**Question:** Cause of False positive D-xylose test includes all of the following, except

A. Malabsorption
B. Liver disease
C. Small bowel resection
D. Acid-base imbalance

**Core Concept:**
The D-xylose test is a diagnostic procedure used to evaluate small bowel absorption. When a patient has a false positive result, it can be due to various causes. D-xylose is a non-digestible sugar that is absorbed primarily in the small intestine. If absorption is impaired, it leads to a false positive test result.

**Why the Correct Answer is Right:**
The correct answer (D) is "acid-base imbalance" because an acid-base imbalance primarily affects the acid-base balance in the blood, rather than directly influencing small bowel absorption or D-xylose absorption. Acid-base imbalance is a condition that alters pH levels in the blood, which is unrelated to the functioning of the small bowel and D-xylose absorption.

**Why Each Wrong Option is Incorrect:**

A. Malabsorption: Malabsorption refers to the inability of the body to absorb certain nutrients and substances properly, which can lead to false positive D-xylose test results due to impaired absorption of D-xylose in the small intestine. This option is incorrect because it does affect D-xylose absorption and leads to false positive results.

B. Liver disease: Liver disease can lead to altered liver function and potential malabsorption, potentially causing a false positive D-xylose test result. However, liver disease does not directly affect the small bowel and D-xylose absorption, so this option is incorrect.

C. Small bowel resection: Small bowel resection involves surgical removal of part of the small intestine, which directly affects the portion of the small bowel responsible for D-xylose absorption. Consequently, a patient with a history of small bowel resection will usually have a false positive D-xylose test result. This option is incorrect as it is a cause of false positive D-xylose test result due to impaired absorption in the small intestine.

**Clinical Pearl:**
A false positive D-xylose test result can be seen in various conditions such as malabsorption syndromes (e.g., celiac disease), malnutrition, and certain medications. In contrast, a true positive result is indicative of malabsorption. Understanding the causes of false positive results is crucial for interpreting D-xylose test results accurately and making appropriate diagnoses based on these results.