A 45-year-old woman is brought to the emergency department because of a 6-hour history of constant right flank pain, fever, pain with urination, and blood in the urine. Antibiotic treatment was initiated 2 weeks ago for a urinary tract infection caused by Proteus mirabilis. She is writhing on the hospital bed, unable to find a comfortable position. Her temperature is 38.3°C (101°F), pulse is 110/min, respirations are 30/min, and blood pressure is 160/80 mm Hg. Abdominal examination shows no abnormalities except for tenderness of the right flank to palpation. Urinalysis shows 1 + blood and a pH of 7.5. A spiral CT scan of the abdomen shows a staghorn right renal calculus. This renal calculus is most likely composed of which of the following?

A 30-year-old woman comes to the physician for a health maintenance examination. She is training for a marathon and has been running up to 20 miles daily. She states that as long as she has adequate caloric intake, she feels well on long-distance runs of up to 20 miles. Physical examination shows no abnormalities. Her fasting serum glucose concentration is 60 mg/dL. After her glucose stores have been depleted, which of the following organs, in addition to the liver, is most likely to release newly produced glucose in this patient?

A 10-year-old girl is referred to a cardiologist because of a 6-year history of a murmur. She is asymptomatic. Physical examination shows a grade 2/6, systolic ejection murmur heard over the left sternal border. An ECG shows right axis deviation and right ventricular hypertrophy. She undergoes cardiac catheterization. Oxygen saturation findings are shown in the block diagram. This patient most likely has which of the following congenital heart defects?

A 35-year-old woman comes to the physician because of fever and left flank pain for 2 days. She has had several similar episodes during the past 4 years, all of which resolved with antibiotic therapy. Her temperature is 38.6°C (101.5°F). Physical examination shows exquisite left costovertebral angle tenderness. Urinalysis shows small numbers of WBCs and WBC casts, and numerous triple phosphate crystals. A course of antibiotic therapy does not resolve the pain and the patient undergoes resection of the left kidney. A photograph of the patient’s resected kidney is shown. Which of the following was the most likely causal organism in this patient’s disease process?

A 55-year-old woman with a history of alcohol dependence has severe epigastric pain and is vomiting large amounts of blood. She has slightly yellow skin and conjunctivae. Her abdomen is large and distended. The bleeding vessels are most likely enlarged due to increased blood flow directly supplied by which of the following veins?

A 10-year-old girl is brought to the physician by her mother because of increased hair growth on her face and increased muscle mass during the past 3 months. Breast development is Tanner stage 1, and pubic hair development is Tanner stage 5. Physical examination shows clitorimegaly. Pelvic examination shows a normal-appearing vagina. Serum studies show:

An unregulated increase in hormone production by which of the following types of cells is the most likely cause of this patient’s hirsutism?

A 35-year-old woman with leiomyomata uteri undergoes an experimental treatment that involves instillation of an embolizing agent directly into the vessels that feed the leiomyomata. During this procedure, in order to reach the involved vessels, which of the following is the most direct course of the catheter after entering the femoral artery?

A 69-year-old woman is brought to the emergency department because of confusion and light-headedness for 45 minutes. She has a 5-year history of type 2 diabetes mellitus treated with glipizide. Recently, the dose of glipizide was increased. Her vital signs are normal. Physical examination shows no abnormalities. Her blood glucose concentration is 43 mg/dL. Intravenous infusion of glucose is begun. Which of the following is the most likely explanation for hypoglycemia in this patient?

A 70-year-old woman comes to the physician for advice after her husband of 45 years suddenly dies of cardiac arrest. She wants to donate $1,000,000 to a small city’s department of public health to decrease the number of sudden cardiac deaths. She asks the physician to recommend the most effective way to put this money to use. She says, “I want to see the results of my donation over the next 1 to 2 years.” The patient is most likely to accomplish her goal if she contributes to which of the following?

A 44-year-old man comes to the physician for a follow-up examination 1 month after receiving a cadaveric kidney transplant. He says he feels well. Current medications include mycophenolate and prednisone. Physical examination shows an arteriovenous fistula in the left upper extremity and a well-healing surgical wound over the right lower quadrant of the abdomen. Serum studies show a urea nitrogen concentration of 44 mg/dL and creatinine concentration of 2.6 mg/dL, compared with 21 mg/dL and 1.8 mg/dL, respectively, 2 weeks ago. Examination of a biopsy specimen of the transplanted kidney shows an inflammatory infiltrate affecting the small arterioles. These changes are most likely caused by which of the following mechanisms?

A 20-year-old man with sickle cell disease has chronic hemolytic anemia and has frequent painful crises that require transfusions. Hydroxyurea treatment significantly decreases the painful crises and transfusion requirements. Which of the following is the most likely mechanism of the beneficial effects of this treatment?

A 65-year-old man comes to the physician because of a 3-month history of substernal chest pain that occurs after eating. Physical examination shows no abnormalities except for systolic hypertension. Results of an exercise stress test are positive. The table shown depicts the results of an exercise stress test in 1000 patients at similar risk compared with the presence or absence of coronary artery disease (CAD).

Based on these data, which of the following is the pretest probability of CAD in this patient?

A previously healthy 6-year-old boy is brought to the physician by his mother because of a 1 -week history of an itchy rash in his armpits, both hands and feet, and groin. The itching is most intense at night and keeps him awake. His vital signs are within normal limits. Examination of the skin shows multiple erythematous papules, some with burrows and many of which are excoriated, similar to the ones shown in the photograph. Which of the following questions to the mother will be most helpful in establishing the diagnosis?

A 3-year-old boy is brought to the physician because of a 4-hour history of abdominal pain and vomiting. His mother says that she also has occasionally noticed several 20-cm, white worms in his stool during the past month. He recently immigrated to the USA from India with his family. Abdominal examination shows marked distention and tympany. Bowel sounds are high pitched. Which of the following is the most likely causal organism?

A 64-year-old woman comes to the physician because of a 6-month history of heartburn and difficulty swallowing solid food and liquid. She has not had nausea or vomiting. She also has a 2-year history of pain and swelling of her wrists and hands. She has not seen a physician in 5 years. She takes no medications. She does not smoke. Physical examination shows no wrinkles on the face and neck. Her vital signs are within normal limits. There is synovial thickening of the wrists bilaterally. A photograph of the left hand is shown. Abdominal examination shows no abnormalities. Which of the following sets of findings is most likely on esophageal manometry?

A 45-year-old man is undergoing a surgical procedure. Which of the following maneuvers by the anesthesiologist would result in an increase in intracranial pressure?

An investigator is studying the effects of succinylcholine and Drug X on muscle contraction in an experimental animal model. During the study, the force of contraction of abdominal muscles is recorded after the administration of succinylcholine alone. In a separate experiment, Drug X is administered concurrently with succinylcholine. Results show that the phase I neuromuscular blockade induced by succinylcholine is enhanced by concurrent administration of Drug X. However, when Drug X is administered during the succinylcholine-induced phase II neuromuscular blockade, it is found that Drug X reverses the effects of succinylcholine. Drug X is most likely which of the following?

A 60-year-old man comes to the emergency department because of swelling of his right elbow that began after he struck it against the edge of a file cabinet earlier that day. On physical examination, the tip of the olecranon is obscured by a golf ball-sized fluctuant mass with well-defined borders. The mass is swollen, mildly tender, and smooth. Range of motion of the elbow is normal. Which of the following structures was most likely injured in this patient?

A female newborn delivered at 26 weeks’ gestation is found to have hyaline membrane disease. She is intubated and mechanically ventilated. Her vital signs are continuously monitored, and inspired oxygen is maintained at a level that will sustain an oxygen saturation between 92% and 95%. The primary goal of this treatment is protection of which of the following structures?

Which of the following abnormalities is most likely to result from occlusion of the vessel indicated by the arrow in the vertebral angiogram shown?

A 3-year-old boy is brought to the emergency department by his father because of bleeding from a cut on his left arm after he fell off his tricycle 1 hour ago. Physical examination shows a 2-cm shallow laceration on the left upper extremity. The laceration has stopped bleeding and is covered with a clot. This finding results from hepatic synthesis of which of the following?

A 48-year-old man comes to the emergency department because of a 3-day history of fever, chills, headache, and nonproductive cough. He underwent renal transplantation 5 years ago. Current medications include corticosteroids. His temperature is 40°C (104°F). Coarse rhonchi are heard over the right lower lobe on auscultation. A chest x-ray shows right lobar pneumonia with small pleural effusions. The patient is treated with an antibiotic that inhibits DNA gyrase. This drug is most likely which of the following?

A 7-year-old boy is brought to the physician by his mother because of a 3-hour history of pain and stiffness of his neck. Two days ago, he fell off his bike and hurt his neck. Physical examination shows decreased range of motion of the neck. Neurologic examination shows no abnormalities. AP and lateral x-rays of the cervical spine show congenital fusion of the atlas to the occipital bone associated with C2-3 vertebral fusion. Flexion and extension of the neck are most likely placing additional strain on which of the following structures in this patient because of his congenital abnormalities?

A 1-year-old girl is admitted to the hospital because of failure to thrive. She has had frequent, loose stools for 6 months. She has not gained weight satisfactorily during this period. She is at the 3rd percentile for length and weight. Physical examination shows facial edema. Laboratory studies show hypoalbuminemia. Examination of the contents of the duodenum postprandially show:

A deficiency of which of the following enzymes is the most likely cause of these findings?

An 82-year-old woman with type 2 diabetes mellitus and painful neuropathy comes to the physician for a follow-up examination. At her last visit 3 months ago, the physician prescribed a topical cream and recommended use of acetaminophen as needed for pain. The patient reports that the topical therapy helped more than she expected and did decrease her need for acetaminophen. Physical examination shows no change in her condition. The prescribed cream most likely depletes which of the following substances from sensory nerve endings?

A 16-year-old boy with intellectual disability is admitted to the hospital because of severe respiratory distress. Physical examination shows dislocation of the ocular lenses bilaterally, dyspnea, and tenderness and edema of the left lower extremity. Serum concentrations of methionine and homocysteine are increased, and serum cystine concentration is decreased. This patient most likely has a defect of which of the following enzymes?

A 70-year-old man comes to the office because of a 6-day history of abdominal pain. He has no history of major medical illness and takes no medications. His vital signs are within normal limits. Physical examination shows epigastric tenderness. A CT scan of the abdomen shows a mass in the liver. As part of a study, electron microscopy of a biopsy specimen of the mass is done. Results show nuclear chromatin margination under the nuclear membrane, intact cell membranes, and cells that are smaller in size than normal cells in the tissue. The mechanism causing the cell size anomaly in this patient was most likely triggered by the release of which of the following substances into the cytoplasm?

An investigator creates Drug Z that interferes with protein synthesis by binding to the anticodon on the human tRNA shown in the diagram. Drug Z is most likely binding in the place of which of the following codons?

A 20-year-old woman is brought to the emergency department by her roommate 30 minutes after she ingested a large quantity of acetaminophen tablets during a suicide attempt. The physician asks her why she tried to kill herself. She replies tearfully, “My boyfriend told me that he doesn’t want to see me again, and he won’t return any of my phone calls. I loved him more than I’ve loved anyone else in my entire life. I was going to marry him! Now I hate his guts for what he’s done to me. I just wanted to die.” On further questioning, the physician learns that she had only two dates with this man. She tells the physician, “I just can’t bear being alone. But I can tell that you understand. You’re the only doctor who’s ever understood how I feel.” This patient most likely has which of the following types of personality disorders?

A 67-year-old man comes to the physician because of a 2-month history of unexplained weight loss. He has a 50-year history of type 1 diabetes mellitus. He underwent gallstone removal 12 years ago. He has smoked 1 pack of cigarettes daily for 45 years. He is 188 cm (6 ft 2 in) tall and weighs 120 kg (265 lb); BMI is 34 kg/m2. Physical examination shows no other abnormalities. Serum studies show a calcium concentration of 11 mg/dL. An abdominal CT scan shows a pancreatic mass. A biopsy specimen of the mass shows pancreatic adenocarcinoma. Which of the following is the strongest predisposing risk factor for pancreatic cancer in this patient?

A 5-year-old boy who had intrauterine growth restriction has continued to grow slowly. Psychomotor development show that he has uniparental maternal heterodisomy for chromosome 7. Which of the following mechanisms best explains his slow growth?

A 34-year-old woman comes to the office because of a 6-month history of progressive swelling of her hands and feet. Her blood pressure is 140/89 mm Hg. Physical examination shows 1+ edema of the hands and 2+ edema of the feet. Serum studies show a potassium concentration of 3.3 mEq/L, decreased aldosterone concentration and plasma renin activity, and increased cortisokcortisone ratio. After questioning, it is found that the patient has been consuming a nutritional supplement she obtained from the Internet during the past 10 months. Serum studies obtained after the patient stops using the supplement are within the reference ranges. The supplement this patient consumed most likely inhibited the activity of which of the following enzymes?

A 1-year-old boy is admitted to the hospital for antimicrobial treatment of perianal pain and erythema. He has a history of recurrent infections, including an admission to the hospital at the age of 2 weeks because of high-grade fever and swelling and redness around the umbilical cord stump. Physical examination shows perianal erythema and tenderness but no fluctuance. Laboratory studies show:

This patient most likely has a genetic deficiency of which of the following immune system components?

A full-term female newborn is evaluated shortly after birth. Pregnancy and delivery were uncomplicated. During the first 5 minutes after delivery, which of the following is most likely to be increased in this newborn?

A 57-year-old man comes to the physician because of increasingly severe joint pain and weakness during the past 2 months. Physical examination shows pallor. Laboratory studies show:

A chimeric growth-promoting protein with which of the following activities is most likely encoded in this patient due to the presence of this chromosome?

A 25-year-old man comes to the physician because of a 6-week history of daytime fatigue, irritability, and emotional lability; he has had a 4.5-kg (10-lb) weight loss during this period. He says that he is sleep-deprived, but he is unable to fall asleep readily. He is a medical student and has recently finished an intensive care unit rotation where he often worked days and nights. He is currently on an outpatient rotation and will be starting vacation next week. Physical examination shows no abnormalities. Which of the following recommendations by the physician is most appropriate to improve this patient’s sleep hygiene?

A 10-month-old female infant is brought to the physician because of a 1 -day history of a rash. Her mother says that the infant also had a 3-day history of high fever and irritability, which spontaneously resolved 2 days ago. The patient is alert and playful. Her temperature is 37°C (98.6°F). Physical examination shows the findings in the photograph. Which of the following is the most likely causal agent?

A 3685-g (8-lb 2-oz) male newborn is delivered vaginally at term to a 26-year-old primigravid woman. Pregnancy and delivery were uncomplicated. Apgar scores are 9 and 9 at 1 and 5 minutes, respectively. Physical examination shows no abnormalities. An antibiotic ointment is applied to his eyes to prevent ocular infections. Inhibition of which of the following is most likely to occur with this treatment?

A 37-year-old woman is brought to the emergency department after her husband found her unconscious. Her temperature is 36°C (96.8°F), pulse is 128/min, and blood pressure is 70/40 mm Hg. Physical examination shows cool, pale extremities, jugular venous distention, faint peripheral pulses, and crackles over the bottom two thirds of both lung fields. Heart sounds are normal, and there are no murmurs. She withdraws to painful stimuli in all four extremities. This patient is most likely experiencing which of the following types of shock?

A 10-year-old girl is brought to the physician by her parents 30 minutes after she sustained a red ant bite to her right foot. The parents report that within 15 minutes, redness and swelling occurred at the site of the bite. Physical examination shows edema and erythema at the wound site. The action of which of the following chemical mediators on postcapillary venules is the most likely cause of these findings?

A 34-year-old woman is brought to the emergency department 30 minutes after being involved in a motor vehicle collision. Sensation to pain is decreased over the left lower extremity. Which of the following labeled regions on the diagram of the spinal cord shown is most likely damaged in this patient?

A 24-year-old woman at 28 weeks’ gestation is brought to the emergency department because of a 3-hour history of shortness of breath. She has asthma, but she currently takes no medications. Her pulse is 100/min, respirations are 32/min, and blood pressure is 120/83 mm Hg. Physical examination shows the use of accessory muscles of respiration. Diffuse inspiratory and expiratory wheezes are heard. An inhaled β2-adrenergic agonist is administered. Which of the following findings is most likely in this patient after this therapy?

A study is conducted to assess body mass index (BMI) in a group of 100 patients with type 2 diabetes mellitus. Results show a mean (± standard error of the mean) BMI of 31 kg/m2 (± 4 kg/m2). The 99% confidence intervals for this measurement are 20.7 to 41.3. The 95% confidence intervals are 23.3 to 38.8. Based on this information, which of the following best represents the number of individuals who have a BMI between 38.8 kg/m2 and 41.3 kg/m2?

A 54-year-old woman comes to the physician because of a 3-month history of fatigue and a persistent cough productive of colorless mucoid sputum. She also has had a 14-kg (30-lb) weight loss during this period. She has smoked 2 packs of cigarettes daily for 25 years. She is 168 cm (5 ft 6 in) tall and now weighs 52 kg (115 lb); BMI is 19 kg/m2. Percussion of the chest shows hyperresonance. Her serum calcium concentration is 12.8 mg/dL. A chest x-ray shows a mass in the right middle lobe of the lung near the hilum. Examination of aspirate from the mass shows malignant cells. The neoplasm in this patient is most likely which of the following?

A 15-month-old boy is brought to the physician by his mother because of a 9-month history of recurrent bacterial infections. The patient has not had recurrent viral infections. He is at the 10th percentile for length and weight. Physical examination shows multiple areas of honey yellow, crusted lesions over the lower extremities. A Gram stain of one of the lesions shows many gram-positive cocci in clusters but no leukocytes. Laboratory studies show no abnormalities except for a leukocyte count of 30,000/mm3. This patient most likely has a rare autosomal recessive disease leading to a lack of CD18 expression. The leukocytes would be deficient in which of the following characteristics?

During a clinical study, a researcher finds that as children approach puberty, the consumption of milk in the diet is partially replaced by the consumption of soft drinks. This results in a decrease in calcium intake. This dietary change is most likely to have which of the following effects on bone mineralization or metabolism?

A 3-year-old boy is brought to the physician because of developmental delay. He has a history of a cleft palate that was repaired surgically at the age of 1 year. He did not walk until the age of 18 months and did not speak any words until the age of 20 months. His height and weight are at the 5th percentile; his head circumference is below the 5th percentile. Examination shows ptosis and a smooth philtrum. Maternal use of which of the following substances during pregnancy is the most likely cause of this patient’s condition?

A 52-year-old man comes to the physician because of inability to achieve an erection 6 weeks after undergoing operative removal of a tumor on the distal portion of the rectum. During the excision, the tumor was found to be extensively attached to the posterior aspect of the prostate. Damage to which of the following nerves is the most likely cause of this patient’s symptoms?

A 58-year-old man with chronic pancreatitis comes to the physician because of a 3-week history of greasy, foul-smelling stools. The stools are difficult to flush. There is no associated blood or mucus. He is 178 cm (5 ft 10 in) tall and weighs 65 kg (143 lb); BMI is 21 kg/m2. Vital signs are normal. Physical examination shows no abnormalities; there is no jaundice. Which of the following recommendations is most appropriate for this patient?

A 64-year-old homeless man with alcoholism is brought to the emergency department by police after he was found wandering aimlessly in a city park. He has weakness, fatigue, and hunger. He appears disheveled and cachectic. His temperature is 38.2°C (100.8°F), pulse is 110/min, respirations are 20/min, and blood pressure is 134/82 mm Hg. Physical examination shows mild scleral icterus, numerous skin abrasions, and 1+ edema of the lower extremities. He is oriented to person but not to place or time. Laboratory studies show:

A photomicrograph of a peripheral blood smear is shown. A deficiency of which of the following best accounts for the hematologic findings in this patient?