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Intestine

Basic Anatomy and Physiology

Pathology

Developmental Anomalies

Segmental

Segmental anomalies of the intestines are common and range from incomplete occlusion (stenosis) to complete occlusion (atresia) of the lumen.

Atresia ani
  • A common congenital defect of the lower gastrointestinal tract.
  • Both the anus and rectum can be affected.
  • Occurs in all species but is most often seen in calves and pigs.
Atresia coli
  • Considered the most common segmental anomaly of the intestine in domestic animals.
  • Can affect in particular the spiral colon of Holstein calves and the small colon of foals.
Atresia ilei
  • It is less common to see atresia in the small intestine.
  • Mostly seen in calves.

Persistent Meckel's diverticulum

  • Meckel's diverticulum is a remnant of the omphalomesenteric duct of the yolk sac.
  • Is usually an incidental finding though it can be associated with impaction and or intussusception.

Megacolon

  • Occurs in cats, dogs, and pigs.
  • May be due to a lack of myenteric plexuses that occurs when neuroblasts fail to migrate from the nerual crest to the colorectal myenteric plexuses.
  • Congenital colonic agangliosis, a condition occurring in white foals, can lead to megacolon. It is thought to be an autosomal recessive condition.


References

Brown CC, Baker DC, Barker IK: Alimentary System. In: Jubb, Kennedy and Palmer's Pathology of Domestic Animals, ed. Maxie MG, 5th ed., pp. 1-296. Elsevier, Philadelphia, PA, 2007.

McGavin DM & Zachary, JF: Pathologic Basis of Veterinary Disease, 4th ed, pp. 301-393. Elsevier, St. Louis, Missouri, 2007.

Physical Disturbances

Obstruction

Intestinal obstruction can be the sequel to either mechanical or functional causes. Mechanical obstruction occurs due to physical blockage of the intestinal lumen whereas functional obstruction results from a decrease or inhibition of intestinal motility due to loss of smooth muscle contraction. (Brown et. al, 2007).

Physical

Physical obstruction of the intestine, either acute or chronic, can occur in all species of animals. Acute obstruction usually involves the upper or middle small intestine whereas chronic obstruction typically occurs in the distal small intestine or large intestine. Causes of obstruction can be divided into three main categories: intraluminal, intramural, or extrinsic. Intraluminal causes include food impaction and foreign bodies, intramural causes include neoplasia and extrinsic causes include adhesions, neoplasia and prostate enlargement.

Enteroliths [picture]
Foreign Bodies
Impaction
Extrinsic

Neoplasia, Adhesions, Prostate enlargement

Functional
Megacolon
Dysautonomia

Grass sickness in horses, Feline

Displacement

Hernias
Internal
External
Volvulus and Torsion
Ruminants

caecal dilatation and torsion

Equine

right and left dorsal displacement colonic torsion and volvulus

Intussusception
Renosplenic entrapment

Vascular Disturbances

pathogenesis

Venous congestion

Arterial thromboembolism

Inflammation

pathogenesis

  • enteritis
  • typhlitis
  • colitis
  • proctitis

? about subheadings as many fit under specific pathogens notes subcategorising by types of enteritis???

Diseases of the epithelium

Diseases of absorptive enterocytes
Diseases of undifferentiated crypt cells

Diseases of the lamina propria

Inflammatory bowel disease

description of

Lymphocytic/plasmacytic enteritis
Idiopathic mucosal colitis
Eosinophilic enteritis
Granulomatous enteritis
Colitis
Typhlocolitis

in dogs: pipe to species specific section includes histiocytic unlcerative colitis trichuris vulpis, pipe to parasites

Neoplastic and Proliferative Lesions

description

Intesinal adenoma

Intestinal adenocarcinoma

Lymphoma

Mast cell tumours

Intestinal stromal tumours

Diarrhoea

definition and pathogenesis characteristics of l.i. diarrhoea

Miscellaneous

Caecal or large intestine rupture

Diverticula

Intestinal lipofuscinosis

Diseases due to pathogens

Bacteria, Viral, Mycotic brief explanation then pipe to different page

Bacterial

brief explanation

Escherichia coli

description

Enterotoxogenic colibacillosis
Enteropatholgenic colibacillosis
Postweaning colibacillosis
Enteroinvasive colibacillosis
Septicaemic colibacillosis

Salmonellosis

description Link to salmonellosis in specific species

Peracute Salmonella septicaemia
Acute enteric salmonellosis
Chronic enteric salmonellosis

Clostridial enteritis

description

Clostridium perfringens type A
Clostridium perfringens type B
Clostridium perfringens type C
Clostridium perfringens type D
Other Clostridial diseases
Clostridium difficile
= Clostridium piliforme

Yersiniosis

Lawsonian intracellularis

Campylobacter spp.

Paratuberculosis (Johne's disease)

Viral

description Bovine viral diarrhoea Rinderpest Peste des petits ruminants Malignant catarrhal fever Herpesvirus Adenovirus Coronavirus Rotavirus Parvovirus

Mycotic

description Intestinal phycomycosis and aspergillosis Candidiasis Intestinal histoplasmosis

Diseases in Animal Species

Avian

coccidiosis

Carnivores

Cats

Panleucopenia Feline infectious peritonitis Feline leukaemia Feline immunodeficiency virus

Dogs

Parvovirus 2 Distemper Salmonella Rotavirus Coronavirus Ascarids Hookworms Giardiasis Neoplasms Salmon poisoning Haemorrhagic enteritis

Horses

Rhodococcus equi Equine monocytic ehrlichiosis Equine granulomatous enteritis Clostridial enteritis Lawsonian associated Potomac horse fever Parasites Antibiotic associated diarrhoea

Rabbits

Ruminants

Bovine viral diarrhoea Rinderpest Malignant catarrhal fever Paratuberculosis Chlamydiosis Parasitism (list specifics to l.i.) Copper deficiency Salmonellosis Yersiniosis Coccidiosis Escherichia coli Poisoning Winter dysentery

Swine

Rotavirus Transmissible gastroenteritis Escherichia coli Salmonella Lawsonian intracellularis Swine dysentery Porcine circovirus 2 Intestinal spirochaetosis Ascaris suum

Parasites

Cryptosporidiosis Giaridasis Ascariasis Hookworm diseas Trichuriasis Strongyloidosis Pinworms Cestodes Trematodes

Clinical Pathology

Approach to diagnosis of large intestinal disease

Laboratory evaluation of large intestinal disease

Diarrhoea

Weight loss

Routine diagnostic procedures

Further tests