ABSTRACT
Mechanical large bowel obstruction (LBO) occurs when there is occlusion of the lumen of the colon or rectum resulting in dilatation proximal to the site of obstruction with associated symptoms. This chapter focuses on summarising non-malignant, mechanical causes of LBO. Colonic volvulus occurs with twisting or torsion of a redundant colon around its mesentery in an axial rotation resulting in obstruction. Risk factors for volvulus include a congenitally unfixed colon, advanced age, congenital bands, hyperperistalsis, chronic constipation, idiopathic megacolon, neurologic and psychiatric disease or previous surgery. Diagnosis of volvulus is suspected given the history of presentation, clinical exam and imaging. Transverse colon volvulus can be seen on plain films as well with several findings consistent with the diagnosis: a dilated, air-filled colon with abrupt termination at the splenic flexure, two widely separated air-fluid levels representing the transverse colon and caecum and an empty descending and sigmoid colon.
