A 6-year-old male with acute kidney injury and enlarged kidneys: Answers

Based on the presence of acute kidney injury (AKI) with bland urine and history of ibuprofen use, we considered acute interstitial nephritis (AIN), keeping in mind AIN secondary to systemic diseases such as sarcoidosis and systemic lupus erythematosus because of fever and joint pain for a few weeks. Tubulointerstitial nephritis with uveitis syndrome (TINU) was also considered for which ophthalmology was consulted and examination was normal. Although AIN may present with enlarged kidneys, this patient’s nephromegaly was very significant. We related the nephromegaly initially to AIN, while including in the differential benign or malignant infiltrative diseases. The patient’s LDH was elevated; however, uric acid was normal and his CBC other than microcytic anemia was normal. Obstructive uropathy should also be in the differential diagnosis; however, this was excluded by ultrasound.

In children with AKI, urinalysis and kidney/ bladder ultrasound are the usual initial tests to guide diagnosis. As in our case, the bland urinary sediment, absence of hematuria and proteinuria, directed us towards a tubulointerstitial disorder, rather than glomerulonephritis. Ultrasound excluded obstruction and showed enlarged kidneys, which guided us to perform a kidney biopsy when the patient did not improve after discontinuation of the presumed offending agent (ibuprofen) and hydration. Additional testing should be guided based on the patient’s history and examination findings. The presence of body aches, low-grade fever, and tenderness over the left elbow prompted further testing including CBC with Differential, blood culture, lactate dehydrogenase (LDH), uric acid (UA), and creatine kinase (CK).

A kidney biopsy was done in this patient to establish diagnosis in view of persistent elevation in creatinine despite supportive treatment. The decision of performing a kidney biopsy is not as clear in patients with AKI and bland urine sediment. In patients with AIN, the severity of inflammation seen on kidney pathology may indicate the need to use corticosteroids and this was the main reason for the biopsy in our patient.