Page 33 - Gastrointestinal Bleeding (Xuất huyết tiêu hóa)

CHAPTER 20 Gastrointestinal Bleeding 307

ischemia. Because angioectasia can occur elsewhere in the GI disruption of von Willebrand proteins during passage through
tract, other mechanisms are postulated, including a response to the stenotic aortic valve; the acquired von Willebrand disease, in 20
mucosal irritation or local ischemia, as occurs after radiation. turn, increases the risk of bleeding from angioectasia. 323,324 Sev-
Most angioectasias occur in patients older than 60 years of age eral series have reported cessation of bleeding from angioectasia
and can involve any segment of the GI tract. Usually, the lesions after aortic valve replacement, even though the angioectasias per-
are multiple in a given segment of intestine. Approximately 20% sisted, an observation consistent with the hypothesis that bleed-
(and probably more) of patients have angioectasias in at least 2 ing was the result of the damaged von Willebrand factors that
sections of the GI tract. 314,315 normalized after aortic valve replacement. 325
In studies of asymptomatic persons who underwent colo- Overt or obscure GI bleeding occurs in approximately 20%
noscopy, angioectasias were found in 1% to 3%. 316,317 In these of patients with a left ventricular assist device, especially in older
persons, the angioectasias were mostly in the right colon, with patients, with angioectasia as one of the most frequent causes of
the following distribution: cecum, 37%; ascending colon, 17%; bleeding. 326-328 Possible pathophysiologic mechanisms for angio-
transverse colon, 7%; descending colon, 7%; sigmoid colon, ectasia formation and bleeding include loss of von Willebrand
18%; and rectum, 14%. Among asymptomatic persons found factor related to shear stress, which results in impaired platelet
incidentally to have colonic angioectasia, no bleeding occurred aggregation, and intestinal hypoperfusion related to increased
during a 3-year follow up. vascular luminal pressure and lowered pulse pressure. 328 Because
Several conditions appear to be associated with an increased many older persons with bleeding from intestinal angioectasia
frequency of angioectasia. Patients with chronic kidney disease have cardiovascular disease but not severe aortic stenosis, other
and uremia have an increased rate of intestinal angioectasias. A cardiovascular disorders such as mild to moderate aortic steno-
study of patients with and without chronic kidney disease who sis, aortic sclerosis, hypertrophic cardiomyopathy, and peripheral
had obscure GI bleeding found angioectasia as the presump- vascular disease may result in sufficiently high shear stress to dis-
tive source in 47%, compared with 18% of those without kid- rupt von Willebrand factors and contribute to bleeding angioec-
ney disease. 318 The increased risk of bleeding from angioectasia tasias. 325
in patients with chronic kidney disease may be associated with On endoscopy, an angioectasia appears as a 2 to 10 mm red
uremia-induced platelet dysfunction. lesion, with arborizing ectatic blood vessels that emanate from a
von Willebrand disease (congenital or acquired) has also been central vessel (Fig. 20.23). Application of pressure on an angio-
associated with bleeding angioectasia. 319 von Willebrand’s fac- ectasia with an endoscopic probe may cause the lesion to blanch.
tor is needed for effective platelet aggregation. A well-controlled One study has suggested that sedation of a patient with a nar-
prospective study found that almost all patients with bleeding cotic during endoscopy can make visualization of angioectasia
UGI and colonic angioectasias, as opposed to nonbleeding angio- difficult because of transient mucosal or submucosal hypoperfu-
ectasias or bleeding diverticulosis, had acquired von Willebrand sion, which leads to decreased filling or causes vasoconstriction,
disease associated with selective loss of the largest multimeric and that reversal with naloxone, an opioid antagonist, can make
forms of von Willebrand factor, as well as with aortic stenosis. 320 the angioectasia more prominent. 329 In practice, however, this
Because the large von Willebrand multimers promote primary maneuver is unlikely to be useful clinically and might make the
hemostasis in a microcirculation characterized by high shear patient more uncomfortable.
forces, as occurs in angioectasia, the loss of the large multimers Angioectasias can be treated endoscopically with various
may explain why bleeding occurs in some patients with angioec- modalities, including epinephrine injection, thermal probe coag-
tasias. ulation, argon plasma coagulation, hemoclips, and band ligation.
Aortic stenosis has been associated with GI bleeding from Assessing efficacy can be difficult, given the heterogeneity of
angioectasia (Heyde syndrome). 321 This association is controver- affected patients and intermittent nature of the blood loss. One
sial because both conditions are common, and an association may series of 16 patients with transfusion-requiring bleeding from
not imply cause and effect. 322 Nevertheless, aortic stenosis has angioectasia found no difference in the frequency of continued
been shown to be associated with an acquired form of von Wil- bleeding (50%) whether treatment was with surgery, endoscopic
lebrand disease in 67% to 92% of patients because of mechanical therapy, or blood transfusions alone, presumably because of the

A B
Fig. 20.23 Endoscopic appearance of jejunal angioectasia before (A) and after (B) multipolar probe electrocoagulation.