 |
 |
 |
 |
 |
 |
 |
|
|
|||||||
| Discussion |
A 35-year-old woman presented with a history of intermittent melena
since 15 yrs .Her clinical examination was unremarkable. Her hemoglobin
was 4.8 gm%.
RADIOLOGICAL Examination:
Plain and contrast enhanced CT scans of the abdomen as also a small bowel
enema were normal. An RBC Scan revealed active bleed in the small intestine
(Fig.1).
 |
|
Fig.
1
|
Selective superior mesenteric
angiography showed a densely vascular tuft of tortuous, hypertrophied arteries
and early draining veins in the distal ileum (Figs 2a and 2b , 3)
 |
 |
 |
|
Fig.
2a
|
Fig.
2b
|
Fig.
3
|
Resection of the affected segment of the intestine was planned. Preoperatively,
methylene blue angiography for accurate localization of the affected segment
was performed so as to limit the extent of resection. At this time, superior
mesenteric angiography and superselective catherisation of the feeding vessel
was done using the "Mass transit" microcatheter system (Cordis). The patient
was shifted to the operating room with the catheter in situ - securing the
sheath and catheter to the groin. After exploration and evacuation of the
small bowel, 1 cc of methylene blue was injected through microcatheter to
delineate affected small bowel. (Fig 4).
 |
|
Fig.
4
|
The stained bowel was
resected and an anastomosis was done.
The histopathological finding was consistent with an arteriovenous malformation
of the intestine.
DISCUSSION:
Vascular lesions of the
GI tract are being recognized more frequently as a source of bleeding because
endoscopy and angiography are used more extensively. Angiodysplasia is an
important vascular lesion of the GI tract and represents a source of significant
morbidity from bleeding.
Galdabini first used the name angiodysplasia in 1974; however, confusion
about the exact nature of these lesions resulted in a multitude of terms
that included arteriovenous malformation, hemangioma, telangiectasia, and
vascular ectasia. These terms have varying pathophysiologies, with a common
presentation of GI bleeding.
Angiodysplasia is a degenerative lesion of previously healthy blood vessels
found most commonly in the cecum and proximal ascending colon. It is the
most common vascular abnormality of the GI tract. After diverticulosis,
it is the second leading cause of lower GI bleeding in patients older than
60 years. Angiodysplasia may account for approximately 6% of cases of lower
GI bleeding. It may be observed incidentally at colonoscopy in as many as
0.8% of patients older than 50 years. Seventy-seven percent of angiodysplasias
are located in the cecum and ascending colon, 15% in the jejunum and ileum,
and the remainder are distributed throughout the alimentary tract.
Repeated episodes of colonic distention are associated with transient increases
in lumen pressure and size. This results in multiple episodes of increasing
wall tension with obstruction of submucosal venous outflow, especially where
these vessels pierce the smooth muscle layers of the colon. Over many years,
this process causes gradual dilation of the submucosal veins and, eventually,
dilation of the venules and arteriolar capillary units feeding them. Ultimately,
the capillary rings dilate, the precapillary sphincters lose their competency,
and a small arteriovenous communication forms. This accounts for the characteristic
early-filling vein observed during mesenteric angiography. The exact cause
is unknown, but theories include degenerative changes of small blood vessels
associated with aging (most widely accepted theory).
Angiodysplasia may present as solitary or multiple vascular lesions. Unlike
congenital or neoplastic vascular lesions of the GI tract, this lesion is
not associated with angiomatous lesions of the skin or other viscera. Angiodysplasia
manifests only through GI bleeding. Most patients with angiodysplasia do
not experience GI bleeding; less than 10% actively bleed. However, because
lesions may be located throughout the GI tract and because bleeding may
be brisk or occult, presentation ranges from hematemesis or hematochezia
to occult anemia. Despite the fact that bleeding from angiodysplasia usually
is self-limited, patients with angiodysplasia can manifest chronic or recurrent
bleeding. In general, bleeding usually is low-grade and painless, which
is attributed to the venous source of bleeding. Angiodysplastic lesions
often are present in more than one location within the GI tract, and presentation
may vary during a patient's clinical course. Hematemesis frequently is observed
in patients with angiodysplasia of the upper GI tract.Bleeding from colonic
lesions most often is chronic and low grade, but as many as 15% of patients
present with acute massive hemorrhage. Patients with colonic angiodysplasia
may present with hematochezia (0-60%), melena (0-26%), hemoccult positive
stool (4-47%), or iron deficiency anemia (0-51%). Melena occurs in at least
one fourth of patients with colonic bleeding. Spontaneous cessation of bleeding
(occurring in 90% of patients) is the rule for lesions located in any part
of the GI tract.
Radionuclide scanning using technetium Tc 99m-labeled red blood cells or
99mTc sulfur colloid is helpful in detecting and localizing active bleeding
from angiodysplasia. Scanning can detect bleeding with rates as low as 0.1
mL/min. The intermittent bleeding nature of angiodysplasia has limited the
utility of radionuclide studies in this disorder.
Selective mesenteric angiography is a useful diagnostic technique, especially
in patients with massive bleeding in whom a colonoscopic diagnosis is difficult.
The most frequent and the earliest angiographic sign is that of a densely
opacified, dilated, and slowly emptying draining vein within the intestinal
wall. This vein is detected during the venous phase of the study and is
present in more than 90% of lesions. As the lesion progresses, a vascular
tuft may become apparent during the arterial phase of the study. This is
observed in as many as 70-80% of patients. It represents an extension of
the dilation process to the mucosal venules. The latest sign, an early-filling
vein, may be observed in the arterial phase, indicating a more developed
arteriovenous communication through the angiodysplastic lesion. It is observed
in only 60-70% of cases of angiodysplasia.
Methylene blue angiography has a role in delineating the affected bowel
segment and make intra operative resection of the segment easy.