A 54-year-old man comes to the physician because of a 3-day history of low back pain. His temperature is 38.3°C (101°F), pulse is 75/min, and blood pressure is 120/80 mm Hg. Physical examination shows right-sided flank tenderness to percussion. A CT scan of the abdomen shows a lesion consistent with an abscess along the posterior medial aspect of the right kidney. Extension of this process into this patient’s pelvis is most likely to occur along which of the following surfaces?

A 1 -year-old boy receives a left cochlear implant that consists of an array of electrodes. Six months ago, he was diagnosed with severe bilateral hearing deficit. Which of the following elements of the auditory system must remain intact for this patient to perceive auditory stimulation via activation of the electrodes in the implant?

A 27-year-old man comes to the physician because of a 3-hour history of nausea, cramping abdominal pain, and diarrhea. His symptoms developed 24 hours after he ate at a wedding reception; several other people who ate at the reception have similar symptoms. A culture of the stool grows Salmonella enterica. He is able to maintain oral hydration. His symptoms begin to resolve within 36 hours but persist in a milder form for several more days. Which of the following is most likely to occur if this patient is treated with antibiotics?

A 5-month-old boy is admitted to the hospital because of frequent episodes of pneumonia, otitis media, diarrhea, and failure to thrive since birth. Physical examination shows rachitic, rosary-like abnormalities of the rib cage and wasting. Laboratory findings show an absolute lymphocyte count of 400/mm3 (N=1500-3000), and markedly decreased T- and B-lymphocyte counts. The lymphocyte count does not increase in response to mitogens, and there are decreased concentrations of immunoglobulins that do not increase after immunizations. This patient most likely has an enzymatic defect at which of the following steps in the metabolic pathway shown?

A 30-year-old man comes to the physician because of a 2-month history of constant numbness of his right hand. He says he has had intermittent numbness of his right hand for the past 2 years. He says that sometimes the numbness awakens him from sleep. He is a right-handed carpenter. Occasionally at work he needs to rest for a few minutes when the numbness increases. Neurologic examination shows mild atrophy of the right thenar eminence. There is mild weakness of the right abductor pollicis brevis muscle. Sensation to touch is most likely to be decreased or abnormal in which of the following areas?

A 43-year-old man comes to the physician for a follow-up examination. Ten years ago, he underwent cardiac valve replacement. Chest x-rays are shown. Based on these findings, which of the following valves was most likely replaced in this patient?

A healthy 21 -year-old woman is participating in a study of an experimental drug. Various cardiac measurements before and after administration of the drug are shown:

Assuming that no reflex adjustments have occurred, which of the following best describes the mechanism of action of this drug?

A 21-year-old man is brought by ambulance to the emergency department 30 minutes after sustaining a gunshot wound to the leg. He is unconscious. His pulse is 150/min, respirations are 26/min and spontaneous, and blood pressure is 80/60 mm Hg. Physical examination shows pallor. Which of the following sets of changes is most likely in this patient compared with a normal baseline?

The effects of drug X alone, drug X and cholinesterase, and drug X and atropine on an isolated gastrointestinal muscle are shown in the bar chart. Drug X is most likely which of the following?

The prevalence of a disease is three times greater in women than in men, but the incidence of the disease is no different in women than it is in men. Which of the following best explains these findings?

A 53-year-old woman is brought to the emergency department because of double vision for 8 hours. Her temperature is 36.1 °C (97°F), pulse is 88/min, and blood pressure is 218/116 mm Hg. She has smoked 3 packs of cigarettes daily for 30 years. Neurologic examination shows a right-sided ptosis and inability to move the right eye medially or vertically. The right pupil is dilated and nonreactive to light. An MRI of the brain stem shows a lesion of the right cerebral peduncle. Which of the following additional physical findings is most likely in this patient?

A 23-year-old woman comes to the physician because of a 3-week history of frequent thirst and urination; she also has had a 3-kg (6.6-lb) weight loss during this period. Physical examination shows dehydration and tachypnea. Serum studies show a glucose concentration of 330 mg/dL, 2+ ketones, and pH of 7.2. Following the administration of intravenous fluids and insulin, there is marked improvement. The activity of which of the following enzymes has most likely increased in this patient’s hepatocytes because of this treatment?

A 43-year-old man comes to the physician because of progressive shortness of breath during the past year. He is a stockbroker and has had no environmental exposure to toxins. When asked about his smoking habits, he says he smoked marijuana in college and afterwards, until the age of 28 years. He has not smoked any substance since then. He was adopted as a child and does not know his family history. His respirations are 29/min. Diffuse wheezing is heard on auscultation of the chest. Abdominal examination shows mild hepatomegaly. Pulmonary function tests show a decreased FEV1 and decreased diffusing capacity. A chest x-ray shows hyperinflation consistent with air trapping mostly in the lung bases. A CT scan of the chest is shown. Which of the following is the most likely cause of these findings?

A 45-year-old woman has a 2-week history of a heart murmur and hepatomegaly. She has a 3-month history of flushing with hypotension and crampy diarrhea. Which of the following is the most likely site of a primary neoplasm in this patient?

A 55-year-old man with type 1 diabetes mellitus comes to the physician because of intermittent burning pain of his feet during the past 4 months. Examination of the feet shows allodynia bilaterally. Sensation to pinprick is decreased. Motor strength, deep tendon reflexes, joint position, and vibration sense are normal. Which of the following is the most likely cause of the pain in this patient?

Which of the following labeled structures in the sagittal MRI of a knee is largely responsible for preventing excessive posterior movement of the tibia with respect to the femur?

A 65-year-old woman with stage I estrogen receptor-positive breast carcinoma undergoes a mastectomy and radiation therapy. After completion of the chemotherapy, she begins treatment with tamoxifen. The initial site of binding of this agent to its receptor most likely occurs in which of the following areas of the tumor cells?

In a patient with HIV-1 infection, the viral genome is most likely to be found in helper T lymphocytes and which of the following?

A 55-year-old woman is brought to the physician because of a 6-month-history of progressive difficulty walking. Neurologic examination shows spasticity, hyperreflexia, and clonus in the lower extremities. Babinski sign is present bilaterally. A drug with which of the following mechanisms of action will most likely decrease the spasticity in this patient?

A 60-year-old man comes to the physician because of a 6-month history of nonproductive cough, increased skin pigmentation, and swollen feet; he has had a 10-kg (22-lb) weight loss during this period. Physical examination shows hyperpigmentation, muscle wasting, and pedal edema. Laboratory studies show a decreased serum potassium concentration, increased serum concentrations of adrenocorticotropic hormone and cortisol, and metabolic alkalosis. Administration of high-dose dexamethasone has no effect on the serum cortisol concentration. Which of the following is the most likely cause of the findings in this patient?

An otherwise healthy 25-year-old woman in the third trimester of an uncomplicated pregnancy has a hemoglobin concentration of 10.5 g/dL and a hematocrit of 30%. The mean corpuscular volume and mean corpuscular hemoglobin are within the reference range. Which of the following is the most likely cause of her anemia?

Which of the following is the implication of degeneracy of the genetic code?

A 92-year-old woman who was recently admitted to a nursing home because of progressive dementia has large purpuric lesions over the dorsa of both forearms and hands. Her family states that she has had similar lesions on and off for years and that, to the best of their knowledge, these lesions occur in the absence of trauma. The woman appears well cared for and has no other indications of recent or remote injury. Her platelet count is normal. Which of the following is the most likely explanation for the purpura?

A 5-year-old girl is brought to the physician because of a 4-day history of stumbling gait, muscle rigidity, slurred speech, and decreased cognitive function. Ophthalmologic examination shows decreased visual acuity and inability to discern colors. Assays of isolated muscle mitochondria show decreased ability to oxidize NADH but normal FADH2 oxidation. Which of the following electron transport chain complexes is most likely impaired in this patient?

A 42-year-old woman comes to the physician 2 weeks after she found a nodule in the left side of her neck. She is otherwise asymptomatic. Physical abnormalities. She undergoes a thyroid scan with 123I, a nondestructive isotope. After 1 week, the largest amount of circulating 123I would most likely be in which of the following?

A 16-year-old girl comes to the clinic because of vaginal itching for the past 5 days. She requests that her parents not be informed about the appointment. During the examination, she says she occasionally has unprotected sexual intercourse and asks for oral contraceptives. Preliminary laboratory studies show gram-negative diplococci. Which of the following is the most appropriate next step in patient care?

A 36-year-old man is brought to the emergency department 30 minutes after he sustained burns in a house fire. He is 185 cm (6 ft 1 in) tall and weighs 86 kg (190 lb); BMI is 25 kg/m2. Physical examination shows second-degree burns over approximately 40% of the body surface area. Intravenous fluids are administered, and he is admitted to the intensive care unit for supportive care. Compared with a healthy individual, which of the following best represents this patient’s nutritional and fluid requirements?

A prospective study is done to assess the relative efficacy of two different antihypertensive medications, both of which were shown to be efficacious in placebo-controlled trials. In the study, patients with hypertension were randomly assigned to receive one of two antihypertensive medications. At the conclusion of the study, some participants reported inconsistent adherence to their medication regimen, while others reported discontinuing their study medication altogether before the primary outcome (blood pressure measurement after 30 days) was obtained. A few of these patients who discontinued their study medication were prescribed the other group’s study medication by their primary care physician and were taking it at the time of the primary outcome measurement. In their primary analysis, which of the following methods should the investigators use to analyze data from the patients who were not adherent to the medication regimen?

A 35-year-old man comes to the physician 1 day after he noticed a painless mass on the right side of his scrotum. Examination of the scrotum shows a 2-cm, firm, nontender mass on the right that cannot be separated from the right testis. Ultrasonography of the scrotum is shown. Metastases from this site are most likely to appear in which of the following lymph node groups?

A healthy 30-year-old woman participates in a study of cardiovascular function as it relates to posture. Placed in a room with a comfortable temperature (72°F) and humidity (40%), she moves from a standing to a supine position. Which of the following sets of changes is most likely to be observed in this woman’s cardiovascular status?

An 18-year-old man comes to the physician 12 hours after the sudden onset of fever, chills, intense muscle aches, and headache. He has recently been on a hunting trip in Arkansas. His temperature is 39.4°C (103°F), pulse is 110/min, respirations are 18/min, and blood pressure is 110/80 mm Hg. Physical examination shows diaphoresis but no rash. A diagnosis of ehrlichiosis is made. The most appropriate treatment for this patient is an antibiotic with which of the following mechanisms of action?

A 4-year-old girl is conscious but unable to breathe spontaneously for 3 hours following uncomplicated removal of a branchial cleft cyst. The procedure was done under general anesthesia with sevoflurane. Succinylcholine was administered for intubation. Which of the following is the most likely cause of the prolonged apnea in this patient?

A 2-year-old girl is brought to the emergency department by her parents because of a 1-day history of respiratory difficulty. She visited her grandparents 2 days ago; they live on a farm with well water and a septic system. Physical examination shows cyanosis, tachypnea, tachycardia, and subcostal and intercostal retractions. A drop of blood from a fingerstick is brown and remains the same color when placed on a piece of filter paper. Arterial blood gas analysis on room air shows a Po2 and pH within the reference ranges. Her oxygen saturation is decreased. Which of the following is the most likely cause of this patient’s condition?

A female newborn is delivered at 26 weeks’ gestation and develops grunting and chest retractions shortly after birth. She is intubated and mechanically ventilated. A chest x-ray 8 hours later shows bilateral pulmonary infiltrates. The newborn dies the following day, and an autopsy is done. Which of the following findings is most likely on microscopic examination of the lungs?

A 64-year-old man comes to the physician because of a 6-month history of progressive shortness of breath with exertion. He was diagnosed with a hematological malignancy 4 years ago. His pulse is 85/min and blood pressure is 115/60 mm Hg. Physical examination and chest x-ray show no abnormalities. Echocardiography shows a greater than normal echodense ventricular wall with normal thickness. Right-sided cardiac catheterization shows resistance to diastolic filling. A right ventricular endomyocardial biopsy specimen shows interstitial deposits of pink proteinaceous material and degeneration of myocytes. Which of the following is the most likely precursor of the proteinaceous material found in this patient’s heart?

A 23-year-old woman who was recently diagnosed with rheumatoid arthritis comes to the physician for a follow-up examination. Two months ago, she began treatment with adalimumab, which binds with tumor necrosis factor-a. The patient says that her symptoms have not improved. Physical examination shows mild swelling of the joints of the wrists, hands, ankles, and feet. Which of the following immune system components is most likely contributing to this patient’s symptoms?

A 30-year-old woman comes to the physician for a follow-up examination because of a 10-year history of recurrent renal calculi. The calculi have primarily been composed of calcium oxalate. Physical examination shows no abnormalities. Serum calcium and phosphorus concentrations are within the reference ranges. A 24-hour urine collection shows an increased calcium concentration. The physician recommends that the patient increase her consumption of water and decrease her consumption of sodium and protein. The physician also recommends pharmacotherapy with a drug that decreases urinary calcium concentrations. Which of the following is the most likely mechanism of action of this drug?

A 25-year-old man comes to the emergency department because of a 3-day history of abdominal cramps and diarrhea. He appears anxious. Physical examination shows piloerection and diffuse abdominal tenderness. Neurologic examination shows no abnormalities. He is oriented to person, place, and time. The most likely cause of this patient’s condition is withdrawal from which of the following substances?

A 43-year-old woman undergoes ultrasonography for suspected cholecystitis. Ultrasonography shows that the right kidney is absent; the left kidney appears normal. The most likely cause of this anomaly is failure of which of the following tissues to respond to the developmental stimulus provided by the growth of the ureteric bud?

A 51-year-old woman comes to the physician because of a 5-month history of occasional vague hip and thigh pain when working in her garden. Physical examination shows no abnormalities. Laboratory studies show an increased serum alkaline phosphatase activity. An x-ray of her right hip and upper leg shows a dense thickening of the bony cortex in the femur. Which of the following is the most likely diagnosis?

A 23-year-old man comes to the physician because of pain in his left leg for 3 days. He has a 9-year history of alcoholism. He has a court hearing scheduled the next day for driving while under the influence and another court hearing scheduled the following week for “fighting in a bar.” He blames “overzealous police” for his legal problems and says that most people are stupid and don’t see things his way, which is the right way. Physical examination shows no abnormalities of the left lower extremity. This patient most likely has which of the following personality disorders?

A 44-year-old man with a 25-year history of alcoholism is brought to the emergency department by his wife because of a 1-day history of confusion. The wife reports that the patient’s personality has recently changed and that he vomited a small amount of blood several days ago. He last consumed alcohol 2 weeks ago. Liver function tests 3 years ago showed abnormal findings. He is alert and disheveled. His pulse is 82/min, respirations are 20/min, and blood pressure is 100/64 mm Hg. Physical examination shows signs of mild dehydration, mild jaundice, spider angiomata over the face and chest, and asterixis. There are no tremors or ophthalmoplegia. The abdomen is distended with bulging flanks and shifting dullness. The spleen tip is palpated 3 cm below the left costal margin. There is testicular atrophy. Mental status examination shows that he is not oriented to time or place. His immediate and recent memory is impaired. Which of the following is the most likely diagnosis?

A paper says, “We chose the sample size to have an 80% power of detecting a 15% mean difference with a significance level (two-sided) of 5%.” If there really is no difference between the groups overall, which of the following best represents the chance that the study will find a statistically significant difference, and what is this error called?

A 27-year-old man comes to the physician because he is concerned about his skin. He says that he has had similar problems with hypopigmented skin for 2 years but that the condition has been exacerbated in recent months. A photograph of the affected skin is shown. The remainder of the physical examination shows no other abnormalities. Which of the following is the most likely causal organism?

A 69-year-old woman is brought to the physician by her son because of a 2-month history of memory problems, difficulty walking, and urinary incontinence. He says, “She’s always been very sharp, but recently she’s had a lot of trouble functioning.” She has forgotten on several occasions to turn off the stove when cooking, and she once forgot she had turned on the bathtub until she noticed water coming down the walls from the upstairs bathroom. She also is unsteady on her feet and has fallen down at home on several occasions. She reports that her mood is fine. Physical examination shows mild nystagmus. She has a broad-based gait and is unable to walk in a straight line without assistance. Neurologic examination shows no other focal findings. Mini-Mental State Examination score is 20/30. Which of the following is the most likely diagnosis?

A 20-year-old man comes to the emergency department 30 minutes after fainting while playing basketball. He has felt tired for the past 3 months. A systolic murmur is heard at the left sternal border. The murmur increases when he strains against a closed glottis and decreases when he lies supine with his legs elevated. Which of the following is the most likely diagnosis?

A 32-year-old woman comes to the physician because of a 7-day history of sneezing, nasal stuffiness, and watery eyes. She has a history of similar symptoms each spring while gardening. Her temperature is 37°C (98.6°F). Which of the following types of cells are most likely to be increased in her nasal secretions as a result of this reaction?

A 44-year-old woman comes to the physician because of a 3-day history of a persistent nosebleed and a diffuse rash. She has no history of major medical illness and takes aspirin occasionally for headaches. Her vital signs are within normal limits. A photograph of her left foot is shown. Similar findings are on the torso and upper and lower extremities. Laboratory studies show:

Which of the following is the most likely diagnosis?

A pharmaceutical company develops a new opioid drug (Drug X) that binds to the same receptor as morphine does. Drug X is compared with morphine to test its analgesic effect. The graph shows the log dose-response curves for morphine and Drug X. Based on these results, which of the following best describes Drug X?

Alterations of the p53 tumor suppressor gene are most likely seen in patients who have which of the following neoplasms?