Gastroenterology
1. A 27-year-old man with a history of IV drug use was found to have abnormal liver function tests
Further work-up including serologic tests for viral hepatitis show
Hepatitis B surface antibody (HBsAb) negative
Hepatitis B surface antigen (HBsAg) positive
Hepatitis core antibody (HBcAb) positive
Hepatitis B surface antibody (HBsAb) negative
Hepatitis B e antibody (HBeAb) positive
Hepatitis B e antigen (HBeAg) negative
Which of the following statements is true regarding this patient?
He is a chronic hepatitis B virus (HBV) carrier with high infectivity.
He is in the incubation period of HBV.
He is a chronic HBV carrier with low infectivity.
He has recovered from HBV infection and is immune to HBV.
Answer: C
Explanation: In the interpretation of results of hepatitis B serologic tests, the following facts should be considered: during the incubation period (i.e., before the onset of clinical manifestations) HbsAg, HbeAg, and HBV DNA become detectable in the serum. At the onset of clinical symptoms (e.g., jaundice), an increase in the serum transaminases antibodies occurs and antibodies to HBc become detectable (HBc antibodies). Initially, the HBc antibodies are IgM and thereafter IgG; these latter antibodies persist for years. HBs antibodies become detectable late in convalescence. A rise in HBs antibodies in combination with a loss of HbsAg, HbeAg, and HBV DNA indicate the presence of immunity to HBV. HbeAg and HBV DNA are markers of active viral replication and thus indicate high infectivity. The loss of HbeAg and appearance of anti-HbeAb indicates a less infective stage.
2. A 23-year-old woman experienced watery diarrhea, nausea, vomiting, and abdominal cramps 6 hours after eating a salad and a hamburger in a local restaurant. The most likely organism causing her disease is
Vibrio vulnificus
Listeria monocytogenes
Yersinia enterocolitica
Clostridium welchii
Staphylococcus aureus
Answer: E
Explanation: Staphylococcal food poisoning is manifested 2 to 6 hours after eating food (salad, potato salads) contaminated by a preformed enterotoxin. Yersinia is most commonly associated with the ingestion of improperly cooked meat, but symptoms generally begin more than 1 day after ingestion of the contaminated food. Symptoms resulting from L. monocytogenes also occur more than 24 hours after the ingestion of contaminated foods (milk, ice cream, and poultry). V. vulnificus-associated food poisoning presents usually 24 to 48 hours after the ingestion of contaminated seafood (usually oysters). C. welchii is not associated with food poisoning. The two clostridia associated with food poisoning are C. perfringens and C. botulinum.
3. A 35-year-old man presents with diarrhea for 10 days, characterized by frequent, low-volume stools with the presence of mucus. He also complained of subjective fever and lower abdominal pain. The presence of leukocytes in stool is consistent with which organism?
Clostridium perfringens
S. aureus
Giardia lamblia
Enterobius vermicularis
Entamoeba histolytica
Answer: E
Explanation: The presence of large numbers of leukocytes in stool is diagnostic of colonic mucosal inflammation and should suggest infection with enteroinvasive organisms such as Shigella, E. histolytica, Salmonella, Campylobacter, invasive Escherichia coli, or Y. enterocolitica. Those organisms that cause diarrhea by a noninvasive mechanism (Giardia lamblia, enterotoxigenic E. coli, Vibrio cholerae) are not associated with leukocytes in the stool
4. Acetaminophen is an important cause of acute hepatic failure. All of the following statements about acetaminophen toxicity are correct, except
Significant liver injury usually occurs with doses of more than 10 - 15 g.
Alcoholics are more susceptible to liver injury even with a low dose.
N-acetylcysteine is most effective when administered within 10 hours of ingestion.
Hemodialysis is effective in the management of hepatotoxicity.
Survivors of acetaminophen-induced hepatotoxicity do not experience any progressive or residual liver damage.
Answer: D
Explanation: Acetaminophen overdose causes acute liver failure. Significant liver injury usually occurs with doses of >10 to 15 g, most frequently taken in a suicide attempt. The liver injury is caused by toxic metabolites of acetaminophen formed by the microsomal cytochrome P-450-dependent drug-metabolizing system. Because ethanol induces this cytochrome P-450 system, severe hepatotoxicity can be seen in alcoholics, even with lower dosages of acetaminophen. N-acetylcysteine administered early after ingestion (i.e., <24 hours) reduces the severity of liver necrosis. Acetaminophen and its metabolites are not cleared by hemodialysis. Survivors of acute acetaminophen toxicity usually recover completely without progressive or residual liver damage.
5. Which statement about esophageal cancer is true?
Dysphagia is an early manifestation.
The most common type of esophageal cancer in the United States is adenocarcinoma.
Esophageal cancer is most commonly located in the proximal third of the esophagus.
Most esophageal cancers are not resectable at presentation.
Barrett's syndrome is associated with squamous carcinoma.
Answer: D
Explanation: Most esophageal cancers are asymptomatic, and at the time of diagnosis most are unresectable. Barrett's syndrome is associated with adenocarcinoma of the esophagus. Despite the increasing incidence of adenocarcinoma, the most common type of esophageal carcinoma in the United States is squamous cell carcinoma, which generally is located in the distal third of the esophagus.
6. A 42-year-old man presents with intermittent dysphagia to solids and liquids and regurgitation of food. He has lost 4 pounds in 2 months. His physical exam is normal. A barium swallow reveals a dilated esophageal body, with the distal esophagus terminating in a narrow end. Which one of the following options is the most appropriate long-term therapy?
Isosorbide dinitrate
Metoclopramide
Dilation with balloon
Nifedipine
Dilation with rubber tube (bougie)
Asnwer: C
Explanation: Achalasia is best treated with mechanical disruption of the lower esophageal sphincter. Dilation with a large Hurst bougie may give temporary relief; a few patients have been maintained with weekly self-dilations, but this treatment is no longer recommended. Much more effective is dilation with a pneumatic balloon (bag) under radiographic control. A successful approach to long-term pharmacologic management of achalasia has not been established. Short-term improvement in clinical symptoms and in scintigraphic esophageal emptying may occur with isosorbide mononitrate, a long-acting nitrate, or with nifedipine, a calcium-channel blocker. Promotility agents like metoclopramide increase the lower esophageal sphincter pressure and thus are contraindicated in achalasia.
7. A 45-year-old male executive comes to your office complaining of epigastric pain for 2 months. His primary physician prescribed him H2-blockers 3 weeks ago, which have produced only partial relief of his symptoms. His weight is stable. His physical exam is normal. An upper endoscopy reveals a 1-cm duodenal ulcer. Which of the following risk factors is not associated with the development of ulcer disease?
Daily use of nonsteroidal anti-inflammatory drugs (NSAIDs)
Gastric infection with H. pylori
Emotional stress
Cigarette smoking
Gastrin-secreting tumors
Answer: C
Explanation: Although considered a risk factor in the past, several studies showed that emotional stress is not a risk factor for the development of duodenal ulcer. Daily NSAID use significantly increases the risk of ulcer disease (risk ratio, 10- to 20-fold). Gastric infection with H. pylori increases risk about five- to sevenfold. Cigarette smoking doubles the risk of duodenal ulcer. At least 90% of those patients with Zollinger-Ellison syndrome have duodenal ulcer.
8. A 20-year-old white woman presents with jaundice and malaise of 2 weeks' duration. Her boyfriend had some form of hepatitis several months before. Initial laboratory studies reveal alanine transaminase (ALT) of 211 U/L, aspartate transaminase (AST) of 194 U/L, and bilirubin of 5.4 mg/dL. HBsAg and anti-HBc IgM are positive. Which of the following statements regarding acute hepatitis B is false?
About 90% of patients with acute hepatitis B will recover completely.
About 1% of patients with acute hepatitis B can experience fulminant hepatic failure.
Chronic hepatitis B carrier state will develop in 10% of patients.
Interferon administration in the acute phase of infection prevents the development of the chronic hepatitis B carrier state.
Answer: D
Explanation: Ninety to 95% of otherwise healthy adult patients with acute hepatitis B recover completely and become HBsAg negative. About 1% experience massive necrosis, and 5 to 10% of patients who remain HBsAg positive beyond 6 months are at increased risk of chronic hepatitis. Interferon given during acute hepatitis B infection has not shown any benefit.
9. A 51-year-old woman presents with abdominal pain, weight loss, early satiety, and night sweats. On physical exam she appears cachectic, multiple enlarged lymph nodes are present in her neck (supraclavicular area), and a mass is palpated in the epigastrium. Laboratory data reveal a hemoglobin of 8 g/dL and a normal WBC count. Which of the following is the most appropriate next step in establishing the diagnosis?
Upper GI series
Peripheral blood smear
CT of the abdomen
Upper endoscopy with biopsy
Exploratory laparotomy
Answer: D
Explanation: This patient has lymphoma of the stomach. Lymphoma of the stomach can resemble superficially spreading carcinoma, linitis plastica, or solitary adenocarcinoma. Gastroscopy with directed biopsy and brush cytology gives a higher yield than was previously appreciated, especially in the presence of exophytic lesions. Lymphoma of the stomach frequently presents radiographically as a bulky mass and less frequently as a diffusely infiltrating tumor-the most common form of secondary lymphoma-giving the appearance of large folds on upper GI series, frequently associated with multiple nodular defects and ulcerations. Although CT may be useful to evaluate the extent of disease, it will not provide a specific diagnosis. Exploratory laparotomy is useful for staging and therapeutic resection where possible.
10. Which of the following features best distinguishes Crohn's disease from ulcerative colitis?
Oral ulcers
Rectal bleeding
Continuous colonic involvement on endoscopy
Noncaseating granulomas
Crypt abscesses
Answer: D
Explanation: Oral ulcerations can occur both in Crohn's disease and ulcerative colitis. Rectal bleeding and continuous involvement of the colon may be also seen in both Crohn's disease and ulcerative colitis. The presence of crypt abscesses does not distinguish ulcerative colitis from Crohn's disease; however, noncaseating granulomas, when present, are pathognomonic of Crohn's disease.
posted by eDoctor @ 1:57 AM
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