Kaplan PANCE Practice Question of the Day

PANCE Practice Question for March 9th

A 2-year-old girl is brought to the emergency department because she looked "unwell" and has not wanted to get out of bed for 24 hours. She had a diarrheal illness 1 week ago marked by fever and bloody diarrhea, from which she had recovered. Two days ago, however, she developed reduced appetite and lethargy. She has had only 2 wet diapers in the last 36 hours. She was previously a well child and at the regular clinic visits normal growth and development were noted. Examination shows an irritable, pale child who has petechiae and edema. Vital signs reveal the blood pressure 102/74 mm Hg, pulse 136/min, and respirations 26/min. Lung and abdominal examinations are normal. Laboratory studies show:

Hemoglobin	7.1g/dL
WBCs	222 x 10⁹/L (normal 5,000-10,000)
Differential:
Polymorphs	38%
Lymphocytes	52%
Monocytes	8%
Platelets	80 x 10⁹/L
Blood film	Fragmented red blood cells
Prothrombin time	12.1 sec
Partial thromboplastin time	32 sec
Serum sodium	132 mEq/L
Serum potassium	6.3 mEq/L
Serum chloride	106 mEq/L
Serum bicarbonate	16 mEq/L
Blood urea nitrogen	32 mg/dL
Serum creatinine	3.1 mg/dL

Which of the following is the appropriate next step in management?

The correct answer is C. This patient has presented in acute renal failure, which is manifested by oliguria (<400-500 mL/24h) elevated blood urea nitrogen and creatinine, and hyperkalemia. Given the clinical picture, the most likely etiology is hemolytic uremic syndrome (HUS). HUS is the most common cause of acute renal failure in young children and most frequently follows an episode of gastroenteritis caused by an enterohemorrhagic strain of Escherichia coli (0157:H7). Endothelial injury to the kidneys leads to renal failure, whereas damage to red blood cells and platelets in the kidneys leads to the thrombocytopenia and microangiopathic hemolytic anemia. The management is supportive care of the renal failure, which is self-limited in most cases. Given the marked elevation of creatinine as well as hyperkalemia in this patient, the most appropriate choice would be to initiate dialysis.

Children who present with oliguria may benefit from a normal saline bolus (choice A) if the intravascular volume is depleted. The patient in this vignette demonstrates signs of fluid overload, however, and a bolus of IV fluids is inappropriate in this setting.

Steroids such as methylprednisolone (choice B) are used for renal diseases such as lupus nephritis and nephrotic syndrome. They have no role in the treatment of HUS

Plasmapheresis (choice D) is useful in adult patients who have thrombotic thrombocytopenic purpura, but not in children who have HUS.

Because of the presence of fluid overload and hyperkalemia, red blood cell transfusion (choice E) is not safe in this patient until peritoneal dialysis has been instituted.

PEARL: Hemolytic uremic syndrome (HUS) is common after infection with Escherichia coli (O157:H7). Endothelial injury to the kidneys leads to renal failure, which is diagnosed by oliguria, elevated blood urea nitrogen and creatinine, and hyperkalemia. In the instance of marked elevation of potassium and creatinine, the first step would be dialysis, then continued supportive treatment.

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PANCE Practice Question for March 9th

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