Renal / Urology - Anatomy/Physiology (pre-clinical)

Question 1

Function of afferent arteriole, efferent arteriole, and glomerulus

Answer 1

Blood enters glomerulus via afferent arteriole, gets filtered by yhe glomerulus, then filtrate-depleted blood exits glomerulus and goes back into circulation (via efferent arteriole)

Question 2

3 main holistic functions of the renal system

Answer 2

1. Filtration - removal of metabolic products and toxins from the blood for excretion
2. Regulation - of fluid balance (BP), electrolyte imbalance, and acid-base balance (pH)
3. Production/Activation - of hormones involved in erythrogenesis, Ca2+ metabolism, and the regulation of blood pressure (RAAS)

Question 3

Functions of kidney

Answer 3

• Maintains blood volume (through excretion or retention of fluid)
• maintains concentration of ions within blood
• maintains pH of blood (acid-base balance) - modulation of hydrogen ions and bicarbonate
• produces glucose by gluconeogenesis - usually minimal contribution to glucose production, except when fasting where glucose production increases
• activates vitamin D –> controls calcium and phosphorus metabolism
• excretes metabolic waste (urea + creatinine, water-soluble drugs, toxins)
• renin production (RAAS system)
• new RBC production (EPO)

Question 4

Describe this graph

Answer 4

• GFR is determined by the net filtration pressure across the glomerular capillaries
• blood flow is proportional to changes in pressure - ie. increased blood flow = increased pressure

Question 5

How is renal blood flow controlled?

Answer 5

• Increased/Decreased afferent/efferent arteriolar resistance has effects on renal blood flow and net ultrafiltration pressure

Question 6

Glomerular haemodynamics

Answer 6

Question 7

Name 2 mediators of renal blood flow that cause vasoconstriction + how they work

Answer 7

1. Sympathetic nerves (‘fight or flight’)
   - norepinephrine released –> causes increased resistance of both afferent/efferent arterioles
   - this causes a decreased in renal blood flow and GFR
   - this prevents fluid loss
   .
2. RAAS (angiotensin II)
   - ANG II constricts both afferent/efferent arterioles, but works with prostaglandins to constrict efferent > afferent
   - this maintains GFR when renal perfusion is low

Question 8

Name 2 mediators of renal blood flow that cause vasodilation + how they work

Answer 8

1. Prostaglandins
   - dampen renal vasoconstrictor effects (esp. on afferent arterioles)
   - therefore, prevents severe/harmful vasoconstriction and renal ischaemia
   .
2. Natriuretic peptides (ANP and BNP)
   - ANP and BNP released by heart in response to increased blood pressure
   - causes vasodilation of afferent > efferent arterioles
   - this increases renal blood flow and GFR
   - (ANP also inhibits secretion of renin, therefore decreases ANG II lvls)

Question 9

Why is autoregulation of renal blood flow in response to systemic BP important and what are the 2 processes involved?

Answer 9

• to maintain renal blood flow and GFR within narrow limits, despite changes in mean material pressure (BP)
  .
  1. Myogenic response
• afferent arterioles can constrict/relax in response to BP –> helps prevent excessive increases in RBF and GFR when systemic BP increases/decreases
• eg. BP increases –> afferent arteriole constricts –> increased afferent arteriolar resistance –> decreased RBF –> decreased GFR –> maintained RBF/GFR (no excessive increase)
  .
  2. Tubulo-glomerular feedback mechanism
• increase in arterial pressure (BP) increases filtration (GFR) and therefore Na+ and Cl- in proximal tubule
• increase in Na+ ions is sensed by macula densa cells of the JGA
• macula densa cells then release paracrine agents which triggers contraction of nearby vascular smooth-muscle cells in afferent arteriole
• this increases afferent arteriolar resistance, which decreases GFR, counteracting the initial increase in GFR

Question 10

Glomerular filtration VIDEO

Answer 10

https://www.youtube.com/watch?v=9A2dAyWyK6o

Question 11

Which of the following would cause the greatest decrease in GFR in a person with otherwise normal kidneys?

• Decrease in renal arterial pressure from 100 to 80 mmHg
• 50% increase in proximal tubular sodium reabsorption
• 50% decrease in afferent arteriolar resistance
• 50% decrease in efferent arteriolar resistance
• 5 mmHg decrease in Bowman’s capsule pressure

Answer 11

50% decrease in efferent arteriolar resistance

• causes a substantial decrease in GFR

(a decrease in renal arterial pressure from 100 to 80 mmHg would only cause a slight reduction in GFR because of autoregulation)

(the other options would tend to increase GFR)

Question 12

Net contribution by the kidneys to whole-body glucose production is minimal (<10%) except under conditions of ________ , when they can contribute up to 30% to 40%.

fill in the blank

Answer 12

Net contribution by the kidneys to whole-body glucose production is minimal (<10%) except under conditions of prolonged fasting, when they can contribute up to 30% to 40%.

Question 13

Which of the following, compared with normal, might you expect to find 3 weeks after a patient ingested a toxin that caused sustained impairment of proximal tubular NaCl reabsorption? Assuming no change in diet or ingestion of electrolytes.

• No change in GFR, no change in afferent arteriolar resistance
• Decreased GFR, increased afferent arteriolar resistance
• Increased GFR, increased afferent arteriolar resistance
• Increased GFR, decrease afferent arteriolar resistance

Answer 13

Decreased GFR, increased afferent arteriolar resistance

• impairment of proximal tubular NaCl reabsorption would increase NaCl delivery to the macula densa, which in turn would cause a tubuloglomerular feedback-mediated increase in afferent arteriolar resistance (the increased afferent arteriolar resistance would decrease GFR)

Question 14

Which mediator acts to selectively modulate the sympathetic vasoconstrictive effects on the afferent arterioles to prevent sustained damage?

• Brain natriuretic peptide
• Prostaglandin
• Angiotensin II

Answer 14

Prostaglandin

Question 15

A selective decrease in efferent arteriolar resistance would ______ glomerular hydrostatic pressure, ______ GFR, and ______ renal blood flow.

insert increase or decrease

Answer 15

A selective decrease in efferent arteriolar resistance would decrease glomerular hydrostatic pressure, decrease GFR, and increase renal blood flow.

Question 16

What is an acid?

What is a base?

What is a weak acid?

What is a buffer?

Answer 16

• Acid –> H+ donor (fully dissociates into H+ ions in water
• Base –> H+ acceptor
• Weak acid –> only partially dissociates into hydrogen ions (H+) when dissolved in water
• Buffer (buffered solution) –> weak acids or weak bases (addition of acid or base does not affect pH of solution)

Question 17

• Disturbances of HCO3 are primary _________ disorders.
• Disturbances of CO2 are primary __________ disorders.

Answer 17

• Disturbances of HCO3 are primary metabolic disorders.
• Disturbances of CO2 are primary respiratory disorders.

Question 18

Arterial pH for:
- Acidemia
- Alkalemia

Answer 18

• Acidemia - arterial pH <7.35
• Alkalemia - arterial pH >7.45

Question 19

Renin Angiotensin Aldosterone System - Video

Answer 19

Dr Matt and Dr Mike: https://www.youtube.com/watch?v=ibjodC7Ft7U

Question 20

What cells in the afferent arteriole release renin?

Answer 20

Juxtaglomerular cells (granular cells) - baroreceptors

Question 21

Name 3 ways in which renin is stimulated to be released (triggers)

Answer 21

1. Drop in BP in afferent arteriole (renal perfusion) - detected by juxtaglomerular cells (baroreceptors)
2. Drop in Na+ concentration in DCT - detected by macula densa cells (chemoreceptors)
3. Increased sympathetic NS innervation - fight or flight response
   .
   (note: macula densa cells and juxtaglomerular cells are connected by connective tissue)
   (sympathetic NS directly innervates the juxtoglomerular (granular) cells to release renin)

Question 22

Where is the majority of sodium (Na+) reabsorbed back into the body?

Answer 22

Proximal tubule of the kidney - 65%

Question 23

Describe the process of how angiotensin II is produced.

Answer 23

• Renin is released by kidney
• Angiotensinogen is released by liver into the bloodstream
• Renin converts angiotensinogen into angiotensin I
  .
• Lungs produce ACE
• ACE converts angiotensin I into angiotensin II

Question 24

What are the functions of angiotensin II?

Answer 24

1. Generalised vasoconstrictor - increases BP
2. Constricts smooth muscle of efferent arteriole - increases filtration rate (GFR) which increases Na+ in DCT –> -ve feedback loop
3. Stimulates adrenal cortex to release aldosterone - aldosterone increases Na+ reabsorption into the body –> wherever sodium goes, water follows –> increases BV –> increases BP
4. Stimulates release of ADH from posterior pituitary gland (hypothalamus) - ADH travels to DCT and collecting ducts, and increases water reabsoprtion –> increases BV –> increases BP

Question 25

Label the internal features of the kidney . - Minor calyx, major calyx, renal cortex, renal medulla, renal pelvis, renal pyramid, ureter

Answer 25

Question 26

Label the features of the bladder . - Apex, fundus (base), inferior surface, neck, ureter, urethra, superior surface

Answer 26

Question 27

Label the structures that are located near the kidneys . - hepatic flexure of colon, liver, duodenum, spleen, stomach, splenic flexure of colon, pancreas

Answer 27

Question 28

What causes a horseshoe kidney?

Answer 28

- In embryology, the kidneys start off located near to the sacrum and then as the abdominal cavity grows they ascend to reach their final position in upper lumbar region - As the kidneys ascend, they rotate medially - this can cause the lower poles of the kidneys to come into contact with each other --> *this can then cause fusion of the lower poles creating a horseshoe kidney*

Question 29

What artery prevents the ascent of a horseshoe kidney during embryological development to its normal position?

Answer 29

Inferior mesenteric artery

Question 30

Why does renal carcinoma tend to present at a late stage rather than early stage?

Answer 30

- A space occupying lesion in the kidney will not cause any obvious symptoms in the early stages as there are no closely related structures that will be affected by its growth - The innervation of the kidney is autonomic meaning that there are very few sensory fibres present and a small lesion would not be detected

Question 31

How does the anatomy of the kidney allow for a portion of the kidney to be removed rather than removal of the whole organ?

Answer 31

The kidneys develop embryologically as lobular structures and the blood supply is dictated by this development

Question 32

John had a CT MRI scan that revealed a mass in his left kidney (renal carcinoma), it was found early and surgically removed. If John hadn’t been so lucky, which lymph nodes would the tumour spread to and which structures would be most likely affected first?

Answer 32

Renal and caval lymph nodes

Question 33

John had a CT MRI scan that revealed a mass in his left kidney (renal carcinoma), it was found early and surgically removed. If John had suffered from haematogenous metastases, which structure would most likely be affected first?

Answer 33

The lungs as the tumour will invade the renal veins then the IVC and will pass through the heart and to the lungs

Question 34

How does the anatomy of the left and right renal veins differ? How would this affect the likelihood of haematogenous metastatic spread?

Answer 34

- The right renal vein is shorter - *due to the proximity of the course of the inferior vena cava (ie. the IVC is on the right side of the body so the right renal vein doesn't have to travel as far)* - The shorter distance also means that haematogenous metastatic spread can happen quicker and will likely spread to the vena cava and heart, resulting in lung cancer

Question 35

Cancer of which kidney is more likely to metastasise, and cause lung cancer as an example

Answer 35

A carcinoma of the right kidney is more likely to metastasize and cause lung cancer - *right renal vein is shorter, haematogenous metastatic spread can happen quicker* - spread via renal vein to IVC to heart to lungs --> lung cancer

Question 36

Note the internal folded appearance of the anterolateral and superior walls of the bladder. Why do these walls have a folded nature?

Answer 36

To allow for distension of the bladder (ie. allow the bladder to stretch)

Question 37

The detrusor muscle is located within the anterolateral and superior walls of the bladder and contains both longitudinal and circular smooth muscle. What is the function of the detrusor muscle?

Answer 37

To contract the bladder wall during voiding

Question 38

Label the urinary tract. . - Sphincter, ureter x2, urethra, bladder, kidney x2

Answer 38

Question 39

Note the angle and level at which the ureters enter the bladder. What is the functional reason for this?

Answer 39

To create a pseudo-valve preventing reflux of urine to the kidneys

Question 40

Renal calculi (kidney stones) can become lodged in the ureter. What are the 3 locations that these most commonly occur at?

Answer 40

- Uteropelvic junction (UPJ) - The point where the ureter passes the pelvic brim/external iliac artery - The point at which the ureter enters the bladder (ureterovesical junction)

Question 41

Pain caused by renal calculi is described as ‘excruciating’. This pain can be caused by directly affecting the muscles relating to the kidney and ureter. Identify these muscles using the diagram

Answer 41

Question 42

Which structures does the ureter pass as it descends to the bladder?

Answer 42

Psoas, pelvic brim at the bifurcation of common iliac, lateral pelvic wall

Question 43

Renal calculi are commonly found in three areas. For each area, explain how the anatomy causes this: - Uteropelvic junction - As the ureter passes the common iliac artery - As the ureter enters the bladder

Answer 43

- Uteropelvic junction: *the ureter becomes angled and narrowed as it leaves the renal pelvis and becomes the ureter* - As the ureter passes the common iliac artery: *passes over the pelvic brim which can narrow or kink the ureter* - As the ureter enters the bladder: *the oblique entry of the ureter into the bladder creates a pseudivalve*

Question 44

Warren was surprised that the site for his nephrostomy was in his loin area. Anatomically, what are the two main advantages of accessing the kidney from this area?

Answer 44

- Able to access the retroperitoneal space easily - Can avoid entering the peritoneal cavity and damaging other structures

Question 45

Warren had kidney stones (renal calculi). Why was his pain ‘colicky’ in nature?

Answer 45

Intermittent pain due to peristaltic action on calculi

Question 46

What is the innervation of the ureter?

Answer 46

Autonomic innervation of structure (T10-L1/2)

Question 47

Where can kidney stone (renal colic) pain be referred to (ie. where is the pain typically described as being)?

Answer 47

Loin to groin