Kidney/Electrolytes

Question 1

Which one of the following is an indication for urgent dialysis in a patient with an acute kidney injury? (check one)
-Encephalopathy
-A potassium level of 5.5 mEq/L (N 3.4–4.5)
-Pulmonary edema that is responsive to diuretics
- Negligible urine output for 2 hours
-A urine output of 500 mL over 24 hours

Answer 1

Encephalopathy

Uremic complications such as encephalopathy, neuropathy, or pericarditis are indications for urgent dialysis in patients with acute kidney injury. Other indications include a potassium level >6.5 mEq/L, pulmonary edema that is not responsive to diuretics, negligible urine output for >6 hours, and a urine output of <200 mL over 24 hours.

Question 2

Which one of the following is the most likely cause of acute kidney injury in a patient with eosinophiluria? (check one)
Rhabdomyolysis
Poststreptococcal glomerulonephritis
Acute interstitial nephritis
Ethylene glycol poisoning
Tumor lysis syndrome

Answer 2

Acute interstitial nephritis

The presence of eosinophiluria in a patient with acute kidney injury (AKI) suggests acute interstitial nephritis, which is typically an allergic reaction to medications such as penicillins, sulfa-containing antibiotics and diuretics, NSAIDs, proton pump inhibitors, etc. Patients with acute interstitial nephritis may also present with a rash, fever, eosinophilia, and other constitutional symptoms. The combination of elevated levels of creatine kinase or myoglobin, a dipstick positive for blood but negative for RBCs, and a history of muscle trauma would suggest rhabdomyolysis. An elevated uric acid level along with a history of rapidly proliferating tumors or recent chemotherapy suggests tumor lysis syndrome and malignancy. Poisoning with ethylene glycol or methanol should be suspected in a patient with AKI and altered mental status with an increased anion gap and osmolar gap. An elevated antistreptolysin O titer suggests poststreptococcal glomerulonephritis when combined with a history of recent pharyngitis.

Question 3

Which one of the following intravenous agents is the best INITIAL management for hypercalcemic crisis? (check one)
Furosemide
Pamidronate
Hydrocortisone
Saline

Answer 3

Saline

The initial management of hypercalcemic crisis involves volume repletion and hydration. The combination of inadequate fluid intake and the inability of hypercalcemic patients to conserve free water can lead to calcium levels >14–15 mg/dL. Because patients often have a fluid deficiency of 4–5 liters, delivering 1000 mL of normal saline during the first hour, followed by 250–300 mL/hour, may decrease the hypercalcemia to less than critical levels (<13 mg/dL). If the clinical status is not satisfactory after hydration alone, then renal excretion of calcium can be enhanced by saline diuresis using furosemide.

Intravenous pamidronate, a bisphosphonate, reduces the hypercalcemia of malignancy and is best used in the semi-acute setting, since calcium levels do not start to fall for 24 hours. Glucocorticoids are useful in the treatment of hypercalcemia associated with certain malignancies (multiple myeloma, leukemia, several lymphomas, and breast cancer) or with vitamin D intoxication. The onset of action, however, takes several days, with the effect lasting days to weeks.

Question 4

A 36-year-old female presents with a several-week history of polyuria and intense thirst. She currently takes no medications. On examination her blood pressure and pulse rate are normal, and she is clinically euvolemic. Laboratory tests, including serum electrolyte levels, renal function tests, and plasma glucose, are all normal. A urinalysis is significant only for low specific gravity. Her 24-hour urine output is >5 L with low urine osmolality.

The most likely cause of this patient’s condition is a deficiency of (check one)
angiotensin II
aldosterone
renin
insulin
arginine vasopressin

Answer 4

arginine vasopressin

This patient has diabetes insipidus, which is caused by a deficiency in the secretion or renal action of arginine vasopressin (AVP). AVP, also known as antidiuretic hormone, is produced in the posterior pituitary gland and the route of secretion is generally regulated by the osmolality of body fluid stores, including intravascular volume. Its chief action is the concentration of urine in the distal tubules of the kidney. Both low secretion of AVP from the pituitary and reduced antidiuretic action on the kidney can be primary or secondary, and the causes are numerous.

Patients with diabetes insipidus present with profound urinary volume, increased frequency of urination, and thirst. The urine is very dilute, with an osmolality <300 mOsm/L. Further workup will help determine the specific type of diabetes insipidus and its cause, which is necessary for appropriate treatment.

Low levels of aldosterone, plasma renin activity, or angiotensin would cause abnormal blood pressure, electrolyte levels, and/or renal function. Insulin deficiency results in diabetes mellitus.

Question 5

You prescribe enalapril (Vasotec) for a 68-year-old male with heart failure. At a follow-up visit 6 weeks later the patient’s serum creatinine level is 2.5 mg/dL (N 0.6–1.5) and his serum potassium level is 5.7 mEq/L (N 3.4–4.8). His baseline values were normal.

Which one of the following is a side effect of ACE inhibitors that is the most likely cause of these changes in renal function?
(check one)
Toxicity to the proximal renal tubules
Impaired autoregulation of glomerular blood flow
Microangiopathic arteriolar thrombosis
Rhabdomyolysis
Interstitial nephritis

Answer 5

Impaired autoregulation of glomerular blood flow

Blood flow to the kidney is autoregulated so as to sustain pressure within the glomerulus. This is influenced by angiotensin II–related vasoconstriction. ACE inhibitors can impair the kidney’s autoregulatory function, resulting in a decreased glomerular filtration rate and possibly acute renal injury. This is usually reversible if it is recognized and the offending agent stopped. NSAIDs can exert a similar effect, but they can also cause glomerulonephritis and interstitial nephritis. Statins, haloperidol, and drugs of abuse (cocaine, heroin) can cause rhabdomyolysis with the release of myoglobin, which causes acute renal injury. Thrombotic microangiopathy is a rare mechanism of injury to the kidney, and may be caused by clopidogrel, quinine, or certain chemotherapeutic agents.

Question 6

A 56-year-old male with diabetes mellitus, hypertension, and chronic renal insufficiency presents for follow-up of his chronic medical conditions. Results of his most recent metabolic panel included an estimated glomerular filtration rate of 30 mL/min/1.73 m2 (N >60) and a calcium level of 10.4 mg/dL (N 8.5–10.2). Medication reconciliation reveals he is not taking the sevelamer (Renagel, Renvela) prescribed by the consulting nephrologist.

You explain to the patient that he should be taking sevelamer to lower his serum calcium. The drug accomplishes this by?
(check one)
Blocking the effect of parathyroid hormone
Blocking excessive vitamin D levels, thus decreasing intestinal calcium absorption and increasing renal calcium excretion
Blocking intestinal absorption of phosphate, which lowers parathyroid hormone secretion
Directly blocking excessive calcium absorption in the intestines
Directly increasing the renal excretion of both calcium and phosphate

Answer 6

Blocking intestinal absorption of phosphate, which lowers parathyroid hormone secretion

This patient has secondary hyperparathyroidism, a common cause of hypercalcemia in patients with chronic renal insufficiency. Sevelamer is a newer synthetic agent in the therapeutic class of phosphate binders, which includes calcium acetate. Decreasing serum phosphate lowers the feedback stimulation of parathyroid hormone secretion by the parathyroid gland, which is often excessive in chronic renal insufficiency. Normalizing parathyroid levels improves serum calcium levels.

Question 7

Which one of the following metabolic abnormalities is most likely to be seen in patients with stage 4 kidney disease?
(check one)
Hyperaldosteronism
Hyperparathyroidism
Hypothyroidism
Hypogonadism
Type 2 diabetes mellitus

Answer 7

Hyperparathyroidism

Hyperparathyroidism is present in more than half of patients who have a glomerular filtration rate <60 mL/min, and is independently associated with increased mortality and an increased prevalence of cardiovascular disease. In patients with stage 4 chronic kidney disease, current guidelines recommend monitoring of serum calcium and phosphate levels every 3–6 months and bone-specific alkaline phosphatase activity every 6–12 months with the goal of normalizing these values. The other metabolic abnormalities listed are less common than hyperparathyroidism.

Question 8

A 42-year-old male with a history of chronic hepatitis C develops left leg cellulitis and is treated with cephalexin (Keflex). He returns to your office 5 days later for follow-up, and the cellulitis is responding favorably to treatment. However, the patient has a generalized maculopapular rash and a low-grade fever, which he says began 3 days ago. He also complains of arthralgias. You admit him to the hospital for further evaluation.

His serum creatinine level is 3.2 mg/dL (N 0.6–1.5), which is elevated from his baseline level of 0.8 mg/dL. A urinalysis is normal, except for the presence of occasional eosinophils. The remainder of his evaluation, including liver enzyme levels and renal ultrasonography, is normal.

Which one of the following is the most appropriate next step in the management of this patient?
(check one)
A postvoid residual urine volume
A hepatitis C viral load and genotype
Discontinuing cephalexin
Antibiotics to cover methicillin-resistant Staphylococcus aureus (MRSA)
Aggressive fluid resuscitation with normal saline

Answer 8

Discontinuing cephalexin

Acute kidney injury (AKI) is currently defined as either a rise in serum creatinine or a reduction in urine output. Creatinine must increase by at least 0.3 mg/dL, or to 50% above baseline within a 24–48 hour period. A reduction in urine output to 0.5 mL/kg/hr for longer than 6 hours also meets the criteria. Acute interstitial nephritis is an intrinsic renal cause of AKI. These patients are often nonoliguric. A history of recent medication use is key to the diagnosis, as cephalosporins and penicillin analogues are the most common causes. Approximately one-third of patients present with a maculopapular rash, fever, and arthralgias. Eosinophilia and sterile pyuria may also be seen in addition to eosinophiluria. Discontinuation of the offending drug is the cornerstone of management.

Although up to 30% of patients with chronic hepatitis C infection have some kidney involvement, acute interstitial nephritis is uncommon. Measuring postvoid residual urine volume is indicated if an obstructive cause for the AKI is suspected. Starting an antibiotic to cover methicillin-resistant Staphylococcus aureus (MRSA) is not indicated.

Question 9

Which one of the following medications is most likely to cause hypokalemia?

(check one)
Albuterol (Proventil, Ventolin)
Doxazosin (Cardura)
Erythromycin
Felodipine (Plendil)
Lisinopril (Prinivil, Zestril)

Answer 9

Albuterol (Proventil, Ventolin)

β-Agonists activate potassium uptake by the cells. This includes bronchodilators and tocolytic agents. Other agents that can induce hypokalemia include pseudoephedrine and insulin. Diuretics, particularly thiazides, can also cause hypokalemia as a result of the renal loss of potassium.

Question 10

A 75-year-old white female presents with hyponatremia, with a serum level of 118 mEq/L, a urine osmolality >100 mOsm/kg H2O, and a serum osmolality of 242 mOsm/kg H2O. She complains of some fatigue, but is alert and oriented. Her blood pressure is 136/82 mm Hg. She has normal thyroid, adrenal, cardiac, hepatic, and renal function. You admit her to the hospital for treatment and observation. Which one of the following is the most appropriate initial treatment? (check one)
Administration of 3% normal saline
Administration of normal saline
Free water restriction
Demeclocycline (Declomycin)

Answer 10

Free water restriction

This patient probably has the syndrome of inappropriate secretion of antidiuretic hormone (SIADH). SIADH can be caused by CNS tumors, various infections such as meningitis, and pneumonia. Several drugs can cause this condition, including amiodarone, carbamazepine, SSRIs, and chlorpromazine. In this fairly asymptomatic patient, initial management should be free water restriction. As she is hemodynamically stable, she does not need normal saline. Moreover, administration of normal saline may exacerbate the hyponatremia, as the sodium may be rapidly excreted while the water is retained. If she had a rapid onset and neurologic symptoms such as seizures, hypertonic saline could be given. Correction should be slow, with a goal of no more than a 1-2 mmol/L/hr increase in the sodium level; a normal sodium level should not be reached within the first 48 hours of treatment. Demeclocycline is appropriate for patients who cannot adhere to the requirement for fluid restriction, or who have recalcitrant hyponatremia despite restriction.

Question 11

The most common cause of proteinuria in children is: (check one)
Acute postinfectious glomerulonephritis
Lupus glomerulonephritis
Hydronephrosis
Orthostatic proteinuria
Reflux nephropathy

Answer 11

Orthostatic proteinuria

Orthostatic proteinuria accounts for up to 60% of all cases of asymptomatic proteinuria reported in children, with an even higher incidence in adolescents.

Question 12

In an 11-year-old male with dark brown urine and hand and foot edema, which one of the following would be most suggestive of glomerulonephritis? (check one)
WBC casts in the urine
RBC casts in the urine
Eosinophils in the urine
Positive serum antinuclear antibody levels
Elevated C3 and C4 complement levels

Answer 12

RBC casts in the urine

Acute glomerulonephritis (AGN) in children manifests as brown or cola-colored urine, which may be painless or associated with mild flank or abdominal pain. There are many etiologies of AGN but the most common in children are IgA nephropathy (which may directly follow an acute upper respiratory tract infection) and acute poststreptococcal glomerulonephritis following a streptococcal throat or skin infection (usually 7–21 days later). In cases with more severe renal involvement, patients may develop hypertension, edema, and oliguria. RBC casts are the classic finding on urinalysis in a patient with AGN. WBC casts are seen in acute pyelonephritis, often manifested by high fever, and costovertebral angle or flank pain and tenderness. Patients may also appear septic. Positive serum antinuclear antibodies are associated with lupus nephritis. Urine eosinophils are seen in drug-induced tubulointerstitial nephritis. Serum complement levels are reduced, not elevated, in various forms of acute glomerulopathies, including poststreptococcal AGN.

Question 13

A 70-year-old male with a COPD exacerbation is found to have a sodium level of 127 mEq/L (N 135–145). He is alert and oriented although he is in mild respiratory distress. After an appropriate evaluation, you determine that he has euvolemic hyponatremia from the syndrome of inappropriate secretion of antidiuretic hormone (SIADH), due to his worsening lung disease.

Aside from addressing his COPD, which one of the following is the most appropriate initial treatment for his hyponatremia? (check one)
Fluid restriction
Salt restriction
Hypertonic saline
Furosemide (Lasix)
Tolvaptan (Samsca)

Answer 13

Fluid restriction

The treatment for euvolemic hyponatremia involves correcting the underlying cause and restricting fluid intake. A fluid restriction of 500 mL less than the daily urine output is a reasonable goal, although adherence can be difficult. The intake of salt as well as protein should not be restricted. The use of hypertonic saline is restricted to cases of severe symptomatic hyponatremia. Diuretics such as furosemide factor into managing hypervolemic hyponatremia but not euvolemic hyponatremia. Vaptans such as tolvaptan are vasopressin receptor antagonists that may be considered for short-term use in addition to fluid restriction for select cases of severe asymptomatic hyponatremia, defined as a sodium level <125 mEq/L.

Question 14

A 45-year-old male with no past medical history presents to the urgent care clinic with hematuria and left-sided intermittent flank and inguinal pain. He has mild nausea but does not have any vomiting, fever, or other urinary symptoms. His vital signs are normal. He appears uncomfortable, but a physical examination is otherwise unremarkable. A urinalysis shows RBCs but no signs of infection. Same-day noncontrast CT shows a 3.5-mm left-sided ureteral stone. This is his first kidney stone.

In addition to encouraging oral hydration and pain control with NSAIDs, which one of the following would be appropriate in the management of this ureteral stone? (check one)
Observation only
Oral allopurinol (Zyloprim)
Oral cephalexin
Intravenous hydration with 2 L of lactated Ringer solution
Referral for surgical stone removal

Answer 14

Observation only

Ureteral stones 4 mm typically pass without intervention within 40 days. This patient is hemodynamically stable without signs of infection and therefore should be managed conservatively with oral hydration and pain control. α1-Blockers such as tamsulosin can be used to aid in the passage of ureteral stones >5 mm. Allopurinol can be used to reduce stone recurrence in patients with calcium oxalate stones but does not have a role in the management of existing stones. There is no indication for antibiotics. Intravenous fluids are not indicated as the patient is not vomiting. Because this patient’s stone should pass without intervention, referral for surgical stone removal would not be appropriate.

Question 15

Which one of the following is true regarding medication dosage adjustments for patients with chronic kidney disease? (check one)
Loading doses should usually be adjusted
Adjustments typically are not necessary until the glomerular filtration rate is <20 mL/min/1.73m2>
A normal serum creatinine value indicates that no adjustment is necessary
Serum drug levels are usually required for making adjustments
A reduction of dose, an increase in dosing interval, or both may be necessary

Answer 15

A reduction of dose, an increase in dosing interval, or both may be necessary

Many medications require dosage adjustments in patients with chronic kidney disease. Medications are adjusted based on the estimated glomerular filtration rate (GFR) or creatinine clearance. Most medication adjustments require a reduction in the dose, lengthening of the dosing interval, or both. Loading doses of medications usually do not need to be adjusted. Medication adjustments are divided into three groups, based on whether the GFR is >50 mL/min/1.73m2, 10-50 mL/min/1.73m2, or <10 mL/min/1.73m2. The production and excretion of creatinine decreases in older patients, so a normal serum creatinine level does not always correlate with normal kidney function. Serum drug levels typically are not required for adjusting medications in patients with chronic kidney disease.

Question 16

A 75-year-old patient with underlying chronic renal failure requires cardiac catheterization. Which one of the following interventions is most likely to help prevent acute renal failure due to contrast-induced nephropathy? (check one)
Hydration with normal saline and mannitol
Hydration with sodium bicarbonate-containing fluids
Hydration plus a loop diuretic
Administering fenoldopam (Corlopam) prior to the procedure
Infusion of natriuretic peptides prior to the procedure

Answer 16

Hydration with sodium bicarbonate-containing fluids

Several studies have demonstrated that hydration with sodium bicarbonate-containing fluids reduces the risk of contrast-induced nephropathy in those undergoing cardiac catheterization. Studies of interventions to prevent renal failure in patients at high risk have shown that mannitol plus hydration does not reduce acute renal failure compared to hydration alone. Randomized, controlled trials have shown that fenoldopam does not decrease the need for dialysis or improve survival. One systematic review found that low-osmolality contrast media reduced nephrotoxicity in persons with underlying renal failure requiring studies using contrast. One systematic review and one subsequent randomized, controlled trial found that adding loop diuretics to fluids was not effective and may actually increase the possibility of acute renal failure compared to fluids alone. A large randomized, controlled trial found no significant difference between natriuretic peptides and placebo in preventing acute renal failure induced by contrast media.

Question 17

A 47-year-old male with chronic kidney disease is being treated with epoetin alfa (Procrit). His hemoglobin level is 11.3 g/dL (N 13.0-18.0). Which one of the following would be most appropriate with regard to his epoetin alfa regimen? (check one)
Increase the dosage until the hemoglobin level is >12.0 g/dL
Increase the frequency of injections, using the same dose
Decrease the frequency of injections, using the same dose
Continue the current regimen

Answer 17

Continue the current regimen

In patients with renal failure, the risk for death and serious cardiovascular events is increased with higher hemoglobin levels (≥13.5 g/dL), and it is therefore recommended that levels be maintained at 10-12 g/dL. Studies have also demonstrated less mortality and morbidity when the dosage of epoetin alfa is set to achieve a target hemoglobin of <12 g/dL.

Question 18

A 62-year-old male is admitted to the hospital with acute renal failure. A renal biopsy confirms the diagnosis of acute interstitial nephritis (AIN). Infection and immune-associated causes are ruled out, and you consider medications as a potential cause. Which one of the following would be most likely to cause AIN? (check one)
Chronic daily use of metoprolol (Lopressor)
Twice-daily use of ibuprofen for 2 weeks
Initiation of lisinopril (Prinivil, Zestril) therapy 1 week ago
A 5-day course of azithromycin (Zithromax) 6 months ago
Intermittent use of acetaminophen, up to 4 g/day

Answer 18

Twice-daily use of ibuprofen for 2 weeks

Acute interstitial nephritis (AIN) is often drug-induced. Discontinuation of medications that are likely to cause AIN is the most important first step in management. If these medications are withdrawn early, most patients can be expected to recover normal renal function. Of the medications listed, ibuprofen is the most likely offending agent, because all NSAIDs are known to be associated with AIN. Development of AIN usually becomes evident approximately 2 weeks after starting a medication and is not dose-related. Other medications strongly associated with AIN include various antibiotics (particularly cephalosporins, penicillins, sulfonamides, aminoglycosides, and rifampin), diuretics, and miscellaneous medications such as allopurinol.

Question 19

Which one of the following medications commonly causes hyponatremia in the elderly? (check one)
Amlodipine (Norvasc)
Amoxicillin
Atorvastatin (Lipitor)
Escitalopram (Lexapro)
Spironolactone (Aldactone)

Answer 19

Escitalopram (Lexapro)

A possible side effect of SSRIs is hyponatremia, which is more pronounced in the elderly. This fact is particularly pertinent in elderly patients with poorly controlled psychiatric illness who are more inclined to psychogenic polydipsia, which also leads to hyponatremia. Amlodipine is known to cause peripheral edema, dizziness, and medication-induced hepatitis. Amoxicillin causes eosinophilia and ALT and AST elevations. Atorvastatin causes elevations in ALT, AST, and creatine kinase levels. Spironolactone causes hyperkalemia and hyperuricemia, but it is not known to cause hyponatremia.

Question 20

In a patient with hyperuricemia with an elevated uric acid level but no prior episodes of acute gout, which one of the following is recommended? (check one)
No urate-lowering medication
Allopurinol (Zyloprim), 100 mg daily
Febuxostat (Uloric), 40 mg daily
Naproxen, 250 mg three times daily
Probenecid, 100 mg twice daily

Answer 20

No urate-lowering medication

Uric acid–lowering treatment is recommended for all patients with an elevated uric acid level who have had two or more gout flareups per year. Consider starting it in patients with a second flareup occurring more than 1 year later, those without an attack but who are at high risk, such as in those with kidney stones, patients with a uric acid level ≥9.0 mg/dL, or patients with stage 3 or greater chronic kidney disease.

There is no benefit for urate lowering in asymptomatic patients with an elevated uric acid level who have never had an acute episode of gout, thus allopurinol, febuxostat, and probenecid would not be appropriate. NSAIDs, colchicine, or corticosteroids are recommended for gout prophylaxis for the first 3–6 months after initiating urate-lowering therapy to prevent acute flares, but this patient has no history of acute gout. Additionally, vitamin C is not effective.

Question 21

A 69-year-old male presents for follow-up of hypertension treated with spironolactone (Aldactone) and amlodipine (Norvasc). His past medical history is remarkable only for a kidney stone several years ago. A physical examination is unremarkable. A comprehensive metabolic panel is unremarkable except for a calcium level of 12.0 mg/dL (N 8.0–10.0).

Which one of the following is the most likely cause of his elevated calcium level? (check one)
Excessive ingestion of calcium supplements
His current medication regimen
Occult malignancy
Primary hyperparathyroidism
Vitamin D deficiency

Answer 21

Primary hyperparathyroidism

The most common cause of hypercalcemia is hyperparathyroidism. This is seldom symptomatic and is often discovered through routine blood testing. Hypercalcemia due to cancer can be caused by secretion of the parathyroid hormone–related protein and by osteoclastic bone resorption. Other causes of hypercalcemia include thiazide diuretics, lithium, vitamin D intoxication, hyperthyroidism, milk alkali syndrome from excessive calcium antacid ingestion, adrenal insufficiency, and lymphoma.

Question 22

A healthy 80-year-old female sees you for a routine visit. She is active and follows a healthy diet. She is enthusiastic about vitamin supplements and asks you regularly about their benefits. Her laboratory chemistry profile demonstrates a persistent calcium level elevation at 10.9 mg/dL (N 8.5–10.2).

You review her prescription medications and do not find any associated with hypercalcemia. You also review her calcium and vitamin D intake. Because you know about her tendency to take supplements, you consider other vitamins that may contribute to the hypercalcemia.

Excessive intake of which one of the following would be the most likely explanation for these findings? (check one)
Vitamin A
Vitamin B1
Vitamin C
Vitamin E
Vitamin K

Answer 22

Vitamin A

Vitamin A intoxication can cause hypercalcemia. This includes analogs of vitamin A such as those used to treat acne. The excessive intake of vitamin A is associated with multisystem effects that can include bone resorption and hypercalcemia. Sources of preformed vitamin A include supplements as well as animal sources such as liver, fish liver oil, dairy, and eggs. Vitamin A toxicity should be considered in unexplained cases of parathyroid hormone–independent hypercalcemia. Vitamins B1, C, E, and K are not associated with hypercalcemia.

Question 23

A 64-year-old female with hypertension, diabetes mellitus, hyperlipidemia, and chronic kidney disease has had headaches that have been escalating over the past 6 months and are associated with double vision and ataxia. Her medications include lisinopril (Prinivil, Zestril) and atorvastatin (Lipitor). She weighs 61 kg (135 lb) and her blood pressure is 144/64 mm Hg. A basic metabolic panel is normal except for a creatinine level of 2.1 mg/dL (N 0.6–1.1) and an estimated glomerular filtration rate of 26 mL/min/1.73 m2.

You decide to order MRI of the brain. Which one of the following would be most appropriate with regard to the use of gadolinium contrast in this patient? (check one)
Use of gadolinium if the patient’s blood pressure is controlled to a goal systolic pressure of <130 mm Hg
Use of gadolinium if the patient is pretreated with n-acetylcysteine and intravenous normal saline
Use of gadolinium if lisinopril is stopped 48 hours before the MRI
Avoiding the use of gadolinium contrast

Answer 23

Avoiding the use of gadolinium contrast

The use of gadolinium contrast has been associated with acute kidney injury and also with the development of nephrogenic systemic sclerosis in patients with stage 4 or 5 chronic kidney disease. Because of these risks, the FDA recommends avoiding gadolinium contrast in patients with a glomerular filtration rate <30 mL/min/1.73 m2, as well as in patients with acute renal failure. The risk of nephrogenic systemic sclerosis is not affected by blood pressure, medications, intravenous hydration, or pretreatment with n-acetylcysteine.

Question 24

A 47-year-old male presents with bilateral lower extremity edema of undetermined etiology extending to the proximal lower extremities, associated with fatigue. His lipid levels were also very high on recent testing. He does not take any daily medications and his thyroid function is normal. The only significant findings on examination are lower extremity edema and some periorbital edema.

Which one of the following urine tests could help confirm the most likely diagnosis? (check one)
Crystals
Ketones
pH
Protein
Specific gravity

Answer 24

Protein

Nephrotic syndrome includes peripheral edema, heavy proteinuria, and hypoalbuminemia. Hyperlipidemia also occurs frequently and can be significant. Nephrotic-range proteinuria is a spot urine showing a protein/creatinine ratio >3.0–3.5 mg protein/mg creatinine or a 24-hour urine collection showing >3.0–3.5 g of protein. Testing urine for ketones, pH, specific gravity, or crystals does not help to diagnose nephrotic syndrome.

Question 25

You see a patient with a serum sodium level of 122 mEq/L (N 135–145) and a serum osmolality of 255 mOsm/kg H2O (N 280–295). Which one of the following would best correlate with a diagnosis of syndrome of inappropriate antidiuresis? (check one)
A fractional excretion of sodium below 1%
Elevated urine osmolality
Elevated serum glucose
Elevated BUN
Low plasma arginine vasopressin

Answer 25

Elevated urine osmolality

The syndrome of inappropriate antidiuresis (SIAD, formerly SIADH) is related to a variety
of pulmonary and central nervous system disorders in which hyponatremia and
hypo-osmolality are paradoxically associated with an inappropriately concentrated urine.
Most cases are associated with increased levels of the antidiuretic hormone arginine
vasopressin (AVP). Making a diagnosis of SIAD requires that the patient be euvolemic and
has not taken diuretics within the past 24–48 hours, and the urine osmolality must be high
in conjunction with both low serum sodium and low osmolality. The BUN should be normal
or low and the fractional excretion of sodium >1%.
Fluid restriction (<800 cc/24 hrs) over several days will correct the
hyponatremia/hypo-osmolality, but definitive treatment requires eliminating the underlying
cause, if possible. In the case of severe, acute hyponatremia with symptoms such as
confusion, obtundation, or seizures, hypertonic (3%) saline can be slowly infused
intravenously but might have dangerous neurologic side effects.
Elevated serum glucose levels may cause a factitious hyponatremia, but not SIAD.

Question 26

A 38-year-old female with diabetes mellitus controlled by diet has a sodium level of 130 mEq/L (N 136–145) on a routine basic metabolic panel. She does not use any dietary supplements and is not taking a diuretic. You consider a diagnosis of syndrome of inappropriate secretion of antidiuretic hormone (SIADH) and take additional history and order additional laboratory studies.

Which one of the following would be most consistent with SIADH? (check one)
A history of excessive beer drinking
A history of polydipsia
A serum glucose level of 350 mg/dL (N 70-100)
A urine sodium level of 40 mEq/L (N 20)
A urine osmolality of 90 mOsm/kg (N 300-900)

Answer 26

A urine sodium level of 40 mEq/L (N 20)

A diagnosis of the syndrome of inappropriate secretion of antidiuretic hormone (SIADH) generally starts with the discovery of hyponatremia and is confirmed after all other possible causes are excluded. The root cause is the pathologic secretion of antidiuretic hormone (ADH), which can occur in response to some drugs and a variety of conditions, including infections, tumors, and dysregulation in the nervous system involving sympathetic tone and baroreflex response. Inappropriate release of ADH increases free water reabsorption, which increases circulating blood volume, dilutes sodium, and lowers hematocrit and hemoglobin. Urine output is often lowered because of this reabsorption, and the urine is more concentrated (urine osmolality > plasma osmolality) with sodium levels >20 mEq/L. Modest weight gain may be noted as a result of the increased blood volume.

Polydipsia also causes dilution of serum sodium and hemodilution but results in dilution of urine. Excessive beer drinking may result in hyponatremia and hypokalemia (beer potomania) as a result of overhydration with a fluid containing inadequate solute. Laboratory testing for sodium can be falsely reduced in a hyperglycemic state. A simple calculation can correct for this: Corrected (Na+) = Measured (Na+) + (2.4 × glucose (mg/dL) – 100 mg/dL)/100 mg/dL.

Question 27

Which one of the following is a cause of pseudohyponatremia? (check one)
Hypercalcemia
Hyperkalemia
Hypermagnesemia
Hyperphosphatemia
Hypertriglyceridemia

Answer 27

Hypertriglyceridemia

Plasma sodium concentration measurements can be unreliable in patients with severe hyperlipidemia or hyperproteinemia (pseudohyponatremia). The other electrolyte abnormalities do not cause hyponatremia.

Question 28

A 42-year-old male comes to your office with acute right flank pain that awakened him from sleep. The pain is colicky and he says it is the most intense pain that he has ever felt. The findings on a physical examination, in addition to blood on his urinalysis, make you suspect a urinary tract stone.

Which one of the following imaging modalities would be most appropriate for confirming your suspicion? (check one)
Abdominal radiography (KUB)
Standard CT of the abdomen and pelvis with intravenous contrast
Low-dose helical (spiral) noncontrast CT of the abdomen and pelvis
MRI of the abdomen and pelvis without contrast
Ultrasonography of the kidneys and bladder

Answer 28

Low-dose helical (spiral) noncontrast CT of the abdomen and pelvis

Because many radiologic options are available for detecting suspected urolithiasis, and many contexts might affect their use, the American College of Radiology established appropriateness criteria to aid the selection process. These guidelines rate the appropriateness of CT, ultrasonography, radiography, and MRI for three categories of patients: (1) those presenting with a suspected stone, (2) those with recurrent stone symptoms, and (3) those with abdominal pain in pregnancy. Each modality is rated on a scale from 9 (most appropriate) to 1 (least appropriate).

For suspected stone disease in the case presented, the most appropriate imaging modality is helical (spiral) noncontrast CT of the abdomen and pelvis with a rating of 8 (usually appropriate). Standard CT of the abdomen and pelvis with intravenous contrast has an appropriateness rating of 2 (usually not appropriate). Abdominal radiography (KUB) has an appropriateness rating of 3 (usually not appropriate). MRI of the abdomen and pelvis without contrast has a rating of 4 (may be appropriate). Ultrasonography of the kidneys and bladder is appropriate in pregnancy, but in the case presented it is given an appropriateness rating of 6 (may be appropriate).

Question 29

A 47-year-old female with a 10-year history of type 2 diabetes mellitus is concerned about
the recent onset of swelling in her legs accompanied by a sudden weight gain of 8 lb. She
is also experiencing increased fatigue and shortness of breath with mild exertion.
On examination she has a blood pressure of 150/95 mm Hg, which is above her baseline
of 130/85 mm Hg. Her lungs are clear to auscultation and a cardiac examination is also
normal. She has no hepatosplenomegaly, but her legs are swollen to the level of the
midtibia bilaterally. You are concerned that her symptoms and examination findings may
be related to an underlying renal pathology.
To confirm your suspicion, the most appropriate diagnostic test at this time would be
(check one)
a spot urine protein to creatinine ratio
a 24-hour urine creatinine determination
renal ultrasonography
renal enhanced MRI
renal biopsy

Answer 29

a spot urine protein to creatinine ratio

This patient has type 2 diabetes mellitus and presents with new-onset edema in her lower
extremities, the most common presenting symptom of nephrotic syndrome (NS). Patients
with NS may also report foamy urine, exertional dyspnea or fatigue, and significant
fluid-associated weight gain. A 24-hour urine collection for protein (not creatinine) can be
used to diagnose proteinuria, but the collection process is cumbersome and the specimen
is often collected incorrectly. The protein-to-creatinine ratio from a single urine sample is
commonly used to diagnose nephrotic-range proteinuria. The role of a renal biopsy in
patients with NS is controversial and there are no evidence-based guidelines regarding
indications for a biopsy. Renal ultrasonography may be appropriate to assess for underlying
conditions and/or disease complications if the glomerular filtration rate is reduced. There
is no data to support using MRI in the diagnosis and management of nephrotic syndrome.

Question 30

A 72-year-old female taking hydrochlorothiazide for hypertension develops trigeminal neuralgia and you start her on carbamazepine (Tegretol). She is at risk for which one of the following metabolic consequences? (check one)
Calcium pyrophosphate deposition
Hypercalcemia
Hyponatremia
Hyperuricemia

Answer 30

Hyponatremia

Elderly patients, especially those taking hydrochlorothiazide, are at risk for developing hyponatremia while taking carbamazepine. Carbamazepine is one of the medications that can cause the syndrome of inappropriate antidiuretic hormone secretion, as it interferes with the ability to dilute the urine. It does not lead to the other derangements listed (SOR A).

Question 31

You are co-managing a 59-year-old female with stage 3b chronic kidney disease (CKD) and secondary hyperparathyroidism resulting in osteoporosis. Due to transportation issues, she has been unable to see her specialist and requests that you take over her laboratory surveillance for CKD–bone mineral disorder.

In addition to serum calcium, parathyroid hormone, vitamin D, and creatinine levels and the estimated glomerular filtration rate, which one of the following laboratory values should be routinely monitored? (check one)
Calcitonin
Magnesium
Parathyroid hormone–related peptide
Phosphorus
TSH

Answer 31

Phosphorus

Routine laboratory monitoring is required for patients with chronic kidney disease–bone mineral disorder (CKD-BMD) or secondary hyperparathyroidism due to renal disease. This patient has secondary hyperparathyroidism due to CKD, which interferes with normal calcium, phosphorus, and vitamin D regulation. Parathyroid hormone (PTH) stimulates bone resorption and increases serum calcium and phosphorus levels, and an elevated PTH level can result in significant hypercalcemia and hyperphosphatemia. Controlling these levels through diet and medication reduces fracture risk and mortality. Monitoring calcitonin, magnesium, and TSH levels on a routine basis is not useful for the management of CKD-BMD. PTH-related peptide is useful in diagnosing humoral hypercalcemia of malignancy but does not play a role in CKD-BMD monitoring.

Question 32

A 35-year-old male presents with a 2-week history of lower extremity edema. He is in good health and does not take any medications. You note weight gain, and mild dyspnea with exertion. An examination is unremarkable except for 2+ to 3+ pitting edema of the lower extremities to his knees bilaterally. A CBC and metabolic panel are unremarkable except for a low albumin level. A urinalysis reveals 3+ protein on the dipstick with no microscopic findings.

Which one of the following would be the most appropriate next step? (check one)
Urine microscopy to check for eosinophils
A spot urine protein/creatinine ratio
Renal ultrasonography
Echocardiography
Referral for a renal biopsy

Answer 32

A spot urine protein/creatinine ratio

Individuals with nephrotic syndrome often present with edema and fatigue with no evidence of severe liver
disease or heart failure. Hallmarks of this problem include heavy proteinuria, hypoalbuminemia, and
peripheral edema, often with hyperlipidemia as well. While most of these cases are idiopathic, secondary
causes such as diabetes mellitus, systemic lupus erythematosus, and medication reactions should be
considered.
To confirm proteinuria in the nephrotic range a spot urine protein/creatinine ratio is now suggested instead
of a 24-hour collection of urine. Checking urine for eosinophils has been recommended in the past for
evaluation for acute interstitial nephritis but subsequent studies have shown a lack of specificity and
sensitivity. Renal ultrasonography would be indicated if the glomerular filtration rate were reduced.
Echocardiography would be appropriate if heart failure were suspected. While a renal biopsy is often
recommended, it is most useful in patients with suspected underlying systemic lupus erythematosus or
similar disorders when a biopsy can guide management decisions and prognosis.

Question 33

A 62-year-old female with stage 3 chronic kidney disease and an estimated glomerular filtration rate of 37 mL/min/1.73 m2 is found to have a mildly low ionized calcium level. Which one of the following would you expect to see if her hypocalcemia is secondary to her chronic kidney disease? (check one)
Elevated parathyroid hormone (PTH) and elevated phosphorus
Elevated PTH and low phosphorus
Low PTH and elevated phosphorus
Low PTH and low phosphorus

Answer 33

Elevated parathyroid hormone (PTH) and elevated phosphorus

Chronic kidney disease–mineral and bone disorder (CKD-MBD) is found in many patients with CKD and
is associated with an increased risk of bone fractures and cardiovascular events due to vascular
calcification. In patients with CKD, phosphate is not appropriately excreted and the subsequent
hyperphosphatemia leads to secondary hyperparathyroidism and binding of calcium. Decreased production
of calcitriol in patients with CKD also leads to hypocalcemic hyperparathyroidism. Patients with CKD
stages 3a–5 should have phosphorus, calcium, parathyroid hormone, and 25-hydroxyvitamin D levels
checked regularly, and consultation with a nephrologist or endocrinologist should be obtained if
CKD-MBD is suspected.