Changes

==Description==

==Description==

'''Perineal hernia''' is the protrusion of pelvic or abdominal viscera through the structures of the weakened or ruptured pelvic diaphragm, causing displacement of the perineal skin.  The pelvic diaphragm is composed of the coccygeus, levator ani and external anal sphincter muscles and, due to its proximity to these structures, the rectum is the organ most commonly involved in perineal hernias.  Perineal hernias can be unilateral or bilateral and, depending of their location, they can be further classified as dorsal, ventral, sciatic or caudal hernias (see table).  The herniated content is contained by the perineal fascia and, since the parietal peritoneum is usually intact, this constitutes a true [[Hernia|hernial sac]].  The sac may contain pelvic or retroperitoneal fat, peritoneal fluid, a deviation, dilation or sacculation of the rectum, a rectal diverticulum, the prostate gland, the urinary bladder (which may be retroflexed) or the small intestine and any of these organs may become [[Hernia|incarcerated]] or [[Hernia|stangulated]].  In cats, the sac frequently only contains the rectum.   

'''Perineal hernia''' is the protrusion of pelvic or abdominal viscera through the structures of the weakened or ruptured pelvic diaphragm, causing displacement of the perineal skin.  The pelvic diaphragm is composed of the coccygeus, levator ani and external anal sphincter muscles and, due to its proximity to these structures, the rectum is the organ most commonly involved in perineal hernias.  Perineal hernias can be unilateral or bilateral and, depending of their location, they can be further classified as dorsal, ventral, sciatic or caudal hernias.  The herniated content is contained by the perineal fascia and, since the parietal peritoneum is usually intact, this constitutes a true [[Hernia|hernial sac]].  The sac may contain pelvic or retroperitoneal fat, peritoneal fluid, a deviation, dilation or sacculation of the rectum, a rectal diverticulum, the prostate gland, the urinary bladder (which may be retroflexed) or the small intestine and any of these organs may become [[Hernia|incarcerated]] or [[Hernia|stangulated]].  In cats, the sac frequently only contains the rectum.   

The cause of perineal hernia is not know but several factors have been discussed, all of which are thought to contribute to progressive weakness and atrophy of the muscles of the pelvic diaphragm.  These include:

The cause of perineal hernia is not know but several factors have been discussed, all of which are thought to contribute to progressive weakness and atrophy of the muscles of the pelvic diaphragm.  These include:

*'''Congenital or acquired myopathies''', such as muscular dystrophy and myositis.

*'''Congenital or acquired myopathies''', such as muscular dystrophy and myositis.

*'''Hormonal imbalances''', particularly increases in androgens (or in androgen receptors on the pelvic diaphragm muscles) and relaxin receptors which most commonly occur in male entire dogs.

*'''Hormonal imbalances''', particularly increases in androgens (or in androgen receptors on the pelvic diaphragm muscles) and relaxin receptors which most commonly occur in male entire dogs.

*'''Prostatic enlargement''' is not thought to be a cause of perineal hernia ''per se'' but it contribute to the latter condition as it often produces faecal and urinary tenesmus.

*'''Prostatic enlargement''' is not thought to be a cause of perineal hernia ''per se'' but it may contribute to the latter condition as it often produces faecal and urinary tenesmus.

==Signalment==

==Signalment==