Hematemesis usually represents bleeding proximal to the ligament of Treitz, although the site of blood loss may, on rare occasions, be in the jejunum. The absence of hematemesis does not, however, exclude the possibility of active upper gastrointestinal bleeding. Melena is typically seen with blood loss proximal to the ileocecal valve, where hemoglobin is converted into hematin, which gives the stool its tarry appearance. Right-sided colonic bleeding may also cause melena when transit is slow.

Representative prevalence figures from studies of outpatients and those seen in emergency departments presenting with melena or hematemesis find that about 35% have ulcer disease, 10% Mallory-Weiss tears, 10% esophageal varices, 5% gastritis, and 1% gastric cancer. In 20%, no cause is found, usually because endoscopy is not performed; in 5%, multiple lesions are detected.

Patients with chronic renal failure are at increased risk for bleeding, with vascular malformations and esophagitis being the most common causes.

Hematochezia most often originates in the left side of the colon or anorectal region, although very brisk movement of blood from the right side of the colon, small bowel, or even stomach can lead to a similar presentation. Occult gastrointestinal bleeding may be indicated by a positive result on a test for fecal occult blood or may be suggested by the presence of iron deficiency anemia without apparent cause. The source of occult bleeding may be anywhere in the gastrointestinal tract. In a study of anemic competitive runners, an increase in fecal hemoglobin was detected.

In the setting of severe hematochezia, age has a major influence on the differential diagnosis. In young adults, Meckel diverticulum, inflammatory bowel disease, and polyps lead the list of causes. In adults to age 60 years, diverticulosis, inflammatory bowel disease, and polyps are the predominant etiologies, followed by malignancy and vascular malformations. In persons older than the age of 60 years, vascular malformations, diverticulosis, malignancy, and polyps are responsible for most cases.

Most patients who present with mild to moderate anorectal bleeding have lesions of the anal canal, about 15% have colorectal disease, and about 5% have perianal skin problems. Leading causes include hemorrhoids (about 50%), fissure-in-ano (20%), neoplasm (5%), and inflammatory bowel disease (5%). In close to 10% of cases, no cause is found at the time of the examination. The majority of neoplasms are more than 10 cm above the anus, beyond the reach of digital examination.

In patients with undiagnosed rectal bleeding subjected to colonoscopy, almost half have significant lesions; polyps, inflammatory bowel disease, cancer, diverticular disease, and vascular malformations are the leading findings.

Clinical manifestations are a function of the rate and duration of bleeding. Postural hypotension (an orthostatic fall in blood pressure of <10 mm Hg or an increase in heart rate of >10 beats/min on moving from a supine position to standing) in the setting of known bleeding suggests intravascular volume depletion and serious acute hemorrhage. Fatigue and exertional dyspnea are typical presenting symptoms of anemia resulting from slow, chronic blood loss. Patient descriptions of the volume of bleeding are frequently unreliable. Early predictors of severity of acute lower intestinal tract bleeding include heart rate greater than 100 beats/min, systolic blood pressure less than 115 mm Hg, syncope, nontender abdominal examination, early recurrent rectal bleeding, aspirin use, and two active comorbid conditions.

Patients with gastrointestinal bleeding while taking anticoagulant medication in the therapeutic range are likely to have an underlying lesion and warrant thorough evaluation. In a study examining 3,800 courses of anticoagulant therapy, gastrointestinal bleeding occurred in 45 patients. In 32 patients, a source was determined; 13 had hemorrhoids, 9 had peptic ulcers, 7 had neoplasms, and 3 had other lesions. Risk of severe upper gastrointestinal hemorrhage is significantly increased by concurrent nonsteroidal antiinflammatory drug (NSAID) use, especially in the elderly.

Whenever active bleeding is suspected in a person presenting to the physician’s office, the first priority is to determine the severity and rate of blood loss. The patient should be asked about any postural light-headedness. The precise volume lost is not reliably determined by the history, but reports of very large amounts should be taken seriously. When the patient complains of voluminous blood loss or light-headedness, an immediate check of vital signs for postural hypotension is indicated. Immediate hospital admission should be considered if the systolic blood pressure falls more than 10 to 15 mm Hg or the heart rate increases by more than 10 to 15 beats/min when the patient stands up from a supine position. In acute lower intestinal tract bleeding, a heart rate of greater than 100 beats/min, a systolic blood pressure of less than 115 mm Hg, syncope, nontender abdominal examination, early recurrent rectal bleeding, concurrent aspirin use, or two active comorbid conditions suggest increased risk of severe bleeding.

Risk stratification helps to determine the need for admission and early endoscopic evaluation and treatment. Clinical predictors of poor prognosis include age older than 65 years, comorbid illness or poor overall health status, fresh blood on rectal examination or in the emesis, hypotension, and continued bleeding. A low hemoglobin level is also predictive of increased risk, but decline in hemoglobin or hematocrit in the acute phase of blood loss may be deceptively small if sufficient time for reequilibration of intravascular volume has not elapsed. The Blatchford clinical prediction score (see Table 63-2), a validated risk stratification tool, incorporates many of these elements to help identify persons who require urgent admission and intervention.