Ischemic diseases of the large intestine.

The blood flow within the walls of the digestive tract must be sufficient to maintain its structural and functional integrity. All episodes of vascular insufficiency cause ischemic damage to the organ and carry the threat of diffuse or focal necrosis. Certain forms of ischemic colitis or proctitis arise from episodes of reduced peripheric or splanchnic blood flow; indeed, those that do not culminate in necorsis of the colonic wall are more frequently caused by hemodynamic disorders than by vascular occlusions. The crisis is often mitigated by the development of collateral circulation, which is nevertheless of rather meager quality, such that the patients are very vulnerable to subsequent slight changes in cardiac output. Necrotic, gangrenous ischemic colitis arises from a combination of occlusive damage to the arteries and general hemodynamic disturbances. The vascular insufficiency might be slight or severe, temporary or long-lasting, localized or diffuse. In addition, the attack occurs in a septic medium in the presence of an abundant microbial flora that may be highly pathogenic. Thus infection complicates and aggravates the ischemic damage, with the result that the gangrenous aspect of the lesions tends to hide their ischemic origin. Indeed, the variability of the manifestations of the disease represents one of its primary characteristics and is a function of the different causative factors. A knowledge of the anatomy and pathophysiology of the splanchnic circulation and its hemodynamics is essential for a full appreciation of the diagnosis and treatment of the disorders and for the adoption of the aggressive approach necessary to improve the poor prognosis of ischemic diseases of the colon and rectum. The salient points have been stressed in the present chapter. The features of the different forms of the disease have been described, together with the necessary medical treatment and the indications for surgical for surgical intervention. In the relatively rare cases where operation is necessary, the tactics and techniques have been described. All treatment should be based on (a) constant, prolonged intensive care; (b) precise monitoring of any change in status; and (c) rapid excision of any necrotic (often gangrenous) tissue. Ischemic colitis is most likely to occur in elderly patients with a history of cardiovascular disease, but it is not excluded in younger individuals. It is a frequent entity and is potentially lethal. Although its clinical, radiological, and anatomical characteristics permit its classification as a separate disease, it is often confused with other disorders of the colon. Although the abdominal surgeon is most likely to be concerned with this disease, the vascular surgeon who attacks the lower aorta should always be on the lookout for possible occurrences of segmentary ischemia of the distal colon as a result of his intervention.