angiotensin II (vasoconstrictor) to help dilate blood vessels & decreases aldosterone (promotes sodium & water retention & thus increases volume & pressure) secretion
182
Why is Angiotensin receptor blocker (drug) effective at managing hypertension
block action of angiotensin II
183
Why is calcium channel blocker (drug) effective at managing hypertension
inhibits influx of calcium into vascular smooth muscle cells leading to dilation
184
Why is A1 blocker (drug) effective at managing hypertension
block a1 adrenergic receptors on vascular smooth muscle cells to inhibit vasoconstrictive effects of catecholamines leading to vasodilation
185
Why is aldosterone antagonist (drug) effective at managing hypertension
inhibit action of aldosterone by binding to mineralocorticoid receptors in kidneys to prevent water retention, potassium excretion & vasoconstriction
186
Why is B blocker (drug) effective at managing hypertension
block action of catecholamines & inhibit release of renin
187
Why is thiazide diuretic (drug) effective at managing hypertension
inhibit reabsorption of sodium & chloride ions in distal convoluted tubules of kidneys to reduce blood volume & thus pressure
188
Why is loop diuretic (drug) effective at managing hypertension
inhibit sodium-potassium-chloride co-transporter in thick ascending loop of henle leading to increased secretion
189
What is urinary incontinence
lack of voluntary control of bladder
190
At what age would you expect a puppy to have developed urinary continence
16 weeks (4 months)
191
What abnormality does this radiograph show
192
Give some signs of each level of dehydration
193
define isosthenuria
USG is same as plasma
Kidney is not concentrating or diluting urine
194
What are some clinical signs of chronic kidney disease and why do they occur
195
What is SDMA and how is it useful in diagnosing kidney disease?
196
What is FGF-23 and how might it be useful in diagnosing kidney disease?
197
Why can CKD result in anaemia
198
Why can CKD result in hypertension
199
Why can CKD result in calcium imbalance
200
What clinical signs may you see in a cat with hypertension
201
How can PU/PD, isosthenuria, dehydration be treated in CKD?
IV fluid therapy
Subcut fluid
Encourage water intake
202
How can proteinuria be treated in CKD?
Reduced protein diet
PUFA - reduces inflammation, antioxidant
203
What can be used to treat hyperphosphataemia in CKD?
reduced phosphate diet
phosphate binders
204
What can be used to treat hypocalcaemia in CKD?
calcitriol (vit D)
205
What can be used to treat nausea in CKD?
Gastroprotectants
Anti-nausea e.g., maropitant
206
How can hypokalaemia be treated in CKD?
potassium supplementation
207
Why does H+ concentration of body fluids need be kept constant
Avoid detrimental changes in proteins, enzyme structure and cellular structure
208
What is the equation of removing H+ from the body by the lungs?
209
Describe acid (H+) secretion by the kidneys
free H+ conc in urine is very low
Most H+ secreted bound to filtered buffers e.g., phosphate or ammonia
Must absorb all filtered HCO3- as loss = same effect as adding H+ to plasma
210
What organs are involved in pH regulation
lungs
liver
kidney
211
How does the liver remove H+
metabolises amino acids from protein catabolism to glucose or triglycerides, NH4+ released
212
Describe bicarbonate reclamation in PCT cells
HCO3- is freely filtered into tubular lumen
H+ enters tubular lumen via Na/H pump
HCO3- and H+ react => CO2 (under influence of carbonic anhydrase)
Resulting CO2 diffuses into PCT cells, dissociates in H+ and HCO3-
HCO3- is reabsorbed into the blood via Na3HCO3- co transporter
H+ returns to tubular lumen to react with more HCO3-
213
Describe acid secretion in PCT cells
Kidney has ability to excrete H+ as ammonium (NH4+)
New HCO3- generated in this process
214
What factors control bicarbonate reabsorption in PCT
luminal HCO3- conc
Luminal flow rate
Arterial pCO2
Angiotensin II
215
Describe acidification in distal tubule
H+ secreted in cortical and medullary collecting tubules by active secretion
H+ combine with phosphate buffers => secreted
216
What factors cause increased H+ secretion and HCO3- reabsorption in the kidney?
Increased pCO2
Increased H+, decreased HCO3-
Decreased ECF volume
Increased angiotensin
Increased aldosterone
Hypokalaemia
217
What factors cause decreased H+ secretion and HCO3-reabsorption in the kidney?
Decreased pCO2
Decreased H+, increased HCO3-
Increased ECF volume
Decreased angiontensin
Decreased aldosterone
Hyperkalaemia
218
Describe the effect increased pCO2 has on hydrogen excretion in kidney
Tubular cells respond to increased pCO2 of blood by increased rate of H+ secretion
219
What is the effect of decreased ECF volume on hydrogen excretion in kidney?
Decreased ECF vol stimulates sodium reabsorption => increased H+ secretion and HCO3- reabsorption:
- increased angiotensin II levels stimulates activity of Na+/H+ exchanger
- increased aldosterone levels stimulates H+ secretion by the cortical collecting tubules
- can cause alkalosis due to excess H+ secretion and HCO3- reabsorption
220
How does plasma potassium effect hydrogen excretion in kidney
Hypokalemia stimulates H+ secretion in proximal tubule:
- decreased plasma K => increases H+ conc in renal tubular cells
- stimulates H+ secretion and HCO3- reabsorption
- => alkalosis
Hyperkalemia inhibits H+ secretion in proximal tubule:
- hyperkalemia decreases H+ secretion and HCO3- reabsorption => acidosis
221
What are the uses of arterial & venous blood gas measurement
Arterial:
- assessing respiratory status
- may not reflect changes in periphery
Venous:
- used in metabolic scenarios
- low pH and higher pCO2
- may not be accurate in low flow states
222
Fill in the table for changes in arterial pH
223
What is you diagnosis and what would you do?
metabolic acidosis
give IV fluids so kidneys cant fix issue and then work out the cause
224
What are salts vs electrolytes
225
What are the transport mechanisms in the kidney
226
Describe absorption in the proximal tubule
227
Describe absorption in the Loop of Henle
228
Describe absorption in the distal tubules
229
Describe absorption in the collecting duct
230
What is the effect of aldosterone on potassium in the collecting duct?
Increased activity of Na+/K+ pump - resorbs Na, secretes K
Increased number of K+ channels
231
Describe the effect of insulin on potassium absorption in kidney
Used to shift K+ into cells
Increases activity of Na+/K+ pump
Can be used to treat hyperkalaemia
232
Describe the passage of Ca through the kidney
Free ion - freely filtered
Passive reabsorption in proximal tubules and ascending limb of LoH - driven by Na+
Active transcellular reabsorption in distal tubules
PTH (parathyroid hormone) can increase Ca2+ reabsorption
233
Describe the passage of phosphate in the kidney
Free ion - freely filtered
80% reabsorbed in proximal tubules
Transcellular process: co-transport with Na+ ions
PTH decreases phosphate reabsorption
234
Describe the passage of magnesium in the kidney
Free ion - freely filtered
30% reabsorbed in proximal tubules - paracellular movement driven by Na+
65% reabsorbed in thick ascending limb of LoH due to transepithelial potential
5% reabsorbed in distal tubules via Mg ATPases
Regulated via PTH
235
Describe the passage of glucose in the kidney
Freely filtered
Only reabsorbed in proximal tubule via secondary active reabsorption
As glucose conc increases more of the proximal tubule participates in reabsorption
236
Why is urine concentration control important
Intracellular environments require tightly controlled extracellular environments
ECF is affected by substrate levels and amount of water that it is dissolved in
Body water volume affects circulating volume, tissue perfusion and blood pressure
237
How do kidneys produce dilute urine
normal ion transport (so filtrate gets more dilute) but little ADH so water cannot follow out of lumen
238
How does the kidney produce concentrated urine
kidney reabsorbs lots of water
239
describe water handling in proximal convoluted tubule
High water permeability
Solutes resorbed and water follows by osmosis = isotonic change
Filtrate volume reduced by 65% but osmolality does not change
240
describe water handling in LoH
Variable water permeability depending on location
Descending limb = water permeable
Ascending limb = ions actively pumped out
Produces dilute urine and hypertonic medullary interstitium at base of LoH
240
Describe water handling in collecting ducts
Water permeability varies depending on ADH
Cells and tight junctions are impermeable to water
ADH increases water permeability through aquaporins
Allows water to leave down conc gradient => concentrated urine
241
Describe water handling in distal convoluted tubule
Largely impermeable to water (some ADH effect)
Macula densa and DCT - lots of electrolyte active transport
Filtrate becomes dilute
242
Where is ADH/vasopressin produced
Made in hypothalamus
Released from post. pit in response to osmoreceptors detecting rise in plasma osmolality
243
What is the effect of low ADH levels
No water reabsorption in collecting ducts
Na and Cl continue to be resorbed
Urine gets even more dilute
244
define hyposthenuria
Kidneys are actively diluting urine
Mainly occurs in LoH where water follows solutes out of tubule
245
What is hypersthenuric urine and what does it require?
Concentrated urine (what we expect to find in most animals)
Requires:
- ADH
- DCT/collecting ducts to be responsive to ADH
- hypertonic medullary interstitium
246
Define pollakiuria
frequent passing of urine (not the same as polyuria)
247
define nocturia
urinating at night
248
What factors affect water intake
Ambient temp
Respiratory evaporative loss
Exercise level
Water content of food
Faecal water content
Age
Physiological state e.g., pregnancy
249
What is the exception to PD coming after PU?
psychogenic polydipsia (PP) - excess drinking is behavioural issue => secondary polyuria
250
What are the most common causes of PU/PD in dogs and cats
Renal insufficiency, chronic renal disease
Diabetes mellitus
HAC (dog)
Hyperadrenocorticism (cats)
251
What mechanisms is the production of concentrated urine dependent on
252
What are the causes of primary polyuria
Central diabetes insipidus
Primary nephrogenic diabetes insipidus
Secondary nephrogenic diabetes insipidus
253
describe central diabetes insipidus
the pit gland does not release enough ADH due to hypothalamus or pituitary problem
254
what is the test for central diabetes insipidus
Synthetic ADH => urine concentration increases
255
what is the treatment for central diabetes insipidus
Desmopressin = ADH agonist
maximises low levels of ADH
256
What is nephrogenic diabetes insipidus
Kidney does not respond normally to ADH
Primary/congenital diabetes insipidus:
- aquaporin insertion defect
Secondary/acquired nephrogenic diabetes insipidus:
- variety of renal/metabolic conditions which interfere with normal ADH action
- affects renal tubular function
- or decreases hypertonicity of medullary interstitium => loss of conc gradient
257
What are the mechanisms for renal insufficiency causing PU/PD
Osmotic diuresis in remnant nephrons
Disruption of medullary architecture
Loss of medullary hypertonicity
Decreased functional nephrons
258
How does HAC cause diabetes insipidus
Causes PU/PD by defective ADH release - central diabetes insipidus
Impaired tubule response to ADH action - nephrogenic diabetes insipidus
259
How does hypoadrenocorticism cause PU/PD?
loss of osmotic gradient in renal medulla due to chronic Na wasting => loss of renal medullary hypertonicity => inadequate urine conc
260
How does hyperthyroidism cause primary polyuria
thyrotoxicosis => increased CO and GFR and increased renal medullary blood flow, has potential to decrease renal medullary hypertonicity and urine concentrating ability
Some cats with hyperthyroidism may have primary polydipsia secondary to the effects of high thyroid hormone concs on the thirst centre
261
How does liver disease cause PU/PD?
due to loss of medullary hypertonicity
Liver disease => decreased production of urea => decreased renal medullary hypertonicity
Increased levels of corticosteroids inhibit the release of ADH => central diabetes insipidus
262
How do you test for psychogenic polydipsia
Controlled water deprivation
Dangerous to do if you have not already looked for renal or endocrine causes as dehydration could exacerbate disease
263
Define dysuria
pain associated with urination
264
What are the likely clinical signs of UTIs and urolithiasis?
stranguria - straining to pee
Haematuria
Pollakiuria - frequent, small volume urinations
265
What is the common clinical sign seen is prostatic hypoplasia?
flat poo
faecal tenesmus
stranguria
haematuria
