Robbin's Review - Ch.17 (GI)

A 19-year-old man is advised by other family members to see his physician because genetic screening has detected a disease in other family members. On physical examination, a stool sample is positive for occult blood. A colonoscopy is performed, followed by a colectomy. The figure shows the gross appearance of the mucosal surface of the colectomy specimen. Molecular analysis of this patient's normal fibroblasts is most likely to show a mutation in which of the following genes? □ (A) APC □ (B) p53 □ (C) K-RAS □ (D) HNPCC □ (E) NOD2

A. APC

A 38-year-old woman has had nausea for the past 6 months. She reports no vomiting or diarrhea. On physical examination, there are no remarkable findings. Upper gastrointestinal endoscopy shows diffuse gastric mucosal erythema with focal mucosal erosions, but no ulcerations. The esophageal and duodenal mucosal surfaces appear normal. Microscopic examination of gastric biopsy specimens shows increased numbers of neutrophils, lymphocytes, and plasma cells in the mucosa; edema; focal mucosal hemorrhage; and loss of the surface epithelium. No Helicobacter pylori organisms are seen. Laboratory studies show a normal serum gastrin level. Which of the following pharmacologic agents is most likely to produce these findings? □ (A) Acetylsalicylic acid (aspirin) □ (B) Acyclovir □ (C) Chlorpromazine □ (D) Cimetidine □ (E) Clindamycin □ (F) Omeprazole

A. Acetylsalicyclic acid (aspirin)

A 68-year-old woman has had substernal pain after meals for many years. For the past year, she has had increased difficulty swallowing liquids and solids. On physical examination, there are no remarkable findings. Upper gastrointestinal endoscopy shows a lower esophageal mass that nearly occludes the lumen of the esophagus. A biopsy specimen of this mass is most likely to show which of the following neoplasms? □ (A) Adenocarcinoma □ (B) Leiomyosarcoma □ (C) Squamous cell carcinoma □ (D) Non-Hodgkin lymphoma □ (E) Carcinoid tumor

A. Adenocarcinoma

A 70-year-old man saw his physician for a routine health maintenance examination. On physical examination, there were no remarkable findings, but a stool sample was positive for occult blood. A colonoscopy was performed and showed a 5- cm sessile mass in the upper portion of the descending colon at 50 cm from the anal verge. The histologic appearance at low power of a biopsy specimen of the lesion is shown in the figure. The patient refused further work-up and treatment. Five years later, he sees his physician because of constipation, microcytic anemia, and a 5-kg weight loss over the past 6 months. On surgical exploration, there is a 7-cm mass encircling the descending colon. Which of the following neoplasms is he now most likely to have? □ (A) Adenocarcinoma □ (B) Non-Hodgkin lymphoma □ (C) Carcinoid tumor □ (D) Leiomyosarcoma □ (E) Mucinous cystadenoma □ (F) Squamous cell carcinoma □ (G) Villous adenoma

A. Adenocarcinoma

A 49-year-old woman sees her physician because she has had abdominal cramps and diarrhea with six stools per day for the past month. She has a history of similar episodes of self-limited pain and diarrhea, which have occurred several times during the past 20 years. Each episode lasts about 2 weeks and resolves without treatment. Findings on physical examination are unremarkable, but a stool sample is positive for occult blood. Laboratory studies show no ova or parasites in the stool. Colonoscopy shows diffuse and uninterrupted mucosal inflammation and superficial ulceration extending from the rectum to the ascending colon. Colonic biopsy specimens from the area show a diffuse, predominantly mononuclear infiltrate in the lamina propria. The patient is at high risk of developing which of the following complications? □ (A) Adenocarcinoma of the colon □ (B) Diverticulitis □ (C) Primary biliary cirrhosis □ (D) Fat malabsorption □ (E) Pseudomembranous colitis □ (F) Perirectal fistula formation

A. Adenocarcinoma of the colon

A 27-year-old man has had intermittent cramping abdominal pain and low-volume diarrhea for several weeks. On physical examination, he is afebrile; there is mild lower abdominal tenderness but no masses, and bowel sounds are present. A stool sample is positive for occult blood. The symptoms subside within 1 week. Six months later, the abdominal pain recurs with perianal pain. On physical examination, there is now a perirectal fistula. Colonoscopy shows many areas of mucosal edema and ulceration and some areas that appear normal. Microscopic examination of a biopsy specimen from an ulcerated area shows a patchy acute and chronic inflammatory infiltrate, crypt abscesses, and several noncaseating granulomas. Which of the following underlying disease processes best explains these findings? □ (A) Crohn disease □ (B) Amebiasis □ (C) Shigellosis □ (D) Sarcoidosis □ (E) Ulcerative colitis

A. Crohn disease

A neonate born at 32 weeks' gestation was in stable condition and feeding well 3 days after birth. There was no respiratory distress. On day 4, the infant's abdomen was tender and appeared distended. A stool sample was positive for occult blood. Laboratory studies showed leukocytosis and a blood culture positive for growth of Escherichia coli. The infant died of septic shock. Which of the following is most likely to be found at autopsy? □ (A) Dark red necrotic ileum and cecum □ (B) Markedly dilated colon above the sigmoid □ (C) Purulent ascitic fluid □ (D) Markedly enlarged mesenteric lymph nodes □ (E) A 5-cm mass in the retroperitoneum

A. Dark red necrotic ileum and cecum

A 35-year-old woman has had increasing lower back pain for 5 years. At various times during the past year, she also has had arthritic pain involving the knees, hips, and wrists. A stool sample is positive for occult blood. A pelvic radiograph shows changes consistent with sacroiliitis. A colonoscopy is performed, and she undergoes a total colectomy. The figure shows the gross appearance of the colectomy specimen. What is the most likely diagnosis? □ (A) Dysregulated CD4+ T-cell responses □ (B) Cross-reaction of antibodies against gut bacteria □ (C) Auto-antibodies directed against tropomyosin □ (D) Mutations in the NOD2 gene □ (E) Germline inheritance of the APC gene mutation

A. Dysregulated CD4+ T-cell responses

A 51-year-old man has sudden onset of massive emesis of bright red blood. On physical examination, his temperature is 36.9°C, pulse is 103/min, respirations are 19/min, and blood pressure is 85/50 mm Hg. Laboratory studies show a hematocrit of 21%. The serologic test result for HBsAg is positive. He has had no prior episodes of hematemesis. The hematemesis is most likely to be a consequence of which of the following? □ (A) Esophageal varices □ (B) Barrett's esophagus □ (C) Candida albicans infection □ (D) Reflux esophagitis □ (E) Squamous cell carcinoma □ (F) Zenker diverticulum

A. Esophageal varices

A 50-year-old woman has a history of peptic ulcer disease for which she has been treated with omeprazole. She has had nausea with vomiting for the past 2 months. Upper GI endoscopy reveals 3 circumscribed, round, smooth lesions in the gastric body from 1 to 2 cm in diameter. Biopsies are taken and microscopically show the lesions to consist of irregular glands that are cystically dilated and lined by flattened parietal and chief cells. No inflammation, H. pylori, metaplasia, or dysplasia is present. What is the most likely diagnosis? □ (A) Fundic gland polyps □ (B) Gastric adenomas □ (C) Hyperplastic polyps □ (D) Hypertrophic gastropathy

A. Fundic gland polyps

A 35-year-old man has had epigastric pain for more than 1 year. The pain tends to occur 2 to 3 hours after a meal and is relieved if he takes antacids or eats more food. He has noticed a 4-kg weight gain in the past year. He does not smoke and drinks 1 glass of Johannisberg Riesling daily. The result of a urea breath test is positive, and a gastric biopsy specimen contains urease. He begins a 2-week course of antibiotics, but on day 4, he feels better and discontinues treatment. Several weeks later, the epigastric pain recurs. If the patient does not seek further treatment, which of the following complications is he most likely to develop? □ (A) Hematemesis □ (B) Fat malabsorption □ (C) Hepatic metastases □ (D) Carcinoid syndrome □ (E) Vitamin B12 deficiency

A. Hematemesis

A 24-year-old woman gives birth to an infant at term after an uncomplicated pregnancy. Apgar scores are 9 and 10 at 1 and 5 minutes after birth. The infant's length and weight are at the 55th percentile. There is no significant passage of meconium. Three days after birth, the infant vomits all oral feedings. On physical examination, the infant is afebrile, but the abdomen is distended and tender, and bowel sounds are reduced. An abdominal ultrasound scan shows marked colonic dilation above a narrow segment in the sigmoid region. A biopsy specimen from the narrowed region shows an absence of ganglion cells in the muscle wall and submucosa. Which of the following is most likely to produce these findings? □ (A) Hirschsprung disease □ (B) Trisomy 21 □ (C) Volvulus □ (D) Colonic atresia □ (E) Necrotizing enterocolitis

A. Hirschsprung disease

For the past year, a 20-year-old man has had increasingly voluminous, bulky, foul-smelling stools and a 10-kg weight loss. There is no history of hematemesis or melena. He has some bloating, but no abdominal pain. On physical examination, there are no palpable abdominal masses, and bowel sounds are present. Which of the following laboratory findings is most likely to be present on examination of his stool? □ (A) Increased stool fat □ (B) Giardia lamblia cysts □ (C) Occult blood □ (D) Vibrio cholerae

A. Increased stool fat

A 43-year-old woman has become increasingly tired and listless over the past 5 months. She has had menometrorrhagia for the past 3 months. On physical examination, there are no remarkable findings except for a positive result on stool guaiac testing. Laboratory studies show hemoglobin, 9.2 g/dL; hematocrit, 27.3%; and MCV, 75 μm3. Pelvic ultrasound reveals an enlarged uterus. A Pap smear shows abnormal cells of probable endometrial origin. Colonoscopy is performed, followed by partial colectomy; the gross appearance of the lesion is shown in the figure. Which of the following molecular abnormalities has most likely led to these findings? □ (A) Mutation in a DNA mismatch-repair gene □ (B) Germline inheritance of APC gene mutation □ (C) Tyrosine kinase activation owing to c-KIT mutation □ (D) Homozygous loss of PTEN gene □ (E) Inactivation of the Rb protein by HPV-16

A. Mutation in a DNA mismatch-repair gene

After an uncomplicated pregnancy, a 23-year-old woman, G2, P1, gave birth at term to a boy of normal weight and length. The infant initially did well, but at 6 weeks, he began feeding poorly for 1 week, and his mother noticed that much of the milk he ingested was forcefully vomited within 1 hour. On physical examination, the infant is afebrile, and there are no external anomalies. The physician palpates a midabdominal mass. Bowel sounds are active. The medical history indicates that the mother and her first child had the same illness during infancy. Which of the following conditions is most likely to explain these findings? □ (A) Pyloric stenosis □ (B) Tracheoesophageal fistula □ (C) Diaphragmatic hernia □ (D) Duodenal atresia □ (E) Annular pancreas

A. Pyloric stenosis

A 57-year-old man goes to the emergency department because of increasing abdominal pain with distention that developed over the past 24 hours. On physical examination, there is diffuse abdominal tenderness. The abdomen is tympanitic, without a fluid wave, and bowel sounds are nearly absent. There is a well-healed, 5-cm transverse scar in the right lower quadrant of the abdomen. There is no caput medusae. A stool sample is negative for occult blood. An abdominal plain film shows dilated loops of small bowel with air-fluid levels, but there is no free air. At laparotomy, the surgeon notices a 20-cm portion of reddish black ileum that changes abruptly to pink-appearing bowel on distal and proximal margins. The patient's medical history is significant only for an appendectomy at age 25. Which of the following is most likely to have produced these findings? □ (A) Adenocarcinoma of the ileum □ (B) Adhesions □ (C) Angiodysplasia □ (D) Crohn disease □ (E) Indirect inguinal hernia □ (F) Intussusception □ (G) Volvulus

B. Adhesions

A clinical study of adult patients with chronic bloody diarrhea is performed. One group of these patients is found to have a statistically increased likelihood for the following: antibodies to Saccharomyces cerevisiae but not anti-neutrophil cytoplasmic autoantibodies, NOD2 gene polymorphisms, 50% concordance rate in monozygous twins, higher rate of cigarette smoking, TH1 immune cell activation, vitamin K deficiency, pernicious anemia, and gallstones. Which of the following diseases is this group of patients most likely to have? □ (A) Angiodysplasia □ (B) Crohn disease □ (C) Diverticulitis □ (D) Ischemic enteritis □ (E) Ulcerative colitis

B. Crohn disease

A 16-year-old boy who is receiving chemotherapy for acute lymphoblastic leukemia sees the physician because he has had pain for 1 week when he swallows food. Physical examination shows no abnormal findings. Upper gastrointestinal endoscopy shows 0.5- to 0.8-cm mucosal ulcers in the region of the mid to lower esophagus. The shallow ulcers are round and sharply demarcated, and have an erythematous base. Which of the following is most likely to produce these findings? □ (A) Aphthous ulcerations □ (B) Herpes simplex esophagitis □ (C) Gastroesophageal reflux disease □ (D) Candida esophagitis □ (E) Mallory-Weiss syndrome

B. Herpes simplex esophagitis

A 65-year-old woman goes to her physician for a routine health maintenance examination. A stool sample is positive for occult blood. CT scan of the abdomen shows numerous air-filled, 1-cm outpouchings of the sigmoid and descending colon. Which of the following complications is most likely to develop in this patient? □ (A) Adenocarcinoma □ (B) Pericolic abscess □ (C) Bowel obstruction □ (D) Malabsorption □ (E) Toxic megacolon

B. Pericolic abscess

A 45-year-old woman is being treated in the hospital for pneumonia complicated by septicemia. She has required multiple antibiotics and was intubated and mechanically ventilated earlier in the course. On day 20 of hospitalization, she has abdominal distention. Bowel sounds are absent, and an abdominal radiograph shows dilated loops of small bowel suggestive of ileus. She has a low volume of bloody stool that is positive for Clostridium difficile toxin. At laparotomy, a portion of distal ileum and cecum is resected. The gross appearance of the mucosal surface is shown in the figure. What is the most likely diagnosis? □ (A) Mesenteric arterial thrombosis □ (B) Pseudomembranous enterocolitis □ (C) Intussusception □ (D) Cecal volvulus □ (E) Toxic megacolon

B. Pseudomembranous enterocolitis

A 70-year-old man with a lengthy history of chronic alcoholism has had increasing difficulty swallowing and has noticed a 6-kg weight loss over the past 2 months. On physical examination, there are no remarkable findings. Upper gastrointestinal endoscopy shows a 3-cm ulcerative mass in the midesophagus that partially occludes the esophageal lumen. Esophagectomy is performed; the gross appearance of the lesion is shown in the figure. Which of the following is most likely to be seen on microscopic section of this mass? □ (A) Multinucleated cells with intranuclear inclusions □ (B) Squamous cell carcinoma □ (C) Dense collagenous scar □ (D) Adenocarcinoma □ (E) Thrombosed vascular channels

B. Squamous cell carcinoma

A potluck lunch party is held at the office at noon on Thursday. Various meats, salads, breads, and desserts that were brought in earlier that morning are served. Everyone has a good time, and most of the food is consumed. By mid- afternoon, the single office restroom is being used by many employees who have an acute, explosive diarrhea accompanied by abdominal cramping. Which of the following infectious agents is most likely responsible for this turn of events? □ (A) Escherichia coli □ (B) Staphylococcus aureus □ (C) Vibrio parahaemolyticus □ (D) Clostridium difficile □ (E) Salmonella enteritidis □ (F) Bacillus cereus

B. Staph aureus

A 52-year-old, previously healthy man sustained an extensive thermal burn injury involving 70% of the total body surface area of his skin. He was hospitalized in stable condition. Three weeks after the initial burn injury, he had melanotic stools. His blood pressure was 80/40 mm Hg, and his hematocrit was 18%. Soon after, he experienced cardiac arrest and could not be resuscitated. At autopsy, where are gastrointestinal ulcerations most likely to be found in this man? □ (A) Esophagus □ (B) Stomach □ (C) Duodenum □ (D) Ileum □ (E) Colon

B. Stomach

A 70-year-old man takes large quantities of nonsteroidal anti-inflammatory drugs because of chronic degenerative arthritis of the hips and knees. Recently, he has had epigastric pain with nausea and vomiting and an episode of hematemesis. On physical examination, there are no remarkable findings. A gastric biopsy specimen is most likely to show which of the following lesions? □ (A) Epithelial dysplasia □ (B) Hyperplastic polyp □ (C) Acute gastritis □ (D) Adenocarcinoma □ (E) Helicobacter pylori infection

C. Acute gastritis

A 59-year-old man has had increasing difficulty swallowing during the past 6 months. There are no significant findings on physical examination. Upper gastrointestinal endoscopy shows areas of erythematous mucosa above the Z-line. A biopsy specimen from the lower esophagus has the microscopic appearance shown in the figure. Which of the following complications is most likely to occur as a consequence of this patient's condition? □ (A) Hematemesis □ (B) Squamous cell carcinoma □ (C) Adenocarcinoma □ (D) Achalasia □ (E) Lacerations (Mallory-Weiss syndrome)

C. Adenocarcinoma

A 60-year-old man has had increasing fatigue for the past 8 months. On physical examination, he appears pale. On digital rectal examination, no masses are palpable, but a stool sample is positive for occult blood. Physical examination of the abdomen shows active bowel sounds with no masses or areas of tenderness. Laboratory studies show hemoglobin, 8.3 g/dL; hematocrit, 24.6%; MCV, 73 μm3; platelet count, 226,000/mm3; and WBC count, 7640/mm3. Colonoscopy shows no identifiable source of the bleeding. Angiography shows a 1-cm focus of dilated and tortuous vascular channels in the mucosa and submucosa of the cecum. What is the most likely diagnosis? □ (A) Mesenteric vein thrombosis □ (B) Internal hemorrhoids □ (C) Angiodysplasia of the colon □ (D) Collagenous colitis □ (E) Colonic diverticulosis

C. Angiodysplasia of the colon

A 33-year-old man who lives in New York is bothered by a low-volume, mostly watery diarrhea associated with flatulence. The symptoms occur episodically, but they have been persistent for the past year. He has experienced a 5-kg weight loss. He has no fever, nausea, vomiting, or abdominal pain. On physical examination, there are no significant findings. A stool sample is negative for occult blood, ova, and parasites, and a stool culture yields no pathogens. An upper gastrointestinal endoscopy is performed. A biopsy specimen from the upper part of the small bowel shows severe diffuse blunting of villi and a chronic inflammatory infiltrate in the lamina propria. Which of the following serologic tests is most likely to be positive in this patient? □ (A) Anticentromeric antibody □ (B) Anti-DNA topoisomerase I antibody □ (C) Antigliadin antibody □ (D) Antimitochondrial antibody □ (E) Antinuclear antibody

C. Antigliadin Ab

One week after a trip to Central America, a 31-year-old woman had increasingly severe diarrhea. Gross examination of the stools showed mucus and streaks of blood. The diarrheal illness subsided within a couple of weeks, but now the patient has become febrile and has pain in the right upper quadrant of the abdomen. An abdominal ultrasound scan shows a 10-cm, irregular, partly cystic mass in the right hepatic lobe. Which of the following infectious organisms is most likely to produce these findings? □ (A) Giardia lamblia □ (B) Cryptosporidium parvum □ (C) Entamoeba histolytica □ (D) Clostridium difficile □ (E) Strongyloides stercoralis

C. Entamoeba histolytica

A 23-year-old primigravida gives birth at term to a boy. Ultrasound examination before delivery showed polyhydramnios. A single umbilical artery is seen at the time of birth. It is noted that the infant vomits all feedings, then develops a fever and difficulty with respirations within 2 days. A radiograph shows both lungs and the heart are of normal size, but there are pulmonary infiltrates and no stomach bubble. What is the most likely diagnosis? □ (A) Achalasia □ (B) Diaphragmatic hernia □ (C) Esophageal atresia □ (D) Hiatal hernia □ (E) Pyloric stenosis □ (F) Squamous cell carcinoma □ (G) Zenker diverticulum

C. Esophageal atresia

One year after having an acute myocardial infarction, a 55-year-old man saw his physician because of severe abdominal pain and bloody diarrhea. On physical examination, the abdomen was diffusely tender, and bowel sounds were absent. Abdominal plain films showed no free air. Laboratory studies showed a normal CBC and normal levels of serum amylase, lipase, and bilirubin. His condition deteriorated, and he developed irreversible shock. At autopsy, which of the following lesions is most likely to be found? □ (A) Acute appendicitis □ (B) Acute pancreatitis □ (C) Intestinal infarction □ (D) Acute cholecystitis □ (E) Pseudomembranous colitis

C. Intestinal infarction

A 26-year-old man is brought to the emergency department after sustaining abdominal gunshot injuries. At laparotomy, while repairing the small intestine, the surgeon notices a 1-cm mass at the tip of the appendix. The yellow-tan submucosal mass is removed. The electron micrograph of a neoplastic cell from the mass is shown in the figure. Which of the following is the most likely cell of origin of this lesion? □ (A) Lipoblast □ (B) Ganglion cell □ (C) Neuroendocrine cell □ (D) Smooth muscle cell □ (E) Mucin-secreting epithelial cell

C. Neuroendocrine cell

A 57-year-old woman has had burning epigastric pain after meals for more than 1 year. Physical examination shows no abnormal findings. Upper gastrointestinal endoscopy shows an erythematous patch in the lower esophageal mucosa. A biopsy specimen shows basal squamous epithelial hyperplasia, elongation of lamina propria papillae, and scattered intraepithelial neutrophils with some eosinophils. Which of the following is the most likely diagnosis? □ (A) Barrett esophagus □ (B) Esophageal varices □ (C) Reflux esophagitis □ (D) Scleroderma □ (E) Iron deficiency

C. Reflux esophagitis

Over the past 3 months, a 45-year-old woman has noticed that her skin has become progressively more yellow. On physical examination, she is afebrile and has scleral icterus and generalized jaundice. Laboratory studies show total serum bilirubin of 8.9 mg/dL, direct bilirubin of 6.8 mg/dL, serum ALT of 125 U/L, and serum AST of 108 U/L. A liver biopsy specimen shows histologic features of sclerosing cholangitis. Which of the following diseases of the gastrointestinal tract is most likely to coexist with the liver disease? □ (A) Chronic pancreatitis □ (B) Diverticulosis □ (C) Ulcerative colitis □ (D) Celiac sprue □ (E) Peptic ulceration

C. Ulcerative colitis

A 30-year-old woman sees her physician because she has had diarrhea and fatigue and has noticed a 3-kg weight loss over the past 6 months. On physical examination, she is afebrile and has mild muscle wasting, but her motor strength is normal. Laboratory studies show no occult blood, ova, or parasites in the stool. A biopsy specimen from the upper jejunum is obtained, and microscopic findings are reviewed. The patient is placed on a special diet with no wheat or rye grain products. The change in diet produces dramatic improvement. Which of the following microscopic features is most likely to be seen in the biopsy specimen? □ (A) Lymphatic obstruction □ (B) Noncaseating granulomas □ (C) Villous blunting and flattening □ (D) Foamy macrophages within the lamina propria □ (E) Crypt abscesses

C. Villous blunting and flattening

A 30-year-old man has a routine health maintenance examination. A stool sample is positive for occult blood. On colonoscopy, an ulcerative lesion is seen projecting into the cecum. The microscopic appearance of a section of the excised lesion is shown in the figure. Which of the following molecular biologic events is thought to be most critical in the development of such lesions? □ (A) Overexpression of E-cadherin gene □ (B) Amplification of ERBB2 gene □ (C) Germline transmission of a defective RB gene □ (D) A defective DNA mismatch-repair gene

D. A defective DNA mismatch-repair gene

A 53-year-old woman has had nausea, vomiting, and mid epigastric pain for 5 months. On physical examination, there are no significant findings. An upper gastrointestinal radiographic series shows gastric outlet obstruction. Upper gastrointestinal endoscopy shows an ulcerated mass that is 2 × 4 cm at the pylorus. Which of the following neoplasms is most likely to be seen in a biopsy specimen of this mass? □ (A) Non-Hodgkin lymphoma □ (B) Neuroendocrine carcinoma □ (C) Squamous cell carcinoma □ (D) Adenocarcinoma □ (E) Leiomyosarcoma

D. Adenocarcinoma

A 44-year-old woman has had increasing difficulty swallowing liquids and solids for the past 6 months. On physical examination, her fingers have reduced mobility because of taut, nondeforming skin. A barium swallow shows marked dilation of the esophagus with "beaking" in the distal portion, where there is marked luminal narrowing. A biopsy specimen from the lower esophagus shows prominent submucosal fibrosis with little inflammation. Which of the following is most likely to produce these findings? □ (A) Portal hypertension □ (B) Iron deficiency □ (C) Barrett esophagus □ (D) CREST syndrome □ (E) Hiatal hernia

D. CREST syndrome

During summer "Black and White Days," a week-long local community celebration of the dairy industry (Holstein cows are black and white), a 40-year-old man has episodic abdominal bloating, flatulence, and explosive diarrhea. On physical examination, there are no remarkable findings. Laboratory studies show no increase in stool fat and no occult blood, ova, or parasites in the stool. A routine stool culture yields no pathogens. During the rest of the year, the patient does not consume milkshakes or ice cream sodas and is not symptomatic. Which of the following conditions best accounts for these findings? □ (A) Celiac disease □ (B) Autoimmune gastritis □ (C) Cholelithiasis □ (D) Disaccharidase deficiency □ (E) Cystic fibrosis

D. Disaccharidase deficiency

A 51-year-old woman has been feeling increasingly tired for the past 7 months. There are no remarkable findings on physical examination. Laboratory studies include hemoglobin, 9.5 g/dL; hematocrit, 29.1%; MCV, 124 μm3; platelet count, 268,000/mm3; and WBC count, 8350/mm3. The reticulocyte index is low. Hypersegmented polymorphonuclear leukocytes are found on a peripheral blood smear. Antibodies to which of the following are most likely to be found in this patient? □ (A) Gliadin □ (B) Tropheryma whippelii □ (C) Helicobacter pylori □ (D) Gastric H+,K+-ATPase

D. Gastric H+, K+-ATPase

A 20-year-old woman in her ninth month of pregnancy has increasing pain on defecation and notices bright red blood on the toilet paper. She has had no previous gastrointestinal problems. After she gives birth, the rectal pain subsides, and there is no more bleeding. Which of the following is the most likely cause of these findings? □ (A) Angiodysplasia □ (B) Ischemic colitis □ (C) Intussusception □ (D) Hemorrhoids □ (E) Volvulus

D. Hemorrhoids

A 45-year-old woman has had increasing abdominal distention for the past 6 weeks. On physical examination, there is an abdominal fluid wave, and bowel sounds are present. Paracentesis yields 1000 mL of slightly cloudy serous fluid. Cytologic examination of the fluid shows malignant cells consistent with adenocarcinoma. The patient's medical history indicates that she has had no major medical illnesses and no surgical procedures. Which of the following conditions is most likely to have preceded the development of the adenocarcinoma? □ (A) Angiodysplasia □ (B) Crohn disease □ (C) Diverticulosis □ (D) Hereditary nonpolyposis colon carcinoma □ (E) Hirschsprung disease □ (F) Peptic ulcer disease

D. Hereditary nonpolyposis colon carcinoma

A 41-year-old man has been HIV positive for the past 8 years and has been receiving highly active antiretroviral therapy for the past year. For the past 2 weeks, he has experienced pain when swallowing. He has had no episodes of hematemesis and no nausea or vomiting. There are no remarkable findings on physical examination. The CD4+ lymphocyte count is now 285/μL. Which of the following conditions is most likely to produce these findings? □ (A) Esophageal squamous cell carcinoma □ (B) Achalasia □ (C) Lower esophageal fibrosis with stenosis □ (D) Herpes simplex esophagitis □ (E) Gastroesophageal reflux disease

D. Herpes simplex esophagitis

A 52-year-old man has had a 6-kg weight loss and nausea for the past 6 months. He has no vomiting or diarrhea. On physical examination, there are no remarkable findings. Upper gastrointestinal endoscopy shows a 6-cm area of irregular, pale fundic mucosa and loss of the rugal folds. A biopsy specimen shows a monomorphous infiltrate of lymphoid cells. Helicobacter pylori organisms are identified in mucus overlying adjacent mucosa. The patient receives antibiotic therapy for H. pylori, and the repeat biopsy specimen shows a resolution of the infiltrate. What is the most likely diagnosis? □ (A) Chronic gastritis □ (B) Diffuse large B-cell lymphoma □ (C) Autoimmune gastritis □ (D) Mucosa-associated lymphoid tissue tumor □ (E) Crohn disease

D. Mucosa-associated lymphoid tissue tumor

Two days after eating a chicken salad sandwich, a 35-year-old man experiences cramping abdominal pain with fever and watery diarrhea. Physical examination shows mild diffuse abdominal pain on palpation, but there are no masses. Bowel sounds are present. A stool sample is negative for occult blood. He recovers completely within a few days without treatment. Which of the following infectious organisms is most likely to produce these findings? □ (A) Yersinia enterocolitica □ (B) Escherichia coli □ (C) Entamoeba histolytica □ (D) Salmonella enteritidis □ (E) Rotavirus □ (F) Staphylococcus aureus □ (G) Bacillus cereus

D. Salmonella enteritidis

A 59-year-old man has had nausea and vomiting for several months. He has experienced no hematemesis. On physical examination, there is no abdominal tenderness, and bowel sounds are present. Upper gastrointestinal endoscopy shows erythematous areas of mucosa with thickening of the rugal folds in the gastric antrum. The microscopic appearance of a gastric biopsy specimen with a Steiner silver stain is shown in the figure. Which of the following toxins from these organisms is most likely to be present on the luminal surface? □ (A) Cysteine proteinase □ (B) Heat-stable enterotoxin □ (C) Shiga toxin □ (D) Vacuolating toxin □ (E) Verocytotoxin

D. Vacuolating toxin

A 53-year-old woman comes to her physician for a routine health maintenance examination. The only abnormal finding is a stool specimen that contains occult blood. Colonoscopy shows a 1.5-cm, solitary, rounded, erythematous polyp on a 0.5-cm stalk at the splenic flexure. The polyp is removed; its histologic appearance is shown in the figure at low (A) and high (B) magnifications. When the physician discusses these findings with the patient, which of the following statements is most appropriate? □ (A) You have inherited one defective copy of the APC gene □ (B) Other family members probably have colonic polyps □ (C) Many more polyps will appear within the next few years □ (D) There is a high probability that you will develop endometrial cancer □ (E) A detailed work-up to detect metastases from this lesion is not warranted

E. A detailed work-up to detect metastases from this lesion is not warranted

A 22-year-old woman has had several episodes of aspiration of food associated with difficulty swallowing during the past year. On auscultation, crackles are heard at the base of the right lung. A barium swallow shows marked esophageal dilation above the level of the lower esophageal sphincter. A biopsy specimen from the lower esophagus shows an absence of the myenteric ganglia. What is the most likely diagnosis? □ (A) Hiatal hernia □ (B) Plummer-Vinson syndrome □ (C) Barrett esophagus □ (D) Systemic sclerosis □ (E) Achalasia

E. Achalasia

A 27-year-old man has sudden onset of marked abdominal pain. On physical examination, his abdomen is diffusely tender and distended, and bowel sounds are absent. He undergoes surgery, and a 27-cm segment of terminal ileum with a firm, erythematous serosal surface is removed. The microscopic appearance of a section through the excised ileum is shown in the figure. Which of the following additional complications is the patient most likely to develop as a result of this disease process? □ (A) Metastatic adenocarcinoma □ (B) Mesenteric artery thrombosis □ (C) Intussusception □ (D) Hepatic abscess □ (E) Enterocutaneous fistula

E. Enterocutaneous fistula

A 46-year-old woman with a lengthy history of heartburn and dyspepsia experiences sudden onset of abdominal pain. On physical examination, she has severe mid epigastric pain with guarding. Bowel sounds are reduced. An abdominal plain film radiograph shows free air under the left leaf of the diaphragm. The patient is immediately taken to surgery, and a perforated duodenal ulcer is repaired. Which of the following organisms is most likely to have produced these findings? □ (A) Campylobacter jejuni □ (B) Cryptosporidium parvum □ (C) Entamoeba histolytica □ (D) Giardia lamblia □ (E) Helicobacter pylori □ (F) Salmonella typhi □ (G) Shigella flexneri □ (H) Yersinia enterocolitica

E. Helicobacter pylori

An 11-month-old, previously healthy infant has not produced a stool for 1 day. The mother notices that the infant's abdomen is distended. On physical examination, the infant's abdomen is very tender, and bowel sounds are nearly absent. An abdominal plain film radiograph shows no free air, but there are distended loops of small bowel with air-fluid levels. Which of the following is most likely to produce these findings? □ (A) Meckel diverticulum □ (B) Duodenal atresia □ (C) Hirschsprung disease □ (D) Pyloric stenosis □ (E) Intussusception

E. Intussusception

A 68-year-old woman with a history of rheumatic heart disease is hospitalized with severe congestive heart failure. Several days after admission, she develops abdominal distention. On physical examination, she is afebrile. The abdomen is tympanitic, without a fluid wave, and bowel sounds are absent. A stool sample is positive for occult blood. An abdominal plain film shows no free air. Colonoscopy shows patchy areas of mucosal erythema with some overlying tan exudate in the ascending and descending colon. No polyps or masses are found. What is the most likely diagnosis? □ (A) Ulcerative colitis □ (B) Volvulus □ (C) Shigellosis □ (D) Mesenteric vasculitis □ (E) Ischemic colitis

E. Ischemic colitis

A 38-year-old man who has been HIV positive for 10 years has had severe nausea and vomiting for the past 2 weeks. On physical examination, he is afebrile. A stool sample is positive for occult blood. The abdomen is not distended, there are no palpable masses or organomegaly, and bowel sounds are present. The patient has oral thrush. There are several reddish purple, 0.5- to 1-cm nodules on the skin of the trunk. Laboratory studies show a CD4+ lymphocyte count of 118/μL. Upper gastrointestinal endoscopy shows 12 reddish purple, 0.6- to 1.8-cm, gastric mucosal nodules. A biopsy specimen of the nodules is most likely to show which of the following neoplasms? □ (A) Adenocarcinoma □ (B) Non-Hodgkin lymphoma □ (C) Carcinoid tumor □ (D) Gastrointestinal stromal tumor □ (E) Kaposi sarcoma □ (F) Peutz-Jeghers polyp □ (G) Squamous cell carcinoma □ (H) Tubular adenoma

E. Kaposi sarcoma

A 20-year-old woman has had nausea and vague lower abdominal pain for the past 24 hours, but now the pain has become more severe. On physical examination, the pain is worse in the right lower quadrant, and there is rebound tenderness. A stool sample is negative for occult blood. Abdominal plain film radiographs show no free air. The result of a serum pregnancy test is negative. Which of the following laboratory findings is most useful to aid in the diagnosis of this patient? □ (A) Hyperamylasemia □ (B) Hypernatremia □ (C) Increased serum carcinoembryonic antigen □ (D) Increased serum alkaline phosphatase □ (E) Leukocytosis □ (F) Entamoeba histolytica cysts in the stool

E. Leukocytosis

In an epidemiologic study of infections of the gastrointestinal tract, cases of patients from whom definitive cultures were obtained are analyzed for clinical and pathologic findings that may be useful for diagnosis. A subset of patients is identified who initially had abdominal pain and diarrhea during week 1 of their illness. By week 2, these patients had splenomegaly and elevations in serum AST and ALT levels. By week 3, they were septic and had leukopenia. At autopsy, the patients who died were found to have ulceration of Peyer's patches. Which of the following infectious agents is most likely to produce these findings? □ (A) Campylobacter jejuni □ (B) Clostridium perfringens □ (C) Escherichia coli □ (D) Mycobacterium bovis □ (E) Salmonella typhi □ (F) Shigella sonnei □ (G) Yersinia enterocolitica

E. Salmonella typhi

A 67-year-old woman has experienced severe nausea, vomiting, early satiety, and a 9-kg weight loss over the past 4 months. On physical examination, she has mild muscle wasting. Upper gastrointestinal endoscopy shows that the entire gastric mucosa is eroded and has an erythematous, cobblestone appearance. Upper gastrointestinal radiographs show that the stomach is small and shrunken. Which of the following is most likely to be found on histologic examination of a gastric biopsy specimen? □ (A) Early gastric carcinoma □ (B) Gastrointestinal stromal tumor □ (C) Granulomatous inflammation □ (D) Chronic atrophic gastritis □ (E) Signet-ring cell adenocarcinoma

E. Signet-ring cell adenocarcinoma

One day after a meal of raw oysters, a healthy 21-year-old woman develops a profuse, watery diarrhea. On physical examination, her temperature is 37.5°C. A stool sample is negative for occult blood. There is no abdominal distention or tenderness, and bowel sounds are present. The diarrhea subsides over the next 3 days. Which of the following organisms is most likely to produce these findings? □ (A) Yersinia enterocolitica □ (B) Staphylococcus aureus □ (C) Cryptosporidium parvum □ (D) Entamoeba histolytica □ (E) Vibrio parahaemolyticus

E. Vibrio parahaemolyticus

A 30-year-old man has sudden onset of hematemesis after a weekend in which he consumed large amounts of alcohol. The bleeding stops, but he has another episode under similar circumstances 1 month later. Upper gastroesophageal endoscopy shows longitudinal tears at the esophagogastric junction. What is the most likely mechanism to cause his hematemesis? □ (A) Absent myenteric ganglia □ (B) Autoimmune inflammation □ (C) Herpes simplex virus infection □ (D) Portal hypertension □ (E) Vomiting □ (F) Widened diaphragmatic crura

E. Vomiting

A 24-year-old man sees his physician because of abdominal pain and increasing fatigue that has developed over the past 6 months. On physical examination, he is afebrile and appears pale. On palpation, there is mild pain in the right lower quadrant of the abdomen. There are no masses, and bowel sounds are active. Laboratory studies show hemoglobin, 8.9 g/dL; hematocrit, 26.7%; MCV, 74 μm3; platelet count, 255,000/mm3; and WBC count, 7780/mm3. Upper gastrointestinal endoscopy and colonoscopy showed no lesions. One month later, the patient continues to experience the same abdominal pain. Which of the following is most likely to cause this patient's illness? □ (A) Acute appendicitis □ (B) Angiodysplasia □ (C) Celiac sprue □ (D) Diverticulosis □ (E) Giardiasis □ (F) Meckel diverticulum

F. Meckel diverticulum

An 8-month-old, previously healthy infant girl develops a watery diarrhea that lasts for 1 week. The infant has a mild fever during the illness, but has no abdominal pain or swelling. On physical examination, her temperature is 37.7°C. A stool sample is negative for occult blood, ova, or parasites. Her parents are told to give her plenty of fluids, and she recovers fully. Which of the following organisms is most likely to produce these findings? □ (A) Campylobacter jejuni □ (B) Cryptosporidium parvum □ (C) Escherichia coli □ (D) Listeria monocytogenes □ (E) Norwalk virus □ (F) Rotavirus □ (G) Shigella flexneri □ (H) Vibrio cholerae

F. Rotavirus

A 59-year-old man with a lengthy history of chronic alcoholism has noticed increasing abdominal girth for the past 6 months. He has had increasing abdominal pain for the past 2 days. On physical examination, his temperature is 38.2°C. Examination of the abdomen shows a fluid wave and prominent caput medusae over the skin of the abdomen. There is diffuse abdominal tenderness. An abdominal plain film radiograph shows no free air. Paracentesis yields 500 mL of cloudy yellow fluid. Gram stain of the fluid shows gram-negative rods. Which of the following is the most likely diagnosis? □ (A) Appendicitis □ (B) Collagenous colitis □ (C) Diverticulitis □ (D) Ischemic colitis □ (E) Pseudomembranous colitis □ (F) Spontaneous bacterial peritonitis

F. Spontaneous bacterial peritonitis