Tenesmus

n. lack of ability to urinate or defecate (Medicine)

Tenesmus is a feeling of incomplete defecation. It is experienced as an inability or difficulty to empty the bowel at defecation. It is frequently painful and may be accompanied by involuntary straining and other gastrointestinal symptoms."Vesical tenesmus" is a similar condition, referring to difficult or failed attempts to urinate despite the bladder feeling full."Rectal tenesmus" is sometimes used as a retronym to further distinguish defecation-related tenesmus from vesical tenesmus.
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n. tenesmus, lack of ability to urinate or defecate (Medicine)

(n.)
An urgent and distressing sensation, as if a discharge from the intestines must take place, although none can be effected; -- always referred to the lower extremity of the rectum.
  

Noun
1. painful spasm of the anal sphincter along with an urgent desire to defecate without the significant production of feces; associated with irritable bowel syndrome
(hypernym) spasm, cramp, muscle spasm