Gastrointestinal USMLE Step 1
Foregut (Ans- Pharynx to duodenum
Midgut (Ans- Duodenum to proximal 2/3 of transverse colon
Hindgut (Ans- Distal 1/3 of transverse colon to anal canal above pectinate line
Abnormal Rostral Fold Closure (Ans- Developmental defect of anterior abdominal wall that leads to
STERNAL DEFECTS
Abnormal Lateral Fold Closure (Ans- Developmental defect of anterior abdominal wall that leads to
OMPHALOCELE, GASTROSCHISIS
Abnormal Caudal Fold Closure (Ans- Developmental defect of anterior abdominal wall that leads to
BLADDER EXSTROPHY
Duodenal atresia (Ans- Failure to recanalize [Trisomy 21]
Jejunal, Ileal, Colonic atresia (Ans- Due to vascular accident [Apple Peel Atresia]
Midgut development (Ans-
- 6th week = Midgut herniates through umbilical ring
- 10th week = Returns to abdominal cavity + ROTATES around
SUPERIOR MESENTERIC ARTERY [SMA] 1 / 4
Malrotation of midgut leads to (Ans- Omphalocele, intestinal atresia or stenosis, Volvulus
Gastroschisis (Ans- Extrusion of abdominal contents through abdominal folds, not covered by peritoneum
Omphalocele (Ans- Persistence of herniation of abdominal contents into umbilical cord, sealed by peritoneum
Esophageal atresia with distal tracheoesophageal fistula (Ans-
- Esophageal atresia [EA] with distal tracheoesophageal fistula [TEF] =
MOST COMMON [85%]
Clinical Manifestations:
- Drooling
- Choking
- Vomiting w/ first feeding
TEF Allows air into stomach [Visible on CXR] CYANOSIS SECONDARY TO LARYNGOSPASM [To avoid reflux -related aspiration]
Clinical Test: Failure to pass nasogastric tube into stomach
H-Type Pure Tracheoesophageal fistula (Ans- Fistula resembles the letter H
Pure Esophageal atresia (Ans- CXR shows gasless abdomen
Congenital Pyloric Stenosis (Ans- Hypertrophy of pylorus causes obstruction Palpable "OLIVE MASS" in epigastric region 2 / 4
NONBILIOUS PROJECTILE VOMITING at 2 -6 weeks old
Occurs in 1/600 live births, more often in FIRST BORN MALES
Lab Findings:
- Hypokalemia
- Hypochloremia
- Metabolic alkalosis [Secondary to vomiting of gastric acid and
subsequent volume contraction]
Treatment: Surgical incision [Pyloromyotomy]
Pancreas (Ans- Derived from foregut VENTRAL PANCREATIC BUDS contribute to UNCINATE PROCESS and
MAIN PANCREATIC DUCT
DORSAL PANCREATIC BUD alone forms body, tail, isthmus, and accessory pancreatic duct
BOTH VENTRAL and DORSAL buds contribute to PANCREATIC HEAD
Annular Pancreas (Ans- VENTRAL pancreatic duct abnormally encircles 2nd part of duodenum Forms a ring of pancreatic tissue that may cause duodenal narrowing
Pancreas Divisum (Ans- VENTRAL and DORSAL parts fail to fuse at 8 weeks Common anomaly Mostly asymptomatic May cause chronic abdominal pain and/or pancreatitis
Spleen (Ans- Arises in mesentery of stomach [MESODERMAL] Supplied by FOREGUT [CELIAC ARTERY] 3 / 4
Retroperitoneal Structures (Ans- Include GI structures that lack mesentery and non-GI structures Injuries to retroperitoneal structures can cause BLOOD OR GAS ACCUMULATION in retroperitoneal space
SAD PUCKER:
- Suprarenal [Adrenal] Glands
- Aorta and IVC
- Duodenum [2nd-4th parts]
- Pancreas [Except tail]
- Ureters
- Colon [Descending and Ascending]
- Kidneys
- Esophagus [Thoracic portion]
- Rectum [Partially]
Falciform Ligament
(Ans- Connects: Liver to anterior abdominal wall
Structures Contained: Ligamentum teres hepatis [Derived from fetal
UMBILICAL VEIN]
DERIVATIVE OF VENTRAL MESENTERY
Hepatoduodenal Ligament
(Ans- Connects: Liver to duodenum
Structures Contained: Portal triad
- Hepatic artery
- Portal vein
- Common bile duct
Notes:
Pringle maneuver = Ligament may be compressed between thumb and index finger placed in omental foramen to control bleeding Borders the omentum foramen which connects the greater and lesser sacs
- / 4