Review Question - QID 213714

This patient with rising creatinine and white cell casts after starting ceftriaxone most likely has acute interstitial nephritis, which should be treated through discontinuation of the offending medication.

Acute interstitial nephritis is an immune-mediated inflammation of the kidneys. It is most commonly caused by a hypersensitivity reaction to drugs such as diuretics, NSAIDs, antibiotics, and proton pump inhibitors. Other causes include autoimmune diseases such as systemic lupus erythematosus and sarcoidosis. Key findings include a rising creatinine after introduction of the medication with serum eosinophilia and white blood cell casts in the urine. The main treatment for this disorder is discontinuation of the inciting medication and administration of glucocorticoids to suppress inflammation.

Figure/Illustration A shows a urinalysis with a white blood cell cast that is characteristically seen in acute interstitial nephritis. In the illustration, the cast is outlined in blue and some of the individual leukocytes contained within are circled in red. The presence of a white blood cell cast suggests immune-mediated pathology at the level of the tubules.

Incorrect Answers:
Answer 1: Allopurinol administration can be used to treat uric acid stones that are found in gout, which can present with flank pain and increasing creatinine if they inhibit the outflow tracts; however, white cell casts would not be seen in this disease.

Answer 3: Intravenous hydration can be used to treat renal papillary necrosis or continuing ischemia to the kidneys; however, this disease would present with hematuria and pyuria below the level of the tubules. Therefore, this disease would not have white cell casts. Renal papillary necrosis can be caused by sickle cell disease, diabetes, NSAID use, or severe pyelonephritis.

Answer 4: Renal replacement therapy can be used to treat acute tubular necrosis, which can be a cause of increased creatinine days after a patient experiences kidney ischemia; however, this disease would present with muddy brown casts from dead epithelial cells rather than white cell casts.

Answer 5: Surgical removal of stone can be used to treat nephrolithiasis; however, this disease would present with colicky flank pain and hematuria rather than white cell casts.

Bullet Summary:
Drug-induced acute interstitial nephritis should be managed by removal of the inciting medication.