A 3-day-old newborn is brought to the physician because of abdominal distention, inconsolable crying, and 3 episodes of bilious vomiting since the previous evening. He was delivered at home at 40 weeks' gestation by a trained midwife. He has not passed meconium. Physical examination shows abdominal distention, a tight anal sphincter, and an explosive passage of air and feces on removal of the examining finger. Abnormal development of which of the following best explains this patient's condition?
Q12
A 60-year-old gentleman passes away after a car accident. On routine autopsy it is incidentally noted that he has both a ventral and dorsal pancreatic duct. This incidental finding observed by the pathologist is generated due to failure of which of the following embryological processes?
Q13
A 45-year-old woman comes to the physician because of progressive difficulty swallowing solids and liquids over the past 4 months. She has lost 4 kg (9 lb) during this period. There is no history of serious illness. She emigrated to the US from Panama 7 years ago. She does not smoke cigarettes or drink alcohol. Cardiopulmonary examination shows a systolic murmur and an S3 gallop. A barium radiograph of the chest is shown. Histopathologic examination of the esophageal wall is most likely to show which of the following?
Q14
A 3-month-old boy has a malodorous umbilical discharge that developed shortly after umbilical cord separation. He was treated for omphalitis with 3 doses of antibiotics. The vital signs are as follows: blood pressure 70/40 mm Hg, heart rate 125/min, respiratory rate 34/min, and temperature 36.8℃ (98.2℉). On physical examination, he appears active and well-nourished. The skin in the periumbilical region is red and macerated. There is a slight green-yellow discharge from the umbilicus which resembles feces. The remnant of which structure is most likely causing the patient’s symptoms?
Q15
An otherwise healthy 1-month-old girl is brought to the physician because of a 1-day history of multiple episodes of bilious vomiting. She is diagnosed with intestinal malrotation and volvulus and undergoes emergency laparotomy. During surgery, a 3 x 3 cm cystic mass is excised from behind the umbilicus. Microscopic examination of the mass shows mature nonciliated columnar epithelium with some goblet cells lining the inner cyst wall. Dilation of which of the following structures is the most likely cause of this patient's mass?
Q16
A new mother expresses her concerns because her 1-day-old newborn has been having feeding difficulties. The child vomits after every feeding and has had a continuous cough since shortly after birth. The mother denies any greenish coloration of the vomit and says that it is only composed of whitish milk that the baby just had. The child exhibits these coughing spells during the exam, at which time the physician notices the child’s skin becoming cyanotic. The mother states that the child was born vaginally with no complications, although her records show that she had polyhydramnios during her last ultrasound before the delivery. Which of the following is the most likely cause of the patient’s symptoms?
GI development US Medical PG Practice Questions and MCQs
Question 11: A 3-day-old newborn is brought to the physician because of abdominal distention, inconsolable crying, and 3 episodes of bilious vomiting since the previous evening. He was delivered at home at 40 weeks' gestation by a trained midwife. He has not passed meconium. Physical examination shows abdominal distention, a tight anal sphincter, and an explosive passage of air and feces on removal of the examining finger. Abnormal development of which of the following best explains this patient's condition?
A. Submucosa and muscularis externa (Correct Answer)
B. Epithelium and submucosa
C. Muscularis mucosae and lamina propria
D. Muscularis mucosae and serosa
E. Epithelium and lamina propria
Explanation: ***Submucosa and muscularis externa***
- This patient's symptoms (abdominal distention, bilious vomiting, failure to pass meconium, tight anal sphincter with explosive stool passage) are classic for **Hirschsprung disease**.
- Hirschsprung disease is characterized by the absence of **ganglion cells** in the myenteric (Auerbach's) plexus (located between the inner circular and outer longitudinal layers of the muscularis externa) and the submucosal (Meissner's) plexus (located in the submucosa) of the distal colon.
*Epithelium and submucosa*
- The **epithelium** is involved in absorption and secretion, and its primary dysfunction would typically lead to diarrhea or malabsorption, not an obstructive picture like this.
- While the submucosa contains Meissner's plexus, the lack of ganglion cells in the muscularis externa's Auerbach's plexus is equally crucial to the pathophysiology of Hirschsprung disease.
*Muscularis mucosae and lamina propria*
- The **muscularis mucosae** is a thin layer that causes folding of the mucosa, while the **lamina propria** is connective tissue supporting the epithelium; neither is directly implicated in the primary pathology of Hirschsprung disease which involves neural crest cell migration.
- Absence of ganglion cells in these layers would not explain the severe motility disorder observed in Hirschsprung disease involving the entire bowel wall.
*Muscularis mucosae and serosa*
- The **serosa** is the outermost connective tissue layer and is not directly involved in the intrinsic innervation or motility problems seen in Hirschsprung disease.
- Dysfunction of the muscularis mucosae alone would not result in the functional obstruction due to absent peristalsis.
*Epithelium and lamina propria*
- The **epithelium** and **lamina propria** are primarily involved in the digestive and absorptive functions of the gut, and their abnormal development would not typically cause the characteristic features of Hirschsprung disease, which is a neurodevelopmental disorder of the gut.
- The core issue in Hirschsprung disease lies in the neural plexuses controlling motility, not the mucosal lining.
Question 12: A 60-year-old gentleman passes away after a car accident. On routine autopsy it is incidentally noted that he has both a ventral and dorsal pancreatic duct. This incidental finding observed by the pathologist is generated due to failure of which of the following embryological processes?
A. Apoptosis
B. Stem cell differentiation
C. Notochord signaling
D. Neural crest cell migration
E. Fusion (Correct Answer)
Explanation: ***Fusion***
- The pancreas develops from a **ventral and a dorsal bud** that typically **fuse** during development.
- Failure of these two pancreatic buds (and their associated ducts) to completely fuse can result in **pancreas divisum**, where two separate ductal systems persist, corresponding to the dorsal and ventral pancreatic ducts.
*Apoptosis*
- **Apoptosis** (programmed cell death) is crucial for the removal of unwanted cells and sculpting tissues during embryogenesis, such as the formation of digits or the regression of certain structures.
- It does not directly explain the persistence of two separate pancreatic ducts due to non-fusion of developmental buds.
*Stem cell differentiation*
- **Stem cell differentiation** is the process by which less specialized stem cells become more specialized cell types, which is fundamental to organ development and tissue formation.
- While essential for pancreatic development, it doesn't specifically account for the anatomical anomaly of two persistent ducts.
*Notochord signaling*
- **Notochord signaling** is vital for inducing the formation of the neural tube and defining the dorsal-ventral axis of the embryo, as well as influencing the development of other nearby structures.
- This process is not directly related to the fusion of pancreatic buds, which occurs later and is influenced by interactions between mesenchymal and endodermal tissues.
*Neural crest cell migration*
- **Neural crest cells** are multipotent cells that migrate extensively throughout the embryo to form a wide variety of tissues, including parts of the peripheral nervous system, melanocytes, and bone/cartilage of the face and skull.
- Their migratory pathways and derivatives are not directly involved in the development and fusion of the pancreatic ductal system.
Question 13: A 45-year-old woman comes to the physician because of progressive difficulty swallowing solids and liquids over the past 4 months. She has lost 4 kg (9 lb) during this period. There is no history of serious illness. She emigrated to the US from Panama 7 years ago. She does not smoke cigarettes or drink alcohol. Cardiopulmonary examination shows a systolic murmur and an S3 gallop. A barium radiograph of the chest is shown. Histopathologic examination of the esophageal wall is most likely to show which of the following?
A. Presence of intranuclear basophilic inclusions
B. Atrophy of esophageal smooth muscle cells
C. Infiltration of eosinophils in the epithelium
D. Presence of metaplastic columnar epithelium
E. Absence of myenteric plexus neurons (Correct Answer)
Explanation: ***Absence of myenteric plexus neurons***
- This finding is pathognomonic for **Chagas disease** (American trypanosomiasis), caused by *Trypanosoma cruzi*, endemic to Central and South America including Panama.
- The parasite destroys the **myenteric (Auerbach's) plexus neurons** in the esophageal wall, disrupting normal peristalsis and leading to **megaesophagus**.
- This results in **progressive dysphagia for both solids and liquids** and weight loss, as seen in this patient.
- The **cardiac findings** (systolic murmur and S3 gallop) indicate associated **chagasic cardiomyopathy**, another manifestation of chronic Chagas disease.
*Presence of intranuclear basophilic inclusions*
- Suggestive of **cytomegalovirus (CMV) esophagitis**, typically seen in immunocompromised patients (HIV/AIDS, transplant recipients).
- This patient has no immunocompromised state, and CMV does not cause the cardiac manifestations or chronic megaesophagus seen here.
*Atrophy of esophageal smooth muscle cells*
- Not characteristic of Chagas disease or achalasia; these conditions typically show **smooth muscle hypertrophy** due to chronic obstruction.
- Muscle atrophy would not explain the dysphagia, megaesophagus, or cardiac findings.
*Infiltration of eosinophils in the epithelium*
- Indicates **eosinophilic esophagitis**, an allergic condition usually presenting with food impaction and dysphagia mainly for solids.
- Would not explain the cardiac manifestations or the epidemiological connection to Panama.
*Presence of metaplastic columnar epithelium*
- Represents **Barrett's esophagus**, a complication of chronic gastroesophageal reflux disease (GERD).
- The patient's presentation with dysphagia for both solids and liquids, cardiac disease, and megaesophagus on barium study points to a **motility disorder** (Chagas disease), not reflux disease.
Question 14: A 3-month-old boy has a malodorous umbilical discharge that developed shortly after umbilical cord separation. He was treated for omphalitis with 3 doses of antibiotics. The vital signs are as follows: blood pressure 70/40 mm Hg, heart rate 125/min, respiratory rate 34/min, and temperature 36.8℃ (98.2℉). On physical examination, he appears active and well-nourished. The skin in the periumbilical region is red and macerated. There is a slight green-yellow discharge from the umbilicus which resembles feces. The remnant of which structure is most likely causing the patient’s symptoms?
A. Right umbilical artery
B. Omphalomesenteric duct (Correct Answer)
C. Left umbilical artery
D. Umbilical vein
E. Urachus
Explanation: ***Omphalomesenteric duct***
- A persistent **omphalomesenteric duct** (also known as the **vitelline duct**) creates a direct connection between the **small intestine** and the umbilicus, allowing intestinal contents to discharge.
- The description of **malodorous**, **green-yellow discharge resembling feces** strongly indicates a connection to the gastrointestinal tract.
*Right umbilical artery*
- The **umbilical arteries** carry deoxygenated blood and waste products **from the fetus to the placenta** during development.
- Remnants of umbilical arteries do not connect to the gastrointestinal tract or produce fecal-like discharge.
*Left umbilical artery*
- Like the right umbilical artery, the **left umbilical artery** regresses after birth to become the medial umbilical ligament.
- It would not be a source of malodorous, fecal-like umbilical discharge.
*Umbilical vein*
- The **umbilical vein** carries oxygenated blood and nutrients **from the placenta to the fetus**; after birth, it typically obliterates to form the **ligamentum teres hepatis**.
- A patent umbilical vein would not cause fecal-like discharge, though it could be a site of infection or bleeding.
*Urachus*
- The **urachus** is a remnant of the **allantois** and connects the fetal bladder to the umbilicus; a patent urachus can lead to **urinary discharge** from the umbilicus.
- The discharge would be urine, not fecal matter, and would have a characteristic urinary odor and appearance.
Question 15: An otherwise healthy 1-month-old girl is brought to the physician because of a 1-day history of multiple episodes of bilious vomiting. She is diagnosed with intestinal malrotation and volvulus and undergoes emergency laparotomy. During surgery, a 3 x 3 cm cystic mass is excised from behind the umbilicus. Microscopic examination of the mass shows mature nonciliated columnar epithelium with some goblet cells lining the inner cyst wall. Dilation of which of the following structures is the most likely cause of this patient's mass?
A. Urachus
B. Umbilical ring
C. Ovarian follicle
D. Vitelline duct (Correct Answer)
E. Common bile duct
Explanation: ***Vitelline duct***
- The **vitelline (omphalomesenteric) duct** connects the developing midgut to the yolk sac during fetal development and normally obliterates by 7-8 weeks of gestation.
- Incomplete obliteration leads to **omphalomesenteric duct remnants**, which can present as cysts near the umbilicus lined by **intestinal mucosa** (nonciliated columnar epithelium with goblet cells).
- This patient's cystic mass with characteristic **gut-type epithelium** at the umbilical location is diagnostic of a vitelline duct remnant.
*Urachus*
- The urachus is a remnant of the **allantois**, connecting the fetal bladder to the umbilicus. Urachal remnants are lined by **transitional or urothelium**, not columnar epithelium with goblet cells.
- Urachal cysts typically present with umbilical drainage of urine or recurrent infections, with histology showing bladder-type epithelium.
*Umbilical ring*
- The umbilical ring is an **anatomic opening** in the abdominal wall where the umbilical cord passes, not a tubular structure that can form cysts.
- Umbilical hernias or granulomas may occur here, but they do not involve cystic masses lined by intestinal-type epithelium.
*Ovarian follicle*
- Ovarian follicles are located within the **ovaries in the pelvis**, far from the umbilicus.
- The cystic mass described is in an umbilical location with **intestinal epithelium**, completely inconsistent with an ovarian structure.
*Common bile duct*
- Dilation of the common bile duct (**choledochal cyst**) presents with jaundice, abdominal pain, and a right upper quadrant mass, not an umbilical cyst.
- Biliary epithelium is **columnar but typically lacks goblet cells**, which are characteristic of intestinal mucosa.
Question 16: A new mother expresses her concerns because her 1-day-old newborn has been having feeding difficulties. The child vomits after every feeding and has had a continuous cough since shortly after birth. The mother denies any greenish coloration of the vomit and says that it is only composed of whitish milk that the baby just had. The child exhibits these coughing spells during the exam, at which time the physician notices the child’s skin becoming cyanotic. The mother states that the child was born vaginally with no complications, although her records show that she had polyhydramnios during her last ultrasound before the delivery. Which of the following is the most likely cause of the patient’s symptoms?
A. Failure of recanalization of duodenum
B. Obstruction due to failure of rotation of pancreatic tissue
C. Hypertrophy of the pyloric sphincter
D. Failure of neural crest cells to migrate into the myenteric plexus
E. Defective formation of the esophagus with tracheoesophageal connection (Correct Answer)
Explanation: ***Defective formation of the esophagus with tracheoesophageal connection***
- The combination of **feeding difficulties**, vomiting of **undigested milk**, **continuous coughing**, and **cyanosis** during coughing spells in a newborn strongly suggests a **tracheoesophageal fistula (TEF)**, often with **esophageal atresia**.
- **Polyhydramnios** during pregnancy is a classic prenatal sign due to the fetal inability to swallow amniotic fluid.
*Failure of recanalization of duodenum*
- This condition, known as **duodenal atresia**, typically presents with **bilious vomiting** if the obstruction is distal to the ampulla of Vater, or non-bilious if proximal, but typically does not cause continuous coughing or cyanosis during feeds.
- While it causes vomiting, it primarily affects digestion and nutrient absorption, and **polyhydramnios** can also be present due to impaired fetal swallowing.
*Obstruction due to failure of rotation of pancreatic tissue*
- This describes **annular pancreas**, where pancreatic tissue encircles the duodenum, causing obstruction and **vomiting** (often bilious).
- Like duodenal atresia, it doesn't explain the characteristic **coughing and cyanosis** with feeds seen in this case.
*Hypertrophy of the pyloric sphincter*
- **Pyloric stenosis** typically presents later (2-8 weeks of age) with **projectile non-bilious vomiting**, and an **olive-shaped mass** may be palpable in the abdomen.
- It does not cause coughing or cyanosis that correlates directly with feeding in a 1-day-old.
*Failure of neural crest cells to migrate into the myenteric plexus*
- This describes **Hirschsprung disease**, which primarily affects the colon and presents with symptoms of **intestinal obstruction** (e.g., abdominal distension, failure to pass meconium, bilious vomiting if severe).
- It is not associated with feeding difficulties, coughing, or cyanosis in the manner described.
