Although this term still appears in medical dictionaries, most examples of its usage in the BMJ, for example, come from the mid/late 19th and early 20th centuries although there are articles still using it up to the 1960s
"A fit of obstipation occurred in July. He was treated with opiates and distensive nutrient injections, and after a few days passed a quantity of feculent matter, and recovered."
"Constipation certainly exists, and constitutional sluggishness of bowel action was also apparent in my own series of cases, but physiological influences alone did not produce the picture of "psychogenic megacolon." Given a physiological trigger, it still required the intervention of parent-child conflict over bowel function to evoke the state of chronic and intractable obstipation which I was describing."http://www.bmj.com/search?fulltext=obstipatio...
Suggest adding the "dated" flag to both these entries as someone might come across the word in an older English text and need the German equivalent, but it would certainly be better to use the term "constipation" in the DE->EN direction these days.