A 34-year-old woman is brought to the emergency department by ambulance due to nausea, dizziness, and confusion.  Her boyfriend arrives with her and says that he found her lying on the bed next to an empty bottle of aspirin tablets.  When asked about the potential ingestion, the patient admits to swallowing a “bunch of aspirin pills a little more than 12 hours ago” after coming home from work.  She also describes hearing “an annoying buzzing sound that won’t stop.”  Temperature is 38.3 C (101 F) and pulse is 102/min.  She appears agitated and confused.  Which of the following sets of laboratory results is most likely to be found in this patient?

A 68-year-old man comes to the emergency department due to abdominal pain and nausea for the past 2 days.  He has a history of atherosclerotic cardiovascular disease and underwent coronary artery bypass surgery 2 years ago.  Blood pressure is 105/65 mm Hg and heart rate is 120/min and irregular.  Abdominal examination reveals mild diffuse tenderness and decreased bowel sounds.  Laboratory studies are as follows:

ECG shows absent P waves and an irregular rate and rhythm.  CT scan of the abdomen reveals colonic wall thickening and no enhancement with intravenous contrast.  Urinalysis shows acidic urine.  Renal metabolism of which of the following amino acids is most important for maximizing acid excretion in this patient?

A 28-year-old man is found unresponsive by his roommate and is brought to the emergency department.  He has a history of injection drug use.  On physical examination, the patient is obtunded and hypopneic.  The pupils are pinpoint.  Lung auscultation reveals decreased breath sounds bilaterally.  Endotracheal intubation is planned for airway protection and arterial blood gas analysis is performed prior to the procedure while the patient is breathing room air.  This patient’s current acid-base status is best represented by which of the following points on the below graph?

Physiologists are investigating renal autoregulatory mechanisms in an animal species that closely mimics human physiology.  During one of their experiments, renal blood flow and glomerular filtration rate are measured in an anesthetized animal in response to changes in mean arterial pressure.  The data they obtain is shown on the graph below.

Assuming a hematocrit of 0.50, what is the best estimate of the filtration fraction when the mean arterial pressure is 120 mm Hg?

A researcher is studying the effect of various manipulations on kidney blood flow and glomerular filtration.  Which of the following is most likely to both decrease renal plasma flow and increase the filtration fraction?

A longitudinal study is conducted to assess changes in renal function over time in patients with recently diagnosed type 2 diabetes mellitus.  An initial set of laboratory tests is obtained in newly enrolled patients to establish baseline renal function parameters.  The following measurements are taken from a 42-year-old male volunteer.

Which of the following is the best estimate of the filtration fraction in this patient assuming a urine flow of 1.0 mL/min?

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?

A 23-year-old man with type 1 diabetes mellitus is brought to the emergency department due to confusion and weakness.  Symptoms began 2 days ago with mild diarrhea.  The patient has missed several doses of insulin because his appetite has been poor.  On examination, his breath has a fruity odor.  This patient is most likely to demonstrate which of the following urine chemistry patterns?

A 34-year-old missionary in southern Asia is traveling to a remote village and becomes stranded when his bus breaks down.  He has no access to water for 36 hours, during which his urine osmolality reaches 1100 mOsm/L.  Urine concentration depends primarily on the serum level of vasopressin, which is regulated by the neurohypophysis in response to plasma osmolality and blood volume.  Which of the following nephron segments responds to vasopressin by increasing absorption of a specific solute that is important for generating a high medullary concentration gradient?

A 34-year-old woman comes to the physician complaining of frequent urination.  She has tried limiting her fluid intake but found it difficult because she got very thirsty.  The physician assesses the water-conserving function of her kidneys by performing a water restriction test, which shows inappropriately dilute urine.  Laboratory studies drawn during the period of water deprivation show low vasopressin levels.  The physician diagnoses the patient with central diabetes insipidus and explains that her kidneys are unable to absorb the proper amount of water due to defective hormone production.  Which of the following areas of the nephron is normally impermeable to water regardless of serum vasopressin levels?

A 45-year-old woman comes to the office due to polyuria and nocturia.  She has no fever, dysuria, or abdominal pain.  The patient has no significant medical problems and takes no medications.  Her temperature is 36.7 C (98 F), blood pressure is 120/80 mm Hg, and pulse is 76/min.  The patient’s mucous membranes appear dry.  The remainder of her physical examination is normal.  Her urine output and osmolality remain unchanged with water deprivation for several hours, but after administration of desmopressin, urine output decreases and urine osmolality increases.  Renal clearance of which of the following substances would decrease the most after this patient’s injection?

A 23-year-old man comes to the emergency department due to abdominal pain and nausea for the last few hours.  He also reports an episode of vomiting and has noticed that his urine has a fruity odor.  The patient has had increased thirst and urination for the past several days along with weight loss.  He has no known medical problems and takes no medications.  Physical examination reveals pallor with cool extremities.  The abdomen is soft, without tenderness to palpation.  Laboratory studies are ordered to confirm the diagnosis.  Which of the following points on the graph below best corresponds to this patient’s acid-base status?

Nephrologists at a research hospital are investigating the physiologic changes that occur in diabetes insipidus.  The group develops a technique that permits sampling of tubular urine in experimental animals with physiology similar to that of humans.  The animals then undergo hypophysectomy, after which tubular fluid samples are obtained from multiple sites throughout the nephron.  In the absence of antidiuretic hormone, fluid from which of the following sampling sites is most likely to have the highest osmolarity?

A 56-year-old woman with polycystic kidney disease comes to the office for follow up.  Her renal function has been gradually declining, and she is being considered for hemodialysis in the near future.  The patient has recently experienced increasing exertional dyspnea and fatigue but has had no fever, dysuria, or flank pain.  Other medical conditions include hypertension and renal calculi.  Blood pressure is 130/86 mm Hg and pulse is 80/min.  Physical examination shows mucosal pallor.  The lungs are clear on auscultation and heart sounds are normal.  Abdominal examination reveals palpably enlarged kidneys.  There is no lower extremity edema.  Laboratory results show normocytic, normochromic anemia, which is attributed to insufficient hormone production by the kidneys.  This hormone is predominantly secreted by which of the following parts of the kidney?

A 48-year-old woman is evaluated for postcoital bleeding and vaginal discharge.  Pelvic examination shows a friable mass at the cervix that bleeds easily on touch.  Cervical biopsy confirms invasive squamous cell cancer confined to the cervix and uterus.  Lymph node metastases are not seen.  A radical hysterectomy is performed during which the right ureter is accidentally injured but then repaired.  Imaging studies performed after the surgery show a partial obstruction of the right ureter with mild dilation of the proximal collecting system.  Which of the following changes are most likely to be seen in the right kidney?

An experimental substance is infused intravenously at a constant rate into a healthy volunteer.  The substance is known to selectively constrict the efferent arteriole in renal glomeruli.  The rate of infusion is closely controlled during the experiment to allow for only mild constriction of the efferent arteriole.  Which of the following changes in glomerular filtration rate (GFR) and filtration fraction (FF) is most likely to occur during the infusion of this substance?

Renal physiologists are studying how hydration status affects the mechanisms of urine concentration and dilution in humans.  To do this, they developed a technique in experimental animals that permits sampling of tubular fluid in different parts of the nephron.  A tubular fluid sample with an osmolarity of 110 mOsm/L is obtained from a healthy animal after 12 hours of water deprivation.  Assuming the physiology of this animal mirrors human physiology, which of the following sites along the nephron was most likely sampled?

Physiologists are studying how the plasma concentration of various substances affects the degree to which they are excreted in the urine.  During one experiment, a substance freely filtered at the glomerulus is infused intravenously at various rates.  The plasma concentration (mg/mL) and urinary excretion rate (mg/min) of the substance are monitored.  Assuming a constant glomerular filtration rate (GFR) of 100 mL/min, the following observations are made:

Which of the following substances is most likely to demonstrate a similar pattern of filtration and excretion in a healthy adult?

A healthy 32-year-old man enrolls in a clinical study investigating potassium handling by the kidney.  During the study period, he is given oral potassium supplements and potassium levels in the serum and urine are closely monitored.  Compared to the amount of potassium delivered to the glomerular capillaries, the percentage of potassium remaining in this individual’s tubular fluid is most likely to vary by which of the following amounts?

A clinical trial of a novel drug X is being conducted.  Animal studies have shown that the drug is eliminated primarily by the kidneys.  A healthy volunteer of body weight 60 kg (132.3 lb) is recruited, and his glomerular filtration rate is 100 mL/min.  In this volunteer, plasma concentration of the drug, immediately after intravenous administration, is 0.5 mg/mL.  Urinary excretion rate of the drug is found to be 75 mg/min.  When another medication, drug Y, is coadministered, urinary excretion rate of the drug X is 50 mg/min.  Which of the following effects of drug Y on the pharmacokinetics of drug X best explains the findings in this study?

A 24-year-old man who lives at an elevation near sea-level goes on a multiday hiking trip in the Colorado mountains and ascends to an altitude of 4,000 m (13,123 ft).  Over the next 3 days, the patient develops diffuse headaches, nausea, and difficulty sleeping.  The patient also notes mild fatigue and slight dizziness with changes in position.  He has no medical conditions and takes no medications.  He does not use alcohol, tobacco, or illicit drugs.  Which of the following changes in this patient’s acid-base physiology is most likely to be seen?

Scientists investigating the specifics of kidney function in humans develop a new technique allowing them to measure the concentration of various compounds along the length of the proximal tubule.  During an experiment, they record the concentrations of several endogenous substances in the fluid traversing the proximal tubule.  Tubular fluid/plasma ultrafiltrate concentration ratios for the measured substances are shown in the image below:

Which of the following substances are most likely to produce lines 2 and 4, respectively?

A 56-year-old man with chronic renal insufficiency due to polycystic kidney disease is evaluated for placement of an arteriovenous fistula for dialysis access.  Blood pressure is 140/90 mm Hg and pulse is 80/min.  Examination shows 2+ bilateral edema of the lower extremities.  Estimated glomerular filtration rate is 15 mL/min/1.73 m².  Which of the following sets of laboratory findings is most likely in this patient?

A 54-year-old missionary traveling alone in a remote region of Southern Asia becomes lost.  After several days, he arrives at a small village.  However, he has gone 24 hours without food or water, and his urine osmolarity is 1150 mOsm/L.  The majority of the total amount of water filtered by this individual’s glomeruli is reabsorbed in which of the following portions of the nephron?

A 35-year-old man who works as a nurse at a local hospital is brought to the emergency department due to confusion and lethargy.  His temperature is 36.7 C (98 F), blood pressure is 86/48 mm Hg, pulse is 120/min, and respirations are 12/min.  Arterial blood gas results show pH 7.54, PaCO₂ 49 mm Hg, and PaO₂ 85 mm Hg.  Which of the following laboratory studies would be the most useful in determining the cause of this patient’s acid-base abnormality?

A 34-year-old man is brought to the emergency department with new-onset confusion and lethargy.  Laboratory studies, including an arterial blood gas, are obtained.  The changes in his blood gas parameters are shown in the graph below.  Point A represents these parameters at the patient’s physiologic baseline, and point B indicates his state on arrival in the emergency department.

Item 1 of 2

Which of the following is the most likely diagnosis?

Item 2 of 2

Results of the laboratory tests show an increased anion gap metabolic acidosis.  An underlying cause is established, and appropriate treatment is instituted.  Within several hours, the patient’s mental status improves significantly.  Repeat laboratory studies show an increase in serum bicarbonate and sodium levels, a decrease in serum osmolality, and a drop in the serum potassium level.  Which of the following treatments was most likely given to this patient?

Two graphs illustrating the transport rate of solutes across the plasma membrane are shown on the slide below.

Which of the following best explains the difference in the shape of the curves?