Colitis is a general medical term that describes inflammation of the colon, which is the large intestine. This inflammation can disrupt the colon’s ability to properly absorb water and process waste, leading to common symptoms like diarrhea, abdominal pain, and the presence of blood or mucus in the stool. The causes of colitis in children are diverse, ranging from temporary infections to long-term autoimmune conditions.
Infectious Agents
Infectious colitis is the most frequent cause of inflammation in a child’s colon, particularly after the first year of life. These episodes are typically acute, meaning they come on suddenly and resolve once the body clears the pathogen. A variety of bacteria are responsible for this type of acute inflammation.
The most commonly implicated bacterial culprits include species such as Salmonella, Shigella, and Campylobacter. Enterohemorrhagic E. coli (EHEC) is also a well-known cause of hemorrhagic colitis. These infections are generally acquired through the fecal-oral route, often by consuming contaminated food or water.
The bacteria invade the intestinal lining, triggering an inflammatory response where immune cells infiltrate the large intestine’s inner layer. While bacterial causes are the most prevalent, certain viruses, like Cytomegalovirus (CMV), can also cause colitis, especially in children with weakened immune systems. Viral and bacterial colitis usually presents with a short-lived course.
Chronic Inflammatory Bowel Disease
A more significant cause of long-term colitis is Inflammatory Bowel Disease (IBD), which is an umbrella term for chronic conditions resulting from an abnormal immune response. The immune system mistakenly attacks the digestive tract, causing persistent inflammation. The two primary forms of IBD seen in children are Ulcerative Colitis (UC) and Crohn’s Disease (CD).
Ulcerative Colitis
Ulcerative Colitis is characterized by continuous inflammation that is strictly limited to the large intestine and rectum. The inflammation in UC only affects the innermost lining, or mucosa, of the colon. This superficial inflammation leads to the formation of ulcers, which are responsible for the bloody diarrhea often associated with the disease.
Crohn’s Disease
Crohn’s Disease can cause inflammation anywhere along the entire gastrointestinal tract, from the mouth to the anus. Unlike UC, Crohn’s inflammation is discontinuous, appearing in patches interspersed with areas of healthy tissue. Furthermore, CD inflammation is transmural, meaning it extends through all layers of the intestinal wall, a distinction that can lead to complications like strictures and fistulas.
The exact trigger for IBD remains unknown, classifying it as idiopathic. However, it is understood to involve a complex interplay of genetic predisposition and environmental factors. The initial inflammatory response may be triggered by a common virus or bacteria interacting with the child’s immune system, leading to a sustained, inappropriate response.
Dietary and Immune Reactions
Beyond IBD, certain immune-mediated reactions to food proteins can also cause significant colonic inflammation. These conditions are distinct from the autoimmune nature of IBD and from immediate, classic IgE-mediated food allergies. These reactions are often delayed and focused on the gastrointestinal system.
Food Protein-Induced Enterocolitis Syndrome (FPIES)
FPIES is a severe, non-IgE-mediated food allergy that primarily affects infants and toddlers. In FPIES, the ingestion of a trigger food, commonly cow’s milk, soy, or grains, leads to a delayed reaction, typically involving profuse, repetitive vomiting and diarrhea several hours after consumption. The inflammatory mechanism is believed to involve a T-cell-mediated response in the gut, which can result in dehydration.
Eosinophilic Colitis
Eosinophilic Colitis is characterized by an abnormal accumulation of eosinophils, a type of white blood cell, within the colon lining. This build-up is often linked to dietary proteins, and the presence of these inflammatory cells causes chronic irritation and colitis symptoms.
Other Specific Causes
Other specific mechanisms can lead to colitis, often linked to unique circumstances or age groups.
Antibiotic-Associated Colitis
Antibiotic-associated colitis occurs when antibiotic use disrupts the normal, protective balance of gut flora. This disruption allows for the overgrowth of the bacterium Clostridioides difficile (C. diff). C. diff produces powerful toxins that directly damage the colon lining, leading to inflammation and the characteristic symptoms of diarrhea and pseudomembranous colitis. This infection is strongly associated with recent antibiotic exposure.
Necrotizing Enterocolitis (NEC)
NEC is a severe form of colitis seen almost exclusively in newborns, particularly premature infants. This life-threatening disease involves inflammation, injury, and death of tissue in the intestinal wall. The immaturity of the premature infant’s gastrointestinal tract, combined with factors like formula feeding and reduced blood flow, increases the risk of bacterial invasion and resulting tissue necrosis.
Systemic Diseases
Colitis can also be a complication of other systemic diseases, such as Hemolytic Uremic Syndrome (HUS). HUS is often triggered by infection with specific toxin-producing E. coli strains. The toxin damages blood vessels, leading to kidney failure and, in the colon, a form of hemorrhagic colitis.