THE USMLE TIMES - #106
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Welcome to issue #106 of The USMLE Times! Welcome to all new members—and welcome back to those returning!
I’m Paul Ciurysek, MD, founder of The USMLE Guys, and this is The USMLE Times. This daily newsletter aims to provide super high-yield USMLE concepts commonly tested on exam day. All content is FREE! If you’d like to work with me and my team, please see the options at the bottom of today’s newsletter. If you’d like to support my efforts, please share the newsletter with a friend.
Here’s what’s on tap for issue #106 of the USMLE Times:
Question of the Week (Congenital Disorders)
This week’s video training (The Art of USMLE Question Strategy)
Question deep-dive & breakdown
Let’s dive in!
A 1-day-old male newborn is evaluated due to significant respiratory distress shortly after birth. The infant experienced frequent episodes of coughing, choking, and cyanosis when breastfeeding attempts were made. He has not passed meconium since birth, and prenatal ultrasound noted polyhydramnios. Physical examination reveals mild abdominal distension and increased work of breathing with scattered rhonchi on lung auscultation. A nasogastric tube insertion was attempted, but it coiled at 10 cm without reaching the stomach. A chest X-ray confirms the presence of air in the stomach. Which of the following is the most likely diagnosis?
A) Esophageal atresia with a distal tracheoesophageal fistula
B) Isolated tracheoesophageal fistula without esophageal atresia
C) Esophageal atresia with proximal tracheoesophageal fistula
D) Isolated esophageal atresia without a tracheoesophageal fistula
E) Esophageal atresia with both proximal and distal tracheoesophageal fistulas
The answer & question breakdown is at the bottom of the post 👇🏼
🔗 LINKS TO RECENT POSTS
USMLE Times Issue #105 - READ HERE
USMLE Practice Question #109 - TRY IT HERE
USMLE Practice Question #110 - TRY IT HERE
This week’s recommended video 👇🏼
ANSWER + QUESTION BREAKDOWN
The mental model used to answer this question comes from our detailed test-taking skills masterclass (check it out if you want to elevate your USMLE test-taking skills) Here’s how to think through this question:
Step 1. Read the vignette and get the actual question: “Which of the following is the most likely diagnosis?”
Step 2. Determine if this is a 1st order, 2nd order, or 3rd order question. This is 2nd order: 1st. Diagnose the primary abnormality; 2nd: Identify the sub-type of the diagnosed condition.
Step 3. Based on your thoughts from step 2 above, ask yourself: “Based on my assessment of the situation, what’s the most likely sub-type I’m dealing with?”
Step 4. Look at the answer choices and select the one that matches your thoughts from step 3 above.
** Aim to take this mental model into all of your USMLE practice questions **
GENERAL ANALYSIS
This vignette describes a 1-day-old male newborn with respiratory distress, frequent coughing, choking, cyanosis during breastfeeding attempts, and failure to pass meconium. Prenatal ultrasound showed polyhydramnios, and physical examination reveals mild abdominal distension and increased work of breathing. A nasogastric tube insertion attempt failed as it coiled at 10 cm, and a chest X-ray showed the presence of air in the stomach.
Key Concepts:
Esophageal atresia (EA): A congenital condition where the esophagus does not form properly, often associated with a tracheoesophageal fistula (TEF).
The most common form is esophageal atresia with a distal tracheoesophageal fistula (TEF), in which the upper esophagus ends blindly, and the lower esophagus connects to the trachea.
Polyhydramnios during pregnancy is a clue for esophageal atresia because the fetus cannot swallow amniotic fluid properly.
The inability to pass a nasogastric tube into the stomach and the presence of air in the stomach on X-ray are highly suggestive of an abnormal connection between the esophagus and trachea, specifically a TEF.
ANSWER CHOICES:
CHOICE A: Esophageal atresia with a distal tracheoesophageal fistula
Explanation: In this condition, the upper esophagus ends in a blind pouch, while the lower esophagus connects abnormally to the trachea via fistula. This allows air to enter the stomach from the trachea, which explains why air is in the stomach on imaging. The inability to pass a nasogastric tube beyond 10 cm suggests that the upper esophagus is not connected to the stomach.
Why Correct: This is the most common type of esophageal atresia (85% of cases) and perfectly fits this patient's presentation: respiratory distress, choking during feeding, failure to pass meconium, polyhydramnios on prenatal ultrasound, and air in the stomach on X-ray.
CHOICE B: Isolated tracheoesophageal fistula without esophageal atresia
Explanation: In isolated TEF (H-type), there is an abnormal connection between the trachea and esophagus without esophageal atresia. The esophagus remains intact.
Why Incorrect: This would not explain why the nasogastric tube coiled at 10 cm or why it was difficult to pass into the stomach. Isolated TEF typically presents with recurrent respiratory infections but not with immediate feeding difficulties or an inability to pass an NG tube.
CHOICE C: Esophageal atresia with proximal tracheoesophageal fistula
Explanation: In this rare variant, a fistula exists between the upper esophagus and trachea.
Why Incorrect: This variant would not cause air in the stomach because there is no connection between the lower esophagus and trachea. Additionally, it would still cause difficulty passing an NG tube into the stomach.
CHOICE D: Isolated esophageal atresia without a tracheoesophageal fistula
Explanation: In isolated esophageal atresia, there is no connection between either part of the esophagus and the trachea.
Why Incorrect: This would result in no air in the stomach on imaging because there would be no connection between the airway and gastrointestinal tract.
CHOICE E: Gallbladder dysfunction with reduced bile acid production and poor fat emulsification
Explanation: In this rare variant, both esophagus ends have abnormal connections to the trachea.
Why Incorrect: This condition would cause more severe respiratory symptoms due to aspiration from both ends of the esophagus. It is much less common than other forms of EA/TEF.
THE VERDICT…
The most likely diagnosis for this newborn is esophageal atresia with a distal tracheoesophageal fistula, which is characterized by:
Respiratory distress shortly after birth
Cyanosis and choking during feeding attempts
Failure to pass meconium
Polyhydramnios on prenatal ultrasound
Coiling of an NG tube in the upper esophagus
Air in the stomach due to abnormal communication between the lower esophagus and trachea
This is also confirmed by imaging findings showing air in the stomach despite an inability to pass an NG tube.
Correct answer: A) Esophageal atresia with a distal tracheoesophageal fistula
That’s it for issue #106 of The USMLE Times!
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