GI Embryology , Anatomy UWORLD Q&A

A 52-year-old man is brought to the emergency department for hematemesis that began an hour earlier. He has regularly consumed large amounts of alcohol for the last 20 years and has been hospitalized numerous times due to ethanol intoxication. Temperature is 36.7 C (98 F), blood pressure is 90/60 mm Hg, pulse is 106/min, and respirations are 22/min. Physical examination shows jaundice and scleral icterus. Examination of the abdomen reveals a palpable spleen and moderate ascites. Endoscopy reveals bleeding esophageal varices. This patient's current condition most likely resulted from chronic shunting of blood through which of the following veins?

Left gastric vein In cirrhosis, portal hypertension arises from increased resistance to portal flow at the hepatic sinusoids. This causes increased pressure in the portosystemic collateral veins within the lower end of the esophagus, anterior abdomen, and lower rectum. Dilation of these collateral vessels is responsible for the esophageal varices, caput medusae, and anorectal varices commonly seen in patients with cirrhosis.

A 58-year-old man is being evaluated for constipation and weight loss over the last several months. During the past 2 weeks, he has had several episodes of rectal bleeding. The patient has never had a screening colonoscopy. Examination shows a soft and nontender abdomen without masses or organomegaly. Digital rectal examination reveals a firm palpable mass in the rectal vault. Flexible rectosigmoidoscopy shows a large ulcerative mass in the middle third of the rectum extending to the rectosigmoid junction. He undergoes surgical resection of the rectosigmoid colon. Frozen section analysis reveals clear margins of the colon specimen with metastases in the pararectal lymph nodes. Which of the following lymph nodegroups should be sampled in this patient for further assessment of metastatic disease?

Lymphatic drainage of the rectum proximal to the anal dentate line occurs via the inferior mesenteric and internal iliac lymph nodes. Areas distal to the dentate line drain primarily into the inguinal nodes.

A 4-week-old boy is hospitalized with persistent vomiting, fussiness, and feeding intolerance. The emesis was initially clear but became bilious in the last few hours. The infant had been breastfeeding exclusively. His temperature is 37.2 C (99.0 F). Blood pressure and pulse are normal. Physical examination shows a normal abdomen with no rebound or guarding. An upper gastrointestinal series is obtained urgently to evaluate for malrotation and volvulus and shows normal rotation but constriction of the duodenum. An abdominal CT scan reveals pancreatic tissue encircling the duodenum. Which of the following is the most likely cause of this patient's condition?

Annular pancreas, or pancreatic tissue encircling the descending duodenum, is caused by failure of the ventral pancreatic bud to properly migrate and fuse with the dorsal bud during the seventh and eighth week of fetal development. Annular pancreas is usually asymptomatic but may present with duodenal obstruction or pancreatitis.

A 26-year-old previously healthy man is brought to the emergency department after a motor vehicle collision. The patient was driving while wearing a seatbelt when his car was hit on the left side by another vehicle. He has since had persistent left shoulder pain. He also has nausea and hiccups. The patient's blood pressure is 90/60 mm Hg and pulse is 115/min. On examination, he has a bruise on the left lower chest wall with tenderness to palpation along the area. Chest auscultation reveals normal heart sounds and bilaterally equal breath sounds. He has a rigid and tender abdomen. Which of the following is the most likely diagnosis?

Any abdominal process (eg, ruptured spleen, peritonitis, hemoperitoneum) irritating the phrenic nerve sensory fibers around the diaphragm can cause referred pain to the C3-C5 shoulder region (Kehr sign)

A 21-year-old man comes to the emergency department due to abdominal pain, nausea, and vomiting. The patient started having vague periumbilical pain in the morning. Over the next several hours, the pain became more severe, sharper, and localized to the right lower abdominal quadrant. Temperature is 38.3 C (100.9 F), blood pressure is 132/84 mm Hg, pulse is 102/min, and respirations are 12/min. Physical examination shows maximal tenderness in the right lower abdomen two-thirds of the distance from the umbilicus to the anterior superior iliac spine. Bowel sounds are decreased. Laboratory studies reveal a leukocyte count of 16,000/mm3. The change in this patient's pain characteristics is most likely explained by which of the following?

Appendicitis causes dull visceral pain at the umbilicus due to afferent pain fibers entering at the T10 level in the spinal cord. Progressive inflammation in the appendix irritates the parietal peritoneum and abdominal wall to cause more severe somatic pain shifting from the umbilicus to McBurney's point (two-thirds of the distance from the umbilicus to the anterior superior iliac spine).

A 46-year-old woman with a history of hiatal hernia and severe gastroesophageal reflux undergoes antireflux surgery. The reflux symptoms were refractory to medical therapy, so an endoscopic fundoplication procedure is performed. During surgery, the hiatal defect is repaired, and the gastric fundus is mobilized and wrapped around the lower esophagusto reinforce the lower esophageal sphincter. No esophageal or gastric injuries occurred, but a neural structure traversing the esophageal hiatus of the diaphragm was inadvertently injured. Which of the following is the most likely potential effect of this operative injury?

Branches of the vagus nerve (ie, anterior and posterior vagal trunks) pass through the esophageal hiatus. Damage to these branches, which can occur during esophageal hiatal hernia repair (eg, fundoplication), may result in delayed gastric emptying and gastric hypochlorhydria.

A 48-year-old man is evaluated for abdominal pain and diarrhea. The patient characterizes his stool as voluminous and foul smelling. He has no significant past medical history. The patient drinks 6 cans of beer daily. On examination, he has normal bowel sounds and mild epigastric tenderness. A 72-hour stool collection shows excessive excretion of fecal fat. A CT scan of the abdomen is shown in the image below. Involvement of which of the following structures is most likely causing this patient's symptoms?

Chronic pancreatitis often presents with epigastric pain and pancreatic exocrine insufficiency resulting in fat malabsorption/steatorrhea. On abdominal CT scan, the pancreas can be identified by its head in close association with the second part of the duodenum; its body overlying the aorta, left kidney, and renal vessels; and its tail lying within the splenorenal ligament

A term newborn boy is evaluated in the neonatal intensive care unit for respiratory distress. Apgar scores are 2 and 5 at 1 and 5 minutes, respectively. Respirations are 84/min. On examination, the patient has a barrel chest with a scaphoid abdomen and mild cyanosis of his extremities. Auscultation shows absent breath sounds on the left; right lung aeration is normal. Chest x-ray reveals multiple fluid-containing cystic areas on the left and a mediastinal shift to the right. Which of the following embryologic events most likely failed to occur in this patient?

Congenital diaphragmatic hernia is caused by failure of the pleuroperitoneal folds to close. Immediately after birth, newborns have respiratory distress, unilateral decreased breath sounds, and a scaphoid abdomen, with imaging revealing thoracic bowel loops and mediastinal shift.

A 62-year-old man comes to the physician due to intermittent groin pain. The pain is most severe when the patient lifts heavy loads and after a long day at his job as a construction worker. Physical examination shows a right-sided groin bulge directly above the inguinal ligament. The bulge increases in size when he bears down. An ultrasound reveals that the mass originates medial to the inferior epigastric vessels. This patient's condition is most likely caused by which of the following?

Direct inguinal hernias occur most commonly in older men due to weakness of the transversalis fascia. They protrude medial to the inferior epigastric vessels into the Hesselbach triangle and pass only through the superficial inguinal ring with no direct route to the scrotum.

A 74-year-old man comes to the office due to chronic constipation. Bowel movements occur once every 3 days and are hard and pellet-like. The patient frequently strains when he tries to defecate and never feels completely evacuated. The constipation is occasionally so severe that he uses his fingers to remove stool from the anorectal vault. Medical history is significant for Parkinson disease, for which he takes carbidopa-levodopa. Vital signs are unremarkable. A resting tremor is present on physical examination. The abdomen is distended but nontender to palpation. This patient's condition is most likely due to inadequate relaxation of which of the following muscles during defecation?

Dyssynergic defecation occurs when the puborectalis muscle or the internal or external anal sphincter fails to relax during defecation, leading to chronic constipation. Dyssynergic defecation is usually considered a functional disorder and occurs more commonly in the elderly but may also occur with certain neurologic disorders (eg, Parkinson disease, multiple sclerosis) or trauma

A 46-year-old man comes to the emergency department due to severe anal pain. He has a history of chronic constipation and on several occasions has noticed streaks of blood on the tissue paper after wiping. He has no abdominal pain, nausea, vomiting, or weight loss and has no family history of malignancy. His temperature is 36.7 C (98 F). On examination, there are several large, purplish-blue sacs bulging into the analcanal, one of which originates below the dentate line and is extremely tender. Excision of the tender lesion under local anesthesia is planned. The anesthetic agent most likely blocks sensory impulses carried by which of the following structures?

External hemorrhoids, which originate below the dentate line, are covered by modified squamous epithelium and have cutaneous (somatic) nervous innervation from the inferior rectal nerve, a branch of the pudendal nerve.

A 65-year-old woman comes to the emergency department due to nausea, vomiting, and abdominal pain that began about 6 hours ago. She has also had vague pelvic pain over the last few months but says her pain has never been this severe. Temperature is 38.4 C (101 F), blood pressure is 141/90 mm Hg, pulse is 92/min, and respirations are 18/min. Physical examination shows a moderately distended abdomen. There is a tender bulge below the inguinal ligament, lateral to the pubic tubercle. The overlying skin is erythematous. Which of the following structures is most likely immediately lateral to the bulge?

Femoral hernias can present with groin discomfort and a tender bulge on the upper thigh inferior to the inguinal ligament, lateral to the pubic tubercle and lacunar ligament. The structure that lies immediately lateral to the hernia within the femoral sheath is the femoral vein. Incarceration and strangulation are common complications of femoral hernias.

A 24-year-old, previously healthy woman comes to the emergency department due to hematemesis. The patient was binge drinking when she became very nauseated and began vomiting repeatedly. She reports vomiting approximately a cupful of bright red blood during the most recent episode. Blood pressure is 136/78 mm Hg and pulse is 96/min. Physical examination shows mild epigastric tenderness. Endoscopy reveals a longitudinal mucosal laceration in the distal esophagus with active bleeding.Endoscopic treatment is performed, but the bleeding recurs. Angiography with transarterial embolization of the bleeding vessel is planned. A distal branch of which of the following blood vessels is most likely to be embolized during this patient's procedure?

Forceful retching can lead to superficial mucosal lacerations (eg, Mallory-Weiss tears) of the distal esophagus, an area that receives most of its arterial blood supply from branches of the left gastric artery. The proximal esophagus receives arterial blood from the inferior thyroid artery, whereas the midesophagus is supplied by branches of the thoracic aorta.

A 68-year-old woman comes to the emergency department due to a 2-day history of crampy abdominal pain and vomiting. The patient has had no hematemesis, melena, or hematochezia. She has a history of hypertension, type 2 diabetes mellitus, and coronary artery disease. Several months ago, the patient had an episode of acute calculous cholecystitis that was managed non-operatively. Physical examination shows a distended, tympanic abdomen with high-pitched bowel sounds. Abdominal x-ray reveals air in the gallbladder and biliary tree. This patient's gallstone has most likely lodged in which of the following sites?

Gallstone ileus results from passage of a large gallstone through a cholecystenteric fistula into the small bowel, where it ultimately causes obstruction at the ileum. Patients typically present with symptoms/signs of small bowel obstruction, and an abdominal x-ray may reveal gas within the gallbladder and biliary tree.

A 54-year-old man is evaluated for episodic abdominal discomfort, bloating sensation, flatulence, and occasional diarrhea. He has no blood in the stool or weight loss. The patient has tried avoiding dairy products, but the symptoms did not improve. On examination, there is mild epigastric tenderness on deep palpation. Stool occult blood testing is positive. Histopathological evaluation of hyperemic mucosa seen during gastrointestinal endoscopy reveals hyperplasia of branched, tubular submucosal glands containing alkaline secretions. Which of the following areas is the most likely site of biopsy in this patient?

Gastric acid is neutralized by bicarbonate from the submucosal glands of the duodenum (Brunner glands) and from pancreatic duct secretions. Chronic overproduction of gastric acid can lead to hyperplasia of the submucosal glands

A 42-year-old man comes to the office with rectal bleeding. He used to have occasional streaks of bloodon the tissue after wiping, but for the past several days he has seen blood dripping into the toilet at the end of defecation. The patient reports chronic constipation and has to strain while having a bowel movement but has no rectal or abdominal pain. He works as a truck driver, and his diet consists mainly of hamburgers and French fries. Abdominal examination is unremarkable. There is no mass or tenderness on digital rectal examination, but anoscopy shows bulging purplish-blue mucosal lesions above the dentate line. Rubber band ligation of the lesions is most likely to involve which of the following?

Hemorrhoids result from abnormal distension of a portion of the anal arteriovenous plexus. The vascular components of internal hemorrhoids drain into the superior rectal vein, which subsequently drains into the inferior mesenteric vein. Band ligation of hemorrhoids cuts off their blood supply, causing them to degenerate.

A 54-year-old man comes to the office due to several months of heartburn, acid regurgitation, and dysphagia. He has taken antacids and over-the-counter medications without relief. Medical history includes hypertension and hyperlipidemia. The patient does not use tobacco, alcohol, or illicit drugs. Vital signs are within normal limits. BMI is 32 kg/m2. Physical examination is unremarkable. Upright chest x-ray shows an opacity with an air-fluid level behind the heart. A subsequent barium swallow reveals the proximal stomach herniating through the esophageal hiatus. Which of the following pathophysiological changes most likely contributed to this patient's current condition?

Hiatal hernias occur when contents of the abdominal cavity herniate through the diaphragm at the esophageal hiatus into the thoracic cavity. Sliding hiatal hernias occur due to laxity of the phrenoesophageal membrane, leading to herniation of the gastroesophageal junction and proximal stomach, whereas paraesophageal hernias occur due to defects in the membrane, resulting in the gastric fundus herniation.

Researchers studying neural crest cell migration in a human fetus observe normal activity beginning at the 8th week of embryogenesis with interruption during the 12th week, when migration is typically completed. Which of the following structures is most likely to lack innervation as a result of this disruption?

Hirschsprung disease is caused by abnormal migration of neural crest cells (ganglion cell precursors) during embryogenesis. Because neural crest cells migrate caudally down the bowel from the foregut, the rectum is always affected

A 27-year-old woman,gravida 1 para 0, with gestational diabetes mellitus comes to the hospital at 38 weeks gestation for evaluation of abdominal pain. The patient is scheduled for an elective cesarean section at 39 weeks as a recent ultrasound revealed that the estimated fetal weight is 5200g (11 lb 4 oz). Examination reveals that the patient is in active labor and the fetus is in breech presentation; an urgent cesarean section is performed. During the surgery, the rectus abdominus muscle is split vertically, but space appears to be limited. In anticipation of a large-for-gestational-age baby, a decision is made to transect the rectus abdominis muscle. If the rectus abdominis muscle is incised laterally, which of the following structures is at greatest risk of injury?

Horizontal transection of the rectus abdominis muscle must be performed with great caution as the inferior epigastric arteries enter this muscle at the level of the arcuate line. The inferior epigastric arteries below the arcuate line are susceptible to injury (eg, hematoma) due to lack of a supporting posterior rectus sheath

A 3-day-old girl is brought to the emergency department by her parents due to persistent vomiting and refusal to feed. The vomiting began early in the morning and has been a greenish-yellow color. The emesis does not contain blood. The infant appears dehydrated. Her heart rate is 175/min and blood pressure is within normal limits. After initial evaluation is complete, the infant undergoes laparotomy. Findings include a normal-appearing duodenum, the absence of a large segment of jejunum and ileum, and the remainder of the distal ileum winding around a thin vascular stalk. Which of the following intrauterine processes is most likely responsible for this patient's condition?

Intestinal atresia distal to the duodenum occurs due to vascular accidents in utero. "Apple-peel" atresia occurs when the superior mesenteric artery is obstructed. The result is a blind-ending proximal jejunum; a length of absent bowel and mesentery; and, finally, a terminal ileum spiraled around an ileocolic vessel.

A 3-day-old boy is brought to the emergency department due to poor feeding, emesis, and lethargy over the last 24 hours. The patient was born via uncomplicated spontaneous vaginal delivery to a 30-year-old woman who had a normal pregnancy. The boy was discharged from the newborn nursery yesterday and was breastfeeding exclusively until the onset of symptoms. Stool and urine output were normal while he was in the newborn nursery. The patient is afebrile and normotensive but tachycardic and tachypneic. He appears dehydrated, and the abdomen is distended. The patient vomits during the examination, and the vomitus is shown in the exhibit. On laparotomy, fibrous bands are seen extending from the cecum and right colon to the retroperitoneum, causing extrinsic compression of the duodenum. Which of the following embryologic processes most likely failed in this patient?

Intestinal malrotation results when the midgut undergoes incomplete embryological counterclockwise rotation. It can present as intestinal obstruction (due to compression by the adhesive bands) and midgut volvulus (intestinal ischemia due to twisting around the blood vessels).

An 18-year-old man comes to the clinic for evaluation of fatigue. He started to notice the fatigue several months ago, and it has progressively worsened. The patient takes no medications. He does not use alcohol or illicit drugs but smokes a pack of cigarettes daily. Examination shows conjunctival pallor. The abdomen is soft and nontender with no organomegaly. Laboratory evaluation shows hemoglobin is 8.5 g/dL, and stool testing for blood is positive. Further workup reveals mild hemorrhaging within the ileum. Just proximal to the site of hemorrhage is a 5-cm outpouching of intestine.

Meckel diverticulum is a congenital outpouching of the intestine that commonly contains heterotopic gastric mucosa. Hydrochloric acid production by gastric epithelium can lead to intestinal ulceration and subsequent lower gastrointestinal bleeding and anemia.

A 4-year-old girl is brought to the office after her parents noticed dark red blood on her toilet tissue after a bowel movement. She has had no abdominal pain, dysuria, or discomfort with defecation. The girl has no known medical conditions and takes no medications. Temperature is 36.7 C (98.1 F), blood pressure is 100/40 mm Hg, and pulse is 112/min. Examination shows a soft and nontender abdomen, and bowel sounds are present. Hemoglobin is 8 g/dL, and platelet count is 215,000/mm3. Coagulation studies are normal. Sequential imaging using 99mTc-pertechnetate scintigraphy demonstrates focal radiotracer accumulation in the right lower quadrant. Which of the following embryologic processes most likely resulted in this patient's condition?

Meckel diverticulum results from incomplete obliteration of the vitelline duct and usually presents with painless lower gastrointestinal bleeding. 99mTc-pertechnetate localizes to heterotopic gastric mucosa that is often contained within a Meckel diverticulum, and uptake in the periumbilical area or right lower quadrant is diagnostic.

A 30-year-old man comes to the emergency department due to severe abdominal pain. The patient first developed the pain yesterday, and it has become increasingly worse. Over the last few hours, he has also developed bilious emesis. The patient has had no previous surgeries. Temperature is 37.8 C (100 F) and pulse is 110/min. Physical examination shows diffuse abdominal tenderness with guarding during palpation. Abdominal imaging reveals bowel wall thickening within a blind pouch connected to the ileum. A laparotomy is performed. During the procedure, a fibrous band is seen attaching the end of the pouch to the umbilicus. The walls of this pouch are most likely composed of which of the following?

Meckel diverticulum, which classically causes painless hematochezia but can present with acute abdominal pain if inflamed (ie, diverticulitis), is an anatomic connection between the ileum and umbilicus resulting from incomplete obliteration of the vitelline duct. This congenital anomaly is a true diverticulum, consisting of all 3 layers of the intestinal wall (mucosa, submucosa, and muscularis).

A 75-year-old man is brought to the emergency department due to acute-onset profuse vomiting of large amounts of bright red blood. He has had intermittent, dull epigastric pain for the last 3 months. Medical history is significant for chronic obstructive pulmonary disease with multiple exacerbations and lumbar spinal stenosis. The patient has smoked 1 pack of cigarettes daily for 40 years. Blood pressure is 70/40 mm Hg and pulse is 120/min. Examination shows epigastric tenderness. The patient dies an hour after admission despite resuscitation efforts. Autopsy shows a deep peptic ulcer localized proximally on the lesser curvature of the stomach. The ulcer most likely penetrated which of the following arteries?

Most gastric ulcers arise along the lesser curvature of the stomach, usually at the transitional zone between the gastric corpus (body) and antrum. The left and right gastric arteries run along the lesser curvature and are likely to be penetrated by ulcers, causing gastric bleeding.

A 52-year-old man comes to the office for a painless mass in his right groin. He noticed the mass several weeks ago, and it has slowly enlarged. The patient has a history of HIV, for which he takes antiretroviral therapy. He has not had any new sexual partners recently. Temperature is 37.1 C (98.8 F). On examination, several enlarged, hard lymph nodes are palpated in the right inguinal area inferior to the inguinal ligament. An excisional biopsy is performed, and histopathology shows malignant cells. The malignant cells found in this patient most likely originated from which of the following sites?

Most of the cutaneous lymph from the umbilicus down, including the anus below the dentate line, drains to the superficial inguinal lymph nodes. Exceptions are the glans penis and posterior calf, which drain to the deep inguinal nodes.

A 23-year-old-man is brought to the emergency department after he was stabbed in the right upper quadrant of the abdomen. His blood pressure is 70/42 mm Hg, pulse is 135/min, and respirations are 26/min; pulse oximetry shows oxygen saturation of 95% on room air. Physical examination shows a stab wound 2 cm inferior to the right costal margin. The patient's abdomen is firm and distended. Focused assessment with sonography for trauma (FAST) is positive for blood in the right upper quadrant. He is taken for immediate laparotomy, and approximately 1 liter of blood is evacuated from the peritoneal cavity. Brisk, nonpulsatile bleeding is seen emanating from behind the liver. The surgeon occludes the hepatoduodenal ligament, but the patient continues to hemorrhage. Which of the following structures is the most likely source of this patient's bleeding?

Occlusion of the portal triad can be used to distinguish the source of right upper quadrant bleeding. If the bleeding subsides following occlusion, the source is likely to be the hepatic artery or portal vein. If hepatic bleeding persists after occlusion, the inferior vena cava or hepatic veins are likely to be injured

A 56-year-old man comes to the cardiology clinic because of fatigue, palpitations, and exertional dyspnea over the last several weeks. On physical examination, his heart rate is irregular and measures 122 beats per minute, while his blood pressure is 110/70 mm Hg. The patient undergoes further work-up, including ECG, radiographic studies, and laboratory studies. His ECG shows atrial fibrillation and trans-esophageal echocardiography reveals a thrombus in a dilated left atrium. In the event of an interruption of blood flow secondary to arterial occlusion, which of the following organs would be least vulnerable to infarction?

Organ susceptibility to infarction after occlusion of a feeding artery is ranked from greatest to least as follows: central nervous system, myocardium, kidney, spleen, and liver. The presence of a dual and/or collateral blood supply (as seen in the liver, which is supplied by the hepatic artery and portal vein) enables an organ to tolerate arterial occlusion better than those with end-arterial circulations.

Indirect inguinal Male infants

Patent processus vaginalis Originates lateral to inferior epigastric vessels Protrudes through the deep inguinal ring into inguinal canal May extend into the scrotum (following spermatic cord)

A 67-year-old man comes to the emergency department due to progressive fever and lethargy. The patient has also had severe right shoulder and abdominal pain, nausea, and vomiting for the past 2 days. He had an appendectomy during childhood and a pacemaker placed 10 years ago for symptomatic sinus bradycardia. He has no other medical problems and takes no medications. The patient does not use tobacco but drinks an occasional beer. Temperature is 38.4 C (101.1 F), blood pressure is 80/50 mm Hg, and pulse is 120/min and regular. Abdominal examination shows generalized tenderness with rebound tenderness. Right shoulder examination is normal. Upright chest x-ray is shown. Which is the most likely cause of this patient's condition?

Pneumoperitoneum is air or gas in the peritoneal cavity; it can be seen as free air under the diaphragm in an upright chest x-ray. The most common cause is a perforated duodenal ulcer, but perforation can occur anywhere along the gastrointestinal (or female reproductive) tract. Subsequent peritonitis can lead to diffuse abdominal pain with rebound and guarding, sometimes with referred shoulder pain due to diaphragmatic irritation.

A 39-year-old woman is brought to the emergency department after an end-to-end motor vehicle collision. She was a restrained passenger and denies hitting her head or losing consciousness but has had abdominal pain and nausea since the accident. The patient's blood pressure is 115/55 mm Hg and pulse is 96/min and regular. On examination, she has ecchymosis over the area of the seat belt and abdominal tenderness. CT scan of the abdomen reveals a retroperitoneal hematoma. This patient most likely experienced which of the following injuries?

Retroperitoneal hematoma is a common complication of abdominal and pelvic trauma. The pancreas is a retroperitoneal organ, and pancreatic injury is frequently a source of retroperitoneal bleeding

A 64-year-old man comes to the emergency department after an episode of hematemesis. He also reports dark stools and abdominal pain for the past several days. The patient has a history of chronic pancreatitis. Abdominal examination shows epigastric tenderness to palpation. Rectal examination is notable for black, guaiac-positive feces. Upper gastrointestinal endoscopy reveals a bleeding spot within a cluster of enlarged tortuous veins in the gastric fundus. The rest of the stomach and esophagus appears normal. Increased pressure in which of the following vascular structures is the most likely cause of this patient's condition?

Splenic vein The short gastric veins drain blood from the gastric fundus into the splenic vein. Pancreatic inflammation (eg, pancreatitis, pancreatic cancer) can cause a blood clot within the splenic vein, which can increase pressure in the short gastric veins and lead to gastric varices only in the fundus.

A 32-year-old female presents to your office with severe nausea and recurrent bilious vomiting. Her symptoms initially began as postprandial epigastric pain and early satiety, but have progressed over the last two weeks. She works as an actress, and tells you that her symptoms only started when she "landed a role in a soap opera" and was inspired to lose 25 lbs. on a "crash diet". On physical exam, her abdomen is tender and slightly distended with high-pitched bowel sounds. Concerned about a small bowel obstruction, you admit the patient to the hospital. A laparotomy is performed, and it is observed that the angle between her superior mesenteric artery and her aorta is significantly decreased. Which of the following structures is most likely to be obstructed by the artery?

Superior mesenteric artery syndrome occurs when the transverse portion of the duodenum is entrapped between the SMA and aorta, causing symptoms of partial intestinal obstruction. This syndrome occurs when the aortomesenteric angle critically decreases, secondary to diminished mesenteric fat, pronounced lordosis, or surgical correction of scoliosis.

A 58-year-old man comes to the office with upper abdominal pain, fatigue, and anorexia. He says his symptoms began about a month ago and seem to be getting worse. The patient has a history of cirrhosis due to chronic hepatitis C. Physical examination shows cachexia and worsening ascites. Imaging studies reveal a large mass in the right hepatic lobe consistent with unresectable hepatocellular cancer. The patient is scheduled to undergo percutaneous embolization of the artery supplying the tumor. Contrast material administration into which of the following structures is most likely to visually enhance the artery prior to embolization?

The celiac trunk is the first main branch of the abdominal aorta; it provides oxygenated blood to the spleen, stomach, liver, abdominal esophagus, and parts of the duodenum and pancreas. The proper hepatic artery branches off the common hepatic artery from the celiac trunk and provides arterial blood supply to the liver.

A 32-year-old man presents to the emergency department with a one-day history of severe abdominal pain along with nausea and vomiting. His pain is constant and radiates to his back. He admits to "drinking a few beers" with some friends a couple days ago. Laboratory studies reveal significantly elevated amylase and lipase. An abdominal CT shows pancreas divisum, a common congenital anomaly that results from failure of the pancreatic ductal systems of the ventral and dorsal pancreatic primordia to fuse during embryogenesis. Which of the following pancreatic structures is derived from the ventral pancreatic primordium?

The dorsal pancreatic bud forms the majority of pancreatic tissue (body, tail, and most of the head). The ventral pancreatic bud is a precursor of the uncinate process, inferior/posterior portion of the head, and major pancreatic duct (of Wirsung). Failure of the dorsal and ventral pancreatic buds to fuse leads to pancreas divisum. In this condition, the pancreatic ductal systems remain separate, with the accessory duct draining the majority of the pancreas.

A 47-year-old man comes to the office due to dysphagia. The patient says that it feels like food has been getting stuck in his throat over the last month. He has changed his diet to accommodate his symptoms and now consumes only liquid foods. The patient has a long history of postprandial heartburn that sometimes awakens him from sleep. He has treated his heartburn with over-the-counter antacids but usually only has partial relief. A thoracic CT image near the level of the aortic arch is shown below. This patient's symptoms are most likely related to pathology involving which of the following structures?

The esophagus is located between the trachea and the vertebral bodies in the superior thorax. It is typically collapsed with no visible lumen on CT images of the chest.

A 52-year-old man is brought to the emergency department due to repeated vomiting that began 2 hours ago. His vomit is dark brown and has a granular consistency. The patient has a history of dyspepsia, for which he takes over-the-counter antacids as needed and degenerative knee arthritis, for which he takes naproxen regularly. He drinks 2-3 beers daily. Temperature is 36.7 C (98 F), blood pressure is 114/62 mm Hg, pulse is 102/min, and respirations are 14/min. Physical examination reveals mild epigastric tenderness with no rebound or guarding. Hemoglobin is 9 g/dL. Endoscopy shows a deep, bleeding ulcer on the posterior wall of the duodenal bulb. This patient's ulcer has most likely penetrated which of the following arteries?

The gastroduodenal artery lies along the posterior wall of the duodenal bulb and is likely to be eroded by posterior duodenal ulcers. Ulceration into the gastroduodenal artery can be a source of life-threatening hemorrhage.

A 71-year-old man comes to the emergency department due to several episodes of bright red blood per rectum. His recent colonoscopy revealed numerous colonic diverticula. Laboratory studies on admission are notable for a hemoglobin of 8.2 g/dL with an unremarkable coagulation profile. An abdominal angiogram shows active bleeding from the sigmoid colon. Catheter embolization is planned via the femoral artery. During the procedure, the arterial catheter is most likely to proceed in which of the following orders?

The hindgut encompasses the distal one-third of the transverse colon, the descending colon, the sigmoid colon, and the rectum. These structures receive their main arterial blood supply from the inferior mesenteric artery.

A 55-year-old man comes to the office due to swelling in his groin that he first noticed 2 weeks ago. Physical examination shows a bulge above the inguinal ligament that increases in size when the patient is asked to cough. He is referred to a surgeon and scheduled to undergo elective laparoscopic hernia repair. Which of the following landmarks will best aid the surgeon in distinguishing an indirect from a direct inguinal hernia?

The inferior epigastric vessels are useful as a landmark during laparoscopic hernia repair to classify the type of inguinal hernia. Indirect inguinal hernias protrude through the deep inguinal ring into the inguinal canal lateral to the inferior epigastric vessels. In contrast, direct inguinal hernias protrude through Hesselbach's triangle medial to the inferior epigastric vessels.

A 47-year-old morbidly obese woman comes to the physician seeking advice regarding weight loss. She has tried diet and exercise a number of times without success. Her other medical problems include type 2 diabetes mellitus and obstructive sleep apnea. Her body mass index is 43 kg/m2. After a discussion about available surgical options, she expresses interest in the adjustable gastric band, an inflatable silicone device that is placed around the cardiac part of the stomach. In order to encircle the stomach, the band must pass through which of the following structures?

The lesser omentum is a double layer of peritoneum that extends from the liver to the lesser curvature of the stomach and the beginning of the duodenum. It is divided into the hepatogastric and hepatoduodenal ligaments.

A 62-year-old man comes to the emergency department due to acute-onset constipation. His last bowel movement was 4 days ago; before that time, his stools were always regular. Review of systems is positive for dry cough, increasing low back pain, a 9-kg (20-lb) weight loss in the past month, and increasing difficulty with urination. He has smoked 2 packs of cigarettes daily for 30 years. Vital signs are within normal limits. Point tenderness is elicited with palpation over the lower spine. Bilateral lower extremity weakness is present, and sensation is impaired in the perineal region. Chest x-ray reveals a right lung mass. Dysfunction of which of the following nerves best explains this patient's constipation?

The pelvic splanchnic nerves (S2-S4) provide parasympathetic innervation to the bowel and bladder, and their impairment in cauda equina syndrome can cause constipation and difficulty urinating. Other signs of cauda equina syndrome include radicular low back pain and leg weakness (sciatic nerve) as well as saddle anesthesia (pudendal, ilioinguinal nerves).

A 53-year-old man who has not seen a physician in years presents to your office complaining of abdominal distention. He states "Last month my stomach started to swell up and it hasn't gotten any better". He has no other medical problems. The patient admits to drinking 10-12 beers a day for the last 20 years. His temperature is 36.7 C (98 F), blood pressure is 116/72 mm Hg, pulse is 78/min and respirations are 20/min. On examination his abdomen is distended with engorged paraumbilical veins. There is also palmar erythema and multiple spider angiomas are present. You decided to place him on a low-salt diet and start therapy with furosemide and spironolactone, with subsequent improvement of his abdominal distention.Before beginning this patient's treatment, which of the following structures labeled on the image below is expected to have an increased pressure?

The portal vein can be identified on cross-sectional scans lying medial to (or just within) the right lobe of the liver and anterior to the inferior vena cava. The pressure in the portal system is elevated in liver cirrhosis.

A 23-year-old man comes to the office with a 2-week history of malaise, loss of appetite, and vague abdominal pain. The patient has had no nausea, vomiting, changes in his bowel habits, dysuria, urinary frequency, or hematuria. He had an appendectomy for acute appendicitis at age 15; his medical history is otherwise unremarkable. He does not use tobacco or alcohol and has had no recent travel. His father was diagnosed with colon cancer at age 60. Physical examination reveals normal bowel sounds and no guarding or rebound tenderness. Abdominal CT scan obtained as part of this patient's evaluation points to the "spleen". "spleen" originates from which of the following embryologic divisions?

The spleen is a large, wedge-shaped lymphatic organ that is situated in the posterior superior portion of the left abdominal cavity. It is derived from mesoderm in the dorsal mesentery during embryonic development.

A35-year-old man comes to the emergency department due to persistent abdominal pain. Yesterday, during a soccer game, he suffered a full-speed collision with another player. He had diffuse abdominal pain at the time but did not seek care until this morning, when the pain seemed to worsen. As part of the patient's evaluation, a CT scan of the abdomen is obtained and shown in the image below. It is determined that his injury involves an organ that is supplied mainly by an artery of the foreguteven though the organ itself is not a foregut derivative. Which of the following organs is most likely to be injured in this patient?

The spleen is of mesodermal origin (the dorsal mesentery). Although it is supplied by the splenic artery (a branch of the major foregut vessel, the celiac trunk), it is not a foregut derivative.

A 56-year-old man comes to the physician complaining of early satiety, nausea, and vague epigastric pain for the past 4 months. He has a 36-pack-year smoking history and admits to drinking alcohol daily for the past 15 years. On physical examination, the patient appears thin and cachectic. Palpation of his abdomen reveals splenomegaly. Abdominal CT scan shows a large irregular mass extending posteriorly from the greater curvature of the stomach, impinging on the splenic artery and vein as they pass below. Tissues supplied by which of the following arteries would most likely be affected by compression of the splenic artery?

The splenic artery originates from the celiac artery and gives off several branches to the stomach and pancreas (pancreatic, short gastric, and left gastroepiploic arteries) before finally reaching the spleen. Due to poor anastomoses, the gastric tissue supplied by the short gastric arteries is vulnerable to ischemic injury following splenic artery blockage.

A 65-year-old man with a history of hypertension, type 2 diabetes mellitus, and tobacco smoking comes to the office reporting mild back pain. Abdominal examination reveals a bruit, but no pulsatile mass is palpated. Femoral and pedal pulses are symmetric. The patient is sent for ultrasound and is found to have a large infrarenal abdominal aortic aneurysm. Open aneurysm repair is performed. During the procedure, the inferior mesenteric artery is ligated, the diseased portion of the aorta is dissected, and a graft is placed from below the renal arteries to the bifurcation of the aorta. Collateral circulation from which of the following vessels is most likely responsible for preventing ischemia of the descending colon?

The superior mesenteric artery and inferior mesenteric artery are the 2 main vessels supplying the small and large intestines. They are connected by a pair of anastomoses: the marginal artery of Drummond, which is the principal anastomosis, and the inconsistently present arc of Riolan (mesenteric meandering artery).

A 17-year-old girl is brought to the hospital due to abdominal pain, nausea, and vomiting. She began having periumbilical pain and nausea several hours ago and initially attributed her symptoms to some "bad food" she ate at a potluck lunch earlier in the day. However, her pain progressively worsened and became localized to the right lower quadrant. Temperature is 101 F (38.3 C), blood pressure is 124/78 mm Hg, pulse is 92/min, and respirations are 14/min. On examination, the patient has right lower quadrant tenderness with guarding. Laboratory evaluation shows leukocytosis. Surgical intervention is planned. During surgery, which of the following landmarks is most helpful in identifying the diseased organ?

The teniae coli are 3 separate smooth muscle ribbons that travel longitudinally on the outside of the colon and converge at the root of the vermiform appendix. If the appendix cannot be identified by palpation during an appendectomy, it can be located by following the teniae coli to their origin at the cecal base

A 65-year-old man is evaluated in the clinic due to several months of abdominal pain and vomiting. The pain starts 2 to 3 hours after meals, is characterized as crampy, and is often associated with bilious vomiting. Lately, the patient has been tolerating only liquids and has consequently lost 12 lbs in the past 4 months. On physical examination, he has mild epigastric tenderness on deep palpation. Contrast-enhanced CT scan of the abdomen shows an irregular mass in the third portion of the duodenum that is infiltrating beyond the gut wall. If this mass continues to enlarge, which of the following structures is most likely to be compromised in this patient?

The third part of the duodenum courses horizontally across the abdominal aorta and inferior vena cava at the level of the third lumbar vertebra. The superior mesenteric vessels lie anterior to the duodenum at this location.

A 3-year-old boy is brought to the emergency department by his parents after he develops acute abdominal pain and vomiting. Examination shows diffuse tenderness to palpation, and abdominal imaging reveals a foreign body lodged within the intestine, causing a small bowel obstruction. Laparotomy is performed to remove the foreign body; during the procedure, an incidental cyst is discovered. The cyst is connected by a fibrousband to the ileum and the umbilicus. The embryologic defect underlying the formation of this patient's cyst is also associated with which of the following?

The vitelline (omphalomesenteric) duct normally obliterates during early embryologic development. Incomplete obliteration can result in a spectrum of anomalies, including vitelline duct cyst (ie, cyst connected by fibrous bands to the ileum and umbilicus) and Meckel diverticulum

A 6-hour-old boy is in the newborn nursery with feeding difficulties. The patient was born at 39 weeks gestation to a 33-year-old primigravida via cesarean delivery due to failure to progress and late decelerations seen on fetal heart tracing. Apgar scores were 8 and 9, but examination shows an infant with excessive drooling and coughing. Cardiac, respiratory, and abdominal examinations are otherwise normal at rest. When the infant attempts to breastfeed, however, several bouts of coughing and perioral cyanosis develop with oxygen saturation of 85% on room air. Which of the following is the most likely cause of this patient's condition?

Tracheoesophageal fistula with esophageal atresia results from failure of the primitive foregut to appropriately divide into separate trachea and esophageal structures. Infants present shortly after birth with excessive secretions and choking/cyanosis during feeds

A boy is examined in the newborn nursery shortly after birth. He was born full term by vaginal delivery to a 40-year-old woman who did not receive prenatal care. His temperature is 36.7 C (98 F), pulse is 132/min, and respirations are 38/min. Examination shows slanted palpebral fissures, epicanthal folds, thick nuchal folds, and a single palmar crease. The patient has a large, reducible midline abdominal protrusion covered by skin that is more pronounced when he cries. The umbilical stump is at the center of the protrusion. Which of the following is the most likely cause of this patient's abdominal finding?

Umbilical hernias are caused by a defect in the linea alba and present as protrusions at the umbilicus that are soft, reducible, and benign. They can occur in isolation or in association with other conditions, such as Down syndrome.

Direct inguinal Older men

Weakness of transversalis fascia Protrudes medial to the inferior epigastric vessels into Hesselbach's triangle May pass through superficial inguinal ring No direct route into the scrotum

Femoral Women

Widening of the femoral ring Emerges inferior to inguinal ligament Protrudes through the femoral ring into the femoral canal