ACUTE LOWER GASTROINTESTINAL HEMORRHAGE

ACUTE LOWER GASTROINTESTINAL HEMORRHAGE
Definition and Incidence
Acute lower gastrointestinal bleeding is hemorrhage arising distal to the ligament of Treitz.
The colon is the source of hemorrhage in more than 95% to
97% of cases, with the remaining 3% to 5% arising in small bowel sites.
Lower gastrointestinal bleeding accounts for about 15% of major episodes of
gastrointestinal hemorrhage and hence is much less common than upper gastrointestinal bleeding.
The incidence of lower gastrointestinal bleeding increases with age, reflecting the parallel increase in acquired lesions responsible for colonic bleeding: diverticulosis and angiodysplasias.
The differential diagnosis of acute lower gastrointestinal hemorrhage is shown in .
Clinical Presentation

The hallmark of acute lower gastrointestinal hemorrhage is
· hematochezia; passage of bloody stool, blood, or blood clots per rectum.
· If bleeding is slower and of lesser volume, melena may also be a presenting sign, although this is more characteristic of an upper gastrointestinal source.
· Similarly, up to 15% of patients with massive hemorrhage from an upper gastrointestinal source may present with hematochezia, which is indicative of at least 1000 mL of hemorrhage over a short interval from an upper gastrointestinal source.

Roughly half of patients present with both a
· decrease in hemoglobin and hematocrit and hemodynamic instability;
· 30% have orthostatic changes,
· 10% syncope, and
· 19% shock.

Although lower gastrointestinal hemorrhage represents a genuine emergency, it is generally less life-threatening than upper gastrointestinal hemorrhage.
Patients are
· less likely to present in shock,
· more likely to cease bleeding spontaneously,
· and usually have a lower transfusion requirement.

Etiology
Unlike upper gastrointestinal hemorrhage, in which endoscopic findings can accurately identify mucosal lesions responsible for acute hemorrhage, validating the source of an episode of hemorrhage from the colon is more problematic.
First, lower gastrointestinal hemorrhage is characterized by episodes of intermittent hemorrhage;
bleeding may well have ceased by the time the diagnostic procedure is obtained.
Second, up to 42% of patients are found to have multiple potential bleeding sources at the time of diagnostic evaluation.
It is therefore important to have a clear understanding of the significance of findings on diagnostic evaluation and to keep in mind the limited certainty that may accompany some of these findings.
The direct observation of a bleeding lesion or findings of stigmata of recent hemorrhage at endoscopy are required to establish a definitive diagnosis.

Differential Diagnosis of Lower Gastrointestinal
Hemorrhage
Diverticulosis
Angiodysplasia
Neoplasm
Polyps
Meckel’s diverticulum
Inflammatory disorders
Ulcerative colitis
Crohn’s disease
Infectious colitis
Radiation-induced disorders
Nonsteroidal anti-inflammatory drug–associated disorder
Hemorrhoids
Varices
Dieulafoy’s lesions
Osler-Weber-Rendu syndrome
Aortoenteric fistula
Vasculitis
Mesenteric ischemia

Understanding the degree of certainty of a bleeding source is of great importance when contemplating surgical resection to treat hemorrhage.

Diverticulosis
Colonic diverticulosis represents the most common source of lower gastrointestinal hemorrhage,
responsible for 40% to 55% of cases of hemorrhage in most series. Colonic diverticula are common acquired lesions of the abdominal colon.
Although 40% of patients in the 5th decade of life have diverticula,
this incidence rises to 80% by the 9th decade.
Hemorrhage complicates 3% to 5% of patients with diverticulosis.
The anatomic basis for bleeding is thought to be asymmetrical rupture of intramural branches (the vasa recta) of the marginal artery at the dome of the diverticulum or at its antimesenteric margin. It appears likely that luminal traumatic factors, including impacted fecaliths with abrasion of the vessels, lead to hemorrhage.

Hemorrhage is rarely associated with the inflammation of clinical diverticulitis.
Diverticular hemorrhage ceases spontaneously in up to 90% of patients.
Transfusion of greater than 4 units of packed red blood cells is rare.
Although left colon diverticula are more common, bleeding tends to be more common from right colon diverticular sources.
Hemorrhage from right colon lesions may also be of greater rate and volume than that from left-sided diverticula.
After an initial episode of hemorrhage, rebleeding is likely to occur in 10% of patients in the first year; thereafter, the risk for rebleeding increases to 25% at 4 years.

Given the prevalence of colonic diverticulosis, and the fact that most episodes of hemorrhage tend to cease spontaneously, many episodes of lower intestinal hemorrhage are attributed to colonic diverticulosis as a presumptive rather than a definitive diagnosis.

Angiodysplasia
Angiodysplasias are responsible for 3% to 20% of cases of acute lower intestinal bleeding.
Angiodysplasias, also referred to as arteriovenous malformations, are small ectatic blood vessels in the submucosa of the gastrointestinal tract.
The overlying mucosa is often thin, and superficial erosion at the site of an angiodysplasia has been observed on histologic examination of surgical or autopsy specimens.
Angiodysplasias are identified in 1% to 2% of autopsy evaluations and increase in frequency with the age of the patient.
Angiodysplasias may occur throughout the gastrointestinal tract and represent the
most common cause of hemorrhage from the small bowel in patients older than 50 years of age.

Angiodysplasias are evident on colonoscopy as red, flat lesions about 2 to 10 mm in diameter.
Lesions may appear stellate, oval, sharp, or indistinct.
Colonoscopy is the most sensitive method to identify angiodysplasias, although angiography is also able to identify these lesions.
The use of meperidine during colonoscopy may decrease the ability to identify angiodysplasias because of a reduction in mucosal blood flow.
Another study has identified that the use of a narcotic antagonist may increase the size of angiodysplasias and enhance the detection rate.
On angiography, angiodysplasias appear as ectatic, slowly emptying veins or as arteriovenous malformations with brisk, early venous filling.

More than half of angiodysplasias are localized to the right colon, and bleeding from angiodysplasia correlates with this distribution.
Angiodysplasias may be associated with many medical conditions, including end-stage renal disease, aortic stenosis, von Willebrand’s disease, and others.
It is not clear whether this association reflects the greater tendency of angiodysplasias to bleed in these conditions or whether, in fact, angiodysplasias are more common structural findings in them.

Neoplasia
Colonic neoplasms, including
· adenomatous polyps,
· juvenile polyps, and
· carcinomas, present in a variety of manners.

· Typically, bleeding from these lesions is slow, characterized by occult bleeding and secondary anemia.
· These neoplasms can bleed briskly, however, and in some series, up to 20% of cases of acute hemorrhage are ultimately found to arise from colonic polyps or cancers.
· Juvenile polyps are the second most common cause of hemorrhage in patients younger than the age of 20 years.

Inflammatory Conditions
A wide variety of inflammatory conditions can cause acute lower gastrointestinal hemorrhage.
Hemorrhage is rarely the presenting sign; rather, it develops in the course of the disease, and the cause is suspected based on the patient’s history.
Up to 20% of cases of acute lower gastrointestinal hemorrhage may be due to one of these inflammatory conditions.
Most episodes of bleeding cease spontaneously or with specific therapy directed at the cause.

Hemorrhage complicates the course of ulcerative colitis in up to 15% of cases.
Emergency colectomy for persistent hemorrhage accounts for 6% to 10% of emergency surgical colectomies in patients with this disease.
Crohn’s disease is less likely to cause massive colonic hemorrhage and occurs in roughly 1% of patients with this condition.
Infectious causes include Escherichia coli, typhoid, cytomegalovirus, and Clostridium difficile.
Radiation injury is most common in the rectum after pelvic radiotherapy for prostate or gynecologic malignancies.
Bleeding is most common 1 year after radiation treatments but may occur up to 4 years later.
Patients with immunosuppression or acquired immunodeficiency syndrome (AIDS) are at risk for acute lower intestinal hemorrhage from a unique set of causes.
Cytomegalovirus is the most common cause;
Kaposi’s sarcoma, histoplasmosis, and perianal fistulas and fissures are also problematic and
are more likely to hemorrhage in patients with AIDS-induced thrombocytopenia.

Vascular Causes
Vascular causes of acute lower intestinal hemorrhage include the
vasculitides (polyarteritis nodosa, Wegener’s granulomatosis, rheumatoid arthritis, and others),
which are associated with punctate ulceration of the colon and small bowel.
Colonic ischemia with mucosal ulceration and friability may also result in acute hemorrhage, often in the setting of acute abdominal pain and sepsis.
Acute mesenteric ischemia may be heralded by an episode of hematochezia in the context of severe abdominal pain, preexisting vascular disease, arterial embolism risk, or hypercoagulability.
Although hemorrhage is an element in the clinical management of these patients, only rarely does the control of hemorrhage become the major focus of therapy.
Rather, restoration of visceral perfusion is the primary therapeutic objective.

Hemorrhoids
Hemorrhoids are usually noted on physical examination in more than half of patients with lower gastrointestinal hemorrhage.
In fewer than 2% can the hemorrhage be attributed to these lesions, however.
Unless unequivocal signs of bleeding are evident on anoscopy, investigation of the patient for another source of lower intestinal bleeding should be pursued.
Patients with portal hypertension may develop massive hemorrhage from hemorrhoids,
as can patients with HIV-associated thrombocytopenia with hemorrhoids.

Uncommon Causes
Rare causes of lower gastrointestinal hemorrhage include
solitary rectal ulcer,
Dieulafoy’s lesion of the colon,
portal colopathy,
NSAIDs,
intussusception, or
bleeding following colonoscopic biopsy or polypectomy.

Initial Assessment
The initial history and physical examination are directed to determining the potential source of the hemorrhage and the severity of initial hemorrhage.
Most cases eventually are determined to result from angiodysplasia or diverticulosis,
both of which are usually asymptomatic before initial hemorrhage.

Nonetheless, the initial history should exclude other, less common causes of the bleeding.
Specific inquiry should be made regarding use of NSAIDs or anticoagulants.
Abdominal pain or recent diarrhea and fever may point to colitis, either infectious or ischemic.
Patients with prior aortic surgery should be considered to have an aortoenteric fistula until proved to the contrary.
Prior radiation therapy for pelvic malignancy may indicate radiation proctitis.
Recent colonoscopy may suggest bleeding from a biopsy or polypectomy site.
The cause of previous episodes of bleeding should be elicited, as should the possibility of a history of inflammatory bowel disease.
Family history of polyposis syndromes or colonic malignancy may also be pertinent.
Young patients—those less than 30 years of age—are at greatest risk for bleeding from Meckel’s diverticula or intestinal polyps.

Physical examination should include
measurement of orthostatic vital signs
in patients without overt shock.
All patients should be resuscitated, as outlined in the previous section.
Pertinent findings on physical examination may include
scars from previous abdominal incisions,
the presence of abdominal masses, or
skin and oral lesions suggestive of polyposis syndromes.
Stigmata of cirrhosis suggestive of bleeding from hemorrhoids or varices secondary to portal hypertension should be considered.
The rectal examination is important to identify any anorectal pathology, including tumors, ulcers, or polyps.
The color of the rectal contents and the presence of formed stool or blood clot should also be noted.
Anoscopic examination to exclude
hemorrhage from hemorrhoids should be completed.
A nasogastric tube should be inserted to look for blood or coffee ground–like material to exclude an upper gastrointestinal source.
In patients with hematochezia and hemodynamic instability, emergency upper endoscopy is required.

Diagnosis
Emergency surgical intervention for ongoing massive hemorrhage is rarely necessary before attempts are made to localize the precise source of bleeding. ]
This allows an orderly approach to identification of the bleeding site, which is essential for appropriate therapy.
After the patient has been resuscitated and stabilized, diagnostic testing should begin.
The choice of initial investigation remains controversial and is dependent to some degree on local availability of procedures and expertise.
The three options for primary diagnostic testing are colonoscopy, selective visceral angiography, and technetium 99m (99m Tc)-labeled red blood cell scintigraphy. An algorithm for diagnosis of acute lower gastrointestinal bleeding is shown in.
Colonoscopy
Recognition that most episodes of hemorrhage cease spontaneously and that stigmata of bleeding are subtle has led to efforts to perform colonoscopy as early as possible in the course of evaluation.
Urgent colonoscopy, completed within 12 hours of admission, is indicated in patients
who have ceased to have ongoing significant hemorrhage and in
whom resuscitation and hemodynamic stability have been achieved.
In this setting, colonoscopy can be completed after colonic purging.
Positive findings on colonoscopy include
identification of an active bleeding site,
identification of a nonbleeding visible vessel,
clot adherent to a diverticular ulcerated orifice,
clot adherent to a discrete focus of mucosa,
or fresh blood localized to a colonic segment.
Similarly, the finding of fresh blood only in the terminal ileum after a negative upper endoscopy strongly suggests the small bowel as a bleeding source.
It is important that incidental lesions, such as
blood clots in multiple diverticular orifices,
nonbleeding arteriovenous malformation,
nonbleeding polyps, and
nonbleeding diverticula,
are not concluded to be the site of recent hemorrhage.
Hemorrhage can be attributed only to lesions with clear stigmata of bleeding.
Patients presenting with massive lower gastrointestinal hemorrhage are poor candidates for emergency colonoscopy.
The procedure is technically difficult because of the
inability to clear the mucosal surfaces of old or new hemorrhage.
Finding a discrete, actively bleeding vessel in the unprepared bowel is difficult even for the most experienced endoscopist.
Second, patients with massive hemorrhage have hemodynamic instability,
precluding the use of sedation and increasing the risk for hypoxemia and complication.
Further, resuscitation may be compromised during the procedure.
Hence, colonoscopy is most appropriately used as the initial diagnostic procedure in patients presenting with acute hemorrhage that has ceased or in patients with a more moderate degree of bleeding.
Colonoscopy is the procedure of choice in patients who develop hemorrhage after colonoscopic polypectomy.

Selective Visceral Angiography
Mesenteric arteriography has been widely used in the evaluation and treatment of patients with lower gastrointestinal hemorrhage.
Selective injection of radiographic contrast
into the superior mesenteric
or inferior mesenteric arteries
identifies hemorrhage in patients bleeding at a rate of 0.5 mL/min or greater.
The study can accurately identify arterial hemorrhage in 45% to 75% of patients if they are actively bleeding at the time of contrast injection.

Given the characteristic intermittent bleeding seen in lower gastrointestinal hemorrhage associated with diverticulosis, arteriovenous malformations, and other causes, bleeding may have ceased by the time of the study.
Some radiologists have advocated evocative testing,
including intra-arterial vasodilators, heparin, and fibrinolytic agents,
in an effort to identify a bleeding source accurately.
This approach does not appear to be warranted except in patients with refractory intermittent episodes of hemorrhage in a fully staffed suite.
Because 90% of cases of hemorrhage cease spontaneously, and only 10% rebleed, such evocative testing is inappropriate for most patients.

About 10% of patients develop a complication of angiography.
Major complications include
stroke,
renal failure,
femoral artery thrombosis,
lower extremity immobilization, and
hematoma formation.
Given that most patients with lower gastrointestinal hemorrhage are older than 60 years of age, medical comorbidities, including vascular disease and renal insufficiency, may place these patients at high risk for the procedure.
Hence, angiography is reserved for patients with evidence of significant ongoing hemorrhage.

Technetium 99m-Red Blood Cell Scintigraphy
99m Tc-red blood cell scintigraphy has met with mixed success in the diagnosis of lower gastrointestinal hemorrhage.
In this noninvasive nuclear medicine imaging procedure, the patient’s red blood cells are labeled with a technetium isotope and reintroduced into the circulation.
With each bleeding episode, labeled blood is shed into the colonic lumen, creating an isotopic focus that can be imaged with whole abdominal scintigraphy.
Rates of bleeding as low as 0.1 mL/min can be detected.
Images are obtained at distinct intervals after injection, within the first 2 hours, and thereafter at 4- to 6-hour intervals, or at the time of clinical evidence of rebleeding.
After extravasation into the lumen, the blood moves through the colonic lumen generally from the right colon to the left, but occasionally in retrograde fashion because of colonic contractions.
If bleeding is present at the time of injection and initial imaging, 99m Tc-red blood cell scans can accurately identify a source of bleeding in up to 85% of cases.
If bleeding is not active at the time of the initial study, or if delayed bleeding occurs, subsequent imaging to detect the luminal isotope can be inaccurate because of the sporadic movement of the tracer in the gut lumen.
The study is accurate in only 40% to 60% of patients, little better than a 50:50 ratio, to isolate bleeding to the left or right colon.
Hence, patients in whom a surgical resection is anticipated to control recurrent or persistent hemorrhage should have the bleeding confirmed with either a positive angiogram or a positive colonoscopy.
The red blood cell scans serve primarily to target the subsequent confirmatory study.

Treatment
Endoscopic Treatment
Endoscopic therapy includes the use of the same modalities available for upper gastrointestinal hemorrhage.
Thermal heater probes, electrocoagulation, and sclerotherapy have been used.
Reports suggest that electrocoagulation can be successfully applied for bleeding colonic diverticula, although this approach has not been widely embraced.
Efforts at endoscopic control of diverticular hemorrhage may precipitate more significant bleeding.
In contrast, angiodysplasias are readily treated with endoscopic measures.
Acute bleeding can be controlled in up to 80% of patients with bleeding angiodysplasias, although rebleeding may develop in up to 15%.
Care must be taken to avoid precipitating massive hemorrhage when treating angiodysplasias.
Many endoscopists recommend approaching the lesion from the perimeter, obliterating feeder vessels before cauterization of the central vessel.
Endoscopic therapy is also appropriate for patients with bleeding from a recent snare polypectomy site.
Bleeding develops in 1% to 2% of patients after polypectomy and may occur up to 2 weeks after polypectomy.
An endoscopic approach is recommended for these lesions.

Angiographic Treatment
In patients whose bleeding source is identified by angiography, a trial of angiographic therapy may be appropriate as a perioperative temporizing measure or as a definitive measure for high-risk surgical candidates. Provided selective catheterization of a mesenteric vessel leading directly to the bleeding site can be completed,
intra-arterial vasoconstrictor therapy with vasopressin can temporarily achieve control of bleeding in up to 80% of patients.
Rebleeding is common, however, after discontinuing the therapy.
Complications are frequent and serious and include
myocardial ischemia,
pulmonary edema,
mesenteric thrombosis, and
hyponatremia.
Transarterial vasopressin should not be used in patients with
coronary artery disease or
other vascular disease.
The primary role of this therapy is to achieve temporary control of bleeding before emergency definitive surgical resection.

Transcatheter embolization of massive bleeding may also be used for patients who are poor candidates for surgical resection.
Embolization of gelatin sponges or microcoils can achieve temporary control of bleeding from angiodysplasias and diverticula.
Given the lack of collateral blood supply to the colonic wall, these procedures may be complicated by colonic infarction heralded by abdominal pain, fever, and sepsis. Hence,
like vasoconstrictive therapy, this procedure should be restricted to patients who cannot tolerate surgery or as a temporizing measure in massive hemorrhage in patients for whom a definitive surgical resection is imminent.

Surgery
Surgery is indicated for patients with ongoing or recurrent hemorrhage.
Transfusion of more than 6 units of packed red blood cells,
ongoing transfusion requirement,
or persistent hemodynamic instability is an indication for colectomy in acute hemorrhage.
Patients who develop recurrent lower gastrointestinal hemorrhage are also appropriately treated with colectomy because the risk for subsequent hemorrhage increases with time.
Segmental colectomy is indicated in patients with
persistent or recurrent colonic hemorrhage.
Every effort should be made to localize the source of bleeding so that a hemicolectomy can be performed rather than a blind subtotal abdominal colectomy.
Certainty of the site of bleeding is important; operation based on a positive 99m Tc-red blood cell scan alone can result in recurrent hemorrhage in up to 35% of patients. “Blind” total abdominal colectomy carries significantly higher perioperative morbidity, and associated mortality rates approach 25% in some series.
Diarrhea and rapid transit after total abdominal colectomy can also be debilitating conditions for elderly patients.
There is no indication for a blind segmental colectomy, for which rebleeding rates as high as 75% are seen.

Mortality after colectomy for acute lower gastrointestinal hemorrhage overall is less than 5%.
As in upper gastrointestinal hemorrhage, bleeding is not the cause of death; rather,
pneumonia,
cardiovascular events,
and renal failure lead to poor outcomes, primarily in elderly patients with recurrent hemorrhage.
Thoughtful timely management can lead to a successful outcome in most patients.


ACUTE GASTROINTESTINAL HEMORRHAGE FROM AN OBSCURE SOURCE
Definition and Incidence
The small bowel is a rare source of acute hemorrhage.
Only 2% to 5% of patients with acute gastrointestinal hemorrhage are ultimately determined to have bled from a small intestinal source.
This low frequency is fortunate because the small bowel is a difficult organ to visualize and precise detection of the bleeding lesion is characteristically delayed.

Clinical Presentation
The clinical presentation of patients with acute small bowel hemorrhage is
similar to that of acute lower gastrointestinal hemorrhage from a colonic source.
Small bowel hemorrhage is frequently episodic, characterized by recurrent brisk hemorrhage, which ceases spontaneously only to recur weeks or months later.
Most patients are evaluated on multiple occasions after multiple bouts of hemorrhage before a correct diagnosis is made and effective definitive therapy completed.
Szold and associates reported that the typical patient referred with acute gastrointestinal hemorrhage of obscure origin had intermittent episodes of hemorrhage during a 26-month period, had undergone 1 to 20 diagnostic tests, and had received an average of 20 units of packed red blood cells before diagnosis.

Etiology
The causes of hemorrhage identified in the 71 patients as studied by Szold and associates are shown in.
In adults the most common source of bleeding from the small bowel is angiodysplasia,
responsible for 50% to 75% of cases in older patients,
and 30% to 40% of those in younger patients.
These acquired lesions are most common in the right colon but can be found throughout the gastrointestinal tract.

o The telangiectasias of Osler-Weber- Rendu syndrome are distinct from angiodysplasias.
o Most patients with this hereditary disorder present with skin and oral lesions in youth and acquire gastrointestinal lesions with bleeding in the 4th decade of life, or later.
o These telangiectasias are diffuse, and surgical intervention is not appropriate.

o Small bowel tumors are
o the second most common source of bleeding (25%)
o and include collectively gastrointestinal stromal tumors, lymphomas, adenocarcinomas, carcinoids, and metastatic melanomas.

o Less common possibilities include
o Meckel’s diverticulum (more common in children),
o small bowel diverticula,
o Crohn’s disease,
o radiation enteritis,
o ulcers due to NSAIDs,
o celiac sprue,
o and other rare findings.

Initial Assessment
Initial priorities in management are resuscitation followed by prompt diagnostic testing as described for patients with lower gastrointestinal bleeding.
Emergency upper endoscopy is indicated in hemodynamically unstable patients with hematochezia;
patients with melena should have nasogastric aspiration to check for blood in the gastric contents.
If negative, selective visceral angiography or emergency colonoscopy should be completed based on the clinical assessment of the rate and degree of bleeding.
The role of 99m Tc-red blood cell scintigraphy remains controversial, as in lower gastrointestinal hemorrhage.

In the rare patient with significant, ongoing small bowel bleeding at the time of these initial evaluations, a positive small intestinal source may be identified.
Colonoscopy may reveal hemorrhage coming through the ileocecal valve or pooling in the terminal ileum,
whereas selective mesenteric angiography may reveal the bleeding source from any of many possible small bowel sources.
Obviously, it is critical not only to identify the small bowel as the source of hemorrhage but also to identify the precise site within the small bowel, so that a limited bowel resection can be completed.

In most patients, however, bleeding has ceased before the time these studies are completed, and only aggressive subsequent evaluation allows definitive diagnosis and treatment. Primary surgical exploration without investigation is to be condemned because the surgeon is rarely able to identify the actual source of small intestinal bleeding by visual inspection or palpation. Undirected exploration has a high risk of failure and should not be pursued except in patients with acute exsanguinating hemorrhage.

TABLE -- Sources of Obscure Gastrointestinal Bleeding: Findings in 71 Patients Treated with Surgery
Diagnosis Patients (%)
Arteriovenous malformation 40
Small bowel leiomyoma 11
Small bowel adenocarcinoma 7
Small bowel lymphoma 6
Crohn’s disease 6
“Watermelon” stomach 4
Meckel’s diverticulum 4
Small bowel leiomyosarcoma 3
Metastatic colon carcinoma to small bowel 3
Small bowel varices 3
Small bowel melanoma 3
Others 10
Total 100

Diagnosis
The diagnostic evaluation of a patient with suspected bleeding from a small bowel source can be laborious and frustrating.
Most of these patients have already undergone many of the more common and previously described modalities without success.
The choice of diagnostic test varies depending on the particular presentation of the patient.

Spiral Computed Tomography
o CT scanning with intravenous and oral contrast medium is a noninvasive diagnostic tool that is particularly useful if there is concomitant abdominal pain or symptoms of obstruction.
o CT images can identify areas of bowel thickening, mass lesions, or extraintestinal lesions that may be contributing to the patient’s overall symptoms.
o These structural changes may be diagnostic of tumor, inflammatory conditions, or diverticula.

Enteroclysis
o Enteroclysis is a small bowel contrast imaging study that can correctly identify mass lesions and structural mucosal processes, such as inflammatory or ulcerated lesions, in up to 80% of cases.
o It is unable, however, to identify angiodysplasias, the most common source of bleeding in these patients.
o Though still popular at some institutions,
o enteroclysis is poorly tolerated by patients
o and many centers have abandoned its use.
o When used strictly to evaluate the source of occult small intestinal bleeding, enteroclysis has a reported yield of only 10% to 21%.
o The ordinary small bowel follow-through contrast study is not adequate to evaluate these patients and should not be used, with a reported diagnostic yield of only 0 to 5.6%.

Meckel’s Scans
o Meckel’s diverticula may contain ectopic acid-secreting gastric mucosa that can lead to ulceration of the adjacent small bowel mucosa.
o The parietal cells in the gastric mucosa take up 99m Tc pertechnetate, allowing imaging by a gamma camera.
o Congenital duplications of the intestinal tract may also contain ectopic gastric mucosa and be imaged with this test.
o This procedure should be the initial evaluation in young patients (those <30 years of age), in whom Meckel’s diverticulum is the most common cause of small intestinal bleeding.

Small Bowel Endoscopy
o Small bowel endoscopy, enteroscopy, has historically been completed by two methods.
o However, the recent introduction of video capsule endoscopy has greatly diminished the use of these technically challenging procedures.
o “Push” small bowel endoscopy uses a pediatric colonoscope to visualize the proximal small bowel directly.
o The procedure is of limited value because only the proximal jejunum and duodenum can be visualized, even by skilled endoscopists.
o The Sonde (pull) enteroscopy has been abandoned in the United States.
o In this interesting historical method, a small fiberoptic imaging scope was “pulled” through the small bowel lumen by peristalsis to the ileocecal valve.
o Several hours later, the enteroscope was slowly pulled back through the intestine, and a careful inspection of the mucosa was completed through the 120-degree vision angle lens.
o Although fine mucosal lesions and angiodysplasias could be identified with this technique, localization and therapy could not be accomplished.

Video Capsule Endoscopy
o The Given wireless video capsule endoscope is an 11 × 26-mm capsule containing a miniature video camera, light source, battery, and transmitter.
o It transmits video images to a torso-mounted recorder system at a rate of two images per second, up to 50,000 images overall, after being swallowed by the patient.
o The lens yields an 8-to-1 magnification, and the capsular coating prevents intestinal contents from interfering with the images.
o Relative contraindications include
o obstructive symptoms,
o motility disorders,
o and pacemakers.
o The major complication is
o capsule retention, which can occur at a stricture and has been
o reported in 5% of cases, although
o less than 1% of all mandated surgical retrieval.
o Although it has not been available for long, in preliminary reports it has proven far superior to push endoscopy in diagnosis, and is tolerated much better as well.
o It does not have the capacity for therapeutic interventions as yet, nor can precise localizations within the bowel be achieved.
o It is, however, valuable in identifying diffuse disease that would not be amenable to surgical exploration and for identifying lesions for surgical or medical treatment.
o It is also an appropriate test to identify potential small bowel lesions prior to intraoperative endoscopy.

Intraoperative Endoscopy
A combined surgical and endoscopic procedure to evaluate and treat the small bowel sources of bleeding offers the best strategy for success.
During exploratory laparotomy, small bowel enteroscopy is completed by an endoscopist.
The operating surgeon carefully plicates the small bowel over the enteroscope while the lumen is visualized.
The operating room lights are dimmed to image angiodysplasia better by transillumination.
Identification of a mucosal ulcerated lesion or a single or multiple angiodysplasia allows definitive surgical treatment with small bowel resection.
This combined approach may identify a bleeding source in up to 70% of patients; in patients with prior findings noted on video capsule endoscopy or angiography, the precise site of the abnormality can be identified to allow limited small bowel resection.

Treatment
The most common cause of small bowel bleeding, angiodysplasia, should be treated with endoscopic sclerotherapy or coagulation, if the lesion is within reach of the endoscope.
For those in whom endoscopic measures fail, surgical segmental resection of the small bowel is indicated.
Because angiodysplasias are acquired with age, up to 25% of patients develop new hemorrhage from other angiodysplasias in subsequent years; thus, long-term follow-up is required.
With both these and with telangiectasias some success with conjugated estrogen therapy to decrease the frequency and degree of hemorrhage has been reported.

Neoplasms are the second most common cause of small intestinal hemorrhage.
Most are benign, although malignant tumors may also bleed.
Therapy is surgical resection.

Bleeding Meckel’s diverticulum and small bowel diverticula are also appropriately treated with resection as well.

RARE CAUSES OF GASTROINTESTINAL HEMORRHAGE FROM AN OBSCURE SOURCE
Acute gastrointestinal hemorrhage from an obscure source has been reported to occur from a variety of conditions.
These include
radiation enteritis,
small intestinal varices,
Crohn’s disease,
tuberculosis,
syphilis,
typhoid,
histoplasmosis,
vasculitis,
small bowel ulcerated lesions in patients with gastrin-secreting tumors, and
Dieulafoy’s lesions.

Medical treatment is appropriate for most infectious causes and in patients with Zollinger-Ellison syndrome.
Enterectomy is required in the other conditions.

Disorders of the pancreas can cause acute gastrointestinal hemorrhage as blood is delivered into the duodenum through the pancreatic duct.
Such bleeding has been reported in the setting of acute pseudoaneurysms after pancreatectomy and in pancreatic tumors.
Bleeding is a rare complication of these disorders.
Angiography may confirm the presence of a pseudoaneurysm and allow angiographic embolization for acute hemorrhage control.
Pancreatic resection may be appropriate, depending on the clinical condition.

The liver may also be the source of presumed acute gastrointestinal hemorrhage.
Bleeding into the hepatic duct presents as gastrointestinal hemorrhage as blood enters the duodenum from the common bile duct, a condition known as hemobilia.
Hemobilia has been reported to occur secondary to
hepatic trauma with intrahepatic hematoma,
hepatic aneurysms
or other vascular malformations,
hepatic tumors,
hepatic abscess,
or after hepatic resection
or percutaneous liver biopsy.
This diagnosis is usually considered when endoscopic visualization during acute hemorrhage shows blood entering the duodenum at the ampulla of Vater, depending on the clinical scenario.
Selective visceral angiography is usually required to define the source and often allows definitive management by intra-arterial embolization.