Lower gastrointestinal bleeding overview

# Overview
Lower gastrointestinal bleeding is defined as blood loss originating distal to the ligament of Treitz. It accounts for 24% to 33% of all hospital admissions for gastrointestinal bleeding and is responsible for 1% of hospital admissions in the United States. It can present with frank blood loss per rectum or may be occult in nature, presenting with anemia. Bleeding can vary in severity from passage of small amounts of blood to massive life-threatening hemorrhage. Acute LGIB is described as bleeding of recent onset, which may result in hemodynamic instability and need for blood transfusion. Most commonly originates in the colon or ano-rectum; only 5% arise in the small bowel. Etiologies vary among adult, elderly, and pediatric populations. Ninety percent of lower gastrointestinal bleeding stop spontaneously; however, the underlying etiology needs to be diagnosed and treated accordingly. Overall mortality is less than 4%, but may be higher in elderly populations and in those with comorbid disease. Even bleeding of moderate rate can have significant sequel in a group of patients with the comorbid disease. A thorough history and detailed examination are essential steps in establishing the cause and the source of bleeding. Patients with severe bleeding or hemodynamic disturbance require hospitalization and urgent investigation. It is essential to distinguish between lower gastrointestinal bleeding and brisk upper gastrointestinal bleeding as they can present with similar symptoms. Treatment depends on the cause and the severity of the bleeding.

# Historical Perspective
Roman encyclopedist, Aulus Cornelius Celsus, was the first to describe band ligation treatment for hemorrhoidal bleeding. In the 1700s, Alexis Littre described the association between diverticular diseases and bleeding. In 1885, Allchin gave a detailed description of ulcerative colitis which can present with bleeding. Until 1967, mesenteric ischemia was a diagnostic dilemma. In 1887, Welch proposed that ischemic bowel changes occur secondary to 80% stenosis of superior mesenteric artery (SMA) resulting in bleeding as a complication.

# Classification
Lower gastrointestinal bleeding may be classified based on the severity of bleeding into occult, moderate and severe bleeding.

# Pathophysiology
Superior mesenteric artery and inferior mesenteric artery are the two major blood vessels that supply lower gastrointestinal tract. Disruption of this blood vessel junction by any of the disease process results in bleeding. Diverticulosis is the most common etiology of lower GI bleeding accounting for 30% of all cases, followed by ano-rectal disease, ischemia of bowel, inflammatory bowel disease (IBD), neoplasia, and arteriovenous (AV) malformations. The characteristic gross and microscopic findings of lower gastrointestinal tracts depends upon the underlying pathology.

# Causes
Common causes of lower gastrointestinal tract bleeding include diverticulosis, angiodysplasia, ischemic colitis, colorectal cancer, anorectal diseases, infectious colitis and inflammatory bowel disease. Less common causes of lower gastrointestinal tract include colonic polyps, radiation proctitis, and rectal varices.

# Differentiating lower gastrointestinal bleeding from Other Diseases
Several diseases present with lower gastrointestinal bleeding and must be differentiated from each other. The common diseases responsible for lower GI bleeding include diverticulosis, angiodysplasia, hemorrhoids, anal fissures, mesenteric Ischemia, ischemic colitis, inflammatory bowel disease, and colo-rectal carcinoma.

# Epidemiology and Demographics
The prevalence of lower gastrointestinal bleeding is approximately 20 per 100,000 population in the United States. Lower gastrointestinal bleed is more common in men than women.

# Risk Factors
Common risk factors in the development of lower GI bleeding include advancing age, previous history of gastrointestinal bleed, chronic constipation, hematologic disorders, anticoagulants medications, non-steroidal anti-inflammatory drugs, and human immunodeficiency virus infection.

# Screening
There is insufficient evidence to recommend routine screening for lower gastrointestinal bleeding.

# Natural History, Complications, and Prognosis
If left untreated 90% of the time lower gastrointestinal bleeding is usually self-limited. However, massive blood loss can result in a severe drop in blood pressure resulting in decreased blood supply to organ systems leading to death. Hypovolemic shock and symptomatic anemia are the most common direct complications of LGIB. Prognosis is generally good, and the 1-year mortality rate of patients with lower gastrointestinal bleeding is less than four percent.

# Diagnosis

## Diagnostic Study of Choice
Colonoscopy is the gold standard test for the diagnosis of lower gastrointestinal bleeding. However, Endoscopy is the investigation of choice in cases of lower gastrointestinal bleeding caused by ischemic colitis or colonoscopy is unequivocal.

## History and Symptoms
The hallmark symptom of LGIB is bleeding per rectum or frank blood in stools. The presentation of associated symptoms depends upon the source of the bleeding and underlying etiology. Associated symptoms of lower gastrointestinal bleeding include fever, abdominal pain, bloody diarrhea, dehydration, history of constipation, and hypotension in severe cases, and weight loss. A detailed description of the nature of the blood loss can also help in pinpointing the likely source of bleeding.

## Physical Examination
The most common physical examination finding is the passage of frank blood per rectum (hematochezia).

## Laboratory Findings
The essential blood work in diagnosing lower gastrointestinal bleeding includes a complete blood count, renal function and liver function tests, and coagulation studies. Although not diagnostic, a blood type and crossmatch should be done in patients who present with life-threatening bleeding.

## Electrocardiogram
There are no specific ECG findings associated with lower gastrointestinal bleeding. However, an electrocardiogram is be performed in order to exclude arrhythmia and cardiac causes of hypotension (following acute MI).

## X-ray
There are no abdominal x-ray findings associated with lower gastrointestinal bleeding. However, an x-ray may be helpful in the diagnosing the complications of underlying disease.

## Ultrasound
There are no specific ultrasound findings associated with lower gastrointestinal bleeding. However, ultrasound can be useful in diagnosing various etiology or conditions responsible for lower gastrointestinal bleeding.

## CT scan
Helical CT scanning of the abdomen and pelvis is recommended when a routine workup fails to determine the cause of active gastrointestinal bleeding. Findings of helical CT scan in lower gastrointestinal bleeding include vascular extravasation of the contrast medium, contrast enhancement of the bowel wall, thickening of the bowel wall, hyperdensity of the peri-bowel fat, and vascular dilatations.

## MRI
There are no MRI findings associated with lower gastrointestinal bleeding.

## Other Imaging Findings
Other imaging studies include angiography and radionuclide imaging that can be helpful in diagnosing lower gastrointestinal bleeding.

## Other Diagnostic Studies
Nasogastric tube lavage may be helpful in the diagnosis of lower gastrointestinal bleeding. Nasogastrictube lavage helps in differentiating lower gastrointestinal bleeding from upper gastrointestinal bleeding. Evidence of old (brown colored or 'coffee grounds') or fresh blood on NGT aspirate documents presence of upper gastrointestinal bleeding. Evidence of bilious material rules out bleeding distal to the pylorus.

# Treatment

## Medical Therapy
The aims of treatment are to resuscitate the patient, identify the source of blood loss and stop any ongoing bleeding, and reduce the risk of a recurrent bleed. It is essential to identify patients who are high risk. This would include elderly patients; those with severe ongoing bleeding or recurrent bleeding; and patients with multiple comorbid conditions, in particular, those patients with cardiac, renal, respiratory, and liver disease. Treatment depends on the mode of presentation, the severity of the bleed, and the underlying pathology. Bleeding points can be treated with endoscopy, interventional radiology, or surgery. After identification of the source of bleeding using endoscopy, therapeutic options include monopolar or bipolar diathermy, argon plasma coagulation (APC), epinephrine injections, and endoloops and hemoclips, used individually or in combination. These methods can be used to treat many of the causes of LGIB, including diverticular bleeding, angiodysplasia, radiation proctitis, and post-polypectomy bleeding interventional radiology can be used to visualize a bleeding vessel and to stop the bleeding through embolization of the vessel. Surgery may be required if less invasive measures cannot be applied or are not effective. Pharmacotherapy is only used as an adjuvant therapy for all patients with LGIB. Epinephrine is used alone or in conjunction with other surgical techniques to treat a variety of causes of LGIB.

## Surgery
Emergency surgery may be needed to control bleeding in about 10% to 25% of patients in whom nonoperative management is unsuccessful or unavailable. The various endoscopic interventions employed in the management of lower gastrointestinal bleeding include argon plasma coagulation, bipolar or Heater probe, endoloops and hemoclips, and interventional radiology.

## Primary Prevention
Effective measures for the primary prevention of lower GI bleeding include techniques to prevent the related conditions. Promoting a healthy lifestyle by eating a healthy diet, exercising lightly, and avoiding alcohol and tobacco can reduce the risk associated conditions.

## Secondary Prevention
Secondary primary preventive measures of lower gastrointestinal bleeding is similar to primary prevention.