Differential Diagnosis for the 1-Month-Old Boy with Projectile Vomiting
Single Most Likely Diagnosis
- Pyloric Stenosis: The clinical presentation of projectile vomiting in a 1-month-old boy, especially with the vomiting occurring after every feeding and the presence of a palpable mass in the right upper quadrant (consistent with a pyloric "olive"), strongly suggests pyloric stenosis. The condition is characterized by the thickening of the pylorus muscle, leading to gastric outlet obstruction. The electrolyte imbalance, with hypochloremic, hypokalemic metabolic alkalosis, is consistent with this diagnosis due to the loss of gastric contents (hydrochloric acid) rich in hydrogen and chloride ions, leading to a compensatory increase in bicarbonate and a decrease in potassium levels as the body tries to conserve hydrogen ions.
Other Likely Diagnoses
- Gastroesophageal Reflux Disease (GERD): Although less likely given the projectile nature of the vomiting and the presence of a palpable mass, GERD could cause significant vomiting. However, it typically does not result in the severe electrolyte imbalance seen in this patient unless there's a significant component of pylorospasm or other complicating factors.
- Infectious Gastroenteritis: This could cause vomiting but usually is accompanied by diarrhea, fever, or other symptoms not present in this case. The absence of bile or blood in the vomit and the specific electrolyte pattern also make this less likely.
Do Not Miss Diagnoses
- Intestinal Obstruction: Although the abdomen is described as soft and nondistended, any condition causing intestinal obstruction (e.g., volvulus, intussusception) could lead to vomiting and must be considered due to the potential for severe consequences if missed.
- Congenital Adrenal Hyperplasia: This condition can cause vomiting in neonates due to salt-wasting forms of the disease, leading to electrolyte imbalances. However, the pattern of electrolyte imbalance and the clinical presentation would typically differ.
Rare Diagnoses
- Congenital Chloride Diarrhea: A rare condition characterized by chronic diarrhea rich in chloride, leading to hypochloremic metabolic alkalosis. It's less likely given the patient's symptoms of vomiting rather than diarrhea.
- Bartter Syndrome: A rare genetic disorder affecting the kidneys' ability to reabsorb potassium, leading to hypokalemic metabolic alkalosis. The clinical presentation and age of onset might not perfectly align with this patient's scenario.