A 54-year-old man with small cell lung cancer presents with lethargy, confusion, and muscle cramps. Blood work shows an increase in plasma levels of antidiuretic hormone (ADH), possibly from the ectopic production of ADH. In patients with the syndrome of inappropriate antidiuretic hormone (SIADH), which of the following will increase?
A
The concentration of plasma sodium
B
Intracellular volume
C
Urinary flow
D
Plasma oncotic pressure
E
Plasma osmolarity
Answers
Answer:
a. 100 mg/min
b. 200 mg/min
c. 300 mg/min
d. 400 mg/min
e. 500 mg/min
371. A 16-year-old girl presents for her annual high school athletic physical. She states that she seems more tired than usual, she has been having muscle cramps in her calves, and her legs get very weak and sore after running and playing soccer. Her blood pressure is 160/100 mm Hg, and her ECG shows a prolonged QT interval and the presence of a U wave. Blood analysis shows hypokalemia, metabolic alkalosis, and decreases in plasma renin activity and aldosterone concentration. Her clinical condition is reversed after she is placed on the diuretic amiloride. Based on this finding, which of the following renal transport processes is the major defect causing her metabolic disorder?
a. Greater than normal sodium reabsorption by the proximal tubules
b. Greater than normal sodium reabsorption by the cortical collecting ducts
c. Inability of the distal nephron to secrete hydrogen
d. Inability of the distal nephron to secrete potassium ion
e. Inability to concentrate urine
372. A previously well 12-year-old boy is brought to the emergency department with vomiting and severe abdominal cramps after a prolonged period of exercise. Elevated levels of serum creatinine and blood urea nitrogen (BUN) suggest acute renal failure. Following treatment and recovery, his serum uric acid concentration (0.6 mg/dL) remains consistently below normal. To determine if his low serum uric acid level is related to renal dysfunction, uric acid clearance studies are conducted and the following data are obtained:
Urine flow rate = 1 mL/min
Urine [uric acid] = 36 mg/dL
Which of the following is the patient’s uric acid clearance?
a. 6 mL/min
b. 12 mL/min
c. 24 mL/min
d. 48 mL/min
e. 60 mL/min
373. A 69-year-old man presents with symptoms of thirst and dizziness, and physical evidence of orthostatic hypotension and tachycardia, decreased skin turgor, dry mucous membranes, reduced axillary sweating, and reduced jugular venous pressure. He was recently placed on an angiotensin-converting enzyme (ACE) inhibitor for his hypertension. Urinalysis reveals a reduction in the fractional excretion of sodium and the presence of acellular hyaline casts. The internist suspects acute renal failure of prerenal origin associated with increased renin secretion by the kidney. A stimulus for increasing renal renin secretion is an increase in which of the following?
a. Angiotensin II
b. Atrial natriuretic peptide (ANP)
c. GFR
d. Mean blood pressure
e. Sympathetic nerve activity
374. A patient with uncontrolled hypertension is placed on a new diuretic targeted to act on the Na+ reabsorption site from the basolateral surface of the renal epithelial cells. Which of the following transport processes is the new drug affecting?
a. Facilitated diffusion
b. Na+/H+ exchange
c. Na+ –glucose cotransport
d. Na+ –K+ pump
e. Solvent drag
375. A 28-year-old woman presents to her physician’s office with fatigue, malaise, and orthostatic dizziness. When asked what medications she is taking, she stated that she has been taking 800 mg ibuprofen four to six times a day for painful menstrual cramps. Serum creatinine was elevated to 2.1 mg/dL. Which of the following is most likely to produce an increase in GFR in patients with acute renal failure?
a. Administration of angiotensin II
b. Contraction of glomerular mesangial cells
c. Dilation of afferent arterioles
d. Increased renin release from the juxtaglomerular apparatus
e. Volume depletion
Answer:
Intracellular volume and plasma osmolarity will increase in patients with the syndrome of inappropriate antidiuretic hormone (SIADH).
Explanation:
Small cell lung cancer is a condition in which the tissues of the lungs develop malignant (cancer) cells. Small cell lung cancer can come in two different forms. Coughing and breathlessness are two indicators of small cell lung cancer. Sodium, potassium, chloride, blood, and urine osmolality tests, as well as occasionally an ADH measurement, can all be used to screen for SIADH. Sometimes, a test for ADH suppression with water loading is conducted. First, a dilution of blood solutes in the extracellular fluid (ECF) space results in hypo osmolality, which includes hyponatremia, or low salt levels. Cells then inflate, increasing the volume of the intracellular space, almost instantaneously.
Shrinkage of the intracellular volume is caused by an increase in plasma sodium (plasma osmolality), which draws water out of the cell. Increased intracellular volume results from hyponatremia, which is characterized by decreased plasma osmolality.