<unk>  is commonly caused by constipation, by reflexive withholding of stool, by various physiological, psychological, or neurological disorders, or from surgery (a somewhat rare occurrence). The colon normally removes excess water from feces. If the feces or stool remains in the colon too long due to conditioned withholding or incidental constipation, so much water is removed that the stool becomes hard, and becomes painful for the child to expel in an ordinary bowel movement. A vicious cycle can develop, where the child may avoid moving his/her bowels in order to avoid the "expected" painful toilet episode. This cycle can result in so deeply conditioning the holding response that the rectal anal inhibitory response (RAIR) or anismus results. The RAIR has been shown to occur even under anesthesia and when voluntary control is lost. The hardened stool continues to build up and stretches the colon or rectum to the point where the normal sensations associated with impending bowel movements do not occur. Eventually, softer stool leaks around the blockage and cannot be withheld by the anus, resulting in soiling. The child typically has no control over these leakage accidents, and may not be able to feel that they have occurred or are about to occur due to the loss of sensation in the rectum and the RAIR. Strong emotional reactions typically result from failed and repeated attempts to control this highly aversive bodily product. These reactions then in turn may complicate conventional treatments using stool softeners, sitting demands, and behavioral strategies. The onset of<unk>  is most often benign. The usual onset is associated with toilet training, demands that the child sit for long periods of time, and intense negative parental reactions to feces. Beginning school or preschool is another major environmental trigger with shared bathrooms. Feuding parents, siblings, moving, and divorce can also inhibit toileting behaviors and promote constipation. An initiating cause may become less relevant as chronic stimuli predominate.
Encopresis
Petrissage
Hydrodissection
UroVysion
Capsulorhexis
Denudation 
Inspissation
Couching 