[Calculous renal failure and pregnancy].

Obstructive renal failure is a rare but serious complication of pregnancy. Although most cases are due to extrinsic compression, renal tract obstruction can also be due to intraluminal precipitation of sulfadiazine prescribed for maternofoetal toxoplasmosis. The diagnosis is suggested by clinical history, ultrasound (radiolucent stones situated anywhere in the renal tract) and especially analysis of the urine pellet (wheat sheaf formation of yellowish crystals). Urinary drainage by double J stent or percutaneous nephrotomy is indicated in the absence of clinical improvement in response to symptomatic treatment and adequate alkaline rehydration. The risk of sulfadiazine crystallization must be systematically prevented by a sufficient water intake and urinary alkalinization right from the start of treatment.