A robust male baby with vigorous feeding and immediate vomiting at 2 months of age. Most probable diagnosis is:
Vigorous feeding immediately followed by vomiting could point to a mechanical obstruction. In infants, common causes include pyloric stenosis, which is more common in males, typically presents around 2-3 months old. The vomiting is usually projectile, and the baby is otherwise healthy and feeding well. Another possibility might be GER (gastroesophageal reflux), but that's more likely in younger infants and the vomiting isn't usually immediate. Hypertrophic pyloric stenosis is a classic differential here.
Looking at the options, the correct answer is likely pyloric stenosis. Let's check the options again. The user didn't list the options, but common options for this question would include pyloric stenosis, GER, intestinal obstruction, etc. The key features here are age, sex, and presentation. Pyloric stenosis is more common in males, presents around 2-3 months, with non-bilious vomiting after feeding. The baby is otherwise well, which differentiates it from other conditions like sepsis or metabolic issues.
The other options: GER might cause vomiting but not typically immediate and projectile. Intestinal obstruction would have bilious vomiting, and the baby would be unwell. Malrotation with volvulus is another possibility but usually presents with bilious vomiting and other signs of obstruction.
Clinical pearl: Remember the "2-month-old male with projectile vomiting" is a classic presentation of pyloric stenosis. Diagnosis is often confirmed with ultrasound showing a thickened pyloric muscle. Treatment is pyloromyotomy. High-yield fact for exams.
**Core Concept**
This question tests recognition of **hypertrophic pyloric stenosis (HPS)**, a common cause of **projectile vomiting** in infants aged 2–3 months. It involves hypertrophy of the **pyloric muscle**, leading to gastric outlet obstruction.
**Why the Correct Answer is Right**
HPS presents with **non-bilious, projectile vomiting** after feeding, often in a **male infant** (male-to-female ratio of 4:1). The baby remains **hungry and vigorous**, with **normal stools**. Pathologically, the pyloric muscle thickens (>3 mm on ultrasound), narrowing the pyloric lumen. Diagnosis is confirmed via **abdominal ultrasound** (classically showing a "string sign" or "crescent sign").
**Why Each Wrong Option is Incorrect**
**Option A:** *Gastroesophageal reflux (GER)* causes **intermittent, non-projectile vomiting** and is less likely to present with immediate post-feeding vomiting.
**Option B:** *Intestinal malrotation* typically presents with **bilious vomiting**, **abdominal distension**, and **systemic toxicity** (e.g., sepsis), not a well-appearing infant.
**Option C:** *Congenital pyloric atresia* is a **congenital anomaly** with **complete obstruction**, leading to **polyhydramnios** in utero and **early neonatal vomiting**, not at 2 months.
**Clinical Pearl / High