UNILATERAL RENAL LIMPHANGIECTASIA. REPORT OF ONE CASE. Renal lymphangiectasia is a rare disorder characterized by the presence of cystic masses in renal parenchyma, renal sinus or perinephric space. This condition, congenital or acquired, is probable caused by an alteration of renal lymphatic drainage to retroperitoneal lymph ducts . We report  a 48-year-old woman, who consulted in  the emergency room due to left flank pain and microscopic hematuria. Blood pressure and renal function were normal. A CT scan showed a multilocular cystic mass in the left renal sinus without alterations in the renal parenchyma. Renal lymphangiomatosis was diagnosed. The pain subsided with analgesics and did not recur. Annual clinical and ultrasound follow-up was suggested. (Rev Med Chile…) (Key-words:  Hematuria; Hydronephrosis; Lymphangiomatosis)