Blood in stool
Blood in stool looks different depending on how early it enters the digestive tract—and thus how much digestive action it has been exposed to—and how much there is. The term can refer either to melena, with a black appearance, typically originating from upper gastrointestinal bleeding; or to hematochezia, with a red color, typically originating from lower gastrointestinal bleeding. Evaluation of the blood found in stool depends on its characteristics, in terms of color, quantity and other features, which can point to its source, but more serious conditions can present with a mixed picture, or with the form of bleeding that is found in another section of the tract. The term "blood in stool" is usually only used to describe visible blood, and not fecal occult blood, which is found only after physical examination and chemical laboratory testing.
In infants, the Apt test, a test that is particularly useful in cases where a newborn has blood in stool or vomit, can be used to distinguish fetal hemoglobin from maternal blood based on the differences in composition of fetal hemoglobin as compared to the hemoglobin found in adults. A non-harmful cause of neonatal bleeding include swallowed maternal blood during birth; However, serious causes include Necrotizing Enterocolitis, a severe inflammatory condition affecting premature infants, and midgut volvulus, a life-threatening twisting that requires emergency surgery.
Differential diagnoses
Blood in the stool can come from many sources. The causes range from not harmful to very serious conditions. A common way to divide causes of bleeding is based on the source of bleeding. The GI tract can be divided into upper and lower, with some causes of bleeding affecting the entire tract. Blood in the stool often appears different depending on its source. These differences can help when diagnosing these conditions. The rate of bleeding can also make blood in the stool look different from typical cases.Upper GI tract
The upper GI tract is defined as the organs involved in digestion above the ligament of Treitz and comprises the esophagus, stomach, and duodenum. Upper gastrointestinal bleeding is typically characterized by melena. Bright red blood may be seen with active, rapid bleeding.Pathophysiology
The development of blood in a person's stool results from a variety of conditions, which can be divided into major categories of disease. These broad categories include cancerous processes or abnormal structure of bowel wall, inflammatory disease, colitis caused by infection or medications and vascular compromise.Cancer
- Colorectal cancer
- Gastric cancer
Gut wall changes
Motility
The gut wall is important for the movement of waste products through the GI tract. Repetitive attempts to have a bowel movement can lead to tearing around the exit of the rectum- Constipation
Structural
- Peptic ulcer disease—divided into either duodenal or gastric ulcers, most common causes include:
- * Nonsteroidal anti-inflammatory drugs—the use of these medications results in a structural change in the wall of the gut, namely ulcers, and potential blood in the stool.
- * H. pylori infection—this bacterial infection can erode the wall of the stomach or duodenum, leading to a structural change in the stomach wall and bleeding in the stool.
- * Chronic disease
- Diverticulitis and diverticulosis result from an out pouching of the colonic mucosa, or gut wall, leading to a breakdown of weak gut wall and an increased susceptibility to infection due to the bacteria in the GI tract, thus the potential for vascular compromise, the collection of bacteria in the area of perforation, the abnormal formation of communication between another part of the hollow GI tract, or blockage of the bowel.
- Meckel's diverticulum is a congenital remnant of the omphalo-mesenteric duct that connected the fetal yolk sac to the intestines which is normal closed off and destroyed during the process of development. If a portion, or all of this duct remains a diverticulum or fistula can result, leading to the potential for a source of bleeding.
Inflammatory bowel
- Crohn's disease
- Ulcerative colitis
Colitis
- Enteritis—inflammation of the small intestine, which has many causes including autoimmune conditions, certain drugs, radiation therapy, and Coeliac disease.
Infectious colitis
- Food poisoning—the bacteria that is associated with bloody diarrhea is typically E. coli
- Campylobacter enteritis
- Shigellosis
- Salmonellosis
- Bacterial gastroenteritis
- * Campylobacter jejuni
- * Clostridioides difficile
- * Escherichia coli enteritis—most common cause of travelers' diarrhea
- * Salmonella enterica
- * Shigella dysenteriae see also dysentery
- Staphylococcus aureus
- ''Entamoeba histolytica''
Drug-induced colitis
- Radiation enteritis
Vascular compromise
- Angiodysplasia of the GI tract
- Arteriovenous malformation
- Anal fissure
- Anal intercourse
- Esophageal varices
- Hemorrhoids
- * Internal hemorrhoids are covered by a layer of mucosa and epithelium, making them more likely to bleed, but typically do not cause pain.
- * External hemorrhoids are less likely to bleed, they are covered by a different type of epithelium but can cause significant pain as a result of thrombosis of the blood vessels within them.
- Polypectomy during a colonoscopy can lead to a small amount of bleeding seen in the stool after the procedure
Other causes
- Blood in the diet, for example, the traditional diet of the Maasai includes much blood drawn from cattle.
Diagnosis
- Digital rectal exam and fecal occult blood test
- Colonoscopy
- Anoscopy
- Esophagogastroduodenoscopy
- Capsule endoscopy
- CT Scan
Hematochezia is defined as bright red blood seen in the toilet either inside of, or surrounding the stool.
Hematochezia is typically presumed to come from the lower portion of the GI tract, and the initial steps of diagnosis include a digital rectal exam with fecal occult blood test, which if positive, will lead to a colonoscopy. If the person has a large amount of blood in their stool, an Esophagogastroduodenoscopy test may be necessary. If no source of bleeding is found on these examinations, a capsule endoscopy may be performed, in order to more closely examine the small bowel, which cannot be seen with the other types of studies. With melena, a digital rectal exam with fecal occult blood test is often also performed, however the suspicion for a source from the upper GI tract is higher, leading first to the use of esophagogastroduodenoscopy with the other tests being required if no source is identified. The anoscopy is another type of examination, which can be used along with a colonoscopy, which exams the rectum and distal portion of the descending colon.
| Color | Medical term | Frequency | Quantity | Examples of types of bleeding considered |
| Bright red | Hematochezia | Occasional occurrence of blood | Small | Hemorrhoids, inflammatory conditions, polyps |
| Bright red | Hematochezia | Increased stooling, blood with every stool | Large | Rapid bleeding, e.g. ulcer, varices |
| Dark red/black | Melena | Blood with every stool | Difficult to measure, mixed in with stool | Slow bleeding, cancer, ulcer, |
Other features
may also be found in stool.A texture described as tarry stool is generally associated with dark black stool seen in partially digested blood. This is generally associated with melena.
Patient age
A person's age is an important consideration when assessing the cause of the bleeding.| Age | Group | Types of bleeding considered |
| <20 years | Pediatric | Inherited/autoimmune condition or structural |
| 20–60 years | Middle aged | Inherited/autoimmune condition, vascular malformation |
| >60 years | Elderly | Vascular malformation, liver disease, cancer |