What is the most likely explanation for this patient's chronic diarrhea?

Question

A 15-year-old high school freshman is brought to the clinic by his mother because of chronic diarrhea. The mother states that for the past couple of years her son has had diarrhea after many meals. The patient states that the diarrhea seems the absolute worst after his school lunches. He describes his symptoms as cramping abdominal pain and gas followed by diarrhea. His stools are watery with no specific smell. He denies any nausea, vomiting, constipation, weight loss, or fatigue. He has had no recent illness, injuries, or foreign travel. His past medical history is unremarkable. He denies tobacco, alcohol, or drug use. His parents are both healthy. On examination you see a relaxed young man breathing comfortably. His vital signs are normal and his head, eyes, ears, throat, neck, cardiac, and pulmonary examinations are normal. His abdomen is soft and nondistended. His bowel sounds are active and he has no tenderness, no enlarged organs, and no rebound or guarding. His rectal examination is nontender with no blood on the glove. You collect a stool sample for further study.

A) Malabsorption syndrome
B) Osmotic diarrhea
C) Secretory diarrhea

Answer 1

B) Osmotic diarrhea

Usually related to lactose intolerance, watery diarrhea often follows meal ingestion. Crampy abdominal pain, distension, and gas often accompany symptoms. Diarrhea is often provoked by pizza, milkshakes, yogurt, and other lactose-containing foods. This condition is more common in African-Americans, Latinos, Native Americans, and Asians.