1. health and fitness
2. disease

Acute Lower Gastrointestinal Hemorrhage
When compared with upper GI hemorrhage, lower GI bleeding is a much less frequent reason for hospitalization—it is
about 20% as common as bleeding from a location proximal to the ligament of Treitz. The incidence of lower GI bleeding,
however, increases with age, and lower GI bleeding may be more common in older patients. In more than 95% of patients
with lower GI bleeding, the source of hemorrhage is the colon. The small intestine is only occasionally responsible and,
because these lesions are not typically diagnosed with the combination of upper and lower endoscopy, they will be
considered later (see “Acute Gastrointestinal Hemorrhage from an Obscure Source”). In general, the incidence of lower GI
bleeding increases with age and the cause is often age-related (Table 48-3). Specifically, vascular lesions and diverticular
disease affect all age groups but have an increasing incidence in middle-aged and older adults. In the pediatric
population, intussusception is most commonly responsible, whereas Meckel's diverticulum must be considered in the
differential diagnosis in the young adult. The clinical presentation of lower GI bleeding ranges from severe hemorrhage
[3]
with diverticular disease or vascular lesions to a minor inconvenience secondary to anal fissure or hemorrhoids.
Table 48-3 -- Differential Diagnosis of Lower Gastrointestinal Hemorrhage
COLONIC BLEEDING*
SMALL BOWEL BLEEDING[†]
30%-40% Diverticular disease
Angiodysplasias
5%-10% Ischemia
Erosions, ulcers (e.g., from potassium, NSAIDs)
5%-15% Anorectal disease
Crohn's disease
5%-10% Neoplasia
Radiation
3%-8% Infectious colitis
Meckel's diverticulum
3%-7% Postpolypectomy
Neoplasia
3%-4% Inflammatory bowel disease Aortoenteric fistula
3% Angiodysplasia
1%-3% Radiation colitis, proctitis
1%-5% Other
10%-25% Unknown
Adapted from Strate LL: Lower gastrointestinal bleeding: Epidemiology and diagnosis. Gastroenterol Clin North Am
34:643–664, 2005
* 95% of cases.
5% of cases.
Diagnosis
Lower GI bleeding typically presents with hematochezia, which can range from bright red blood to old clots. If the bleeding
is slower or from a more proximal source, lower GI bleeding often presents as melena. Hemorrhage from the lower GI
tract tends to be less severe and more intermittent, and usually ceases more spontaneously than upper GI bleeding.
When compared with upper GI bleeding, no diagnostic modality is as sensitive or specific as endoscopy for making an
accurate diagnosis in lower GI bleeding. Diagnostic evaluation is further complicated by the observation that in up to 40%
of patients with lower GI bleeding, more than one potential source for bleeding is identified. If more than one source is
identified, it is critical to confirm the responsible lesion before initiating aggressive therapy. This approach may
occasionally require a period of observation with several episodes of bleeding before a definitive diagnosis can be made.
In up to 25% of patients with lower GI hemorrhage, the bleeding source is never accurately identified.
An algorithm for the evaluation of lower GI hemorrhage is shown in Figure 48-12. Once resuscitation has been initiated,
the first step in the workup is to rule out anorectal bleeding with a digital rectal examination, anoscopy, and/or
sigmoidoscopy. With significant bleeding, it is also important to eliminate an upper GI source. An NG aspirate that
contains bile and no blood effectively rules out upper tract bleeding in most patients. However, when emergent surgery for
life-threatening hemorrhage is being contemplated, preoperative or intraoperative EGD is usually appropriate. This is
particularly relevant if blind subtotal colectomy for massive hemorrhage is being considered.
FIGURE 48-12
Algorithm for diagnosis and management of lower GI hemorrhage. NGT, Nasogastric tube.
Subsequent evaluation depends on the magnitude of the hemorrhage. With major and/or persistent bleeding, the workup
should progress depending on the patient's hemodynamic stability. The truly unstable patient who continues to bleed and
requires ongoing aggressive resuscitation belongs in the operating room for expeditious diagnosis and surgical
intervention. When hemorrhage is intermediate, resuscitation and hemodynamic stability permit a more directed
evaluation and therapeutic intervention. Colonoscopy is the mainstay here because it allows visualization of the pathology
and therapeutic intervention in colonic, rectal, and distal ileal sources of bleeding. The usual adjuncts to colonoscopy
include a tagged RBC scan and angiography. If these modalities are not diagnostic, the source of the hemorrhage is
considered obscure; such lesions and their evaluation are considered in the last section of this chapter.
Colonoscopy
Colonoscopy is most appropriate in the setting of minimal to moderate bleeding; major hemorrhage interferes significantly
with visualization and the diagnostic yield is low. In addition, in the unstable patient, sedation and manipulation may be
associated with additional complications and can interfere with resuscitation. Although the blood is cathartic, gentle
preparation with polyethylene glycol, orally or through an NG tube, can improve visualization. Findings may include an
actively bleeding site, clot adherent to a focus of mucosa or diverticular orifice, or blood localized to a specific colonic
segment, although this can be misleading because of retrograde peristalsis in the colon. Polyps, cancers, and
inflammatory causes can frequently be seen. Unfortunately, angiodysplasias are often difficult to visualize, particularly in
the unstable patient with mesenteric vascular constriction. Diverticula are identified in most patients, whether or not they
are the source of the hemorrhage. Despite these limitations, the diagnostic yield in experienced hands is reasonable. For
example, some studies have reported that colonoscopy is successful in identifying the bleeding source in up to 95% of
[43]
patients. Most of the bleeding is secondary to angiodysplasias or diverticuli.
Radionuclide Scanning
99m
Radionuclide scanning with technetium-99m ( Tc–labeled RBC) is the most sensitive but least accurate method for
localizing GI bleeding. With this technique, the patient's own red cells are labeled and reinjected. The labeled blood is
extravasated into the GI tract lumen, creating a focus that can be detected scintigraphically. Initially, images are obtained
frequently and then at 4-hour intervals, for up to 24 hours. The RBC scan can detect bleeding as slow as 0.1 mL/min and
[3]
is reported to be more than 90% sensitive (Fig. 48-13). Unfortunately, the spatial resolution is low and blood may move
retrograde in the colon or distally in the small bowel. Reported accuracy of localization is in the range of only 40% to 60%
and it is particularly inaccurate for distinguishing right-sided from left-sided colonic bleeding. The RBC scan is not usually
used as a definitive study before surgery but instead as a guide to the usefulness of angiography; if the RBC scan is
negative or only positive after several hours, angiography is unlikely to be revealing. Such an approach avoids the
significant morbidity of angiography.
FIGURE 48-13
Positive red blood cell scan localizing the bleeding to the left lower quadrant.
(Courtesy Dr. Richard A. Baum, MD, Brigham and Women's Hospital, Boston.)
Mesenteric Angiography
Selective angiography, using the superior or inferior mesenteric arteries, can detect hemorrhage in the range of 0.5 to
1.0 mL/min but is generally only used for the diagnosis of ongoing hemorrhage. It can be particularly useful in identifying
the vascular patterns of angiodysplasias. It may also be used for localizing actively bleeding diverticula. In addition, it has
therapeutic capabilities. Catheter-directed vasopressin infusion can provide temporary control of bleeding, permitting
hemodynamic stabilization, although as many as 50% of patients will rebleed when the medication is discontinued. It can
also be used for embolization. Although the more limited collateral circulation of the colon has made this less appealing
than in the upper GI tract, it has been have suggested that these techniques can be used safely in most patients.
Typically, such therapy is reserved for patients whose underlying condition precludes surgical therapy. Unfortunately,
angiography is associated with a significant risk of complications, including hematoma, arterial thrombosis, contrast
reaction, and acute renal failure.
Treatment
Therapeutic approaches with lower GI bleeding are clearly dependent on the lesion identified. The criteria for surgery,
shown in Box 48-2, are similar to those for upper GI hemorrhage, although there is a stronger tendency to delay until the
site is clearly localized.
Specific Causes of Lower GI Bleeding
Colonic Bleeding
Diverticular Disease
In the United States, diverticula are the most common cause of significant lower GI bleeding. Some series have
[3]
suggested that diverticula are responsible for up to 55% of cases. In the past, diverticula were thought to be rare in
patients younger than 40 years but is now an increasingly common diagnosis in this age group. Diverticulosis affects more
than two thirds of the Western population who are in their 80s. Only 3% to 15% of individuals with diverticulosis
experience any bleeding. Bleeding generally occurs at the neck of the diverticulum and is believed to be secondary to
bleeding from the vasa recti as they penetrate through the submucosa. Of those that bleed, more than 75% stop
[3]
spontaneously, although approximately 10% will rebleed within a year and almost 50% within 10 years. Although
diverticular disease is much more common on the left side, right-sided disease is responsible for more than 50% of the
bleeding.
The best method of diagnosis and treatment is colonoscopy, although success is sometimes limited by the large amount
of bleeding. If the bleeding diverticulum can be identified, epinephrine injection may control the bleeding. Electrocautery
can also be used and, most recently, endoscopic clips have been successfully applied to control the hemorrhage. If
bleeding ceases with these maneuvers or ceases spontaneously, expectant management may be appropriate; however,
this requires clinical judgment based on the amount of the hemorrhage and any comorbidities, particularly cardiac
disease.
If none of these maneuvers is successful or if hemorrhage recurs, angiography with embolization can be considered.
Superselective embolization of the bleeding colonic vessel has gained popularity, with high success rates (>90%),
[44]
although the risk of ischemic complications continues to be of concern. Under these circumstances, colonic resection is
indicated. Certainty of the site of bleeding is critical. Blind hemicolectomy is associated with rebleeding in more than 50%
of patients, and operation based on RBC scan localization alone can result in recurrent hemorrhage in up to one third of
[45]
patients. Subtotal colectomy does not eliminate the risk of recurrent hemorrhage and, when compared with segmental
resection, is accompanied by a significant increase in morbidity, particularly diarrhea in older patients, in whom the
[45]
remaining rectum may never adapt. Mortality of emergent subtotal colectomy for bleeding is almost 30%.
Angiodysplasia
In some reports, hemorrhage secondary to these vascular lesions accounts for up to 40% of lower GI bleeding; however,
[3]
most recent reports have noted the incidence to be much lower. Angiodysplasias of the intestine, also referred to
as arteriovenous malformations (AVMs), are distinct from hemangiomas and true congenital AVMS. They are thought to
be acquired degenerative lesions secondary to progressive dilation of normal blood vessels within the submucosa of the
intestine. Angiodysplasias have an equal gender distribution and are almost uniformly found in patients older than 50
years. These lesions are notably associated with aortic stenosis and renal failure, especially in older patients. The
hemorrhage tends to arise from the right side of the colon, with the cecum being the most common location, although they
can occur in the rest of the colon and small bowel. Most patients present with chronic bleeding but, in up to 15%,
hemorrhage may be massive. Bleeding stops spontaneously in most cases, but approximately 50% will rebleed within 5
years.
These lesions can be diagnosed by colonoscopy or angiography. During colonoscopy, they appear as red stellate lesions
with a surrounding rim of pale mucosa and can be treated with sclerotherapy or electrocautery. Angiography
demonstrates dilated, slowly emptying veins and, sometimes, early venous filling. If these lesions are discovered
incidentally, no further therapy is indicated. In acutely bleeding patients, they have been successfully treated with intraarterial vasopressin, selective gel foam embolization, endoscopic electrocoagulation, or injection with sclerosing agents. If
these measures fail, or bleeding recurs and the lesion has been localized, segmental resection, most commonly a right
colectomy, is effective.
Neoplasia
Colorectal carcinoma is an uncommon cause of significant lower GI hemorrhage but is probably the most important one to
rule out because more than 150,000 Americans are diagnosed annually with this type of cancer. The bleeding is usually
painless, intermittent, and slow in nature and is frequently associated with iron deficiency anemia. Polyps can also bleed
but the bleeding usually occurs after a polypectomy. Bleeding in the pediatric population is discussed in Chapter 67;
juvenile polyps are the second most common cause of bleeding in patients younger than 20 years. Occasionally other
colonic neoplasms, most notably GISTs, can be associated with massive hemorrhage. The best diagnostic tool is
colonoscopy. If the bleeding is attributable to a polyp, it can be treated with endoscopic therapy.
Anorectal Disease
The major causes of anorectal outlet bleeding are internal hemorrhoids, anal fissures, and colorectal neoplasia. Although
hemorrhoids are the most common of these entities, they only account for 5% to 10% of all acute lower GI bleeding. In
general, anorectal hemorrhage is low-volume bleeding that presents as bright red blood per rectum, which is seen in the
toilet and on the toilet paper. Most hemorrhoidal bleeding arises from internal hemorrhoids; these are painless and often
accompanied by prolapsing tissue that reduces spontaneously or has to be reduced manually by the patient (Fig. 48-14).
Anal fissure, on the other hand, produces painful bleeding after a bowel movement; bleeding is only occasionally the main
symptom in these patients (Fig. 48-15).
FIGURE 48-14
Bleeding and prolapsed hemorrhoids.
FIGURE 48-15
Anal fissure that can be a source of lower GI bleeding.
Because anorectal disease is common, a careful investigation to rule out all other sources of bleeding, especially
malignancy, is imperative before lower GI bleeding can be attributed to such pathology. Anal fissure can be treated
medically with stool-bulking agents (e.g., psyllium [Metamucil]), increased water intake, stool softeners, and topical
nitroglycerin ointment or diltiazem to relieve sphincter spasm and promote healing. Internal hemorrhoids should be treated
with bulking agents, increased dietary fiber, and adequate hydration. Office-based interventions, including rubber band
ligation, injectable sclerosing agents, and infrared coagulation, have also been used. If these measures fail, surgical
hemorrhoidectomy may be needed. Most anorectal bleeding is self-limited and responds to dietary and local measures.
Colitis
Inflammation of the colon is caused by a number of disease processes, including inflammatory bowel disease (e.g.,
Crohn's disease, ulcerative colitis, indeterminate colitis), infectious colitis (0157:H7 Escherichia coli,cytomegalovirus
[CMV], Salmonella, Shigella, and Campylobacter spp., and Clostridium difficile), radiation proctitis after treatment for
pelvic malignancies, and ischemia.
Ulcerative colitis (UC) is more likely than Crohn's disease to present with GI bleeding. UC is a mucosal disease that starts
distally in the rectum and progresses proximally to occasionally involve the entire colon. Patients can present with up to
20 bloody bowel movements daily. These are accompanied by crampy abdominal pain, tenesmus and, occasionally,
abdominal pain. The diagnosis is secured by a careful history and flexible endoscopy with biopsy. Medical therapy with
steroids, 5-aminosalicylic acid (ASA) compounds, immunomodulatory agents, and supportive care are the mainstays of
treatment. Surgical therapy is rarely indicated in the acute setting unless the patient develops a toxic megacolon or
hemorrhage refractory to medical management.
In contrast, Crohn's disease typically is associated with guaiac-positive diarrhea and mucus-filled bowel movements, but
not with bright red blood. Crohn's disease can affect the entire GI tract. It is characterized by skip lesions, transmural
thickening of the bowel wall, and granuloma formation. The diagnosis is made with endoscopy and contrast studies.
Medical management consists of steroids, antibiotics, immunomodulators and ASA compounds. Because Crohn's disease
is a relapsing and remitting disease, surgical therapy is used as a last resort. Massive colonic hemorrhage complicates
[46]
ulcerative colitis in up to 15% of affected patients, whereas it only occurs in 1% of those with Crohn's colitis.
Infectious colitis can cause bloody diarrhea. The diagnosis is usually established from the history and stool culture. C.
difficile and CMV colitis deserve special attention. C. difficile colitis usually present with explosive, foul-smelling diarrhea in
a patient with prior antibiotic use and/or hospitalization. Bloody bowel movements are not common but can be present,
especially in severe cases in which there is associated mucosal sloughing. In North America, there has been an upsurge
in the frequency and severity of C. difficile-associated colitis in the last 15 years. Treatment consists of stopping
antibiotics, supportive care, and oral or IV metronidazole or oral vancomycin. CMV colitis should be suspected in any
immunocompromised patient who presents with bloody diarrhea. Endoscopy with biopsy confirms the diagnosis;
treatment is IV ganciclovir.
Radiation proctitis has become more common in the last 30 or 40 years as the use of radiation to treat rectal cancer,
prostate cancer, and gynecologic malignancies has increased. Patients present with bright red blood per rectum, diarrhea,
tenesmus, and crampy pelvic pain. Flexible endoscopy reveals the characteristic bleeding telangiectasias (Fig. 48-16).
Treatment consists of antidiarrheals, hydrocortisone enemas, and endoscopic APC. In cases of persistent bleeding,
ablation with 4% formalin solution usually works well.
A, Rectal bleeding secondary to radiation damage. B, Effective control after application of argon
plasma coagulation treatment. (Courtesy Dr. David L. Carr-Locke, Brigham and Women's Hospital, Boston.)
FIGURE 48-16
Mesenteric Ischemia
Mesenteric ischemia can be secondary to acute or chronic arterial or venous insufficiency. Predisposing factors include
preexisting cardiovascular disease (e.g., atrial fibrillation, congestive heart failure, acute myocardial infarction), recent
abdominal vascular surgery, hypercoagulable states, medications (e.g., vasopressors, digoxin), and vasculitis. Acute
colonic ischemia is the most common form of mesenteric ischemia. It tends to occur in the watershed areas of the splenic
flexure and rectosigmoid colon, but can be right-sided in up to 40% of patients. Patients present with abdominal pain and
bloody diarrhea. CT will often show a thickened bowel wall. The diagnosis is generally confirmed with flexible endoscopy,
which reveals edema, hemorrhage, and a demarcation between the normal and abnormal mucosa. Treatment focuses on
supportive care consisting of bowel rest, IV antibiotics, cardiovascular support, and correction of the low-flow state. In
85% of cases, the ischemia is self-limited and resolves without incident, although some patients develop a colonic
stricture. In the other 15% of cases, surgery is indicated because of progressive ischemia and gangrene. Marked
leukocytosis, fever, a fluid requirement, tachycardia, acidosis, and peritonitis indicate a failure of the ischemia to resolve
and the need for surgical intervention. During the surgery, resection of the ischemic intestine and creation of an end
[47]
ostomy is indicated.
Copyright © 2014 Elsevier Inc. All rights reserved.