Background: Anterior lumbar interbody fusion (ALIF) has become widely accepted for the treatment of discogenic low back pain, achieving similar radiological and clinical treatments to other techniques. To describe sigma perforation and septic peritonitis as a potentially fatal complication after an anterior interbody fusion.Case report: A 63-year-old women consulted to the emergency room for diffuse abdominal pain and nausea after a L5-S1 ALIF 5 days prior. Blood tests and X-Rays showed no alterations. A CT scan showed intraabdominal liquid and a pneumoperitoneum, later evolving to septic shock. An emergent laparotomy was performed to repair a 1 cm-long perforation of the minor sigma. One year later, patient was with no pain neither X-ray alteration. Conclusion:Potential complications of an anterior lumbar approach include iliac vein injury, thrombosis, or retrograde ejaculation. However, bowel injuries are uncommon, and a case of septic peritonitis after a sigma perforation, with high morbidity, has never been described before.