Alimentary System Flashcards
Measurement used to assess the angulation of the check tooth occlusal surface
With the mouth closed the rostral aspect of the mandible should be pushed sideways and the distance of the lateral movement of the lower incisors in relation to the upper before separation of the incisors (as the angled occlusal surfaces of opposing check teeth come into contact)
Major significance of parrot mouth
overgrowth of rostral aspect of 106 and 206 and caudal aspect of 311 and 411
describe the problem
cheek teeth slab fracture
Equine tooth anatomy
When describing disorders of the incisors and “overjet” refers to
Rostral projection of the upper incisors in a horizontal plane
What is a major significance of overjet
Affected horses commonly have overgrowths of the rostral aspects of 106 and 206 and of the caudal aspect of 311and 411
In affected foals how is overjet surgically corrected
Incisor orthodontic brace by placing steel wires (a tension band) around the upper incisors and fixing these wires around 506 and 606 (or 507 and 607) to retard growth of the premaxilla and maxilla
Best performed at around 3 months of age but it can be of value up to 8 months old
considerations of orthodontic brace when overbite is present
The tension may cause further caudoventral deviation of the upper incisors and premaxilla toward the rostral aspect of the lower incisors
In such foals a biteplate can additionally be fitted along with the orthodontic brace to promote indirect occlusion between the upper and lower incisors
Describe underbite ‘Sow Mouth”
Prognathism (under jaw, underbite) is rare in horses, except in miniature horses and is usually clinically insignificant unless there is total lack of occlusion between the upper and lower incisors
Eventually will develop a concave upper incisor occlusal surface which has been termed a frown and may develop lower 06 and upper 11 overgrowth
Retained deciduous incisors
Normally lie rostral (labial) to their permanent counterparts they can cause the permanent incisor to be displaced caudally (lingually)
Management of horse with incisor fractures
First aid - Tetanus prophylaxis and prolonged (7-10 days) antibiotics therapy, regional nerve block (mental or infraorbital nerve) followed by removal of any loose dental fragments and debridement of any exposed pulp as a main treatment when possible an endodontic treatment should be attempted
Define diastemata
Space that develops between the occlusal aspects of adjacent cheek teeth, mandibular cheek teeth are most commonly affected requiring the use of endoscopy or intraoral mirrors or obtaining 10-15 degree latero-oblique radiograph with the horse’s mouth open
best treatment for diastemata
In mature horses, widen problematic diastemata to about 4-6 mm wide on the occlusal surface
Describe rostral positioning of the maxillary cheek teeth
Common dental abnormality, invariably occurring in conjunction with overbite, eventually leading to the development of focal overgrowth of the rostral aspect of the upper 06s which may cut the cheeks and interfere with the bite
Similar overgrowth on the caudal aspect of 311 and 411 frequently go undetected and can lacerate the tongue, wear down the opposite check teeth (maxillary 11s) to gum level an even penetrate the hard palate or lacerate the greater palatine artery
Idiopathic fractures of cheek teeth
Most commonly slab fractures occur through the two lateral pulp cavities (pulp horns #1 and #2) usually upper 09s
Maxillary cheek teeth slab fractures site usually becomes filled with fibrous food, thus laterally displacing the smaller lateral cheek teeth fragments into the cheeks, causing buccal lacerations with subsequent quidding and biting problems
midline (sagittal) fractures of the maxillary cheek teeth
Occur less commonly than slab fracture
09s are most commonly affected
Believed to be secondary to advanced infundibular caries with coalescence of two carious infundibula leading to mechanical weakening, followed by fracture of the cheek teeth
List the equine dental tumors
Ameloblastoma (non-calcified epithelial tumors), ameloblastic odontoma (contains dentine, cementum, and enamel), odontoma (calcified) cementoma or more commonly combination of them (combined odontoma)
oral cavity tumors
Most common is SCC, other primary or metastatic tumors include melanoma, fibrosarcoma, hemangiosarcoma, lymphosarcoma, rhabdomyoma, rhabdomyosarcoma, and chondrosarcoma of the tongue
List the major salivary glands in the equine patient
Paired parotid, mandibular (submaxillary), and polystomatic sublingual glands, also smaller buccal, labial, lingual, and palatine salivary glands
Salivary secretions by different glands
Parotid secrete mainly serous fluids, whereas the mandibular and sublingual produce a combination of serous and mucous fluids
Describe the mandibular salivary gland
Extend from the atlantal fossa to the basihyoid bone
Most of its lateral surface is covered by the parotid salivary gland and partly by the mandible, and its medial surface covers the larynx, common carotid, vagosympathetic truck, and guttural pouch
The duct opens a few centimeters rostrolateral to the lingual frenulum at the sublingual caruncle
treatment for lacerated salivary glands
Fresh wounds of the parotid gland can be debrided and reconstructed with a multilayer closure starting with the parotid capsule, possible suture penetration to the glandular tissue provide a nidus for calculus formation and should be avoided
Primary closure of an acutely lacerated duct or a nonhealing salivary fistula is facilitated by suturing it over an intraluminal tube or by placing tree sutures to oppose the two cut ends as a triangle and suturing between the apices
options to manage chronic parotid salivary duct fistula
Surgical removal of the gland, duct ligation or chemical ablation of the gland
Discuss duct ligation
The parotid duct is located where it crosses the tendon of insertion of the sternomandibularis muscle close to its origin from the gland
2-3 heavy-gauge nonabsorbable sutures should be used and should not be tied to tightly to prevent cutting through the duct wall, the distal suture is tied first to distribute resulting back-pressure after ligation
Discuss chemical ablation
10% formalin (currently recommended), 2% chlorhexidine, 2% and 3% silver nitrate
When using 10% formalin the duct is cannulated and a ligature tied to prevent leakage
35 mL of formalin is injected through the cannula and left in place for 90 seconds and then allowed to drain out, the cannula is left in place for 36 hours
Cessation of salivary secretions occurs in 3 weeks
Describe Sialoliths
Hard concretions composed mostly of calcium carbonate and organic matter that develop within a salivary duct or less commonly gland
Affect older horses and the parotid duct is most commonly involved and usually occur singularly, typically a nonpainful, movable, firm structure is palpable on the lateral aspect of the face near the rostral end of the facial crest
Definitive treatment is removal, direct intraoral incision over the sialolith, leaving the wound to heal by second intention is preferred
Can be also removed by external longitudinal incision of the duct
Describe mucocele and ranula
Mucocele or sialocele refers to a pocket of saliva in a space not lined by epithelium
Ranula (“honey cyst”) represents a mucocele of one of the sublingual salivary glands ducts and is seen as bluish-tinged cyst on the floor of the mouth
How is the wall of the esophagus composed
4 layers (1) a fibrous layer (tunica adventitia) (2) muscular layer (tunica muscularis) (3) submucosal layer (tela submucosa) (4) and mucous membrane (tunica mucosa)
Muscular layers are striated from the pharynx to the base of the heart where they gradually blend into smooth muscle, on surgical incision separates easily into two distinct layers, the elastic inner layer composed of mucosa and submucosa freely movable within the relatively inelastic outer muscular layer and adventitia
what provides the greatest tensile strength on closure of an esophageal incision
The mucosa which is covered with stratified squamous epithelium and lies in longitudinal folds that obliterate the lumen
blood supply and innervation to the equine esophagus
Arterial supply to the cervical part originates from the carotid arteries, the thoracic and abdominal is supplied by the bronchoesophageal and gastric arteries
Innervation is derived from the ninth (Glossopharyngeal) and tenth (Vagus) cranial nerves and the sympathetic trunk as well as mesenteric ganglion cells within the muscle layers
Diagnostic imaging of the equine esophagus
Ultrasonography, radiography (esophagography) survey films are necessary
Barium paste (85% wt/vol with water 120ml) outline longitudinal mucosal folds
Liquid barium (72% wt/vol with water, 480 ml) demonstrate strictures and associated prestenotic dilation as well as space-occupying masses that displace the esophagus
Liquid barium (480 ml) followed by air (480 ml) delivered by dose syringe under pressure provides double-contrast study which gives the best definition of mucosal lesions
surgical approaches to the equine esophagus
Three surgical approaches: ventral cervical best used for esophagotomy, esophagomyotomy, and resections involving the proximal third of the cervical esophagus, ventrolateral approach recommended for placing a feeding tube in the midcervical esophagus (esophagostomy) or for approaching the distal one fourth of the cervical esophagus, thoracotomy is necessary to approach the distal half
Ventral approach to the equine esophagus
Dorsal recumbency, 10 cm skin incision, the paired sternothyroid, sternohyoid and omohyoid muscles are separated along the midline to expose the trachea and blunt separation of fascia along the left side of the trachea exposes the esophagus
- ventrolateral approach to the equine esophagus
Standing, dorsal or right lateral recumbency, 5 cm skin incision (for feeding tube placement) is made just ventral to the jugular vein the sternocephalicus and brachiocephalicus muscles are separated and the deep cervical fascia is incised to expose the esophagus it may be necessary to incise the cutaneous coli muscle in the distal cervical area
Describe esophagotomy
Dorsal recumbency, the skin of the ventral surface of the neck is prepared
10 cm skin incision to approach the esophagus, care should be taken to preserve the small vessels that supply the esophagus
Elevation of the esophagus from its bed of adventitia should be avoided, the left carotid sheath, containing the carotid artery, vagus and recurrent laryngeal nerves should be retracted laterally
Esophagus is incised through the muscle, submucosa and mucosa cranial to or caudal to or directly over a foreign body
Closure with simple continuous suture of 3-0 polypropylene with knots tied to the lumen, Drain placement
Esophageal stricture
Narrowing of the esophageal lumen due to stricture is usually annular lesion and can be classified into 3 types depending on the anatomic location and induration and fibrosis (1) mural lesions involving only the adventitia and muscularis (2) esophageal rings or webs that involve only mucosa and submucosa and (3) annular stenosis that involve all layers of the esophageal wall
Describe the considerations for esophageal stricture surgery
Esophageal lumen was maximally reduced (strictures) 30 days after circumferential ulceration, after which lumen diameter increased to normal by 60 days, therefore surgical intervention should be delayed for 60 days after original insult
Discuss esophagomyotomy
Esophagus is incised longitudinally to the level of the mucosa, through the stricture, and 1 cm distal and proximal to it, from this single incision the muscularis is separated by sharp dissection from the mucosa around the entire circumference of the esophagus when the mucosa is freed in this manner, removal of portion of the muscularis or multiple myotomy incisions are seldom necessary, the myotomy is not sutures and the approach incision is closed and drained in a routine manner
Describe esophageal diverticulum
Usually acquired lesions that result from contraction of periesophageal fibrous scar tissue causing outward traction and tenting of all layers of the esophageal wall (traction or true diverticulum) they can also occur from protrusion of mucosa and submucosa through a defect in the esophageal muscularis (pulsion or false diverticulum)
What are the regions of the equine stomach
Cardia at the opening of the esophagus, the fundus (which forms a blind sac), the body and the pyloric region
The cardia and pyloric region lie adjacent to each other, the cardia is attached to the diaphragm by the gastrosplenic ligament which is a continuation of the phrenicosplenic ligament and gastrosplenic ligament on the left side of the abdomen
Greater omentum attaches along the grater curvature of the stomach and it blends into a blind potential space called the omental bursa, the entrance to this bursa is the
Epiploic foramen, the lesser omentum which connects the stomach and duodenum to the liver consist in hepatogastric and hepatoduodenal ligaments
blood supply to the equine stomach
From the celiac artery and venous drainage from the stomach is via gastric veins to the portal vein
what are the 4 regions of the stomach
Based on the type of mucosal lining (orad-to-aborad order) nonglandular stratified squamous epithelium, cardiac epithelium, proper gastric mucosa (glandular mucosa) and pyloric mucosa
Describe the proper gastric mucosa
Contains secretory glands containing HCL-secreting parietal cells and pepsinogen-secreting zymogen cells, also contain enterochromaffin-like (ECL) cells that secrete histamine in response to various stimuli, which in turn amplifies HCL secretion by parietal cells
Describe the pyloric mucosa
Contains both G-cells which secrete gastrin and D-cells which secrete somatostatin, these hormones enhance or reduce gastric acid secretion respectively
layers of the stratified squamous epithelium
Outer stratum corneum, the stratum transitionale, stratum spinosum, and the basal stratum germinativum
Which structures are mainly responsible for the barrier function
Interepithelial tight junctions in the stratum corneum and muco-substances secreted by the stratum spinosum
mechanisms of gastric repair
Highly dependent of the extend of the injury, superficial erosions can be rapidly covered by migration of epithelium adjacent to the wound a process termed epithelial restitution, however, ulceration (full-thickness disruption of mucosa and penetration of the muscularis mucosa) requires repair of submucosal vasculature and matrix, initiated by formation of granulation tissue, which supplies connective tissue elements and microvasculature necessary for mucosal reconstruction
what is the aim of treatment for gastric ulceration
Aimed at elevating the pH of the gastric contents, which may be achieved with a number of histamine receptor (H2) antagonist such as ranitidine (6.6mg.kg PO every 8 hours or 1.5-2 mg/kg IV every 6-8 hours) or proton pump inhibitors such as omeprazole (2-4 mg/kg PO every 24 hours)
Causes of gastric outflow obstructions
May be the result of pyloric stenosis which can be caused by congenital muscular hypertrophy or by development of a mass at the pylorus that reduces gastric outflow
A mass may develop at the pylorus associated with gastroduodenal ulceration or neoplasia
principle of surgery for treatment of gastric outflow obstructions
Bypass of the pylorus, typically by performing a gastrojejunostomy, alternatively a series of bypass techniques can be performed depending on the location of the obstructions including gastroduodenostomy, duodenojejunostomy and a jejunojejunostomy along the previous two techniques to allow outflow of proximal small intestinal contents
Heineke-Mikulicz technique
A full-thickness longitudinal incision through the pylorus is closed transversely
What has been reported to improve long term outcome when performing a gastrojejunostomy
Aligning the jejunum from left to right (oral to aboral portions of the jejunum) along a relatively avascular region of the caudal ventral aspect of the stomach
prognosis for foals with gastric outflow obstructions
In one report 46% survived, in a more recent report 69%
Obstructions to the duodenum, adhesions to the duodenum, and postoperative ileus were significantly associated with decreased long-term survival
How is the spleen suspended within the peritoneal cavity
By means of the phrenicosplenic and renosplenic ligaments and attached to the stomach by the gastrosplenic ligament, the latter continues with the superficial wall of the greater omentum
indications for surgery of the spleen
Primarily for research purposes, aid in the evaluation of the cardiovascular system during exercise
Splenomegaly with or without splenic infarction and rupture have been the only reported diseases requiring splenectomy
Other possibilities include neoplasia, trauma, infarctions, and possibly an autoimmune disease
Preoperative considerations include assessment of hydration, acid-base status, and clotting function
surgical approaches to splenectomy
All described approaches are performed from the left side
Between the last two ribs or by resection of the 18th rib, 17th rib, or 16th rib
Laparoscopic assisted splenectomy
What should be considered when selecting a surgical approach
The caudal reflection of the pleural cavity
The lateral thoracic wall attaches to the diaphragm along a line called the diaphragmatic line of pleural reflection, this line extends from the 8th and 9th costal cartilages dorsocaudally in a gentle increasing curve, so that its most caudal aspect is about the middle of the cranial border of the last rib forming the caudal border of the pleural cavity
Discuss closure of the renosplenic space
Advocated to prevent recurrence of left dorsal displacement of the large colon
The technique involves suturing the most dorsal visceral surface of the spleen to the renosplenic ligament to eliminate the area between the spleen and the left kidney to which the large colon frequently becomes displaced
The use of polypropylene mesh has been described
Discuss clinical pathology as a colic diagnostic tool
Critical part of the assessment and treatment of colic patients
High PCV and low TP has been associated with poor prognosis in horses with both small and large intestine disease
Hematologic changes useful diagnosing with inflammation, endotoxemia, and sepsis
Leukopenia, neutropenia with appearance of immature and toxic neutrophils, lymphopenia, and thrombocytopenia
Discuss electrolyte profile
Horses loosing fluids from reflux or diarrhea often present with low sodium, potassium, calcium and bicarbonate levels
Because of lactate is the product of anaerobic glycolysis, its measurement may reflect ischemic injury and may aid in determining prognosis
Horses with large colon volvulus a serum lactate concentration greater than 6 mmol/L has been associated with poor prognosis for survival
Anion gap allows the indirect measurement of lactate and is of value determining prognosis
Which enzyme is elevated in horses with large right dorsal colon displacement
Increased in serum gama-glutamyltransferase (GGT) due to obstruction of the bile duct
Discuss Abdominocentesis
Peritoneal fluid can be examined as both a diagnostic and prognostic aids
Aseptically preparing the most dependant part of the abdomen on or slightly right of midline to avoid the spleen and inserting an 18-gauge needle, blade and teat cannula can be used as well
Describe clinical biochemistry on peritoneal fluid
To determine factors including fibrinogen, lactate, phosphate, glucose and pH
Describe peritoneal fluid in septic peritonitis
The serum and peritoneal fluid glucose levels can be compared, a difference of greater than 50 mg/dL between the serum and peritoneal fluid glucose level, a low peritoneal fluid glucose level (less than 30 mg/dL) and pH of less than 7.3 are indicators of septic peritonitis
when ultrasounding a horse a sensitivity of 67% and 100% specificity in diagnosing a large colon volvulus is given with a colonic wall thickness of
9mm
describe the Ultrasonographic changes of right dorsal colitis
Can be confirmed by ultrasonography performed between the 10th and 14th right intercostal space, changes include a thickened colon wall and hypoechoic layer of submucosal edema and inflammatory infiltrate
what is the sensitivity and specificity of radiography for diagnosis of enterolithiasis
76.9% and 94.4% respectively
When diagnosing septic peritonitis what is the difference between serum and peritoneal fluid glucose
A difference greater than 50mg/dL between serum and peritoneal fluid glucose, a low peritoneal fluid glucose (<30mg/dL), and pH of less than 7.3 are indicators of septic peritonitis
what is the most common approach to the equine abdomen
Ventral midline approach performed through the ventral midline, specifically through the linea alba, because it allows exteriorization of 75% of the intestinal tract. The stomach, duodenum, distal ileum, dorsal body and base of the cecum, distal right dorsal colon, transverse colon, and terminal descending colon are the only segments that cannot be exteriorized
Describe the equine linea alba
Extend from the xiphoid process to the prepubic tendon and contains the median fibrous raphe of the external oblique and transverse abdominal muscle aponeurosis. It consist of dense connective tissue composed of sheets of cross-linked collagen bundles and fibroblast
what is the thickness of the equine linea alba
Gradually increases from craniad, where it measures about 3mm to caudad, where reaches a thickness of approximately 10mm
When closing a celiotomy what closure provides the most strength
A continuous pattern with loops positioned 1.2-1.5 cm from the incisional edge of the linea alba
List the abdominal approaches through the ventral abdominal wall in horses
Ventral midline, paramedian, inguinal, combo of a midline and ventral paramedian, parainguinal, suprapubic paramedian
Describe the ventral paramedian approach
Second most common approach used in colic surgery performed 8-12 cm lateral to the midline can be performed on either side of the midline through the rectus abdominis muscle, care must be taken not to injure the superficial and deep epigastric vessels when encountered
Closure of a ventral paramedian incision
Involves suturing the facia of the rectus abdominis sheath
Describe the flank approach to the equine patient
The skin incision is centered between the tuber coxae and last rib, just proximal to palpable dorsal edge of the internal abdominal oblique muscle, the external abdominal oblique is subsequently sharply divided vertically, whereas the internal abdominal oblique and transverse abdominal muscles are bluntly divided parallel to their fibers
List the types of intestinal obstructions
Simple obstructions, strangulating obstructions, non-strangulating infarctions
Describe strangulating obstructions of the small intestine
Result from simultaneous occlusion of the intestinal lumen and its blood supply, in most instances, the veins are occluded early in the course of strangulating obstructions than the arteries because of their thinner and more compliant walls, this result in a disparity in blood flow with continued pumping of arterial blood into the intestinal wall, which in the absence of patent outflow causes hemorrhagic lesions termed hemorrhagic strangulating obstructions
Describe ischemic strangulating obstructions
When strangulation exert sufficient pressure on the veins and arterial supply that both are occluded simultaneously, resulting in rapid degeneration of the mucosa
Describe the mechanisms of injury during luminal distention
the nature of the mucosal lesions depend on the degree of intraluminal pressure and appears that the seromuscular layer is more severely affected and it had evidence of mesothelial cell loss, neutrophil infiltration, and edema that progressed after decompression suggesting reperfusion injury
How is the mucosa become injured during ischemia
Villus tip is the region most susceptible to ischemia because of the countercurrent exchange mechanism of blood flow in the small intestinal villus, the countercurrent exchange is attributable to the vascular architecture which consist in central arteriole that courses up to the core of the villus, arborizes at the tip and its drained by venules coursing down the periphery of the villus
