Barbara Lee Bass Carlos Alvarez

Acute major hemorrhage from the small intestine is rare, accounting for only 2 to 4% of cases of acute gastrointestinal hemorrhage. Similarly, "occult" gastrointestinal hemorrhage, bleeding that occurs slowly over an extended period without obvious signs, is determined to be from a small bowel source in fewer than 10% of cases. Hence, bleeding from the small intestine is frequently termed gastrointestinal hemorrhage of obscure origin, a designation reflecting not only the relative infrequency of the condition but also the difficulty in reaching a diagnosis for lesions responsible for hemorrhage from the small bowel luminal surface.[ ] Although the esophagus, stomach, and duodenum are readily evaluated with flexible esophagogastroduodenoscopy and the colon can be thoroughly evaluated with flexible colonoscopy, much of the small bowel mucosa remains out of reach of such effective and readily available endoscopic devices.

Evaluation of patients with acute small bowel hemorrhage is further complicated by the fact that hemorrhage is characterized by episodic bleeding with early spontaneous cessation. This characteristic pattern of bleeding limits the use of dynamic imaging modalities, such as technetium-99m (99m Tc)-labeled red blood cell scintigraphy and selective visceral angiography, which rely on ongoing hemorrhage to detect

bleeding sites. Indeed, the typical patient with hemorrhage from a small bowel source has multiple episodes of hemorrhage, is subjected to numerous diagnostic procedures, and receives a mean of 20 units of packed red blood cells before definitive identification and treatment of the bleeding lesion. This is true despite repeated clinical episodes of obvious gastrointestinal hemorrhage presenting as hematochezia or melena.

Patients with small intestinal lesions presenting with signs of occult gastrointestinal hemorrhage are similarly difficult to evaluate. In such cases, patients present with signs secondary to occult blood loss: anemia, fatigue, or weight loss. The primary evaluation of patients with occult gastrointestinal blood loss usually reveals a source of bleeding from the upper gastrointestinal tract, most commonly related to a peptic

mucosal injury process.1 • Most of the remaining patients have a colonic source of occult bleeding, such as a benign or malignant colonic neoplasm, angiodysplasia, or diverticula, whereas a few have upper gastrointestinal neoplasms. Fewer than 10% of patients have anemia secondary to loss of blood from a small intestinal source.

Clearly, it is both the infrequency of bleeding from the small bowel and the diagnostic limitations of evaluating the small bowel that make diagnosis and treatment of small bowel hemorrhage a vexing clinical problem. A wide variety of rare conditions may be responsible, although the frequency of these lesions varies in the reported series ( Table 20-1 and Table 20-2 ). Delays in diagnosis and treatment are common. It is

therefore imperative that surgeons consider small intestinal sources when patients present with signs of acute or chronic gastrointestinal blood loss not readily found to be due to an identifiable lesion in the upper gastrointestinal tract or the colon. This vigilance allows more timely and prompt therapy of these potentially life-threatening conditions of the small bowel. Surgeons must also be familiar with the diagnostic tools available for evaluation of the small bowel. Optimal evaluation requires multidisciplinary approaches that include the radiologist, gastroenterologist, and surgeon. Most important, blind surgical exploration should be avoided because intraoperative assessment of bleeding

TABLE 20-1 -- Conditions Associated With Small Bowel Bleeding

Neoplastic

Benign

Leiomyoma Hemangioma Hyperplastic polyp Adenomatous polyp Intestinal endometriosis Neurofibromatosis Schwannoma

Malignant

Leiomyosarcoma

Metastatic tumors

Lymphoma

Adenocarcinoma

Carcinoid

Kaposi's sarcoma

Angiosarcoma

Rhabdomyosarcoma

Congenital

Meckel's diverticulum

Intestinal duplication cysts Heterotopic gastric mucosa Ehlers-Danlos syndrome Osler-Weber-Rendu disease

Henoch-Schonlein purpura Churg-Strauss syndrome Celiac sprue Hemophilia von Willebrand's disease

Trauma

Postprocedural Foreign-body ingestion Blunt and penetrating trauma Acquired

Inflammatory diseases Crohn's disease

Jejunoileal diverticula Radiation enteritis

Celiac sprue Vascular diseases

Angiodysplasia Telangiectasia Dieulafoy's lesions Intussusception Arterioenteric fistulas

Portoenteric varices

Mesenteric venous insufficiency Vasculitis and autoimmune disease

Polyarteritis nodosa Graft-versus-host disease

Wegener's granulomatosis Systemic lupus erythematosus Thrombotic thrombocytopenic purpura Amyloidosis Sarcoidosis

Drug-induced NSAID use

Anticoagulants Infectious

Cytomegalovirus Tuberculosis

Salmonella species Shigella species Amebiasis

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