A 25-year-old woman being treated for infective endocarditis is evaluated for new-onset renal dysfunction. The patient has a 2-year history of injection drug use and presented 3 weeks ago with subjective fevers, pleuritic chest pain, and shortness of breath. Chest CT imaging with contrast revealed peripheral nodular opacities consistent with septic emboli, and blood cultures were positive for Enterococcus faecalis. Echocardiography showed tricuspid valve vegetations without valvular insufficiency or abnormal cardiac function. The patient has been receiving intravenous ampicillin and ceftriaxone, and repeat blood cultures have been negative. Yesterday, she was noted to have elevated serum creatinine on routine weekly laboratory studies. The patient has no nausea, vomiting, flank pain, rash, dysuria, or chills. She continues to void regularly with no changes in appearance or volume of her urine.
Temperature is 38.3 C (100.9 F), blood pressure is 122/64 mm Hg, pulse is 90/min, and respirations are 14/min. Physical examination shows no jugular venous distension, and auscultation of the heart and lungs is normal. There is no abdominal or costovertebral angle tenderness. No rash or edema is present.
Repeat laboratory results are as follows:
Which of the following is the most likely diagnosis in this patient?

Question

A 25-year-old woman being treated for infective endocarditis is evaluated for new-onset renal dysfunction.  The patient has a 2-year history of injection drug use and presented 3 weeks ago with subjective fevers, pleuritic chest pain, and shortness of breath.  Chest CT imaging with contrast revealed peripheral nodular opacities consistent with septic emboli, and blood cultures were positive for Enterococcus faecalis.  Echocardiography showed tricuspid valve vegetations without valvular insufficiency or abnormal cardiac function.  The patient has been receiving intravenous ampicillin and ceftriaxone, and repeat blood cultures have been negative.  Yesterday, she was noted to have elevated serum creatinine on routine weekly laboratory studies.  The patient has no nausea, vomiting, flank pain, rash, dysuria, or chills.  She continues to void regularly with no changes in appearance or volume of her urine.
Temperature is 38.3 C (100.9 F), blood pressure is 122/64 mm Hg, pulse is 90/min, and respirations are 14/min.  Physical examination shows no jugular venous distension, and auscultation of the heart and lungs is normal.  There is no abdominal or costovertebral angle tenderness.  No rash or edema is present.
Repeat laboratory results are as follows:
 Which of the following is the most likely diagnosis in this patient?

Quizplus · Accepted Answer

11ec193a_9725_b122_853d_35966f77bd15_MD0002_00 This patient has acute renal failure 2 weeks after initiation of antibiotic therapy with concomitant fever, eosinophilia, and hematuria, pyuria, white blood cell (WBC) casts on urinalysis. This constellation of findings suggests acute interstitial nephritis (AIN), likely due to ampicillin. Up to 75% of cases of AIN are due to drugs, especially antibiotics (eg, penicillins, trimethoprim-sulfamethoxazole), nonsteroidal anti-inflammatory drugs, and proton pump inhibitors. Other causes include autoimmune disorders, malignancy, and certain infections (eg, Legionella). Onset is variable and generally occurs weeks to months after primary exposure; however, symptoms develop more rapidly (days) after second exposure. Clinical features of AIN resemble an allergic response and include fevers, rash, and eosinophilia, although all 3 symptoms occur in only 10% of cases and patients may be asymptomatic. Urinalysis classically shows hematuria, pyuria with white blood cell (WBC) casts, and variable proteinuria. Urinary eosinophils are supportive but are not sensitive or specific. Renal biopsy is diagnostic but is not required if symptoms resolve after drug withdrawal. (Choice A) Cholesterol embolization causes renal failure, sterile pyuria, and WBC casts but typically occurs following percutaneous endovascular procedures in older patients with significant atherosclerosis. This young woman is unlikely to have significant atherosclerosis and has not undergone an invasive procedure in >2 weeks. (Choices B and D) Contrast-induced nephropathy is a type of drug-induced acute tubular necrosis classically seen following CT studies. Renal failure typically occurs 24-48 hours after exposure, and urinalysis would be expected to show muddy brown casts, not WBC casts. (Choice E) Immune complex-mediated glomerulonephritis (eg, membranoproliferative, postinfectious) is characterized by acute renal failure with dysmorphic red blood cells and red blood cell casts, not WBC casts. In addition, postinfectious glomerulonephritis is more common after streptococcal or staphylococcal infections rather than enterococcal infections. Educational objective: Acute interstitial nephritis is characterized by acute renal failure with concurrent fever, rash, and eosinophilia, with sterile pyuria, hematuria, and white blood cell casts on urinalysis. Common causes include antibiotics, nonsteroidal anti-inflammatory drugs, and proton pump inhibitors. __________ References: Acute interstitial nephritis - a reappraisal and update. (http://www.ncbi.nlm.nih.gov/pubmed/25079860)

A 25-Year-Old Woman Being Treated for Infective Endocarditis Is Evaluated