A 12-year-old girl has a history of recurrent bulky stools and abdominal pain since 3 years of age. She has moderate pallor and her weight and height are below the 3rd percentile. Which of the following is the most appropriate investigations to make a specific diagnosis?
**Core Concept**
The girl's symptoms of recurrent bulky stools, abdominal pain, and growth failure suggest a malabsorptive disorder, likely caused by a deficiency of pancreatic enzymes or a problem with small intestine absorption.
**Why the Correct Answer is Right**
The correct investigation is a 72-hour fecal fat collection, which is a sensitive test for diagnosing malabsorption, especially pancreatic insufficiency. Pancreatic insufficiency leads to inadequate production of pancreatic enzymes, resulting in the malabsorption of fats, leading to bulky stools and weight loss. The 72-hour fecal fat collection involves collecting and analyzing feces over a 72-hour period to measure the amount of fat excreted, which helps diagnose malabsorption.
**Why Each Wrong Option is Incorrect**
**Option A:** Upper GI endoscopy is not typically used to diagnose malabsorption, as it is more useful for visualizing the upper gastrointestinal tract and diagnosing conditions like ulcers or tumors.
**Option B:** Upper GI series (barium swallow) is also not the best test for diagnosing malabsorption, as it is more useful for visualizing the upper GI tract and diagnosing conditions like strictures or tumors.
**Option C:** Intestinal biopsy is useful for diagnosing conditions like celiac disease or inflammatory bowel disease, but it is not the best initial test for diagnosing malabsorption.
**Clinical Pearl / High-Yield Fact**
Malabsorption can be caused by a variety of factors, including pancreatic insufficiency, celiac disease, Crohn's disease, and Whipple's disease. A 72-hour fecal fat collection is a useful test for diagnosing malabsorption, especially in patients with symptoms of weight loss, bulky stools, and abdominal pain.
**Correct Answer: C. Intestinal biopsy to assess for small intestine mucosal morphology and enzyme activity.**