A 45-year-old woman comes to the hospital due to sudden-onset, right-sided flank pain that started 12 hours ago. The patient has had fever and malaise for the past 2 weeks and has been taking over-the-counter ibuprofen intermittently for a presumed viral infection. She has had no dyspnea, cough, chest pain, or urinary symptoms. Temperature is 38.7 C (101.7 F), blood pressure is 110/78 mm Hg, pulse is 102/min, and respirations are 16/min. Lung sounds are normal. A 2/6 systolic murmur is present at the cardiac apex. Right flank tenderness is present. The remainder of the examination shows no abnormalities. Laboratory results are as follows: CT scan of the abdomen is shown below:
Which of the following is the most likely cause of this patient's current symptoms?

Question

A 45-year-old woman comes to the hospital due to sudden-onset, right-sided flank pain that started 12 hours ago.  The patient has had fever and malaise for the past 2 weeks and has been taking over-the-counter ibuprofen intermittently for a presumed viral infection.  She has had no dyspnea, cough, chest pain, or urinary symptoms.  Temperature is 38.7 C (101.7 F), blood pressure is 110/78 mm Hg, pulse is 102/min, and respirations are 16/min.  Lung sounds are normal.  A 2/6 systolic murmur is present at the cardiac apex.  Right flank tenderness is present.  The remainder of the examination shows no abnormalities.  Laboratory results are as follows:  CT scan of the abdomen is shown below:
 Which of the following is the most likely cause of this patient's current symptoms?

Quizplus · Accepted Answer

This patient with flank pain, hematuria, proteinuria, and a wedge-shaped renal parenchymal defect noted on CT scan has a renal infarction. Renal infarctions occur from a variety of etiologies (eg, atrial fibrillation, renal artery trauma, hypercoagulability). However, this patient's 2-week history of fevers associated with leukocytosis and possible mitral regurgitation (ie, systolic murmur at the apex) suggests infectious endocarditis (IE). IE results from seeding of the endocardium and cardiac valves during periods of bacteremia (the source of which is not always immediately apparent); embolization of valvular vegetations can result in end-organ (eg, kidney) ischemia and infarction. wedge-shaped renal parenchymal defect Renal infarctions typically manifest with acute flank pain, nausea, and vomiting; fever may also occur. Urinalysis classically demonstrates hematuria and proteinuria without casts. A rise in serum creatinine may occur but is more common with bilateral or very large, unilateral infarction. Other characteristic laboratory abnormalities include an elevated lactate dehydrogenase level, leukocytosis, and elevation in C-reactive protein. A contrast-enhanced CT scan or MRI demonstrating a wedge-shaped cortical infarction is diagnostic. (Choice A) Acute interstitial nephritis typically occurs with certain infections (eg, Legionella) or after initiation of a new drug (eg, antibiotics). Although it may be associated with fevers, patients typically have acute kidney injury with white blood cells (WBCs) and WBC casts on urinalysis. Rash and eosinophilia are also common, and CT scan usually is normal. (Choice B) Acute pyelonephritis is associated with flank pain, fevers, and hematuria; however, pyuria, bacteria, nitrites, and leukocyte esterase are expected on urinalysis. In addition, CT scan typically demonstrates perinephric stranding, not a wedge-shaped defect. (Choice C) Glomerulonephritis can cause hematuria and proteinuria, but red blood cell casts are expected on urinalysis. It is not associated with flank pain, fevers, or a wedge-shaped infarct on CT scan. (Choice D) Nephrolithiasis can cause flank pain and hematuria, but CT scan would be expected to demonstrate a stone within the urinary tract, possibly associated with hydronephrosis. Furthermore, in the absence of infection, fevers and leukocytosis are unexpected. Educational objective: Manifestations of renal infarction include flank pain, nausea, and vomiting; urinalysis demonstrates hematuria and proteinuria without casts. A wedge-shaped cortical infarction on CT scan is diagnostic. Renal infarctions can occur as a sequela of infectious endocarditis, which typically presents with recurrent fever, cardiac murmurs, and leukocytosis.

A 45-Year-Old Woman Comes to the Hospital Due to Sudden-Onset