A 12-year-old boy is brought to the emergency department due to brown urine for the past 2 days. In addition, the patient has had decreased urine output and a mild headache. He has no chronic medical conditions but was treated with oral amoxicillin 18 days ago for pharyngitis. The patient's family history is unremarkable. Temperature is 36.8 C (98.2 F), blood pressure is 150/92 mm Hg, pulse is 89/min, and respirations are 15/min. Physical examination shows a tired-appearing boy with edema in the scrotum and bilateral lower extremities. Laboratory results are as follows: Complement component C3 levels are low. Which of the following is the best next step in management of this patient?

Question

A 12-year-old boy is brought to the emergency department due to brown urine for the past 2 days.  In addition, the patient has had decreased urine output and a mild headache.  He has no chronic medical conditions but was treated with oral amoxicillin 18 days ago for pharyngitis.  The patient's family history is unremarkable.  Temperature is 36.8 C (98.2 F), blood pressure is 150/92 mm Hg, pulse is 89/min, and respirations are 15/min.  Physical examination shows a tired-appearing boy with edema in the scrotum and bilateral lower extremities.  Laboratory results are as follows:  Complement component C3 levels are low.  Which of the following is the best next step in management of this patient?

Quizplus · Accepted Answer

Explanation: 11ec2b69_c09c_93f6_8f63_956c4ab636e3_MD0005_00 This patient has hypertension, hematuria, and low complement component C3 several weeks after group A Streptococcus infection (eg, pharyngitis), findings consistent with acute poststreptococcal glomerulonephritis (APSGN). APSGN, a nephritic syndrome, results from immune complex deposition between the glomerular basement membrane (GBM) and the mesangium, as well as from glomerular damage due to complement (C3) activation and inflammation. Although many cases are characterized by asymptomatic microscopic hematuria that resolves within weeks, fulminant nephritic syndrome can occur, as in this patient. Damage to the glomerulus results in gross hematuria (tea- or cola-colored) usually with red blood cell casts, as well as increased urinary loss of protein, causing decreased intravascular oncotic pressure and third spacing. Acute kidney injury with decreased glomerular filtration (eg, ↑ serum creatinine) and impaired sodium excretion is also characteristic. The aggregate consequence of both sodium and water retention is volume overload with hypertension and edema. Management of APSGN is supportive, and first-line treatment for hypertension and edema is loop diuretics (eg, furosemide). Fluid restriction may be indicated, and caution should be used with intravenous fluids because they may worsen edema and hypertension. Most patients do not require adjunctive therapy with antihypertensives, but calcium channel blockers (eg, nifedipine) should be considered for hypertensive encephalopathy or hypertension refractory to diuresis. (Choice A) Cyclophosphamide is an immunosuppressant used in several nephritic syndromes (eg, anti-GBM disease, pauci-immune vasculitis). However, in APSGN, the deposition of antigen-antibody complexes spontaneously resolves, so immunosuppressive therapy is not needed. (Choice B) Dialysis is rarely required for patients with APSGN. Indications include medically refractory hyperkalemia, marked uremia, or pulmonary edema, none of which are present in this patient. (Choice D) ACE inhibitors (eg, lisinopril) are generally avoided for hypertension in the setting of acute kidney injury because of the risk of exacerbating hyperkalemia. Moreover, this patient's hypertension should be treated with diuresis first. Educational objective: Acute poststreptococcal glomerulonephritis, a complication of group A Streptococcus infection (eg, pharyngitis), typically presents with hematuria, edema, and hypertension. Management is supportive and includes loop diuretics (eg, furosemide) for symptoms of volume overload (eg, hypertension, edema). References: Acute poststreptococcal glomerulonephritis: the most common acute glomerulonephritis. (http://www.ncbi.nlm.nih.gov/pubmed/25554106)

A 12-Year-Old Boy Is Brought to the Emergency Department Due