Acute bloody diarrhea is characterized by the sudden onset of frequent, loose, or watery stools containing visible blood. The term “acute” signifies that the condition begins abruptly and typically lasts less than two weeks. The presence of blood indicates irritation or damage to the lining of the gastrointestinal tract, most commonly the colon, and warrants medical attention to determine the underlying cause.
Infectious and Non-Infectious Causes
The most frequent causes of acute bloody diarrhea are infectious, often involving bacteria that invade the intestinal lining or produce harmful toxins. Shiga toxin-producing Escherichia coli (STEC), particularly the O157:H7 strain, is a significant concern because the toxins it releases can damage the colon and lead to severe complications. Other common bacterial culprits include Shigella, Salmonella, and Campylobacter, which are usually acquired through contaminated food or water.
These bacteria cause inflammation that erodes the mucosal surface of the colon, resulting in the passage of blood and sometimes mucus. The infection is usually localized to the gut, but some pathogens, like certain types of Salmonella, can cause a systemic illness. Less commonly, parasites such as Entamoeba histolytica can also cause acute bloody diarrhea by invading the intestinal wall.
Non-infectious conditions can also present with sudden bloody diarrhea, though they are less frequent in acute cases. An acute flare of Inflammatory Bowel Disease (IBD), such as ulcerative colitis or Crohn’s disease, can cause sudden rectal bleeding and diarrhea. Ischemic colitis results from a temporary reduction in blood flow to the colon, damaging the tissue and leading to bleeding. Specific medications, including some nonsteroidal anti-inflammatory drugs (NSAIDs), can also irritate the gut lining and result in acute gastrointestinal bleeding.
Critical Warning Signs and Associated Symptoms
The presence of blood in the stool requires medical evaluation, but several associated symptoms signal a serious situation. Signs of severe dehydration are a major concern, including a marked reduction in urination, extreme thirst, a rapid heart rate, and confusion. Significant blood loss can also cause symptoms like dizziness, fainting, or paleness.
A high fever, typically over 101.3°F (38.5°C), often indicates a systemic bacterial infection requiring prompt intervention. Severe abdominal pain that does not improve, especially if the abdomen feels rigid or tender, can signal a complicated issue like perforation or severe inflammation. Persistent vomiting is also a serious sign, as it accelerates dehydration and hinders oral rehydration efforts.
The Diagnostic Process
The evaluation begins with a detailed medical history focusing on recent food consumption, travel, contact with sick individuals, and medication use. Clinicians perform a physical examination to assess the patient’s hydration status and check for signs of abdominal tenderness or distension. This initial assessment helps determine the severity of the illness and the likelihood of different causes.
Stool studies are a cornerstone of the diagnostic workup for bloody diarrhea, especially for identifying infectious pathogens. A stool culture helps isolate and identify specific bacteria, such as Salmonella or Shigella. Testing for Shiga toxin is performed separately because its presence is a significant indicator of the most dangerous E. coli infections, even if the organism itself is not easily cultured. Blood tests check for electrolyte imbalances, signs of systemic infection, and monitor kidney function, which can be impaired in severe cases.
Immediate Treatment and Recovery
Immediate treatment for acute bloody diarrhea focuses primarily on supportive care to manage fluid loss and prevent dehydration. Oral Rehydration Solution (ORS), a mixture of water, salts, and sugar, is the standard first-line treatment for replacing lost fluids and electrolytes. In cases of severe dehydration, vomiting, or shock, intravenous (IV) fluids may be required to rapidly restore the body’s fluid balance.
The use of antibiotics is carefully considered and depends heavily on the identified or suspected cause. Antibiotics are generally avoided if a Shiga toxin-producing E. coli infection is suspected or confirmed because the drugs can increase the release of the toxin, potentially raising the risk of Hemolytic Uremic Syndrome (HUS), a serious kidney complication. However, antibiotics may be administered for confirmed infections like shigellosis or campylobacteriosis to shorten the duration and severity of the illness. During recovery, patients are advised to consume a bland, easily digestible diet and gradually resume normal eating habits as symptoms improve.