Renal

Question 1

Which part of the kidney is more prone to ischemic and toxic injury?

Answer 1

Medulla as it only received 3-10% of the overall blood flow to the kidneys.

Question 2

Factors that determine the filtration of molecules at the glomerular capillaries:

Answer 2

• Size (< 4 nm) selectivity - lamina densa
• Charge selectivity - favour positively charged molecules - sialoglycoproteins and peptidoglycans at the capillary endothelium, lamina RI, lamina RE, podocytes all negatively charged

Question 3

What are the 7 functions of the kidneys?

Answer 3

1. Regulation of water and electrolyte balance
2. Regulation of systemic blood pressure and extracellular fluid volume
   a. Determine blood volume: salt and water balance
   b. Production of vasoactive hormones: RAAS
3. Excretion of metabolic waste and foreign substances (uremic retention solutes)
4. Regulation of red blood cell production: erythropoietin (synthesised by interstitial cells)
   a- Stimulus: reduction in partial pressure of oxygen
5. Regulation of acid-base balance
6. Regulation of Vit D production and calcium + phosphate balance
   - Production of calcitriol (active Vit D)
7. Gluconeogenesis

Question 4

What is the GFR of a dog?

Answer 4

3-5mL/kg/min

Question 5

What is the GFR of a cat?

Answer 5

2.5-3.5mL/kg/min

Question 6

What is the macula densa?

Answer 6

Specialised tubular epithelial cells that line the thick ascending loop of Henle at its junction with the distal tubules and sits in close contact with the afferent arterioles

Question 7

What is the autoregulation range of the kidneys?

Answer 7

MAP 80-180mmHg

Question 8

What is autoregulation

Answer 8

Intrinsic ability of kidneys to maintain RBF and GFR for varying BPs between 80-180mmHg

Question 9

Name the 3 main ways Angiotensin II stimulates Na reabsorption:

Answer 9

1. aldosterone secretion
2. vasoconstriction of efferent arterioles
3. direct stimulation of pumps in PT, LOH, DT and collecting tubules (Na-K ATPase, Na-bicarb cotransporter, Na/H+ antiporter luminal)

Question 10

Where is aldosterone’s site of action?

Answer 10

principal cells of cortical collecting tubules

Question 11

What does aldosterone do?

Answer 11

Na reabsorption (Na-K-ATPase basolateral, ENaC at luminal)
K+ secretion (ROMK in luminal)

Question 12

Where does ADH act to increase water reabsorption?

Answer 12

V2 receptor in the late distal tubule and collecting ducts

Question 13

How does ADH reabsorb water?

Answer 13

Synthesis + insertion of aquaporin 2 to luminal membrane

Question 14

Where does ANP act?

Answer 14

• collecting ducts to inhibit Na and water reabsorption
• inhibits renin secretion

Question 15

Which 2 mechanisms create the hyperosmotic medullary interstitium?

Answer 15

• loop of Henle’s countercurrent mechanism
• urea recycling

Question 16

Which 2 mechanisms maintain the hyperosmotic medullary interstitium?

Answer 16

• distal tubule and collecting duct
• vasa recta

Question 17

Function of the pelvic nerve (S2-3):

Answer 17

Sensory: detect stretch, micturition reflexes for bladder emptying
Motor: parasymathetic -> contraction of detrusor muscle

Question 18

Function of the pudendal nerve (S2-S4):

Answer 18

External bladder sphincter (skeletal muscle)
Inhibiting it -> mictrurition

Question 19

Which enzyme is the rate limiting factor in the metabolism of ethylene glycol?

Answer 19

Alcohol dehydrogenase

Question 20

2 most important factors to promote urethral healing:

Answer 20

Good mucosal continuity
Prevention of urine extravasation

Question 21

Why are high chloride containing fluids harmful to the kidneys?

Answer 21

High conc. of Cl delivered to the macula densa which would induce afferent arteriole vasoconstriction and lower GFR, RBF

Question 22

What is the main causative agenet for pyeloneprhitis?

Answer 22

Enterobacteriaceae

Question 23

What is a reasonable first choise for pyeloneprhitis while awaiting C/S?

Answer 23

Fluoroquinolones or cefpodoxime

Question 24

What antibiotic characteristics are best for crossing the prostatic blood barrier?

Answer 24

• lipid soluble
• weakly alkaline
• high pKa

Question 25

What defines recurrent urinary tract infection?

Answer 25

3 or more episodes of clinical bacterial cystitis in prev 12 months OR 2 or more episodes in preceding 6 months

Question 26

Main method of solute removal for intermittent hemodialysis, continuous venovenous haemodialysis (CVVHD)

Answer 26

diffusion

Question 27

Main method of solute removal for slow continuous ultrafiltration (SCUF) and continuous venovenous haemofiltation (CVVH):

Answer 27

convection

Question 28

Difference between SCUF and CVVH:

Answer 28

in CVVH once the ultrafiltrate is removed, it is replaced with a sterile balanced electrolyte solution

Question 29

Which condition is SCUF good for?

Answer 29

CHF - as ultrafiltate is not replaced by anything

Question 30

What method of solute removal does continuous venovenous hemodiafiltration rely on:

Answer 30

Combines diffusion and convection

Question 31

What is convection?

Answer 31

when solutes are dragged with plasma water across the dialysis membrane due to osmotic pressure gradient or hydrostatic pressure (solvent drag)

Question 32

How does diffusion work?

Answer 32

Countercurrent movement of the blood and dialysate across the dialyser semipermeable membrane allows for efficient bidirectional movement of solutes from high -> low concentration

Question 33

what is ultrafiltration?

Answer 33

Process of plasma water removal from the intravascular compartment (and ultimately from the interstitial and intracellular spaces) In IHD and CRRT application of a negative transmembrane pressure to the dialyser will allow plasma water to shift across the membrane into the dialysate and out of the patient

Question 34

what is dialysis?

Answer 34

Dialysis is the movement of solutes between 2 aqueous solutions separated by a semipermeable membrane

Question 35

Toxin factors to consider for extracorporeal removal:

Answer 35

- Vd (<2L/kg) - MW - Degree of protein binding - Water solubility

Question 36

List 10 complications that have been reported with PD in small animals

Answer 36

1. Catheter flow problems – obstruction with omentum, catheter kinking, fibrin clots 2. Catheter exit site leaks – into subcutaneous tissue 3. Catheter exit site and tunnel infection 4. Electrolyte disorders 5. Hypoalbuminemia (most commonly reported) 6. Peritonitis 7. Dyspnoea caused by ↑abdominal pressure or pleural effusion 8. Changes in hydration status (overhydration) 9. Dialysis disequilibrium 10. Hyperglycemia Peritoneal fibrosis

Question 37

Why is urine osmolality better than USG?

Answer 37

Provides more information on renal concentrating ability than USG

Question 38

Difference between urine osmollality and USG

Answer 38

USG = density per unit volume of solution (no. of particles and MW) Osmolality = no. of particles per unit volume of solution