Exotics renal anatomy and physiology

Question 1

Describe nitrogenous waste in aquatic organisms

Answer 1

excrete ammonia directly

Question 2

Describe nitrogenous waste of terrestrial organisms

Answer 2

Mammals, terrestrial amphibians - urea
Birds, reptiles - Uric acid (uricotelism)

Question 3

Describe the features of uric acid

Answer 3

Made in liver
Highly insoluble:
- water conservation
- storage in eggs
Tubular secretion via reptilian-type nephrons
Excretion is independent of:
- urine flow rate
- tubular water reabsorption
- hydration state

Question 4

Describe the causes of gout in birds and reptiles

Answer 4

Hyperuricemia (excess uric acid) => precipitates out of blood into organs and joints => gout (visceral and articular)

Causes:
- renal disease
- high dietary protein - too many AAs => more uric acid
- dehydration - urates produced which cannot be flushed => renal gout
- nephrotoxic drugs - damages renal tubules

Question 5

Describe the composition of urates in birds and reptiles

Answer 5

Precipitate:
- uric acid
- protein
- Na+ (carnivorous)
- K+ (herbivorous)
Enters cloaca and mixes with faecal material

Question 6

Why are birds and reptiles able to excrete urates even when dehydrated?

Answer 6

Uric acid crystals precipitate => no osmotic pressure so does not draw water out with it

Question 7

Why is urinalysis useless in birds and reptiles?

Answer 7

Due to mixing of urine, urate and faecal material

Question 8

Describe the use of the renal portal valve in exotics

Answer 8

Normal:
Valve closed (ACh): limbs => renal portal veins => kidney => caudal vena cave
Stressed or dehydrated:
Valve open (adrenaline): limbs => caudal vena cava

Question 9

How does the renal portal system in exotics protect against ischemic necrosis of the kidney?

Answer 9

Blood from tail/caudal body travels to the heart via the kidney
Portal system ensures blood flow to tubules (does not supply glomerulus)

Question 10

Describe the clinical implications of the renal portal system in exotics

Answer 10

Drug pharmacokinetics:
- if drugs injected into caudal region, goes to kidneys first => damage or excretion
Caudal mesenteric vein:
- contributes to renal portal system
- disease of GIT => kidneys
- toxins from gut

Question 11

Label the fish nephrons

Answer 11

Question 12

Label the freshwater glomerular teleost nephron

Answer 12

Question 13

Label the marine glomerular teleost nephron

Answer 13

Question 14

Label the marine aglomerular teleost nephron

Answer 14

Question 15

Label the reptilian nephron

Answer 15

Question 16

Describe the key difference between fish/reptile and mammalian nephrons

Answer 16

fish/reptile nephrons have no LoH

Question 17

Describe the avian nephrons

Answer 17

70-90% Reptile type nephrons:
- no LoH
- Cortex only
10-30% Mammalian type nephrons:
- LoH
- cortex -> medulla
Limited urine concentration

Question 18

Describe the avian response to dehydration

Answer 18

Aginine vasotocin (avian ADH equivalent)
- stimulated by increased plasma osmolarity
- constricts afferent arteriole (renal portal system maintains perfusion)
-controls tubular water permeability
Urine can be retropulsed from the urodeum into the colon and caecum for sodium-linked water reabsorption

Question 19

Describe sodium linked water reabsorption in the avian/reptilian colon and caecum

Answer 19

Active transport of Na out of colon
Cl ions follow Na
Water follows via osmosis

Question 20

Describe the reptile response to dehydration

Answer 20

Arginine vasotocin => afferent arteriole constriction and increased tubular water permeability
Reverse peristalsis of urine from urodeum => rectum/colon

Question 21

Describe post-renal urine modification in exotics

Answer 21

Cloaca, colon, bladder:
- ions
- water
- protein
- Na+, K+
- urates
Voided urine not reflective of renal function

Question 22

Label the breeding and non-breeding avian urinary system (male)

Answer 22

Question 23

Why can kidney disease cause paralysis in avian species?

Answer 23

Kidneys closely associated with lumbar and sacral plexus - spinal nerves run through kidney parenchyma
Kidney disease => renomegaly => pressure on nerve plexi => paralysis or lameness

Question 24

Describe lizard renal anatomy

Answer 24

Caudal aspect of kidneys fused in many species
Only some species have a bladder

Question 25

Describe the anatomy of the avian kidneys

Answer 25

Paired Retroperitoneal Large

Question 26

Describe snake renal anatomy

Answer 26

Right kidney cranial to left No bladder - urine stored in distal colon or flared ends of ureters

Question 27

Answer 27

Question 28

Describe chelonian renal anatomy

Answer 28

Kidneys in caudal coelom No pelvis, pyramids, cortex or medulla Fewer nephrons Lower GFR Poorly developed glomeruli No LoH (can't concentrate urine)

Question 29

Describe chelonian bladder anatomy

Answer 29

Bladder may have paired accessory bladders Bladder is osmotically permeable (give baths before hibernation to fill accessory bladder)

Question 30

Describe the sexual segment in some male squamates

Answer 30

Cells between distal tubule and collecting duct Cells change at breeding system: - cuboidal => columnar - increase in size - large eosinophilic granules secreted into lumen

Question 31

Describe the salt glands of some avian and reptile species

Answer 31

Modified nasal/lacrimal/salivary glands Excretion of salt without water loss Excreted by burrowing, sneezing, tongue protrusion Dries to white powder (can be confused as fungal infection) High salt exposure => hyperplasia/hypertrophy

Question 32

Describe fish renal anatomy

Answer 32

Single kidney Length of coelom Cranial division: - endocrine - haematopoietic Caudal division: - filtration (nephrons) No LoH => hypo-osmotic urine

Question 33

Describe fish osmoregulation and nitrogenous waste

Answer 33

Water movement by osmosis across skin and gills Nitrogenous waste (ammonia) excreted by gills, some in urine

Question 34

Describe freshwater fish osmoregulation

Answer 34

Ion loss/water gain across gills and skin Kidney excretes water - high GFR Gills: - NaCl active uptake - excrete ammonia Dietary intake NaCl

Question 35

Describe saltwater fish osmoregulation

Answer 35

Lose water across gills and skin Drink seawater to replace Gills: - excrete NaCl - excrete ammonia Kidneys: - small or no glomeruli - remove excess divalent ions (Mg2+)

Question 36

Describe amphibian renal anatomy

Answer 36

Renal portal veins: - blood from hindlimbs => kidney => heart Caecilians (legless, wormlike lizards): - one kidney - full length coelom Caudates (salamanders, newts) and anurans (frogs, toads) - paired kidneys - posterior kidneys - retroperitoneal

Question 37

Describe the amphibian cloacal bladder

Answer 37

Outpouching of cloacal wall No direct connection with excretory ducts Urine seeps into cloaca and is forced into bladder for urine storage Cloacal opening is closed by sphincter muscle

Question 38

Describe osmoregulation of aquatic amphibians

Answer 38

Skin water permeable - prone to evaporative water losses Kidney must excrete excess water Excrete ammonia through gills/skin

Question 39

Describe osmoregulation of terrestrial amphibians

Answer 39

Water conservation important Evaporative losses Urinary bladders stores water (aquaporins control movement) Decreased GFR with reduced water Most excrete urea

Question 40

Describe the clinical relevance of aquatic species osmoregulation

Answer 40

Skin is important for fluid balance and respiration: - disease/damage can be catastrophic for health - no surgical scrubbing (destroys mucous coating) - sensitive to environmental contaminants - minimise handling - can administer fluids and meds by putting them in water - water quality very important

Question 41

What is the issue here?

Answer 41

Articular gout = uric acid deposits in synovial capsules and tendon sheath of joints

Question 42

Describe the murexide test

Answer 42

Used to confirm gout Joint aspirate mixed with nitric acid and dried Ammonia added If turns mauve = uric acid present = gout

Question 43

What are the causes of decreased uric acid secretion?

Answer 43

Question 44

What causes increased uric acid production

Answer 44

excess dietary protein

Question 45

What does pink shell lesions suggest in aquatic species?

Answer 45

septicaemias

Question 46

How can you prevent septicaemia in aquatic species?

Answer 46

Keep enclosure clean Clean water thoroughly Test water quality regularly Remove things that could cause injury Ensure correct temps Balanced diet Reduce stress