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| | 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). | | 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===
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| − | * Acute of chronic mechanical obstruction of the intestine can occur in all species.
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| − | ** Acute obstruction usually involves the upper or middle [[Small Intestine - Anatomy & Physiology|small intestine]]
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| − | ** Chronic obstruction typically occurs in the distal [[Small Intestine - Anatomy & Physiology|small intestine]] or [[Large Intestine - Anatomy & Physiology|large intestine]].
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| − | * Three main categories of causes of obstruciton:
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| − | ** Intraluminal
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| − | *** E.g. foreign bodies, food impaction.
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| − | ** Intramural
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| − | *** E.g. neoplasia
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| − | ** Extrinsic
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| − | *** E.g. adhesions, neoplasia and prostate enlargement.
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| − | ====Intraluminal Obstruction==== | + | ===[[:Category:Intestine - Mechanical Obstruction]]=== |
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| − | =====Foreign Bodies=====
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| − | * Foreign bodies of all types can be found in the intestines.
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| − | * While some may pass through posing no problems, others can cause acute obstruction,
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| − | * Quite common in dogs
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| − | ** Rare in other species - tend to lodge in the oesophagus or in one of the ruminant [[Stomach and Abomasum - Anatomy & Physiology|stomachs]].)
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| − | ** Enteroliths can be seen in horses greater than 4 years of age.
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| − | *** Are stones consisting of magnesium ammonium phosphate around a central nidus (often a metallic foreign body)
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| − | *** Typically lodge at the pelvic flexure or the transverse [[Colon - Anatomy & Physiology|colon]].
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| − | * '''Clinical'''
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| − | ** Obstruction at pylorus produces repeated [[Control of Feeding - Anatomy & Physiology#The Vomit Reflex|vomiting]].
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| − | ** Obstrustion lower down gives less dramatic effect.
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| − | *** Is still a problem if in the middle of the [[Small Intestine - Anatomy & Physiology|small intestine]]s.
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| − | *** May be vague signs; some [[Control of Feeding - Anatomy & Physiology#The Vomit Reflex|vomiting]] and off food.
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| − | * '''Diagnosis'''
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| − | ** May not show up well radiographically (unless radio-opaque) for several days.
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| − | *** May also be objects that are semi solid or soft, e.g.
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| − | **** String
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| − | **** Plastic bags
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| − | **** Stringy things, like pieces of material- particularly in puppies.
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| − | ** Make all of intestines have knotted appearance.
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| − | ** May be seen in horses with baler twine.
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| − | * '''Pathogenesis'''
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| − | ** Smooth, round objects, such as golf balls, lodge especially near the pylorus or lower down.
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| − | ** Occasionally in cattle (piece of rope or piece of tarpaulin) produces a tangled mass in [[The Rumen - Anatomy & Physiology|rumen]].
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| − | ** Cause pressure necrosis and eventually perforation.
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| − | ** Foreign bodies can also be chronic, remaining for long periods of time without causing disturbance.
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| − | =====Impaction=====
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| − | * Impaction of the [[Colon - Anatomy & Physiology|colon]] can occur in all species.
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| − | ** Dog and cat - main cause is dehydrated faecal material.
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| − | ** Horse - faeces, digesta, sand, or fibrous material can all contribute.
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| − | *** There are certain predisposing factors:
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| − | **** Poor dentition
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| − | **** Water deprivation
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| − | **** A high roughage diet
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| − | **** General debility.
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| − | *Antihelminthic administration or large parasite burdens can also lead to impaction.
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| − | ====Extrinsic Obstruction====
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| − | * Obstruction of the intestine due to external factors such as tumours, abscesses, and fibrous adhesions is a common occurrence.
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| − | =====Inflammatory Adhesions=====
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| − | [[Image:colon_adhesions_horse.jpg|thumb|right|150px|colonic adhesions in the horse (Courtesy of Elspeth Milne)]]
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| − | * Arise following gut perforation, peritonitis or surgery.
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| − | * Consist of fibrous tissue bands that may:
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| − | ** Restrict intestinal motility
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| − | ** Cause kinks in the mesentery.
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| − | =====Prostatic Enlargement=====
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| − | * In the dog
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| − | * Can lead to compression of the [[Rectum - Anatomy & Physiology|rectum]]
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| − | =====Neoplasia=====
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| − | * Neoplasi in structures adjacent to the intestines can spread and cause external compression.
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| − | * Pancreatic tumours in particular can extend and impinge on the [[Duodenum - Anatomy & Physiology|duodenum]].
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| − | * Pedicles of tumours such as lipomas in horses can become wound in loops of intestine leading to obstruction and possible strangulation.
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| − | [[Image:Pedunc_lipoma_closeup.jpg|thumb|right|150px|Closeup of a pedunculated lipoma (Courtesy of Elspeth Milne)]]
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| − | * '''Clinical'''
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| − | ** Occasional [[Control of Feeding - Anatomy & Physiology#The Vomit Reflex|vomiting]] and ntermittent [[Intestine Diarrhoea - Pathology|diarrhoea]] over several weeks.
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| − | * '''Pathogenesis'''
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| − | ** Seen occasionally in cat (rarer in dog)
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| − | ** Usually towards end of intestines
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| − | *** E.g. at the ileocaecocolic valve.
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| − | ** Gut proximal to tumour becomes thickened due to hypertrophy of smooth muscle as a result of trying to force ingesta past progessively narrowing lumen.
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| − | ** Produces "hose pipe intestine".
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| − | ** Seen with carcinoma, lymphoma, leiomyoma and other tumours.
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| | ===Functional Obstruction=== | | ===Functional Obstruction=== |