Page 27 - Gastrointestinal Bleeding (Xuất huyết tiêu hóa)

CHAPTER 20 Gastrointestinal Bleeding 301

CT and CT Colonography A prospective study revealed no difference between urgent (≤12
hours after presentation) and elective (36 to 60 hours after pre- 20
Multidetector CT can identify abnormalities in the colon that sentation) colonoscopy in terms of further bleeding, blood trans-
9
could be a source of bleeding, such as diverticulosis, colitis, fusions, hospital days, or hospital charges. Early colonoscopy
masses, and varices. CT is often performed if the patient is hav- (soon after admission) has been associated with a shorter length
ing hematochezia with abdominal pain. One study from France of hospitalization, principally because of improved diagnostic
reported that CT accurately identified 17 of 19 LGI bleeding yield rather than therapeutic intervention. 258
sites, including diverticula, tumors, angiomas, and varices. 253 A consensus on a single approach to patients with severe hema-
Multidetector CT has been shown to be more accurate than tochezia has not been reached, and the approach used depends
technetium-tagged RBC scanning in patients with LGI bleed- on local resources and expertise. In large centers, the approach
ing. 254 detailed in Fig. 20.4 is recommended. With use of an urgent
CT colonography is being used increasingly to screen per- endoscopic approach for diagnosis and treatment, the diagnostic
sons for colonic polyps and cancer and may be of some benefit in yield of definitive and presumptive bleeding sites is more than
patients with LGI bleeding (see Chapter 127). CT colonography 90%, and the estimated direct costs are significantly less than the
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detects large polyps (>1 cm) or cancers with a sensitivity rate of costs associated with an elective evaluation.
90%. 255 Faster multidetector scanners also allow CT angiogra-
phy to be performed, as well as evaluation of the small bowel. Barium Enema
This capability could allow detection of masses and vascular
lesions and is a potential advantage of CT angiography over other Emergency barium enema has no role in patients with LGI
radiologic imaging techniques. bleeding. This test is rarely diagnostic because it cannot demon-
Multidetector CT has been proposed as an early diagnostic strate vascular lesions and may be misleading if only diverticula
step in patients with suspected colonic bleeding to help direct are seen. It fails to detect 50% of polyps larger than 10 mm. 259
colonoscopic evaluation. 256 Because this approach may expose the In addition, the barium contrast liquid can make urgent colonos-
patient to unnecessary radiation, and because nearly all patients copy more difficult by impairing visualization and delaying other
will undergo either urgent or elective colonoscopy anyway, CT studies such as angiography. Subsequent colonoscopy is required
colonography is unlikely to play an important role in the acute for any suspicious lesions seen on barium enema or for lesions
evaluation of patients with LGI bleeding. Moreover, CT angio- that require therapy.
graphic IV contrast can cause acute kidney injury in patients with
renal insufficiency. Role of Surgery

Colonoscopy Surgical management is rarely needed in patients with LGI bleed-
ing because most bleeding is self-limited or easily managed with
Urgent colonoscopy following a rapid bowel purge has been medical or endoscopic therapy. The main indications for surgery
shown to be safe, provide important diagnostic information, and are malignancy, diffuse bleeding that fails to cease with medi-
allow therapeutic intervention. 236,237 Patients usually ingest 6 cal therapy (as in ischemic colitis or UC), and recurrent bleeding
to 8 L of PEG solution orally or via an NG tube over 4 to 6 from a diverticulum. At present, most patients are managed on a
hours until the rectal effluent is clear of stool, blood, and clots. medical service rather than on a surgical service.
Metoclopramide, in a dose of 10 mg, may be given intravenously
before the purge and repeated every 3 to 4 hours to facilitate gas- Causes and Management
tric emptying and reduce nausea. Owing to the potential risks of
high sodium and phosphate loads, sodium phosphate bowel prep- Visualizing active bleeding during colonoscopy is not always
arations should probably be avoided in patients with suspected possible, but colonoscopy permits identification of SRH (vis-
LGI bleeding. ible vessels, adherent clot, or spots) and provides information on
Urgent colonoscopy for LGI bleeding is generally performed the location of the lesion and on risk stratification. The earlier a
6 to 24 hours after the patient is admitted to the hospital. Most colonoscopy is carried out, the higher the chance of detecting an
bleeding stops spontaneously, and thus, colonoscopy is often actively bleeding lesion or SRH. A definite diagnosis of a bleed-
performed semi-electively on the day after initial hospitalization ing lesion can usually be made if active bleeding, a visible vessel,
to allow the patient to receive blood transfusions and the bowel or a clot is seen. A presumptive diagnosis of the cause of bleed-
preparation on the first day of hospitalization. ing can be made if a lesion that is a potential cause of bleeding is
The overall rate of detecting a presumed or definite cause of seen and no other possible sources are identified by anoscopy, full
LGI bleeding by colonoscopy ranges from 48% to 90%, with an colonoscopy with intubation of the terminal ileum, and, in some
average of 68%, based on a review of 13 studies. 238 The prob- cases, push enteroscopy. 28
lem with interpreting these data, however, is that making a defi-
nite diagnosis of the cause of the bleeding is often not possible Diverticulosis
unless a bleeding stigma such as active bleeding, a visible vessel,
an adherent clot, a flat spot, mucosal friability or ulceration, or Colonic diverticula are herniations of colonic mucosa and sub-
the presence of fresh blood limited to a specific segment of the mucosa through the muscular layers of the colon (see Chapter
colon is seen. 121). Histopathologically, diverticula in the colon are actu-
The optimal time for performing urgent bowel prepara- ally pseudodiverticula because they do not contain all layers
tion and colonoscopy is unknown. Theoretically, the sooner an of the colonic wall. Diverticula form when colonic tissue is
endoscopy is performed, the higher the likelihood of finding a pushed out by intraluminal pressure at points of entry of the
lesion (e.g., bleeding diverticulum, polyp stalk) with stigmata small arteries (vasa recta), where they penetrate the circular
that might be amenable to endoscopic hemostasis. A retrospec- muscle layer of the colonic wall. The entry points of the vasa
tive study from the Mayo Clinic, however, suggested that in recta are areas of relative weakness through which the mucosa
patients with diverticular bleeding, the timing of endoscopy (0 to and submucosa can herniate when intraluminal pressure is
12 hours, 12 to 24 hours, or more than 24 hours after admission) increased. 261 Diverticula vary in diameter from a few millime-
is not significantly associated with the finding of active bleeding ters to several centimeters and are located most commonly in
or other stigmata that would prompt colonoscopic hemostasis. 257 the left colon. Most colonic diverticula are asymptomatic and