In patients who have had multiple upper GI endoscopies, colonoscopies, barium studies, and RBC scans without identification of the source of blood loss, enteroscopy needs to be performed. Enteroscopy can be performed either with push enteroscopy or wireless capsule endoscopy. The source of bleeding is most likely from AVMs (or angiodysplasias), usually hiding in the small intestine. Of particular note is that before a patient undergoes enteroscopy the hemoglobin should be 10 or higher to aid in detecting these tiny vessels.

Reference:  Sleisenger MH, Fordtran JS (eds): Gastrointestinal Disease: Pathophysiology, Diagnosis, and Management, 7th ed. Philadelphia, W.B. Saunders, 2003.

Portal pressure and variceal size. The portal to hepatic vein pressure gradient must be > 12 mmHg (normal = 3-6 mmHg) for varices to develop. Beyond this level, there is poor correlation between portal pressure and likelihood of bleeding. The best predictor of impending variceal hemorrhage is size. When varices reach a large size (> 5 mm in diameter), they are more likely to rupture and bleed. At any given pressure, the wall of a large varix is under greater tension than that of a small varix and must be thicker to withstand the pressure.

Reference: Sleisenger MH, Fordtran JS (eds): Gastrointestinal Disease: Pathophysiology, Diagnosis, and Management, 7th ed. Philadelphia, W.B. Saunders, 2003.

Elevation of pressure in the hepatic portal system leads to the development of varices. The normal portal venous pressure is ∼ 10 mmHg but increases to > 20 mmHg in portal hypertension. The causes of portal hypertension are classified as presinusoidal, sinusoidal, and postsinusoidal. The most common cause in the Western world is alcohol-related cirrhosis.

Reference:  Sleisenger MH, Fordtran JS (eds): Gastrointestinal Disease: Pathophysiology, Diagnosis, and Management, 7th ed. Philadelphia, W.B. Saunders, 2003.

Usually. The color of stool depends on colonic transit time. If the stool remains in contact with bacteria that degrade hemoglobin, the resulting stool is melanic. Although right-sided lesions are usually associated with melena (dark, tarry stools) and left-sided lesions with hematochezia (the passage of bright red blood per rectum), the opposite can also be seen. Therefore, the evaluation of a patient with hematochezia must include examination of the proximal colon.

Reference: Sleisenger MH, Fordtran JS (eds): Gastrointestinal Disease: Pathophysiology, Diagnosis, and Management, 7th ed. Philadelphia, W.B. Saunders, 2003.

• Less common causes include

1. Meckel’s diverticulum
2. Ischemic or inflammatory bowel disease
3. Solitary ulcers of the cecum and rectum

Reference: Sleisenger MH, Fordtran JS (eds): Gastrointestinal Disease: Pathophysiology, Diagnosis, and Management, 7th ed. Philadelphia, W.B. Saunders, 2003.

• Hemorrhoids are the most common cause but rarely present with massive bleeding requiring hospitalization.
• Diverticulosis accounts for a significant percentage of cases. Diverticular bleeding may occur from either the right or left colon.
• Angiodysplasia or vascular ectasias are among of the more common well-recognized causes in older patients. They are commonly found in the cecum and ascending colon.
• Neoplasms of the large bowel usually present with chronic occult bleeding but occasionally bleed acutely.

Reference: Sleisenger MH, Fordtran JS (eds): Gastrointestinal Disease: Pathophysiology, Diagnosis, and Management, 7th ed. Philadelphia, W.B. Saunders, 2003.

• Elderly patients (age > 60yr)
• Patients with fresh blood per NG tube or rectum
• Patients who remain hemodynamically unstable despite aggressive resuscitative measures
• Patients who have four or more comorbid illnesses (e.g., cardiac disease, liver disease, diabetes) NSAID use

Reference: Sleisenger MH, Fordtran JS (eds): Gastrointestinal Disease: Pathophysiology, Diagnosis, and Management, 7th ed. Philadelphia, W.B. Saunders, 2003.