MCQs In Nephrology Part II

Q1

A 12-year-old girl is admitted to the hospital with left flank pain and weight loss over a 2-month period. She has no history of fever, vomiting, or diarrhea. Urinalysis is negative. Serum electrolytes are: sodium, 132 mEq/L (132 mmol/L); potassium, 2.6 mEq/L (2.6 mmol/L); chloride, 92 mEq/L (92 mmol/L); bicarbonate, 30 mEq/L (30 mmol/L); creatinine, 0.7 mg/dL (61.9 mcmol/L); and blood urea nitrogen, 15 mg/dL (5.4 mmol/L of urea). She admits to taking her grandmother's diuretics to lose weight.

Of the following, the MOST likely cause of the flank pain is:

A. acute pyelonephritis

B.  autosomal dominant polycystic kidney disease

C.  renal abscess

D. simple renal cyst

E. ureteropelvic junction obstruction

Answer

E

Patients who have UPJ obstruction may be asymptomatic or they may experience intermittent abdominal or flank pain, abdominal fullness, gross hematuria, and dysuria due to infection. Occasionally, mild or moderate UPJ obstruction may be undetected until there is trauma to the kidney or an abnormal flow of urine into the obstructed area. Such insults can occur after copious intake of fluids or the use of diuretics, as seen in the girl described in the vignette.

Furosemide is a loop diuretic that induces an increase in renal excretion of salt and water, inhibiting the Na-K-2Cl cotransporter in the thick ascending limb of Henle loop. Patients who are taking chronic diuretic therapy or abusing diuretics, such as the girl described in the vignette, typically exhibit hypokalemia and alkalosis on routine electrolyte evaluation. Patients who have acute pyelonephritis usually experience flank pain, but the urinalysis reveals white blood cells, nitrites, and bacteria.

 Autosomal dominant polycystic kidney disease (ADPKD) generally is seen in adults and is manifested by hematuria, urinary tract infection, abdominal pain, and hypertension. Findings on urinalysis in patients who have early ADPKD frequently are unremarkable. Electrolyte analysis eventually may reveal azotemia, but hypokalemia and alkalosis are not seen. A patient who has a renal abscess will experience abdominal or flank pain, but also will develop a fever. 

Furthermore, findings on the urinalysis are similar to those seen in acute pyelonephritis. Simple renal cysts are not uncommon and may, if large, cause abdominal discomfort, but results of electrolyte analysis usually are normal in most patients

------------------------------

Q 2

Of the following, the patient MOST likely to develop chronic renal failure is a:

A.  3-year-old boy who has minimal-change nephrotic syndrome

B.  3-year-old girl who has unilateral grade II vesicoureteral reflux

C.  4-year-old boy who has a history of Henoch-Schönlein purpura and persistent nephrotic syndrome

D.  9-year-old boy who has unilateral multicystic kidney dysplasia

E. 10-year-old girl who has immunoglobulin A nephropathy and persistent microscopic 

Answer:

C

-----

Q 3

In addition to vascular thrombosis, the MOST likely complications observed in children who have minimal-change nephrotic syndrome are:

A. acute renal failure

B. chronic renal failure

C.  hypercholesterolemia

D.  hypernatremia

E.  hyponatremia

Answer

C

Nephrotic syndrome (NS) is characterized by proteinuria, hypoalbuminemia, edema, and hypercholesterolemia. 

--------------

A child presents at age 6 months with failure to thrive and rickets. Urinalysis shows 1+ protein and glucosuria. Your differential diagnosis includes nephropathic cystinosis.

Of the following, the test that would BEST confirm the diagnosis is:

A. leukocyte cystine content

B. liver biopsy

C. ophthalmologic examination revealing cystine deposits

D. serum level of cystine

E. urinary excretion of cystine

Answer

A

The diagnosis of cystinosis depends upon recognition of the constellation of symptoms such as polyuria and polydipsia, anorexia, failure to thrive, dehydration, and hyperchloremic metabolic acidosis. Renal wasting of bicarbonate and phosphate and the presence of glucosuria should alert the physician to the likelihood of Fanconi syndrome. The gold standard for diagnosis of cystinosis is the demonstration of cystine accumulation in the tissues and in leukocytes. Liver biopsy may reveal cystine deposits in some but not all patients. A prenatal diagnosis can be made by measuring cystine content in amniotic cells. The finding of needle-shaped opacities in the cornea by slitlamp examination confirms the diagnosis. Serum levels of cystine are generally normal in nephropathic cystinosis. Urinary excretion of cystine may be elevated, but this finding is not specific for the condition. 

--------------------------------

Q 4:

The parents of a 1-month-old infant who was found to have a solitary kidney in utero are asking questions about the status of the infant’s kidney function. The infant is otherwise healthy. Upon the insistence of the family, a serum creatinine and ultrasonography are performed. The serum creatinine is 0.5 mg/dL. Renal ultrasonography demonstrates a 5.5 cm kidney on the right side of the body and absent kidney on the left.

Of the following, the statement that BEST characterizes the renal status of the infant is

A. nephrotoxic agents should be minimized because of decreased nephron mass

B.  this infant is at higher than usual risk for dehydration in the setting of gastroenteritis

C. this infant is likely to require dialysis by adolescence

D. this infant will require annual ultrasonography to screen for renal malignancy

E. toilet training may be more challenging in the future for this infant

Answer

A

The vignette describes a 1-month-old infant with a single kidney and a serum creatinine of 0.5 mg/dL. This infant has unilateral renal agenesis, which has an estimated incidence of 1 in 2,900 newborns. Infants with unilateral renal agenesis have 50% of the expected nephron number. Because of a compensatory increase in the single nephron GFR (SNGFR), the serum creatinine should continue to fall to normal levels for the child’s age over the first 1 to 2 years of life until reaching an expected level of 0.3 mg/dL. Moreover, this single kidney is fully functional and has normal urine concentrating abilities; therefore, an infant with gastroenteritis would not be expected to be at high risk of dehydration in this setting. It is unusual for the doubling of the SNGFR to result in a hyperfiltration injury to the nephron mass and result in proteinuria. As the single kidney should be structurally and functionally normal, screening for hypertension should be done beginning at age 3 years during health maintenance visits. Periodic urinalysis also should be considered to screen for the development of proteinuria. Avoidance of nephrotoxic medications such as nonsteroidal anti-inflammatory drugs, intravenous radiocontrast, and aminoglycoside antibiotics should be considered in children with a single kidney because of the reduced renal reserve in these patients. Also, newborns with renal agenesis have an approximately 30% risk of vesicoureteral reflux (VUR) into their kidneys; therefore, performance of a voiding cystourethrogram to evaluate for VUR is recommended in these patients.

-------------------

Q 5:

A 5-year-old otherwise healthy  girl, who was fully toilet trained at age 3, begins to wet her bed. She complains of some dysuria, but has normal findings on physical examination Of the following, the MOST likely etiology for this child's enuresis is:

A. constipation with rectal distension

B.  diabetes mellitus

C.  nocturnal enuresis

D.  sickle cell trait

E.  urinary tract infection

Answer

E

Children who have inflamed bladders due to infection (cystitis) often present with urinary frequency. They also may have urgency, dysuria, and hematuria. Some children develop secondary enuresis, as described for the child in the vignette. Findings on physical examination of children who have cystitis are normal, with the possible exception of suprapubic tenderness. The urinalysis may reveal blood and protein, positive leukocyte esterase, and positive nitrates. Microscopic examination may reveal white blood cells and bacteria. Cystitis is diagnosed when a urine culture reveals greater than 100,000 cfu/mL of a single organism. In infants and young children, sterile catheterization or suprapubic aspiration is preferable for the collection of urine for culture.

            Primary enuresis refers to involuntary discharge of urine when continence never has been achieved; secondary enuresis is incontinence that develops after at least 1 year of continence. Enuresis may be nocturnal or diurnal. Approximately 10% to 15% of 5-year-old children and 1% of adults have nocturnal enuresis that occurs at least once a month. When findings on physical examination and urinalysis are normal, further testing usually is not helpful in determining an etiology.

            Severe constipation with rectal distension can cause enuresis, but it generally is associated with marked abdominal distension. Polyuria, polydipsia, and polyphagia are expected in a child who has diabetes mellitus. Enuresis has been associated with disorders marked by renal concentrating defects, such as sickle cell disease or trait. However, children who have enuresis due to sickle cell trait are asymptomatic and do not have dysuria.

------------

Q 6


You are evaluating a 10-year-old girl for a health supervision visit. Her weight and height are at
the 50th percentile for age, her blood pressure is 108/64 mm Hg, and there are no unusual
findings on physical examination. A screening urinalysis shows a specific gravity of 1.030, pH of
6.5, 2+ blood, and no protein. Urine microscopy reveals 5 to 10 red blood cells/high-power field.

Of the following, the MOST appropriate next step is

A. abdominal computed tomography scan
B. antinuclear antibody and complement measurement
C. blood urea nitrogen and creatinine measurements
D. referral for cystoscopy
E. repeat urinalysis in 2 weeks

Answer:

E


The child who has asymptomatic, isolated microscopic hematuria is seen frequently in the
ambulatory setting. Results of a urine dipstick test in patients who have hematuria are positive
for blood, indicating the presence of hemoglobin or myoglobin. A microscopic evaluation that
reveals more than 5 red blood cells/high-power field, as described for the girl in the vignette,
confirms the presence of hematuria. Because isolated microscopic hematuria has been found in
4% of children on at least one of four tested samples, evaluation is not recommended unless
hematuria is present on at least two of three urine samples. Accordingly, the girl in the vignette
should undergo repeat urinalysis in 2 weeks.

------

Q 7:


You are seeing an 8-month-old infant for a health supervision visit. He was born at 28 weeks’
gestation, weighed 1,200 g at birth, and has bronchopulmonary dysplasia. His only medication is
furosemide, which he has been receiving for several months.
Of the following, the MOST likely expected abnormality in this infant is

A. hypercalciuria
B. hypermagnesemia
C. hypocalcemia
D. hyponatremic dehydration
E. metabolic acidosis

Answer

A

Useful information about Furosemide


Furosemide is a loop diuretic that acts at the ascending limb of the loop of Henle (LOH).
Normally, approximately 20% to 25% of filtered sodium is reclaimed at this site, so blockade of
sodium reabsorption results in a brisk diuresis, with urinary losses of sodium, potassium, and
chloride. The blocked transporter is the Na+-K+-2Cl- channel.

In addition to direct effects on the electrolytes of this channel, loop diuretics influence
calcium and magnesium transport. Calcium and magnesium are reabsorbed passively in the
ascending limb of the LOH through paracellular transport as a result a gradient derived from
normal sodium chloride transport. The passive reabsorption of calcium is believed to occur
through a paracellular pathway that is facilitated by paracellin-1, a tight junction protein.
Interruption of sodium chloride reabsorption results in impaired calcium reabsorption and
consequent hypercalciuria and increased risk for nephrocalcinosis and kidney stones.

Furosemide also has an effect on the composition of endolymph in the inner ear because
the Na+-K+-2Cl- transporter that is in the ascending limb of the LOH also can be found in the
marginal cells of the cochlear duct of the inner ear. Furosemide induces changes in ion transport
in these cells, reducing endocochlear potentials in the cells, which results in hearing loss.
Ototoxicity is more likely when loop diuretics are used in high doses or are used in conjunction
with other ototoxic agents such as aminoglycosides. Furosemide-induced ototoxicity usually is
temporary, but can be permanent in some cases.

Patients receiving loop diuretics also may develop hypokalemia, metabolic alkalosis, and
hypomagnesemia (from increased urinary losses). Abnormalities in serum calcium are not
typical, despite hypercalciuria. Hypercalciuria can lead to nephrocalcinosis, which can be
longstanding, even after discontinuation of furosemide. Patients receiving furosemide are at risk
for dehydration, but this is typically hypernatremic dehydration; hyponatremic dehydration is
more common with thiazide diuretics.