In the patient described above, the following statement(s) is/are true concerning the possible etiology of bowel obstruction

a. Simple obstruction secondary to an adhesion is most likely to resolve nonoperatively

d. Lower abdominal procedures are more likely to result in obstructive adhesions than are upper abdominal procedures

Peritoneal adhesions account for more than half of small bowel obstruction cases. Lower abdominal procedures such as appendectomy, hysterectomy, and abdominal perineal resection are common precursor operations to account for obstruction although adhesions may follow any abdominal procedure including cholecystectomy, gastrectomy, and abdominal vascular procedures. Simple adhesive obstruction is distinguished from other forms of obstruction by the capacity to resolve without surgical intervention. In recent surveys, as many as 80% of episodes of small bowel obstruction due to adhesions may resolve nonoperatively. The likelihood that an obstruction is due to recurrent malignancy relates to several factors including the origin of the primary malignancy, the stage of the primary malignancy, and the designation of original surgery as curative or palliative. Gastric and pancreatic cancers often present with, or are subsequently complicated by peritoneal carcinomatosis and subsequent obstruction. With respect to colon and rectal carcinomas, as many as 50% of cases presenting with obstruction after resection of the primary may be due to adhesions and not recurrent malignancy.