Management of lower GI bleeding

Resuscitation of the patient is the priority, with airway control and provision of oxygen plus large bore intravenous access. Blood should be taken for estimation of haemoglobin, urea, electrolytes, liver function and coagulation profile. Blood should be cross-matched and blood, and products given as required. Urinary and nasogastric catheters are helpful and arterial blood gas analysis will also help to guide the resuscitative effort. The history is important and evidence should be sought of previous GI bleeding, peptic ulcer or inflammatory bowel disease, liver disease, non-steroidal or warfarin usage. The abdomen and anorectum must be carefully examined and bedside examination of the anal canal and rectum are mandatory. If there is any suspicion of an upper GI source, this should be ruled out by upper GI endoscopy.

Colonoscopy is the diagnostic procedure of choice because of its diagnostic accuracy and therapeutical capability. As many lower GI bleeds subside spontaneously, the traditional management has been to wait, then to prep the bowel and undertake endoscopy. Recent evidence supports the use of early colonoscopy after mechanical bowel preparation. Colonoscopy must only be performed in a stable patient. Endoscopic haemostasis either by adrenaline injection or bipolar coagulation has been shown to reduce the requirement for surgery.

If upper and lower GI tract endoscopy fail to identify a source of bleeding, nuclear scintigraphy may be indicated. The role of technetium-labelled red blood cell scintigraphy in lower GI hemorrhage is controversial because its accuracy in locating the precise site of hemorrhage is variable, with reports of false localisation ranging from 3% to 59%.

Angiography can detect hemorrhage at a rate of 0.5-1 ml/min. The technique is performed via transfemoral placement of an arterial catheter. The hallmark of a positive examination is extravasation of contrast material into the lumen of the bowel. Angiography requires the availability of a skilled radiologist and the overall sensitivity of angiography is variable, and may be as low as 40%. If a bleeding source is identified then vasopressin may be infused down the angiog-raphy catheter. Vasopressin is a pituitary extract that causes arteriolar vasoconstriction and bowel wall contraction. Another angiographic option for control of hemorrhage is selective transcatheter embolisation of the bleeding site.

Emergency operations for acute lower GI bleeding may be required in approximately 15% of patients. The indications for an operation are persistent or recurrent haemorrhage leading to haemodynamic instability despite resuscitation or a high transfusion requirement. In general, patients with ongoing bleeding who have required transfusion of six or more units of blood should undergo an operation. If the bleeding site has been successfully localised, segmental resection is the treatment of choice because of its low morbidity, mortality and rebleed rate. If operation is required before accurate localisation of the bleeding site has been possible, then attempts should be made intraoperatively to identify the precise cause. Blind segmental colectomy should not be performed because of its high risk of rebleeding and associated mortality. Intraoperative colonoscopy should be undertaken; if diagnostic confusion still exists, oesophogastrodueodonoscopy (OGD) should be repeated and a paediatric colonoscope used to perform on-table small-bowel enteroscopy as small intestinal sources such as arteriovenous malformations, diverticula and neoplasia account for up to 5% of all cases of severe lower GI bleeding. If the bleeding site remains unidentified, then subtotal colectomy with ileorectal anastomosis or ileostomy should be undertaken.

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