**Core Concept**
The infant's presentation of recurrent episodes of abdominal pain followed by altered stool is suggestive of a condition where the normal intestinal motility and secretion are disrupted, leading to an abnormal accumulation of intestinal contents.

**Why the Correct Answer is Right**
The most likely diagnosis in this case is Intestinal Obstruction. The infant's symptoms of abdominal pain and altered stool are classic for this condition. The altered stool is likely due to the accumulation of intestinal contents proximal to the obstruction, which then passes through the obstruction and reaches the stool unchanged. Intestinal obstruction can be caused by various factors, including congenital abnormalities, intussusception, or intestinal atresia.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is not directly related to the symptoms described. While urinary tract infections can cause abdominal pain, they do not typically cause altered stool.

**Option B:** This option is a potential cause of abdominal pain, but it does not typically result in altered stool. Gastroenteritis would more likely cause vomiting and diarrhea.

**Option C:** This option is a potential cause of abdominal pain and altered stool, but it is less likely than intestinal obstruction. Intestinal perforation would more likely cause abdominal tenderness and peritoneal signs.

**Clinical Pearl / High-Yield Fact**
The "altered stool" in this scenario is a classic sign of intestinal obstruction, where the stool is often described as "currant jelly" or "tarry" due to the presence of mucus and altered intestinal contents.

**Correct Answer:** D. Intestinal obstruction.