Defecation: Faecal incontinence

12 Defecation


Faecal incontinence




INITIAL PRESENTATION


Appears aware but unable to control the urge; appears unaware and drops faeces when walking, lying down, in bed; has poor control of defecation when excited or during prolonged confinement.



CLINICAL TIP


Dogs with hindlimb weakness or lumbosacral joint (LSJ) pain may be unable to maintain the squatting position and often stand up and defecate while walking.



INTRODUCTION





Defecation reflex



• Filling of the rectum: the internal sphincter contracts pushing faeces back into the colon until the volume is sufficient. At this point, the internal anal sphincter (smooth muscle) relaxes and the external anal sphincter contracts. The external anal sphincter is composed of skeletal muscle innervated by the pudendal nerve formed from sacral segments and nerves S1–3.

• The stimulus for defecation is distention of the rectum.

• Awareness of rectal distension depends on the sacral afferents more than the cerebrum.

• Initiation of defecation by rectal distension activates parasympathetic efferents (pelvic nerve) that contract the colon and inhibit the external anal sphincter and pelvic muscles.

• Facilitation of defecation and expulsion is by the animal adopting the proper posture and the generation of increased abdominal pressure.


Prevention of defecation



1. Reflex by the internal anal sphincter contracts. This occurs, for example, in response to a sudden increase in abdominal pressure or increases in rectal filling.

2. Voluntary: mediated by higher centres (cerebrum).


Faecal incontinence


Faecal incontinence is the inability to control and retain faeces until voluntary conscious defecation is initiated.



SIGNALMENT


A 13-year-old male miniature wirehaired daschund.



CASE PRESENTING SIGNS


Faecal incontinence and urinating in spurts.



CASE HISTORY


A L1–2 IV disc extrusion had occurred 1 month earlier resulting in hindlimb paralysis, urine retention and lack of pain perception in both hindlimbs. Hemilaminectomy at the site decompressed the cord and voluntary movement of the tail had returned despite the paraplegia persisting. The owner reported that the dog urinated in spurts when taken outdoors and held in a standing position. On one occasion the dog pulled itself out of its bed to the backdoor where it had then urinated (which may or may not be a coincidence).

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Sep 3, 2016 | Posted by in SMALL ANIMAL | Comments Off on Defecation: Faecal incontinence
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