Leukocytes, or white blood cells, are a fundamental part of the body’s immune system responsible for fighting infection. Their presence in a stool sample, known as fecal leukocytes, signals an active inflammatory response within the gastrointestinal tract. This inflammation is usually confined to the intestinal lining (mucosa), where immune cells are recruited to combat a threat. A positive result directs medical investigation toward underlying causes involving significant mucosal injury or inflammation.
What Leukocytes in Stool Indicate
The detection of leukocytes in stool strongly suggests inflammatory diarrhea, which is distinct from non-inflammatory causes. This finding means the immune system has mobilized its defenses, causing white blood cells to migrate out of the bloodstream and into the wall of the large intestine. This cellular migration and subsequent immune activity causes symptoms like severe diarrhea, abdominal pain, and sometimes blood or mucus in the stool.
The test is particularly useful for differentiating between causes of diarrhea that invade the intestinal wall and those that simply produce toxins or are purely viral. Conditions that result in a positive fecal leukocyte test involve direct damage to the mucosal tissue, triggering a robust immune reaction. Conversely, diarrhea caused by many viruses or non-invasive bacteria typically does not result in a significant presence of leukocytes because they do not provoke the same destructive inflammatory response in the gut lining.
The presence of leukocytes points toward potential underlying causes, including invasive bacterial infections or chronic bowel diseases. While the traditional fecal leukocyte test indicates inflammation, more accurate markers, such as fecal calprotectin or lactoferrin, are often used today. These proteins are released by white blood cells during inflammation, providing a more reliable measure of intestinal inflammation than direct cell counting.
Diagnosing the Source of Inflammation
Once leukocytes confirm intestinal inflammation, the next step is to pinpoint the specific cause, as treatment depends entirely on the diagnosis. Healthcare providers employ targeted tests to move from a general finding of inflammation to a definitive etiology. The first line of investigation often involves specialized stool tests to identify infectious pathogens.
Stool cultures isolate and identify specific invasive bacteria, such as Salmonella, Shigella, or Campylobacter, common culprits behind inflammatory gastroenteritis. A separate test detects toxins produced by Clostridioides difficile (C. diff), which typically causes severe inflammation after antibiotics. For cases involving travel or specific exposures, testing for parasites like Entamoeba histolytica may also be conducted.
Beyond infectious causes, blood tests assess the body’s overall inflammatory status. These tests look for elevated markers like C-reactive protein (CRP) or the erythrocyte sedimentation rate (ESR), confirming systemic inflammation. They can also reveal anemia, a common complication of chronic intestinal bleeding or poor nutrient absorption associated with long-term inflammatory conditions.
If the initial stool and blood tests do not reveal an acute infection, or if symptoms are chronic and recurrent, an inflammatory bowel disease (IBD) such as Crohn’s disease or ulcerative colitis may be suspected. In these instances, the physician will typically recommend an imaging study or, most definitively, a colonoscopy. This endoscopic procedure allows for direct visualization of the intestinal lining and the collection of tissue biopsies, which are necessary to confirm the diagnosis of chronic inflammatory disease.
Targeted Treatment Protocols
Treating the cause of leukocytes in stool means treating the underlying disease or infection driving the inflammatory response. For many acute infectious cases, such as those caused by Salmonella or some viral infections, the primary treatment is supportive care. This involves oral rehydration therapy to replace lost fluids and electrolytes, with intravenous fluids reserved for severe dehydration.
For bacterial pathogens confirmed to be the cause, specific antibiotic therapy is often required, particularly in cases of severe disease, high fever, or for certain organisms like Shigella. C. diff infection is treated with specific oral antibiotics such as vancomycin or fidaxomicin, which concentrate in the gut to kill the bacteria and prevent recurrence.
An important exception is infection with Shiga toxin-producing E. coli (STEC). In these cases, antibiotics are often avoided due to the potential risk of triggering a severe complication called hemolytic uremic syndrome.
When the diagnosis is chronic inflammatory bowel disease (IBD), treatment shifts to long-term management aimed at suppressing the sustained immune response. Initial therapy involves anti-inflammatory medications like aminosalicylates or corticosteroids to quickly reduce flare-up symptoms. For moderate to severe IBD, treatment progresses to immunomodulators or biologic therapies, which are monoclonal antibodies designed to block specific inflammatory pathways or prevent white blood cells from migrating to the inflamed intestinal tissue.
These sophisticated treatments, such as those that target leukocyte trafficking, halt the continuous recruitment of immune cells to the gut lining, reducing inflammation and allowing the tissue to heal. Regardless of the specific cause, dietary adjustments and rest are important components of recovery, helping to reduce stress on the inflamed digestive system while medical therapies take effect.