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| + | * A hernia is defined as the displacement of the [[Small Intestine - Anatomy & Physiology|small intestine]] through a normal or pathologic foramina. |
| − | ==Introduction==
| + | ** Occasionally, the [[Large Intestine - Anatomy & Physiology|large intestine]] is involved. |
| − | [[Image:hernial sac.jpg|thumb|right|150px|Diagram of a hernial sac (Copyright Elspeth Milne 2007)]]
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| − | A hernia is defined as the displacement of an organ through a normal aperture (a '''true hernia''') or pathological aperture ('''false hernia''' or '''rupture'''). The mobile organs of the abdomen are most commonly displaced through apertures in the abdominal wall, diaphragm, inguinal canal or femoral canal. | |
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| − | In a true abdominal hernia, the displaced organs are contained within a '''hernial sac''' which consists of the parietal peritoneum together with any overlying soft tissues. In an '''external hernia''', the skin forms the outermost layer and the hernial sac and its contents are palpable. '''Internal hernias''' involve an aperture within the abdominal cavity. Since the parietal peritoneum is torn when ruptures occur, these do not have defined hernial sacs.
| + | ====Pathogenesis==== |
| | + | [[Image:hernial sac.jpg|thumb|right|150px|Diagram of a hernial sac (Courtesy of Elspeth Milne)]] |
| | + | * Associated with trauma or the weakening of tissues. |
| | + | ** For example, |
| | + | *** Old age |
| | + | *** Pregnancy |
| | + | *** Straining |
| | + | *** Wound dehiscence. |
| | + | * Most [[Hernia, External|hernias are external]] |
| | + | ** Contents pass through a hernial ring in the abdominal wall. |
| | + | ** Are covered with parietal peritoneum, soft tissue and skin. |
| | + | *** A hernial sac. |
| | + | |
| | + | ====Sequelae==== |
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| − | Hernias may be '''congenital''' or '''acquired'''. Congenital hernias usually result from a failure of physiological apertures (such as the umbilical canal) to close fully during embryonic or neonatal development whereas acquired hernias may be related to trauma, wounds or to physiological weakening of tissues with age, pregnancy or chronic straining.
| + | * The sequelae depend on whether the hernia is reducible, or is an incarceration. |
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| − | ==Pathogenesis==
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| − | The sequelae of a hernia depend on whether the hernia is reducible and if the herniated organs are incarcerated or strangulated.
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| − | ===Reducible hernia=== | + | =====Reducible hernia===== |
| − | The contents of the hernial sac can be moved back to their original position. These hernias tend not to cause clinical disease.
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| − | ===Incarceration===
| + | * The hernial contents are freely moveable. |
| − | If the hernial ring narrows or if the displaced organs expand, the contents of the hernial sac may be trapped or 'incarcerated'. These structures cannot be moved back to their original position and surgical intervention is usually required to increase the size of the hernial ring. Incarcerated hernias also carry a greater risk of strangulation.
| + | * There are NO sequelae. |
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| − | ===Strangulation===
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| − | The contents of the hernial sac are trapped and their blood supply is impaired. Initially, only venous drainage is reduced leading to oedema and congestion but infarction may occur if the arterial blood supply is also affected. Strangulated loops of small intestine are unable to maintain an effective barrier against gastro-intestinal bacteria and bacterial endotoxin, leading to peritonitis, sepsis and endotoxic shock. The intestine may also rupture causing acute septic peritonitis.
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| − | ==Types of hernia== | + | =====Incarceration===== |
| − | *'''[[Umbilical Hernia|Umbilical hernias]]''' are congenital and result from a failure of closure of the foetal umbilical canal. They occur in all of the major domestic species.
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| − | *'''Diaphragmatic hernias''' may be congenital or, much more commonly, [[Diaphragmatic Rupture|diaphragmatic ruptures]] may occur following blunt abdominal trauma in small animals. Congenital diaphragmatic hernias are an unusual cause of small intestinal incarceration and strangulation in horses, manifesting as severe colic. If the septum transversum (the embryonic structure that forms the diaphragm) fails to develop fully, congenital [[Hernia, Peritoneopericardial Diaphragmatic|Peritoneal-Pericardial-Diaphragmatic hernias]] (PPDH) or [[Hernia, Pleuroperitoneal Diaphragmatic|Pleuroperitoneal hernias]] may occur.
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| − | *'''[[Inguinal Hernia|Inguinal/scrotal hernias]]''' may be congenital or acquired. Congenital hernias are rare and usually occur in young male dogs with late testicular descent. It is suggested that this process holds the inguinal canal open for longer than normal, allowing abdominal organs to displace into them. Acquired hernias occur in obese animals (in which the canal is held open by the local accumulation of fat) and in older entire bitches (in which the gravid uterus may be herniated). Inguinal hernias also occur in stallions after castration and may cause severe colic.
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| − | *'''[[Perineal Hernia| Perineal hernias]]''' are true hernias where abdominal organs move into space created by the weakening or rupture of muscles forming the pelvic diapragm and anus. Older male entire dogs are particularly affected and these often have concurrent enlargement of the prostate gland.
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| − | *'''Ventral abdominal ruptures''' occur at sites of wound breakdown (after ventral midline coeliotomy) and in older pregnant mares and cows, particularly those suffering from hydrops uteri.
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| − | *'''Traumatic abdominal ruptures''' may occur at various locations in the abdomen resulting in prepubic ruptures, femoral hernias and paracostal ruptures in cats.
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| − | *'''Omental/mesenteric rents''' may result in internal hernias causing partial or complete intestinal obstruction.
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| − | *'''Epiploic foramen entrapment''' is a form of internal hernia affecting horses. Loops of small intestine may become trapped within the epiploic foramen and omental bursa causing complete intestinal obstruction and severe colic. Anecdotally, horses which 'windsuck' are at particular risk of this form of colic and it requires urgent surgical correction.
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| − | *'''[[Richter's Hernia|Richter's hernia]]''' is a rare form of hernia in which only one wall of the small intestine is trapped in the hernial sac, resulting in a partial intestinal obstruction.
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| − | {{Learning
| + | * The [[Small Intestine - Anatomy & Physiology|small intestine]] contents are trapped. |
| − | |Vetstream = [https://www.vetstream.com/canis/search?s=hernia Hernia] | + | ** The hernia is non-reducible. |
| − | |literature search = [http://www.cabdirect.org/search.html?rowId=1&options1=AND&q1=hernia&occuring1=title&rowId=2&options2=AND&q2=&occuring2=freetext&rowId=3&options3=AND&q3=&occuring3=freetext&publishedstart=2000&publishedend=yyyy&calendarInput=yyyy-mm-dd&la=any&it=any&show=all&x=43&y=15 Hernia publications since 2000]
| + | * Venous drainage is obstruced. |
| − | |full text = [http://www.cabi.org/cabdirect/FullTextPDF/2010/20103304730.pdf '''Biomaterials in the reconstruction of abdominal wall defects in animals: a review.''' Sharma, A. K.; Naveen Kumar; Gangwar, A. K.; Maiti, S. K.; SAARC Agricultural Information Centre (SAIC), Dhaka, Bangladesh, SAARC Journal of Agriculture, 2003, 1, pp 85-98, many ref.]
| + | ** Oedema |
| − | }}
| + | ** Congestion |
| | + | * Adhesions form between the contents and the sac. |
| | + | * Accumulated gas/ ingesta distends the herniated viscus. |
| | + | * Obstruction of lumen leads to |
| | + | ** Rupture |
| | + | ** Peritonitis |
| | + | ** Death. |
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| − | ==References== | + | ====Types of hernia==== |
| − | Fossum, T. W. et. al. (2007) '''Small Animal Surgery (Third Edition)''' ''Mosby Elsevier''
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| − | [http://w3.vet.cornell.edu/nst/nst.asp?Fun=Image&imgID=22114 Image of congenital umbilical hernia in a pig from Cornell Veterinary Medicine]
| + | * '''Umbilical''' - usually congenital. |
| − | | + | * '''Diaphragmatic''' - common following road traffic accidents in the dog and cat. |
| − | | + | * '''Inguinal/scrotal''' - may be: |
| − | {{review}}
| + | ** Congenital |
| − | | + | ** Acquired |
| − | {{OpenPages}}
| + | *** E.g. post castration of stallion |
| − | | + | * '''Perineal''' - old male dogs with prostate enlargement. |
| − | [[Category:Intestine_-_Physical_Disturbances]]
| + | * '''Ventral''' -wound site breakdown, old mares |
| − | [[Category:Peritoneal_Cavity_-_Developmental_Pathology]][[Category:Peritoneal Cavity Diseases - Dog]][[Category:Peritoneal Cavity Diseases - Cat]][[Category:Donkey]][[Category:Peritoneal Diseases - Cattle]][[Category:Peritoneal Diseases - Sheep]]
| + | * '''Omental/mesenteric''' - internal hernias. |
| − | [[Category:Expert_Review]] | + | [[Image:volvulus.jpg|thumb|right|150px|Volvulus (Courtesy of Bristol BioMed Image Archive)]][[Category:Intestine_-_Physical_Disturbances]] |
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| − | [[Category:Peritoneal Cavity Diseases - Horse]] | |
