[Chronic interstitial nephritis caused by analgesics]

Interstitial nephritis secondary to analgesic ingestion is apparently an uncommon subject in pediatric literature. Two cases are reported in this article: case 1 is a girl followed for the last fifteen years when she had lipoid nephrosis which was treated initially with corticosteroids; she responded satisfactorily, but presented frequent relapses. After 8 years, she was given cyclophosphamide plus prednisone and lately, she responded and has remained well. Further on, her urinalysis showed specific gravity of 1,033 and no proteinuria. Five years ago, because of protracted headache due to psychological disturbance, she started to ingest a variety of analgesics in progressively increasing doses. For the last 2 years, abdominal pains, paleness, polydipsia and polyuria have been observed; at present, her blood pressure, serum chemistry, and urine sediment are normal, but there is a marked failure in the renal concentration capacity, as well as marked sodium urinary losses. A percutaneous renal biopsy showed tubulo-interstitial fibrosis and edema with normal glomeruli. Case 2 is a girl with rheumatoid arthritis which appeared 3 years ago; for over one year, the patient was given 15 mg/day prednisone plus 1.5 g. acetylsalycilic acid. She was admitted to the hospital because her osteoarticular problem did not improve. Her blood pressure, blood chemistries and urinary sediment were also normal. LE tests were negative. Renal concentrating capacity was reduced and the renal biopsy showed tubular atrophy; there was intestinal edema and mononuclear infiltration. Chronic interstitial nephritis, secondary to analgesics is supported in both cases; polyuria and a marked defect of renal concentrating capacity are the earliest and most characteristic features. Normal urinary sediment is a common finding leading to erroneous assessment of a lack of renal involvement. Pathological lesions are located in the interstice of the renal medulla and sometimes in the papilla. Early arrest of analgesic ingestion may stop and even reverse the renal lesion and the renal insufficiency.