Obstructed defecation syndrome (ODS) is a type of constipation characterized by two or more of the following symptoms in more than 25 percent of defecation trials: straining, lumpy or hard stools, urgency, sense of incomplete evacuation, pelvic heaviness and manual maneuvers to promote defecation.
obstructed defecation is of two basic types: functional and mechanical. The functional type involves idiopathic megarectum, anismus (pelvic floor dys-synergy), and descending perineal syndrome, while the mechanical type includes rectocele, enterocele, internal rectal intussusception and overt rectal prolapse.
An excessive straining is likely to be the “primummovens", causing tissue weakness and organ descent, and often is due to longterm anxiety, muscle tension and resulting in non-relaxing puborectalis muscle. The increased straining causes pudendal nerve stretch which may lead to a pudendal neuropathy which affects the rectal sensations.
ODS has been also defined as an “iceberg syndrome", as the two most frequent lesions, i.e., rectocele and rectal internal mucosal prolapse, present in more than 90% of patients with ODS, are easily detectable and may be considered “emerging rocks", whereas the “surgical ship" is likely to “sink" due to the “underwater rocks", i.e., the occult lesions.