Stool characteristics that cause angst in patients and parents prompting emergency department visits include changes in color (black, red, white, green, blue), consistency (hard, loose, watery), or frequency (too often, too infrequent) and associated pain.
Melena is a dark maroon (see Fig. 25.36) to black tar-like (see Fig. 25.37 and Fig 25.38) stool typically due to upper gastrointestinal (GI) bleeding of 100 to 200 mL of blood. Melena can occur from lower GI bleeds with delayed transit, swallowed blood from maternal mammary bleeding, epistaxis, or hemoptysis. Substances that cause black stool that are negative for occult blood include iron supplements, bismuth preparations, activated charcoal, and blueberries.
Melena and Maroon Stool. The maroon watery stool with solid melena suggests a brisk bleeding upper gastrointestinal bleed. Esophagogastroduodenoscopy confirmed a briskly bleeding gastric ulcer. (Photo contributor: Maria Ladino, MD.)
Melena. The black tarry appearance of melena in a patient with a duodenal ulcer. (Photo contributor: Alan B. Storrow, MD.)
Melena. Guaiac-positive stool specimen in a patient with melena due to a duodenal ulcer. The fecal occult blood test card contains white paper impregnated with guaiac resin, which turns blue in the presence of hemoglobin after adding hydrogen peroxide (Photo contributor: Lawrence B. Stack, MD.)
Bright red bloody stool (hematochezia) suggests lower GI bleeding and can be caused by colonic polyps, colon cancer, diverticulosis, anal fissures, hemorrhoids, inflammatory bowel disease, aortoenteric fistula, arteriovenous malformations, infectious diarrhea, and coagulopathy. Causes in children include necrotizing enterocolitis, malrotation with midgut volvulus, Hirschsprung disease, milk-protein allergy, intussusception (see Fig. 25.39), Meckel diverticulum, GI duplication cysts, vasculitis, hemolytic uremic syndrome, rectal ulcers, and juvenile polyps (see Fig. 25.40). Causes of red but not bloody stool include cefdinir (see Fig. 25.41), spicy food dyes, red licorice, beets, and red-colored food dyes.
Currant Jelly Stool. Stool mixed with blood and mucus, referred to as “currant jelly” stool, seen in this patient with intussusception. Bloody stools are a late finding in intussusception and occur from bowel ischemia and injury of the entrapped bowel segment. (Photo contributor: Donald H. Arnold, MD.)
Juvenile Polyp. Note blood mixed with normal stool in a 3-year-old patient who passed this juvenile polyp. (Photo contributor: Lawrence B. Stack, MD.)
Cefdinir Stool. Cefdinir combines with iron to form a precipitate that gives stool a characteristic discoloration that is guaiac negative. (Photo contributor: Lawrence B. Stack, MD.)