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A 3-month-old boy is evaluated for large-volume diarrhea and failure to thrive. The patient was born via spontaneous vaginal delivery at 38 weeks gestation. His mother reports that the pregnancy was uncomplicated and there is no family history of gastrointestinal disease. Physical examination shows mild abdominal distension, muscle wasting, and pitting edema. Histochemical evaluation reveals absence of enteropeptidase activity in the proximal intestinal villi. Activity of which of the following substances is most likely impaired in this patient?
- Amylase
- Bile salts
- Lactase
- Pepsin
- Secretin
- Trypsin
A 73-year-old man comes to the emergency department with unstable angina. He undergoes coronary angiography via the femoral approach. A stent is placed in the right coronary artery, and the patient is discharged. He returns to the emergency department 2 days later with blue discoloration of his right toe. He has pain and mild tingling in the affected toe. Medical history is significant for hyperlipidemia and coronary artery disease. On physical examination, the right toe appears cyanotic, and there is livedo reticularis affecting the right thigh. Peripheral pulses in the lower extremities are bilaterally palpable. Serum creatinine is 2.8 mg/dL (preoperatively it was 1.0 mg/dL). Which of the following histopathologic findings would most likely be seen on biopsy of this patient’s kidney?
- Cholesterol clefts in arterial lumen
- Glomerular crescent formation
- Hyperplastic arteriolar changes
- Extensive necrosis of proximal tubular cells
- Tubular obstruction with urate crystals
Physiologists are studying the forces governing glomerular ultrafiltration using a single nephron in an intact kidney of an experimental animal. Hydrostatic pressure in the glomerular capillary and Bowman space is measured using micropipette transducers. Colloid osmotic pressure in the glomerular capillary is estimated using the difference in plasma protein concentration in the afferent and efferent arterioles. The glomerular surface is assumed to be functionally intact with negligible filtration of plasma proteins into the Bowman space. From the data obtained, net filtration pressure is calculated at 10 mm Hg. A substance is instilled into the renal artery, and measurements are repeated. The net filtration pressure after the intervention is 20 mm Hg. Which of the following substances was most likely used in this experiment?
- Albumin concentrate
- Alpha-adrenergic agonist
- Angiotensin II agonist
- Prostaglandin inhibitor
- Vasopressin 2 antagonist
A 69-year-old man is evaluated shortly after undergoing elective surgical repair of a descending thoracic aortic aneurysm. He has weakness in both lower extremities and urinary retention, which were not present before the procedure. The surgery was complicated by significant blood loss requiring multiple transfusions. The patient has a history of osteoarthritis, hypertension, hyperlipidemia, type 2 diabetes mellitus, and coronary artery disease. He also has 70% stenosis of his right carotid artery. Neurologic examination shows flaccid paralysis and loss of pain sensation in the lower extremities; vibratory sensation is intact. Upper extremity examination reveals no abnormalities. Which of the following is the most likely cause of this patient’s neurologic dysfunction?
- Cervical spondylotic myelopathy
- Epidural hematoma compressing the spinal cord
- Intraoperative cortical stroke
- Lumbar plexopathy
- Spinal cord infarction
A 44-year-old man is brought to the emergency department after he was found unresponsive at the scene of a high-speed motor vehicle collision. The paramedics report that he was the unrestrained driver, and the passenger in his car was pronounced dead at the scene. The patient was intubated and rushed to the hospital. On arrival, his blood pressure is 78/40 mm Hg, pulse is 135/min, and pulse oximetry is 96% on mechanical ventilation with 40% oxygen. Rapid infusion of isotonic fluids is initiated. Trauma primary survey reveals an intubated man with appropriate spinal precautions. There is bruising and the imprint of the steering wheel across the anterior chest. The trachea is midline, and breath sounds are clear on the right but diminished on the left. Neck veins are collapsed bilaterally. Heart sounds are normal. All four extremities are pale and cool to the touch. There is no obvious external hemorrhage. Portable chest x-ray shows multiple rib fractures, opacification of the left hemithorax, and a widened mediastinum. ECG shows sinus tachycardia. Which of the following is the most likely diagnosis?
- Bronchial rupture
- Diaphragmatic rupture
- Esophageal rupture
- Myocardial contusion
- Myocardial rupture
- Neurogenic shock
- Thoracic aortic injury
A 4-month-old boy is brought to the office for “noisy breathing.” The patient’s parents first noticed a harsh sound when he cried at age 2 weeks, but it has gotten louder over the past month, especially when he is lying on his back. The noise seems to improve when the patient is held upright or during “tummy time.” He does not appear to have labored breathing and has never turned blue. The patient has had occasional, small spit-ups after feeds but has been growing well along the 60th percentile for weight. He was born at full term without complications during pregnancy or labor and delivery. On physical examination, the patient has inspiratory stridor when he is supine that improves when he is prone. The remainder of the examination is normal. Which of the following would confirm the most likely diagnosis for this patient?
- Chest radiography
- CT scan of the neck
- Flexible fiberoptic laryngoscopy
- Fluoroscopic barium swallow
- MR angiography of the neck
- Plain radiograph of the neck
A bedside ultrasound reveals a low, posterior placenta that extends over the internal cervical os. The patient continues to have heavy vaginal bleeding, and a cesarean delivery is performed under spinal anesthesia. The neonate and placenta are delivered without difficulty. During repair of the uterine incision, she reports difficulty breathing shortly before becoming unresponsive. Blood pressure is 70/40 mm Hg, pulse is 124/min, and respirations are 34/min. Pulse oximetry is 86% on room air. A lung examination reveals decreased breath sounds bilaterally. Endotracheal intubation is performed, and the airway is secured. Profuse bleeding is noted from the uterine incision and placental bed. Examination of the Foley catheter reveals frank blood in the collection bag. Which of the following most likely led to this patient’s decompensation?
- Amniotic fluid embolism
- High spinal anesthesia
- Local anesthetic systemic toxicity
- Placenta accreta
- Preeclampsia with pulmonary edema
A 6-month-old boy is brought to the office by his mother due to fever for 3 days. He has been irritable for the past 2 days. The patient normally drinks 6-oz bottles of expressed breast milk, but he has been taking < 3 oz per feed and voiding less frequently than usual. He has had no rash, cough, congestion, vomiting, or diarrhea. The patient takes no medications and has no known allergies. Temperature is 38.9 C (102 F). He is irritable but easily consoled by his mother. Mucous membranes are moist, and tears are present with crying. Tympanic membranes are gray and translucent bilaterally, and the oropharynx is normal. Cardiopulmonary examination is normal. The abdomen is soft, nontender, and nondistended. The penis is uncircumcised. Urine catheterization is performed, and urine dipstick analysis reveals the following:
| Specific gravity | 1.020 |
| Protein | none |
| Blood | trace |
| Leukocyte esterase | moderate |
| Nitrites | positive |
Oral antibiotics are started, and the patient is afebrile within 36 hours. Urine culture yields >50,000 colony-forming units of Escherichia coli. After completion of the therapeutic antibiotic course, which of the following is the best next step in management of this patient?
- Begin prophylactic antibiotics
- No other intervention is indicated
- Perform renal and bladder ultrasound
- Perform renal scintigraphy
- Recommend circumcision
A 7-year-old boy is brought to the emergency department due to a dog bite to the face. The father states the patient approached their dog, who was sleeping, and the dog suddenly snapped and bit him near the right eye. The dog’s vaccines are up to date. The patient has no medical conditions, and his vaccines are up to date. Vital signs are normal. On examination, there are 2 puncture wounds on the lateral forehead. The right eyelid is swollen, and there is a small, horizontal laceration of the lateral aspect of the right upper eyelid; there is fatty tissue protruding at the base of the wound. The pupils are symmetric and reactive to light, and the extraocular movements are intact. Visual acuity is normal. Which of the following structures is most likely injured as a result of the eyelid laceration in this patient?
- Canaliculi
- Levator muscle
- Nasolacrimal duct
- Nasolacrimal sac
- Punctum
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