Gastrointestinal Bleeding, Lower
Sara Karjoo
Chris A. Liacouras
INTRODUCTION
The presence of blood in the gastrointestinal tract is always abnormal. Blood in the stool can occur in several forms: hematochezia (bright red blood on the stool), “currant-jelly” stools (thickened brick-red blood on the stool), melena (dark or black stools), or occult bleeding (normal-appearing stools that test positive by Hemoccult or guaiac testing).
Blood acts as a cathartic that decreases intestinal transit time. Therefore, hematochezia usually signifies colonic disease (i.e., bleeding from a site between the distal colon and the terminal ileum), but it may be the result of profuse proximal gastrointestinal tract bleeding. Melena usually signifies profuse upper intestinal bleeding (above the ligament of Treitz), whereas currant-jelly stools commonly occur when there is shedding of the intestinal mucosa as a result of an active Meckel diverticulum or intussusception. Normal-appearing stools that test positive for blood suggest slow gastrointestinal tract bleeding. Table 34-1 lists causes of bloody stools by site.
HINT: Rapid upper gastrointestinal tract bleeding should always be considered in any child with first-time bloody stools, and a nasogastric tube should be passed for gastric lavage.
DIFFERENTIAL DIAGNOSIS LISTThe following are common causes of hematochezia and melena:
Infectious Causes
Bacterial Infection
Salmonella
Shigella
Campylobacter
Yersinia
Enterohemorrhagic Escherichia coli
Aeromonas
Plesiomonas
Clostridium difficile
Parasitic Infection
Entamoeba histolytica
Balantidium coli
Necator americanus (hookworm)
Strongyloides stercoralis
Ascaris lumbricoides
TABLE 34-1 Causes of Bloody Stools by Site | ||||||||||||||
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Viral Infection
Adenovirus
Rotavirus
Cytomegalovirus
HIV
Neoplastic Causes
Leiomyoma
Lymphoma
Adenocarcinoma
Carcinoid
Traumatic Causes
Anal fissure
Foreign body
Sexual abuse
Congenital or Vascular Causes
Meckel diverticulum
Enteric duplication
Arteriovenous malformation (AVM)
Hemangioma
Hemorrhoids
Rectal varices
Esophageal varices (rapid flow)
Hirschsprung enterocolitis
Inflammatory Causes
Juvenile polyps
Polyposis syndromes
Inflammatory bowel disease
Lymphonodular hyperplasia
Necrotizing enterocolitis
Milk- or soy-protein allergy
Eosinophilic gastroenteritis
Graft-versus-host disease
Vasculitis (systemic lupus erythematosus)
Miscellaneous Causes
Rapid upper gastrointestinal bleeding
Intussusception
Volvulus
Solitary rectal ulcer
Coagulopathy
Thrombocytopenia
Anticoagulant drug therapy
Henoch-Schönlein purpura
Hemolytic uremic syndrome
TABLE 34-2 Foods and Drugs Mimicking Blood in the Stool | ||||||||||||||||||||||||||||||
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HINT: Certain foods, drugs, and occurrences (e.g., menstrual bleeding, hematuria, swallowed maternal blood) can mimic blood in the stool and must be ruled out (Table 34-2).DIFFERENTIAL DIAGNOSIS DISCUSSION
HINT: Lower gastrointestinal tract bleeding in children is most often caused by constipation or infection. Bacterial infections often present with acute abdominal pain, fever, and bloody diarrhea.C. Difficile Colitis (Pseudomembranous Colitis, Antibiotic-Induced Colitis)
Etiology
The toxins produced by C. difficile have cytotoxic effects on the colonic mucosa. Although C. difficile colitis is usually associated with an imbalance of the gastrointestinal flora following the administration of broad-spectrum antibiotics (e.g., clindamycin, amoxicillin, cephalosporin), it can develop in patients with underlying intestinal disorders (e.g., inflammatory bowel disease) and those who have undergone recent abdominal surgery, institutionalized patients (as a result of cross-infection), and, sporadically, in otherwise healthy patients. Although C. difficile can also cause disease in young infants, this age group can have C. difficile carriage in the stool without symptoms. After 2 years of age, C. difficile toxin-positive stools are pathologic.
HINT: Antibiotic-induced colitis commonly occurs within 2 weeks of introducing the drug.Clinical Features
C. difficile is associated with a wide variety of clinical symptoms. Patients may be asymptomatic, or they may experience frequent, painful, bloody diarrhea, a sign of severe, life-threatening colitis. Typically, children present with abdominal pain and frequent bloody, mucus-streaked, foul-smelling, watery stools. Some patients may be dehydrated.
Evaluation
Fresh stool specimens (transported on ice or frozen) should be collected and evaluated for the presence of C. difficile toxins A and B. In patients with persistent bloody diarrhea and a negative microbiologic evaluation, colonoscopy should be performed. Colonoscopy often reveals the classic mucosal pseudomembrane formation (raised yellow plaques).
Treatment
Treatment includes discontinuation of the inciting antibiotic and therapy with oral metronidazole (see Chapter 27, “Diarrhea, Acute”). Typically, oral metronidazole is the first-line therapy, and can be used for a second course if the symptoms recur. Vancomycin is an alternative antibiotic that is used when patients do not respond to metronidazole. Use of vancomycin as first-line therapy is discouraged because there is potential for creating vancomycin-resistant organisms. Symptoms usually resolve within 3 to 5 days. Recurrent episodes may occur following cessation of therapy; in this situation, repeat treatment and further evaluation for other underlying systemic disorders (e.g., inflammatory bowel disease) are indicated. Good hand-washing with water and soap should be encouraged because the C. difficile spores are resistant to regular alcoholic hand rubs. Dehydrated patients require intravenous fluids and the short-term introduction of clear liquids.
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