Spontaneous rupture of a normal renal collecting system during pregnancy is uncommon and all reported cases have occurred in right kidneys. We report a case of spontaneous rupture of the left renal collecting system during pregnancy. A 33-year-old pregnant woman presented with left loin and lower abdominal pain, and signs of preterm labour, at 32 weeks' gestation. An emergency caesarean section was performed for foetal distress but the left loin pain did not subside after delivery. Ultrasonography and a computed tomogram showed a left perinephric collection and urine extravasation, compatible with rupture of the renal collecting system. A percutaneous nephrostomy was inserted and the symptoms subsided. A summary of the literature discussing management of this clinical situation is provided.