Lower gastrointestinal bleeding

Over the last decade, there has been a major shift of emphasis with regard to lower gastrointestinal bleeding. The recognition of angiodysplasia as a not uncommon cause of haemorrhage has led us to reassess much of our earlier teaching. In addition to the other common cause of bleeding, namely diverticular disease, acute bleeding may also occur in inflammatory bowel disease, radiation enteritis, and ischaemic colitis, and may originate from vascular tumours. From a clinical viewpoint, bleeding from the distal small bowel, most often from a Meckel’s diverticulum, cannot be distiguished from bleeding from the proximal colon. Angiodysplasia has come to the fore over the last decade as a major cause of gastrointestinal bleeding. In a Hammersmith series of 67 patients with this problem, 13 per cent presented with an initial acute bleed, 46 per cent with recurrent acute bleeding and 33 per cent with chronic bleeding (usually presenting as anaemia). In 7 per cent of patients, angiodysplasia was an incidental finding on angiography and occurred in association with other lesions’. Case selection is partly responsible for the fact that angiodysplasia was by far the commonest cause of colonic bleeding seen at the Hammersmith Hospital, being nearly ten times as common as acute diverticular bleeding. It was responsible for 74 per cent of all cases of red bleeding per rectum, 18 per cent of all cases of ‘melaena’ and 49 per cent of all cases presenting with anaemia secondary to colonic bleeding. Clearly this pattern of disease reflects the experience of the unit to which patients are referred for angiography in the investigation of bleeding, and does not represent the true incidence of angiodysplasia as a cause of bleeding in the population. When diagnosed by angiography, angiodysplasia is almost always in the caecum or ascending colon. Although a higher incidence of angiodysplastic lesions is seen in the left colon at colonscopy, these rarely show on angiography and do not often cause significant bleeding. Angiodysplasia may be diagnosed either endoscopically or by angiography, though the former may be difficult during an acute bleeding episode. However, most such episodes stop spontaneously, so that this is not a practical difficulty. If angiodysplasia is diagnosed endoscopically then initial treatment should consist of endoscopic coagulation. In some cases this fails and, in occasional patients, angiography demonstrates angiodysplasia which was not visible at endoscopy. In either of these situations, operative treatment may be required. It has become apparent that the presence of angiodysplasia does not necessarily mean that it is the source of bleeding or perhaps the only source of bleeding. Although angiodysplasia is an extremely rare incidental angiographic finding in patients without gastrointestinal bleeding, patients with angiodysplasia frequently have other lesions which are potential sources of haemorrhage. Meckel’s diverticulum appears to be particularly common in this context, and jejunal arteriovenous malformations and small bowel tumours have also been found in association. Experience has shown that it is not possible to be certain about the source of haemorrhage when there are two possible sources of bleeding; if such patients come to laparotomy then both potential sources should be dealt with’. Bleeding diverticular disease has always been problematic. In the days before angiodysplasia was diagnosed commonly, the mystery remained that diverticular disease was always more extensive in the left colon although it was apparent clinically that bleeding occurred more commonly from the right side. In one series of 100 patients with 144 episodes of bleeding, it was noted that in 58 the bleeding was bright red in colour whereas in 42 it was black and tarry3. Left-sided resections were commonly followed by rebleeding, although the disease was more extensive on the left. This led to emphasis being placed on the importance of extensive colectomy when dealing with acute ‘diverticular’ bleeding, or to the need for a temporary transverse colostomy when deciding which half of the colon contained the source of bleeding before resection. It was noted, however, that bleeding was commoner in patients with extensive diverticular disease than in those where the disease was more localized. In today’s context it is very important to question the diagnosis of bleeding diverticular disease. If at all practical, angiography should be employed to determine the site of bleeding. Undoubtedly many patients previously diagnosed as having bleeding diverticular disease were in fact suffering from angiodysplasia. If the patient is losing black tarry stool then angiodysplasia is even more likely, and if a ‘blind’ resection seems warranted then right hemicolectomy might be the logical choice. For severe red bleeding of unknown origin, subtotal resection of the colon may still occasionally be necessary.