**Core Concept**
The diagnosis of celiac sprue involves identifying an adverse immune response to gluten, leading to inflammation and damage in the small intestine. This condition is characterized by the presence of specific autoantibodies and characteristic histopathological changes in the intestinal mucosa.

**Why the Correct Answer is Right**
The definitive diagnosis of celiac sprue is made through a combination of clinical evaluation, serological testing, and histopathological examination of the intestinal biopsy. The presence of anti-tissue transglutaminase antibodies (anti-TTG) or anti-endomysial antibodies (EMA) is a sensitive and specific marker for celiac disease. These autoantibodies are produced in response to the ingestion of gluten and can be detected in the blood of affected individuals. The intestinal biopsy typically shows villous atrophy, crypt hyperplasia, and an increased number of intraepithelial lymphocytes.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because celiac sprue is not typically diagnosed through a stool test. While stool tests may be used to evaluate for malabsorption or gastrointestinal bleeding, they are not specific for celiac disease.
* **Option B:** This option is incorrect because a skin biopsy is not a standard diagnostic tool for celiac sprue. While skin manifestations can be associated with celiac disease, they are not a reliable method for diagnosis.
* **Option C:** This option is incorrect because a liver function test is not specific for celiac sprue. While liver enzymes may be elevated in individuals with celiac disease due to malabsorption, this is not a reliable method for diagnosing the condition.

**Clinical Pearl / High-Yield Fact**
Celiac sprue is a common autoimmune disorder that can be triggered by the ingestion of gluten in susceptible individuals. It is essential to maintain a high index of suspicion for celiac disease in patients with unexplained gastrointestinal symptoms, particularly those with a family history of the condition.

**Correct Answer: D. Intestinal biopsy with histopathological examination and serological testing for anti-tissue transglutaminase antibodies or anti-endomysial antibodies.**