USMLE USMLE-STEP-2 Online Practice Questions and Exam Preparation

USMLE USMLE-STEP-2 Online Questions & Answers

• Question 121:

  A healthy 29-year-old gravida 2 woman at 39 weeks has been in labor for 3 hours. She had a positive vaginal-anal culture for GBS at 37 weeks' gestation. Which one of the following statements is correct?

  A. Asymptomatic rectovaginal colonization is present in 60% of pregnant women.
  B. The transmission rate from mother to baby is approximately 25%.
  C. A rectovaginal culture should have been obtained at the first prenatal visit.
  D. Neonatal sepsis occurs in 1% of colonized mothers.
  E. Treatment with penicillin in labor is necessary only for heavy colonized mothers.
  D. Neonatal sepsis occurs in 1% of colonized mothers.

  ---

  Explanation

  Approximately 20% of pregnant women have positive rectovaginal cultures. Vertical transmission rate from mother to baby is approximately 75%. A rectovaginal culture is not indicated at the first prenatal visit because the pregnant woman may subsequently convert from a negative to a positive culture. For this reason, all pregnant women should have a rectovaginal culture at 3637 gestational weeks. If the woman goes into preterm labor before a culture is obtained, she should be treated with penicillin (gentamicin if she is penicillin allergic). The rate of neonatal sepsis is 1% of colonized mothers, a serious infection that may cause pneumonia, meningitis, and death.

• Question 122:

  A 26-year-old woman complains of a vaginal discharge causing burning and itching of the perineum. The pH of the discharge is 4.5. Which of the following is the most likely cause of her discharge?

  A. monilial vaginitis
  B. trichomonas vaginitis
  C. chlamydial cervicitis
  D. gonococcal cervicitis
  E. bacterial vaginosis
  A. monilial vaginitis

  ---

  Explanation

  The normal pH of the vagina is 3.84.2. In women with a vaginal discharge, a pH less than 5.0 suggests monilial vaginitis or a physiologic discharge of normal squamous cells desquamated from the vaginal epithelium. A pH greater than 5.0 suggests some type of bacterial infection, such as bacterial vaginosis or trichomonas vaginitis. The diagnosis of bacterial vaginosis is based on the presence of 3 of 4 characteristics: pH greater than 4.5, a homogenous thin appearance of the vaginal discharge, a fishy amine odor after the addition of 10% potassium hydroxide (KOH) to the discharge, and clue cells present in 2050% of vaginal epithelial cells. Clue cells are bacteria adherent to the surface of vaginal epithelial cells. Lactobacilli are absent from the vagina in women with bacterial vaginosis. Both chlamydia and gonorrhea infect the cervix and do not change the vaginal pH.

• Question 123:

  A21-year-old previously healthy woman presents with abdominal pain of 48-hour duration. The pain was initially periumbilical and on progression became localized in the right lower quadrant. The woman had nausea and a decreased appetite. She denied dysuria. Her last menstrual period was 2 weeks earlier. On examination, she was febrile (temperature 38.2°C), and was found to have localized tenderness in the right lower quadrant with guarding. Rectal examination was normal. Laboratory examination demonstrated mild leukocytosis.

  For the above patient with abdominal pain, select the most likely diagnosis.

  A. gastroenteritis
  B. regional enteritis
  C. acute appendicitis
  D. perforated peptic ulcer
  E. sigmoid diverticulitis
  F. acute pancreatitis
  G. acute cholecystitis
  H. superior mesenteric artery embolism
  I. ruptured abdominal aortic aneurysm
  J. ruptured ovarian cystK. cecal volvulus
  C. acute appendicitis

  ---

  Explanation

  Acute appendicitis initially presents with periumbilical pain secondary to obstruction of the appendiceal lumen. This is mediated through visceral pain fibers, and because the appendix is from the embryologic midgut, the pain is referred to the umbilicus. With obstruction of a hollow viscus, there may be associated nausea. As the inflammatory process progresses to involve the visceral and parietal peritoneal surfaces, the pain becomes localized directly over the appendix in the right lower quadrant. Fever and leukocytosis are nonspecific signs of an inflammatory process. Gastroenteritis may be associated with nausea, anorexia, and lowgrade fever. Periumbilical pain is colicky and secondary to increased peristalsis. Localized pain and signs of peritoneal irritation are uncommon. Aruptured right ovarian cyst may mimic appendicitis. Patients may exhibit right lower abdominal peritoneal irritation. However, the onset of pain is usually sudden, and the pain is initially felt in the right lower quadrant. These patients do not have anorexia or other gastrointestinal symptoms. The clinical picture of regional enteritis (Crohn's disease) is one of a chronic illness, often associated with weight loss, intermittent cramps, and diarrhea. Fever, tenderness, and a palpable right lower quadrant inflammatory mass may result from complications of ileal involvement. Sigmoid diverticulitis is more common in older patients, often with a prodromal history of irregular bowel habits. There may be left lower quadrant pain and tenderness, with a palpable left-sided inflammatory mass. A cecal volvulus presents with sudden onset of colicky abdominal pain and signs and symptoms of a bowel obstruction, including bilious emesis and abdominal distention. Alcohol-related acute pancreatitis presents with pain referred to the epigastrium, with radiation to the back mediated through the celiac ganglia. The patient may develop abdominal distention secondary to the associated paralytic ileus. Hyperamylasemia and an elevated serum lipase, in this clinical setting, are suggestive of pancreatitis. Perforated peptic ulcer and acute cholecystitis may also present with epigastric pain, and elevations of both serum lipase and amylase. Pain from a perforated ulcer, however, is sudden in onset and may be associated with shoulder-tip pain from diaphragmatic irritation. About 75% of patients with perforated duodenal ulcers have pneumoperitoneum on chest and abdominal radiographs.

  Acute cholecystitis will usually commence after a large meal and initially presents as colicky epigastric pain, progressing to pain localized in the right upper abdomen when transmural inflammation of the gallbladder wall produces peritoneal irritation. Acute mesenteric occlusion presents with sudden onset of severe but poorly localized periumbilical abdominal pain, associated with acidosis. There may be elevation of serum amylase and lipase. A ruptured abdominal aortic aneurysm will present with sudden onset of midabdominal pain, back pain, and hemodynamic instability.

• Question 124:

  Afew weeks after a presumed viral respiratory infection, a 4-year-old girl presents with bruising and petechiae. Bone marrow examination reveals increased numbers of megakaryocytes but is otherwise normal. Hb is 13.5 g/100 mL. Platelet count is 30,000/mm3. Which of the following would be appropriate for this child at this time?

  A. daily prednisone
  B. a transfusion of packed RBCs and platelets
  C. IV gamma globulin
  D. splenectomy
  E. no specific therapy
  E. no specific therapy

  ---

  Explanation

  Most cases of idiopathic thrombocytopenic purpura (ITP) in children are preceded by viral infections and, in contrast to adults, the great majority of children recover spontaneously. Although not all patients require therapy, most authorities suggest treating when the platelet count is less than 20,000. Standard treatment has been oral prednisone. Recently, IV gamma globulin has been shown to be effective. However, this agent is expensive and less convenient than oral prednisone. The child described in the question might reasonably be treated with either agent. Because the child's Hb is 13.3 g/100 mL, there is no indication for transfusion of RBCs. Although the platelet count is very low, platelet transfusions are short lived and generally are indicated only in the presence of serious bleeding, as, for example, from the GI tract. Thus, platelet transfusions are not indicated in this patient. Splenectomy is reserved for the very rare child who does not respond to conservative therapy or who develops chronic ITP.

• Question 125:

  From the below the clinical indications, choose an option for use of immune globulin (IG) in Measles prophylaxis

  A. indicated
  B. not proven effective
  C. not routinely indicated
  D. contraindicated
  E. compulsory
  A. indicated

  ---

  Explanation

  IG given before exposure or within 14 days of exposure is 7585% effective in preventing symptomatic illness from hepatitis A. IG is produced from the plasma of normal adults and does not contain sufficient antibody to prevent hepatitis B infection. Hepatitis B immune globulin (HBIG) is prepared from plasma known to contain high antibody titers for hepatitis B surface antigen (HBsAg) and is specific for hepatitis B. Given immediately postexposure, and again 1 month later, it has a combined efficacy of about 75% in the prevention of hepatitis B. Postexposure IG has not been found effective in the prevention of hepatitis C infection; on the other hand, treatment of early hepatitis C infection is possible, and thus it is important to monitor exposed individuals to determine whether infection occurs. IG administered to individuals exposed to measles infection who are susceptible to the disease has been shown to be effective if given within 6 days of exposure.

  Recent use of IG is a contraindication to immunization with rubella vaccine. IG is not very effective at preventing in utero infection with rubella, and infants with congenital rubella syndrome have been born to women given IG shortly after exposure. IG is not routinely indicated, as it is indicated only if abortion is not elected.

• Question 126:

  A52-year-old woman has had diabetes mellitus since childhood. She has controlled her glucose well and kept her glycohemoglobin (HgbA1C) below 7% (normal, 26%). For which of the following complications is she still at risk, despite excellent glucose control? A. autonomic dysfunction

  A. coronary heart disease
  B. blindness
  C. peripheral neuropathy
  D. peripheral vascular disease
  B. blindness

  ---

  Explanation

  Diabetes mellitus is associated with hyperglycemia, disease of the microvasculature (retinopathy, nephropathy, neuropathy), and macrovascular disease, including CAD and peripheral vascular disease, The Diabetes Control and Complications Trial and other studies have demonstrated that tight control can decrease complications of microvascular disease significantly, but it does not seem to reduce CAD mortality to the same extent.

• Question 127:

  On the second day after an appendectomy, a 33-year-old man complains of chest pain. Vital signs are:

  temperature 102°F, BP 130/70 mmHg, pulse rate 100/m in, and respiration rate 22/min. Room air ABG reveals a pH of 7.50, PCO2 of 29, and PO2 of 49. His WBC count is elevated and CXR shows a right lower lobe infiltrate. Which of the following is the most likely diagnosis?

  A. pulmonary embolism
  B. myocardial infarction
  C. pneumonia
  D. asthma
  E. congestive heart failure
  C. pneumonia

  ---

  Explanation

  Asthma is characterized by bronchospasm and typically causes a prolonged expiratory phase and retention of carbon dioxide. This degree of hypoxia (PO2 of 49) generally would not be seen with asthma. Pulmonary embolism, congestive heart failure, myocardial infarction, or pneumonia all could lead to this degree of hypoxia. The constellation of fever, elevated white count, and localized infiltrate on CXR is most characteristic of pneumonia. The most likely etiology is perioperative aspiration related to general anesthesia.

• Question 128:

  For each newborn with vomiting and illustrated radiographs, select the most likely diagnosis. Aneonate with bile-stained vomiting, abdominal distention, dilated loops of bowel on plain radiographs, and a small-caliber colon on contrast enema

  A. congenital hypertrophic pyloric stenosis
  B. annular pancreas
  C. duodenal atresia
  D. midgut volvulus
  E. intussusception
  F. imperforate anus
  G. Meckel's diverticulum
  H. meconium ileus
  I. Hirschsprung's disease
  J. jejunal atresia
  J. jejunal atresia

  ---

  Explanation

  Pyloric stenosis presents with nonbilious vomiting and gastric distention. An annular pancreas does not result in obstruction, except when it is associated with an underlying duodenal abnormality. Duodenal atresia is associated with Down syndrome. It results in early onset of bilious vomiting from complete duodenal obstruction distal to the ampulla. There is a "double bubble" sign on plain abdominal radiographs from air in the stomach and proximal duodenum. Midgut volvulus is a life-threatening complication of malrotation. It presents with acute onset of bilious vomiting, usually in infants in the first year of life. There is a paucity of gas on plain radiographs, with evidence of duodenal obstruction. UGI contrast study will confirm the abnormal position of the duodenaljejunal junction and may demonstrate a corkscrew of the duodenum from volvulus. Intussusception is uncommon in newborns. Bilious vomiting is unusual at the outset, but may develop if the intussusception has been present for a significant time.

  Imperforate anus can be excluded by clinical examination.

  If unrecognized, the infant will develop a clinical picture of a distal bowel obstruction, with dilated small and large bowel. Meckel's diverticulum can present with obstruction secondary to volvulus around a Meckel's band, with a distal small-bowel obstruction. Contrast enema will demonstrate a normal-caliber decompressed colon, with proximal dilated small bowel. Meconium ileus is associated with cystic fibrosis. Obstruction occurs from inspissated meconium in the terminal ileum. Plain radiographs may demonstrate a "soap bubble" pattern in the right lower quadrant, with a decompressed colon on contrast enema. Hirsch- sprung's disease presents with a distal bowel obstruction and delayed passage of meconium. A contrast enema may demonstrate a transition zone, with a narrow distal aganglionic segment, and proximal colonic dilatation. Jejunal atresia is a result of an intrauterine vascular accident. Infants present with bile- stained vomiting and abdominal distention early after birth. The colon is unused, and characteristically, on contrast enema, it is abnormally small in caliber

• Question 129:

  Several members of a group of young adults camping, cooking, and traveling together in the developing world develop fever, malaise, nausea, and vomiting, and have dark urine. Two have yellow sclera. How could this best have been prevented?

  A. avoiding eating local foods
  B. washing hands before eating
  C. taking prophylactic Pepto Bismol
  D. getting vaccinations
  E. cooking all foods thoroughly and drinking boiled water
  D. getting vaccinations

  ---

  Explanation

  Hepatitis Awas first isolated in 1973. Since then, it has been demonstrated to be conveyed from person to person chiefly by the fecal-oral route. Humans appear to be the only natural host. Outbreaks attributed to food and water supplies are frequently reported. There were an estimated 61,000 new infections in the United States (particularly in the West) in 2003, continuing a trend downward. It does not cause chronic infection. Vaccination is effective and available for persons at risk, including travelers.

  Examples of where outbreaks occur include: among travelers, among young adults clustered together, and in day care environments.

• Question 130:

  A healthy 27-year-old male and his partner have been attempting to conceive for more than 1 year. As part of their evaluation he has a semen analysis. His ejaculate volume is 3.5 mL, sperm concentration is 8 million/mL, sperm motility is 65%, oval forms comprise 60% of the sperm, and fructose is present in the ejaculate.

  The man is treated with clomiphene for a presumptive diagnosis of male factor infertility. Though clomiphene is an unproven and unapproved therapy for male infertility, what is the earliest that a semen analysis should be done to detect an improvement in his semen parameters?

  A. 33 days
  B. 53 days
  C. 73 days
  D. 90 days
  E. 120 days
  D. 90 days

  ---

  Explanation

  The cycle of spermatogenesis is 73 ?5 days.

  This is the time required for maturation of spermatogonia to spermatozoa. The cycle is at different stages along the seminiferous tubules, necessary to ensure the presence of sperm in each ejaculate. Further, spermatozoa require approximately 3 weeks to traverse the ductal system and appear in the ejaculate. Knowing this has important implications: any therapy intended to stimulate spermatogenesis must be continued for at least the duration of one spermatogenic cycle to determine whether there is a beneficial effect. While impaired spermatogenesis may occur late in the cycle of spermatogenesis and improvement with clomiphene may occur sooner, the semen analysis should still be delayed for 90 days to provide better evidence for the presence or absence of improvement in the semen analysis.

  Results must be interpreted with caution because there is great biological variability in semen parameters: what is interpreted as a therapeutic effect may only be natural biological variation. Ultimately, pregnancy is the only meaningful measure of treatment success and pregnancy may have occurred despite the therapy, not because of it.