Author, Donkey, Bureaucrats, Administrators
53,803
edits
Changes
Jump to navigation
Jump to search
Category:Obstruction, Intestinal (view source)
Revision as of 12:17, 31 May 2010
, 12:17, 31 May 2010Created page with 'Intestinal obstruction can be the sequel to either mechanical or functional causes. Mechanical obstruction occurs due to physical blockage of the intestinal lumen whereas functi…'
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).
===Mechanical Obstruction===
* Acute of chronic mechanical obstruction of the intestine can occur in all species.
** Acute obstruction usually involves the upper or middle [[Small Intestine - Anatomy & Physiology|small intestine]]
** Chronic obstruction typically occurs in the distal [[Small Intestine - Anatomy & Physiology|small intestine]] or [[Large Intestine - Anatomy & Physiology|large intestine]].
* Three main categories of causes of obstruciton:
** Intraluminal
*** E.g. foreign bodies, food impaction.
** Intramural
*** E.g. neoplasia
** Extrinsic
*** E.g. adhesions, neoplasia and prostate enlargement.
====Intraluminal Obstruction====
=====Foreign Bodies=====
* Foreign bodies of all types can be found in the intestines.
* While some may pass through posing no problems, others can cause acute obstruction,
* Quite common in dogs
** Rare in other species - tend to lodge in the oesophagus or in one of the ruminant [[Stomach and Abomasum - Anatomy & Physiology|stomachs]].)
** Enteroliths can be seen in horses greater than 4 years of age.
*** Are stones consisting of magnesium ammonium phosphate around a central nidus (often a metallic foreign body)
*** Typically lodge at the pelvic flexure or the transverse [[Colon - Anatomy & Physiology|colon]].
* '''Clinical'''
** Obstruction at pylorus produces repeated [[Control of Feeding - Anatomy & Physiology#The Vomit Reflex|vomiting]].
** Obstrustion lower down gives less dramatic effect.
*** Is still a problem if in the middle of the [[Small Intestine - Anatomy & Physiology|small intestine]]s.
*** May be vague signs; some [[Control of Feeding - Anatomy & Physiology#The Vomit Reflex|vomiting]] and off food.
* '''Diagnosis'''
** May not show up well radiographically (unless radio-opaque) for several days.
*** May also be objects that are semi solid or soft, e.g.
**** String
**** Plastic bags
**** Stringy things, like pieces of material- particularly in puppies.
** Make all of intestines have knotted appearance.
** May be seen in horses with baler twine.
* '''Pathogenesis'''
** Smooth, round objects, such as golf balls, lodge especially near the pylorus or lower down.
** Occasionally in cattle (piece of rope or piece of tarpaulin) produces a tangled mass in [[The Rumen - Anatomy & Physiology|rumen]].
** Cause pressure necrosis and eventually perforation.
** Foreign bodies can also be chronic, remaining for long periods of time without causing disturbance.
=====Impaction=====
* Impaction of the [[Colon - Anatomy & Physiology|colon]] can occur in all species.
** Dog and cat - main cause is dehydrated faecal material.
** Horse - faeces, digesta, sand, or fibrous material can all contribute.
*** There are certain predisposing factors:
**** Poor dentition
**** Water deprivation
**** A high roughage diet
**** General debility.
*Antihelminthic administration or large parasite burdens can also lead to impaction.
====Extrinsic Obstruction====
* Obstruction of the intestine due to external factors such as tumours, abscesses, and fibrous adhesions is a common occurrence.
=====Inflammatory Adhesions=====
[[Image:colon_adhesions_horse.jpg|thumb|right|150px|colonic adhesions in the horse (Courtesy of Elspeth Milne)]]
* Arise following gut perforation, peritonitis or surgery.
* Consist of fibrous tissue bands that may:
** Restrict intestinal motility
** Cause kinks in the mesentery.
=====Prostatic Enlargement=====
* In the dog
* Can lead to compression of the [[Rectum - Anatomy & Physiology|rectum]]
=====Neoplasia=====
* Neoplasi in structures adjacent to the intestines can spread and cause external compression.
* Pancreatic tumours in particular can extend and impinge on the [[Duodenum - Anatomy & Physiology|duodenum]].
* Pedicles of tumours such as lipomas in horses can become wound in loops of intestine leading to obstruction and possible strangulation.
[[Image:Pedunc_lipoma_closeup.jpg|thumb|right|150px|Closeup of a pedunculated lipoma (Courtesy of Elspeth Milne)]]
* '''Clinical'''
** Occasional [[Control of Feeding - Anatomy & Physiology#The Vomit Reflex|vomiting]] and ntermittent [[Intestine Diarrhoea - Pathology|diarrhoea]] over several weeks.
* '''Pathogenesis'''
** Seen occasionally in cat (rarer in dog)
** Usually towards end of intestines
*** E.g. at the ileocaecocolic valve.
** Gut proximal to tumour becomes thickened due to hypertrophy of smooth muscle as a result of trying to force ingesta past progessively narrowing lumen.
** Produces "hose pipe intestine".
** Seen with carcinoma, lymphoma, leiomyoma and other tumours.
===Functional Obstruction===
====Paralytic Ileus====
* A common condition.
* Occurs following trauma or abdominal surgery.
* Stasis of gut flow due to failure of [http://en.wikipedia.org/wiki/Peristalsis| peristalsis].
** Leads to distension with gas and fluid, as well as a flaccid intestinal wall.
=====Causes=====
* Anything which stops peristalsis, e.g.
** Damage to nerve supply to intestine (autonomic nervous system)
** Pain
** Abnormal metabolism
** Toxaemia
** Electrolyte imbalance such as hypocalcaemia, hypomagnesaemia, and hypokalaemia.
* Also in
** Diabetes mellitus
** Uraemia
** Tetanus
** Lead poisoning.
=====Pathology=====
* loss of smooth muscle tone leads to a flaccid bowel.
* Bowel is distended with fluid.
=====Pathogenesis=====
* Intestine susceptible to neurogenic damage during an operation.
* Peristalsis fades away over a few days producing paralytic (adynamic) ileus.
* Particularly occurs if bowel handled roughly, or if serosa gets cold and dry at surgery.
* Very difficult to start peristalsis again but will sometimes respond to pharmacological or electrical stimulation.
* The horse is very susceptible, and the dog is somewhat suscpeitble.
====Dysautonomia====
* Most notably affects horses and cats.
=====Equine dysautonomia, or grass sickness=====
* Most prevalent in the UK and western Europe.
** Common in wetter areas, e.g. the South West.
* Seen in horses out at pasture in late summer and autumn.
* Usually affects young adults.
** 6-7 years old.
* '''Clinical'''
** Acute oneset:
*** Muscular tremors
*** Abdominal pain
*** Does not eat
*** Constipation
*** Become severly tympanic in acute cases
*** Dull and restless
*** Avoid swallowing
*** Salivate excessively
** Degenerative lesions are seen in the autonomic nerve ganglia, including enteric plexuses
** May either:
*** Progress rapidly to death
*** Take a slower clinical course.
**** Eat a bit, but food drops out of mouth
**** Go on to die slowly.
** Some horses recover
*** This is very unlikely, and the condition is usually fatal.
** Clinically difficult to diagnose - signs are confined to the gut.
*** Easy to diagnose on post mortem
* '''Pathology'''
** [[Forestomach - Anatomy & Physiology|Stomach]] and [[Small Intestine - Anatomy & Physiology|small intestine]] large amounts of contain watery yellow fluid.
*** There is an abrupt change in the [[Large Intestine - Anatomy & Physiology|large intestine]], where no fluid is present.
**** [[Large Intestine - Anatomy & Physiology|large intestine]] has very dry mucoid contents.
* '''Pathogenesis'''
** Due to functional obstruction at ileocaecal valve and a degree of paralytic ileus of the [[Small Intestine - Anatomy & Physiology|small intestine]].
** The exact cause is unknown, but a type of bacterial or fungal toxin which may damage autonomic nervous system ganglia may be involved.
*** ''[[Clostridium botulinum]]'' is thought to be involved.
* A similar condition seen in hares
** Certain yeares almost seem to have outbreaks.
* Certain pastures at certain times of year produce grass sickness quite often.
** A definitive diagnosis must be made - if the condition is due to the grazing we need to know.
*** E.g. if on livery or stud grazing, may put people off going there.
* 'Diagnosis'''
** At post mortem look for degenerative changes in coeliaco-mesenteric ganglia - need to examine histologically.
*** Ganglia are peanut sized and found in perirenal fat between adrenal gland and the aorta.
=====Feline dysautonomia, or Key-Gaskell Syndrome=====
[[Image:Ba 250 07.jpg|thumb|right|Histological section of degenerate neuron in feline dysautonomia(Courtesy of Susan Rhind)]]
* Occurs mostly in the UK and continental Europe.
* Is also of unknown aetiology. Suggested causative factors include:
** Environmental toxins
** Infectious agents
** Botulinum toxins .
* Clinical signs:
** Anorexia
** Depression
** Bradycardia
** Decreased lacrimation,
** Altered pupillary dilataion,
** [[Megaoesophagus]]
** Constipation.
* Degenerative lesions of autonomic nerve ganglia can be seen.
* Also occurs in the [[Key-Gaskell Syndrome|oesophagus]].
[[Category:Intestine - Physical Disturbances]]
===Mechanical Obstruction===
* Acute of chronic mechanical obstruction of the intestine can occur in all species.
** Acute obstruction usually involves the upper or middle [[Small Intestine - Anatomy & Physiology|small intestine]]
** Chronic obstruction typically occurs in the distal [[Small Intestine - Anatomy & Physiology|small intestine]] or [[Large Intestine - Anatomy & Physiology|large intestine]].
* Three main categories of causes of obstruciton:
** Intraluminal
*** E.g. foreign bodies, food impaction.
** Intramural
*** E.g. neoplasia
** Extrinsic
*** E.g. adhesions, neoplasia and prostate enlargement.
====Intraluminal Obstruction====
=====Foreign Bodies=====
* Foreign bodies of all types can be found in the intestines.
* While some may pass through posing no problems, others can cause acute obstruction,
* Quite common in dogs
** Rare in other species - tend to lodge in the oesophagus or in one of the ruminant [[Stomach and Abomasum - Anatomy & Physiology|stomachs]].)
** Enteroliths can be seen in horses greater than 4 years of age.
*** Are stones consisting of magnesium ammonium phosphate around a central nidus (often a metallic foreign body)
*** Typically lodge at the pelvic flexure or the transverse [[Colon - Anatomy & Physiology|colon]].
* '''Clinical'''
** Obstruction at pylorus produces repeated [[Control of Feeding - Anatomy & Physiology#The Vomit Reflex|vomiting]].
** Obstrustion lower down gives less dramatic effect.
*** Is still a problem if in the middle of the [[Small Intestine - Anatomy & Physiology|small intestine]]s.
*** May be vague signs; some [[Control of Feeding - Anatomy & Physiology#The Vomit Reflex|vomiting]] and off food.
* '''Diagnosis'''
** May not show up well radiographically (unless radio-opaque) for several days.
*** May also be objects that are semi solid or soft, e.g.
**** String
**** Plastic bags
**** Stringy things, like pieces of material- particularly in puppies.
** Make all of intestines have knotted appearance.
** May be seen in horses with baler twine.
* '''Pathogenesis'''
** Smooth, round objects, such as golf balls, lodge especially near the pylorus or lower down.
** Occasionally in cattle (piece of rope or piece of tarpaulin) produces a tangled mass in [[The Rumen - Anatomy & Physiology|rumen]].
** Cause pressure necrosis and eventually perforation.
** Foreign bodies can also be chronic, remaining for long periods of time without causing disturbance.
=====Impaction=====
* Impaction of the [[Colon - Anatomy & Physiology|colon]] can occur in all species.
** Dog and cat - main cause is dehydrated faecal material.
** Horse - faeces, digesta, sand, or fibrous material can all contribute.
*** There are certain predisposing factors:
**** Poor dentition
**** Water deprivation
**** A high roughage diet
**** General debility.
*Antihelminthic administration or large parasite burdens can also lead to impaction.
====Extrinsic Obstruction====
* Obstruction of the intestine due to external factors such as tumours, abscesses, and fibrous adhesions is a common occurrence.
=====Inflammatory Adhesions=====
[[Image:colon_adhesions_horse.jpg|thumb|right|150px|colonic adhesions in the horse (Courtesy of Elspeth Milne)]]
* Arise following gut perforation, peritonitis or surgery.
* Consist of fibrous tissue bands that may:
** Restrict intestinal motility
** Cause kinks in the mesentery.
=====Prostatic Enlargement=====
* In the dog
* Can lead to compression of the [[Rectum - Anatomy & Physiology|rectum]]
=====Neoplasia=====
* Neoplasi in structures adjacent to the intestines can spread and cause external compression.
* Pancreatic tumours in particular can extend and impinge on the [[Duodenum - Anatomy & Physiology|duodenum]].
* Pedicles of tumours such as lipomas in horses can become wound in loops of intestine leading to obstruction and possible strangulation.
[[Image:Pedunc_lipoma_closeup.jpg|thumb|right|150px|Closeup of a pedunculated lipoma (Courtesy of Elspeth Milne)]]
* '''Clinical'''
** Occasional [[Control of Feeding - Anatomy & Physiology#The Vomit Reflex|vomiting]] and ntermittent [[Intestine Diarrhoea - Pathology|diarrhoea]] over several weeks.
* '''Pathogenesis'''
** Seen occasionally in cat (rarer in dog)
** Usually towards end of intestines
*** E.g. at the ileocaecocolic valve.
** Gut proximal to tumour becomes thickened due to hypertrophy of smooth muscle as a result of trying to force ingesta past progessively narrowing lumen.
** Produces "hose pipe intestine".
** Seen with carcinoma, lymphoma, leiomyoma and other tumours.
===Functional Obstruction===
====Paralytic Ileus====
* A common condition.
* Occurs following trauma or abdominal surgery.
* Stasis of gut flow due to failure of [http://en.wikipedia.org/wiki/Peristalsis| peristalsis].
** Leads to distension with gas and fluid, as well as a flaccid intestinal wall.
=====Causes=====
* Anything which stops peristalsis, e.g.
** Damage to nerve supply to intestine (autonomic nervous system)
** Pain
** Abnormal metabolism
** Toxaemia
** Electrolyte imbalance such as hypocalcaemia, hypomagnesaemia, and hypokalaemia.
* Also in
** Diabetes mellitus
** Uraemia
** Tetanus
** Lead poisoning.
=====Pathology=====
* loss of smooth muscle tone leads to a flaccid bowel.
* Bowel is distended with fluid.
=====Pathogenesis=====
* Intestine susceptible to neurogenic damage during an operation.
* Peristalsis fades away over a few days producing paralytic (adynamic) ileus.
* Particularly occurs if bowel handled roughly, or if serosa gets cold and dry at surgery.
* Very difficult to start peristalsis again but will sometimes respond to pharmacological or electrical stimulation.
* The horse is very susceptible, and the dog is somewhat suscpeitble.
====Dysautonomia====
* Most notably affects horses and cats.
=====Equine dysautonomia, or grass sickness=====
* Most prevalent in the UK and western Europe.
** Common in wetter areas, e.g. the South West.
* Seen in horses out at pasture in late summer and autumn.
* Usually affects young adults.
** 6-7 years old.
* '''Clinical'''
** Acute oneset:
*** Muscular tremors
*** Abdominal pain
*** Does not eat
*** Constipation
*** Become severly tympanic in acute cases
*** Dull and restless
*** Avoid swallowing
*** Salivate excessively
** Degenerative lesions are seen in the autonomic nerve ganglia, including enteric plexuses
** May either:
*** Progress rapidly to death
*** Take a slower clinical course.
**** Eat a bit, but food drops out of mouth
**** Go on to die slowly.
** Some horses recover
*** This is very unlikely, and the condition is usually fatal.
** Clinically difficult to diagnose - signs are confined to the gut.
*** Easy to diagnose on post mortem
* '''Pathology'''
** [[Forestomach - Anatomy & Physiology|Stomach]] and [[Small Intestine - Anatomy & Physiology|small intestine]] large amounts of contain watery yellow fluid.
*** There is an abrupt change in the [[Large Intestine - Anatomy & Physiology|large intestine]], where no fluid is present.
**** [[Large Intestine - Anatomy & Physiology|large intestine]] has very dry mucoid contents.
* '''Pathogenesis'''
** Due to functional obstruction at ileocaecal valve and a degree of paralytic ileus of the [[Small Intestine - Anatomy & Physiology|small intestine]].
** The exact cause is unknown, but a type of bacterial or fungal toxin which may damage autonomic nervous system ganglia may be involved.
*** ''[[Clostridium botulinum]]'' is thought to be involved.
* A similar condition seen in hares
** Certain yeares almost seem to have outbreaks.
* Certain pastures at certain times of year produce grass sickness quite often.
** A definitive diagnosis must be made - if the condition is due to the grazing we need to know.
*** E.g. if on livery or stud grazing, may put people off going there.
* 'Diagnosis'''
** At post mortem look for degenerative changes in coeliaco-mesenteric ganglia - need to examine histologically.
*** Ganglia are peanut sized and found in perirenal fat between adrenal gland and the aorta.
=====Feline dysautonomia, or Key-Gaskell Syndrome=====
[[Image:Ba 250 07.jpg|thumb|right|Histological section of degenerate neuron in feline dysautonomia(Courtesy of Susan Rhind)]]
* Occurs mostly in the UK and continental Europe.
* Is also of unknown aetiology. Suggested causative factors include:
** Environmental toxins
** Infectious agents
** Botulinum toxins .
* Clinical signs:
** Anorexia
** Depression
** Bradycardia
** Decreased lacrimation,
** Altered pupillary dilataion,
** [[Megaoesophagus]]
** Constipation.
* Degenerative lesions of autonomic nerve ganglia can be seen.
* Also occurs in the [[Key-Gaskell Syndrome|oesophagus]].
[[Category:Intestine - Physical Disturbances]]