“Fecal” leucocytes are absent in all of the following, except:
**Core Concept**
Fecal leukocytes are a marker of intestinal inflammation, indicating the presence of neutrophils in the stool. This occurs when there is an invasion of the intestinal mucosa by pathogens, leading to an influx of neutrophils. The presence of fecal leukocytes is often used as a diagnostic tool in conditions such as bacterial gastroenteritis, inflammatory bowel disease, and infectious colitis.
**Why the Correct Answer is Right**
The correct answer is related to a condition where the intestinal mucosa is not invaded by pathogens, resulting in the absence of neutrophils in the stool. In this case, the condition is **A. Lactose Intolerance**. Lactose intolerance occurs when the small intestine does not produce enough lactase enzyme, leading to undigested lactose reaching the large intestine. This results in an osmotic imbalance, causing water and electrolytes to be drawn into the colon, but does not lead to an inflammatory response or the presence of neutrophils.
**Why Each Wrong Option is Incorrect**
* **Option B:** **Ulcerative Colitis** is an inflammatory bowel disease characterized by chronic inflammation of the colon. Neutrophils are present in the stool, making this option incorrect.
* **Option C:** **Hookworm Infection** leads to intestinal inflammation and invasion of the mucosa by the parasite, resulting in the presence of neutrophils in the stool. This option is also incorrect.
**Clinical Pearl / High-Yield Fact**
Fecal leukocytes are a useful diagnostic tool in conditions with intestinal inflammation, but their absence does not rule out all gastrointestinal disorders. A thorough history and physical examination, along with other diagnostic tests, are necessary to determine the underlying cause of gastrointestinal symptoms.
**Correct Answer: A. Lactose Intolerance**