CBL 13: The Horse with Colic

When do the 01 (central) deciduous teeth come through?

6d

When do the 02 (middle) deciduous teeth come through?

6w

When do the 03 (corner) deciduous teeth come through?

6m

When do the 01 (central) permanent teeth come through?

2.5y

When do the 02 (middle) permanent teeth come through?

3.5y

When do the 03 (corner) permanent teeth come through?

4.5y

How many incisors do horses have?

3

How many canines do horses have?

1 (commonly extracted)

How many premolars do horses have?

3 (4 if has wolf tooth)

How many molars do horses have?

3

hypsodont teeth

teeth with high crowns

What are some features of hypsodont teeth that make them beneficial to horses?

• large crown for wear protection

• premolars & molars larger and flatter to grind down plant matter & aid digestion

• large grinding surface

What are dental focal overgrowths caused by?

lack of attrition to crown of tooth

What does lack of attrition to the crown of horse tooth cause?

dental focal overgrowths

What can cause dental focal overgrowths (due to lack of attrition to crown of a tooth)?

• if opposite occlusal surfaces don’t meet

• differences in eruption times of cheek teeth

• tooth loss

• differences in timing of cap shedding

• high starch/low fibre diet

What impacts can dental focal overgrowths have on a horse?

• infection of supporting bones/maxillary sinus

• quidding

• weight loss

• abnormal head carriage, resistance to the bit and head shaking during work

• colic

• diastemas (if overgrown tooth wears away from another tooth excessively)

What are the paranasal sinuses in close association with?

roots of cheek teeth

What is the maxillary sinus divided by & into?

by a thin septum into caudal and rostral sinuses

What tooth does the rostral maxillary sinus have the root of?

first maxillary molar

What paranasal sinus is the root of the first maxillary molar associated with?

rostral maxillary sinus

What teeth does the caudal maxillary sinus have the root of?

second and third molars

What paranasal sinus is the second and third molars associated with in the horse?

caudal maxillary sinus

What nerves are the teeth innervated by?

branches of the trigeminal nerve

What nerves are involved in the neural supply of the teeth?

• trigeminal nerve

• infraorbital nerve

• inferior alveolar nerve

What does the infraorbital nerve enter & innervate?

enters maxillary foramen and innervates the upper incisors and maxillary premolar teeth

What does the inferior alveolar nerve enter and supply?

enters mandibular foramen and supplies mandibular teeth

What is the major blood supply to the teeth?

maxillary artery

Where does the major palatine artery run?

rostrally from major palatine foramen to incisive foramen along lateral border of hard palate

How old is this horse?

3y

How old is this horse?

4y

How old is this horse?

>6y

What type of tooth keeps growing/erupting?

hypsodont

What nerve does the red/pink line show?

trigeminal nerve

What nerve does the green line show?

maxillary

What nerve does the light blue line show?

mandibular

What nerve does the dark blue/purple show?

facial

Which vessels supply the mandibular CT dental arcades?

• inferior alveolar artery

• maxillary artery

• mandibular artery mental artery

What structures should be palpable per rectum in horses?

• uterus, ovaries or inguinal rings

• LDC, LVC

• bladder

• left kidney

• pelvic flexure, nephrosplenic ligament

• abdominal aorta

• descending colon

• spleen - caudal border

• caecum

What are the 2 types of gut motility?

• segmentation

• peristalsis

Segmentation

alternative contractions squeeze material back and forth - no net movement

What does segmentation do/increase?

increase rate of digestion and absorption

Peristalsis

• initiated at a point

• contraction of circular muscle on oral side

• relaxation of circular muscle aboral side

• moves gut contents along GI tract

What does local distension cause? (enteric control)

• oral propagation excitation

• aboral propagating inhibition

• produces peristaltic movement aborally

What does extrinsic control cause? (gut motility - segmentation & peristalsis)

• parasympathetic increases peristalsis (stronger)

• sympathetic decreases peristalsis (weaker)

What is the motility in the SI like?

slow waves frequently

What is the motility in the LI like?

slow waves less frequent than SI

What is the secretion in the SI like?

• mucosa has small circular folds with villi & microvilli

• produces digestive enzymes

What is the secretion in the LI like?

• thick mucosal layer

• mucus secreting glands

What percentage of nutrients does the SI absorb?

90%

What does the LI absorb?

water & remaining nutrients

What is hindgut fermentation?

a process of anaerobic digestion that relies on the metabolic action of bacteria and other microorganisms to break down molecular substrates

At what sites does hindgut fermentation occur?

caecum and colon

What species rely on hindgut fermentation for digestion?

horses and rabbits

What are paraprofessionals?

allied veterinary professionals that work alongside vets by providing specialised care to equids

Name examples of paraprofessionals involved in equine care

• equine dental technicians

• farriers

• musculoskeletal therapists

Name examples of musculoskeletal therapists

• chiropractor

• osteopath

• physiotherapists

How do you build and maintain interprofessional relationships with paraprofessionals to try to safeguard the welfare of animals?

• find one you trust

• set up good referral process

• communication

• keep updated medical records

• provide progress reports

• manage client expectations for both parties

What is abdominal ultrasound useful to determine?

• gut position

• gut wall thickness

• gut distension

• gut motility

• gut content

• free fluid

• need for emergency surgery

What is the ‘interface’ in ultrasounds?

point of apposition between neighbouring structures

How does a pocket of peritoneal fluid appear on ultrasound?

anechoic

How does the equine large colon appear on ultrasound?

hyperechoic

How does the bovine rumen appear on ultrasound?

hyperechoic

Which structure is circled?

SI distended loop

What is the normal ultrasonographic appearance of the liver?

homogeneous, mildly granular echotexture

What is the normal ultrasonographic appearance of the spleen?

homogenously echoic with a fine echotexture

What is the normal ultrasonographic appearance of the lumen of the GI tract?

variable depending on luminal contents

What is the normal ultrasonographic appearance of the mucosa of the GI tract?

hyperechoic with variable thickness

What is the normal ultrasonographic appearance of the submucosa of the GI tract wall?

hyperechoic and relatively narrow

What is the normal ultrasonographic appearance of the muscularis of the GI tract?

hypoechoic with variable thickness

What is the normal ultrasonographic appearance of the serosa of the GI tract?

thin hyperechoic layer, clear identification often difficult

What is the normal ultrasonographic appearance of the stomach?

variable appearance depending on luminal content

What is the normal ultrasonographic appearance of the capsule of the kidney?

thin hyperechoic line

What is the normal ultrasonographic appearance of the cortex of the kidneys?

hyperechoic, fine and uniform echotexture

What is the normal ultrasonographic appearance of the medulla of the kidneys?

hypoechoic to anechoic in comparison to the outer cortex

What is the normal ultrasonographic appearance of the sinus of the kidneys?

hyperechoic structure situated centrally in the kidney

What is the normal ultrasonographic appearance of the bladder?

• outer: hyperechoic

• middle: hypoechoic with 3 smooth muscle layers

What is the normal ultrasonographic appearance of the inner submucosal smooth muscle layer of the bladder?

hyperechoic

What is the normal ultrasonographic appearance of the innermost mucosal layer of the bladder?

hypoechoic

Acoustic enhancement

• below structures transmit sound well

• reduces impedance

• deep to this, structures appear more clear

Acoustic shadowing

• below structures which transmit sound poorly

• increases impedance

• deep to this the structures appear less clear

Does acoustic enhancement reduce or increase impedance?

reduce

Does acoustic shadowing reduce or increase impedance?

increase

What is an ultrasound artefact?

something that is observed on an ultrasound image but is not actually there, is in another place or looks different from what it actually looks like

What happens when ultrasound waves hits pleura?

reverberation

What is peritoneal tap also known as?

abdominocentesis

What are the 2 techniques of abdominocentesis (peritoneal tap)?

• needle

• trocar

At what location do you do abdominocentesis with a needle?

• 4” caudal to xiphoid

• 4” to right of midline

What location do you do abdominocentesis with a trocar?

• 4” caudal to xiphoid

• midline

What abdominal structure might be avoided by the site 4” caudal and to the right of the midline when doing abdominocentesis?

spleen

What structure do you pass through in the ventral midline 4” caudal to the xiphoid when doing abdominocentesis?

linea alba

What physical factor will keep the peritoneal fluid in the abdomen rather than dripping out of your needle? (abdominocentesis)

surface tension

What is the normal colour of peritoneal fluid?

straw coloured, clear fluid

What is the function of peritoneal fluid in horses?

act as lubricant reducing friction when digesting

What is lactate?

ionised form of lactic acid (byproduct of anaerobic metabolism)

What is plasma lactate?

lactate in the bloodstream

Why is measuring blood plasma lactate levels useful?

• in horses with colon increasing BLC can indicate worsening prognosis

• assist in determining severity of conditions and need for intensive care

Colic

abdominal pain

Ileus

temporary slowing of GI motility

What are the risks associated with examining teeth in a horse?

• injuries

• improper handling

• stress and anxiety

• sedation risks

• further injuries/trauma from equipment

Which type of colic is associated with tapeworms, large strongyles, cyathostomins and ascarid worm?

parasitic colic