If the second attempt is unsuccessful, the patient may try a simple bulking agent such as psyllium. Secondary Constipation Sometimes constipation is caused by an underlying medical condition. For example, diabetes mellitus may cause constipation or diarrhea. Colorectal carcinoma may also cause constipation, especially when the tumor mechanically obstructs the bowel lumen or metastasizes to the spinal cord. Colorectal carcinoma may be suspected when the constipated patient also experiences abdominal discomfort, gaseousness, weight loss, malaise, tenesmus, and notices blood in the stool.
Medications are another secondary cause of constipation.
Secondary constipation can also be caused by laxative dependence. Laxative misuse can induce perceived constipation. A patient may be convinced of the necessity for a single daily bowel movement. To reach this goal, he or she might ingest a harsh laxative, such as senna, bisacodyl, castor oil, or casanthranol. Unfortunately, these laxatives do not induce a normal bowel movement.