USMLE-STEP-2 Online Practice Questions and Answers

Correct Answer: B

Testicular cancer is the most common cancer in men between the ages of 20 and 40. Predisposing factors include cryptorchidism, hernias, and testicular atrophy. Abdominal testes are at higher risk than inguinal cryptorchid testes. Family history of testicular or prostate cancer, radiation exposure, or maternal DES seems to play no role. Testicular cancers are divided into nonseminoma and seminoma subtypes. Seminoma represents about 50% of all tumors and generally follows a more indolent course. The primary tumor is treated by inguinal orchiectomy regardless of cell type. Pure seminomas do not require retroperitoneal lymph node dissection, because radiation is usually adequate therapy. Nonseminomatous testicular tumors (embryonal cell, teratocarcinoma, choriocarcinoma, endodermal sinus) are usually treated by retroperitoneal dissection. Serum alpha-fetoprotein (AFP) and hCG levels are markers that are important for diagnosis and as prognostic indicators and are used to monitor therapy. Serum LDH level is often elevated with bulky tumors but is not as specific as either AFP or hCG. CEA is a nonspecific marker elaborated by many adenocarcinomas. PSA is a marker associated with prostate cancer

Correct Answer: C

The most common causes of megaloblastic anemia are folate and vitamin B12 deficiencies. Vitamin B12 deficiency rarely results from inadequate intake, but has been associated with strict vegetarianism. Decreased absorption may be due to insufficient intrinsic factor (as in pernicious anemia and after gastrectomy), malabsorption of the intrinsic factor-vitamin B12 complex in the terminal ileum (as in regional enteritis, sprue, pancreatitis, and after ileectomy), or competition for vitamin B12 by gut bacteria (as in the blind loop syndrome and Diphyllobothrium latum infections). Because diverticulosis and constipation do not interfere with stomach or small-bowel functioning, they are not causes of vitamin B12 deficiency.

Correct Answer: B

Unlike women with overt or pregestational diabetes mellitus, the risk of fetal anomalies is not increased in women with gestational diabetes. Stillbirth rates are increased in women with gestational diabetes if their fasting plasma glucose concentrations are elevated, but not with elevated postprandial glucose concentrations only. The risk of a growth-restricted infant is increased in women with long-standing diabetes and vascular disease, but not in women with gestational diabetes. There is a slight increase in the frequency of fetal macrosomia (birth weight over 4000 g), though shoulder dystocia and brachial plexus injury are infrequent.

Correct Answer: B

Pap smear and colposcopy are screening tests appropriate when there is no visible cervical pathology. In the presence of a lesion, pathologic evaluation is necessary to make a diagnosis. An office cervical biopsy is the procedure of choice to establish the diagnosis. If the diagnosis from the biopsy is cancer, a conization of the cervix is indicated to determine the extent of the disease surface spread as well as depth of stromal invasion. As a general principle, cytology is a screening tool, not a diagnostic test, and any visible lesion (vulvar, vaginal, or cervical) should be biopsied for a definitive diagnosis

Correct Answer: D

The dopamine hypothesis of schizophrenia grew from the observations that medications that block dopamine receptors have antipsychotic activity and medications that stimulate dopamine receptors (amphetamines) can induce psychosis. Serotonin abnormalities have been implicated in mood and anxiety disorders. The biogenic amine hypothesis of mood disorders was based on the finding that tricyclic and MAOI drugs are effective in alleviating the symptoms of depression. The GABAergic system has been implicated in anxiety disorders because benzodiazepines which are GABAergic have antianxiety effects. Acetylcholine abnormalities have been associated with dementia.

Correct Answer: A

Patients with NMS typically demonstrate tachycardia, labile blood pressure, severe muscle rigidity, and severe fever. Serum CPK levels, which can be elevated to more than 100 times normal levels as a result of muscle damage, are the most consistently noted abnormalities in patients with NMS. Although the white blood cell count may be elevated, and blood levels of calcium, iron, and magnesium may be decreased in patients with the syndrome, serum CPK is the most important laboratory study to obtain in a patient with suspected NMS

Correct Answer: D

Gastric ulcers present with symptoms of abdominal pain, aggravated by food, and associated with nausea, vomiting, anorexia, and weight loss. The two principal means of diagnosing a gastric ulcer are UGI radiographs and fiberoptic endoscopy, the latter being the most reliable method. CT scan and endoscopic ultrasound may be helpful in staging gastric cancer, but are not routinely used with benign disease. The failure to respond to 12 weeks of medical management is an indication for surgical therapy to avoid potential complications and to exclude malignancy, despite biopsies obtained by endoscopy that show benign disease.

Correct Answer: J

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

Correct Answer: C

Hib vaccine is recommended for routine immunization of children. Introduction of the Hib conjugate vaccine in the late 1980s was followed by a spectacular decrease in the incidence of H. influenzae meningitis. Anthrax vaccine is used to vaccinate military troops in selected overseas deployment. Rabies vaccine is used for postexposure prophylaxis when children are bitten by potentially rabid mammals. Hepatitis Avaccine is used for children at special risk of such infection. Typhoid vaccine is not routinely recommended for use in the United States but may be indicated for travelers to areas in the developing world where typhoid fever is endemic.

Correct Answer: C

Guidelines for antibiotic prophylaxis of infective endocarditis (IE) underwent a major revision in 2007. Prophylaxis is now only recommended for those patients at highest risk of IE including patients with a prosthetic valve, history of IE, cardiac transplant patients that develop valvulopathy, cyanotic congenital heart disease that remains unrepaired, cyanotic congenital heart disease that has been repaired with a prosthesis during the first 6 months after the procedure or if a defect remains at the site of the prosthesis after 6 months. Congestive heart failure, an S4 gallop, and diabetes do not increase risk. Recommended antibiotic coverage for high-risk patients before dental procedures is amoxicillin 2 g PO 1 hour before the procedures. Penicillin-allergic patients can receive clarithromycin, cephalexin, cefadroxil, or clindamycin as prophylaxis. Streptococci and S. aureus are responsible for the majority of community- acquired native valve endocarditis cases.

In IV drug abusers, S. aureus is responsible for more than 50% of cases, and Candida and Pseudomonas for about 6% each. Patients with prior endocarditis are at high risk. Bacterial endocarditis carries a mortality rate of about 25%, and prevention is of paramount importance. In S. aureus endocarditis in injection drug users, mortality is only 1015%. As many as 40% of cases occur without underlying heart disease. VSD, patent ductus arteriosus, and tetralogy of Fallot are most commonly associated; whereas, ASD is rarely a predisposing factor.