Sodium handling along the nephron — MCQs

A 21-year-old male presents to the emergency department with generalized weakness and fatigue. His past medical history is significant for hypertension refractory to several medications but is otherwise unremarkable. He is afebrile, his pulse is 82/min, respirations are 18/min, and blood pressure is 153/94 mmHg. Labs are as follows: Sodium: 142 mEq/L Potassium: 2.7 mEq/L Bicarbonate: 36 mEq/L Serum pH: 7.5 pCO2: 50 mmHg Aldosterone: Decreased Based on clinical suspicion, a genetic screen is performed, confirming an underlying syndrome due to an autosomal dominant gain of function mutation. Which of the following medications can be given to treat the most likely cause of this patient's symptoms?

A 54-year-old woman comes to the physician for a follow-up examination after presenting with elevated blood pressure readings during her last two visits. After her last visit 2 months ago, she tried controlling her hypertension with weight loss before starting medical therapy, but she has since been unable to lose any weight. Her pulse is 76/min, and blood pressure is 154/90 mm Hg on the right arm and 155/93 mm Hg on the left arm. She agrees to start treatment with a thiazide diuretic. In response to this treatment, which of the following is most likely to decrease?

A 42-year-old man is brought to the emergency room because of confusion. His wife says he has been urinating more frequently than usual for the past 3 days. He has not had fever or dysuria. He has bipolar disorder, for which he takes lithium. His pulse is 105/min, and respirations are 14/min. He is lethargic and oriented only to person. Physical examination shows dry mucous membranes and increased capillary refill time. Laboratory studies show a serum sodium concentration of 158 mEq/L and an antidiuretic hormone (ADH) concentration of 8 pg/mL (N = 1–5). Which of the following is the most likely site of dysfunction in this patient?

On cardiology service rounds, your team sees a patient admitted with an acute congestive heart failure exacerbation. In congestive heart failure, decreased cardiac function leads to decreased renal perfusion, which eventually leads to excess volume retention. To test your knowledge of physiology, your attending asks you which segment of the nephron is responsible for the majority of water absorption. Which of the following is a correct pairing of the segment of the nephron that reabsorbs the majority of all filtered water with the means by which that segment absorbs water?

Which mechanism primarily regulates sodium reabsorption in the collecting duct?

A 17-year-old boy is brought to the physician by his father because of a 7-month history of fatigue, recurrent leg cramps, and increased urinary frequency. His pulse is 94/min and blood pressure is 118/85 mm Hg. Physical examination shows dry mucous membranes. Laboratory studies show: Serum Na+ 130 mEq/L K+ 2.8 mEq/L Cl- 92 mEq/L Mg2+ 1.1 mEq/L Ca2+ 10.6 mg/dL Albumin 5.2 g/dL Urine Ca2+ 70 mg/24 h Cl- 375 mEq/24h (N = 110–250) Arterial blood gas analysis on room air shows a pH of 7.55 and an HCO3- concentration of 45 mEq/L. Impaired function of which of the following structures is the most likely cause of this patient's condition?

A 78-year-old male with history of coronary artery disease, status post coronary stent placement currently on aspirin and clopidogrel was found down in his bathroom by his wife. His GCS score was 3 and an accurate physical exam is limited. A stat non-contrast CT scan of his brain demonstrated a large right parietal intracranial hemorrhage with surrounding edema. He was promptly transferred to the intensive care unit (ICU) for monitoring. Over the next day, his mental status continues to worsen but repeat CT scan shows no new bleeding. In addition, the patient’s urinary output has been >200 cc/hr over the last several hours and increasing. His temperature is 99.0 deg F (37.2 deg C), blood pressure is 125/72 mmHg, pulse is 87/min, and respirations are 13/min. Which of the following values would most likely correspond to the patient’s urine specific gravity, urine osmolality, plasma osmolality, and serum sodium?

A 3-year-old boy is brought to the emergency department with a history of unintentional ingestion of seawater while swimming in the sea. The amount of seawater ingested is not known. There is no history of vomiting. On physical examination, the boy appears confused and is asking for more water to drink. His serum sodium is 152 mmol/L (152 mEq/L). Which of the following changes in volumes and osmolality of body fluids are most likely to be present in this boy?

A 58-year-old Caucasian woman visits her primary care physician for an annual check-up. She has a history of type 2 diabetes mellitus and stage 3A chronic kidney disease. Her estimated glomerular filtration rate has not changed since her last visit. Today, her parathyroid levels are moderately elevated. She lives at home with her husband and 2 children and works as a bank clerk. Her vitals are normal, and her physical examination is unremarkable. Which of the following explains this new finding?

A 38-year-old woman presents to the physician’s clinic with a 6-month history of generalized weakness that usually worsens as the day progresses. She also complains of the drooping of her eyelids and double vision that is worse in the evening. Physical examination reveals bilateral ptosis after a sustained upward gaze and loss of eye convergence which improves upon placing ice packs over the eyes and after the administration of edrophonium. Which of the following is an intrinsic property of the muscle group affected in this patient?