A 46-year-old male referred to the Emergency Department with pain in the left flank. The patient suffered from Crohn's disease. He had not experienced any fever, and a urine strip showed signs of blood. A ureteric calculus was suspected and a computed tomography scan was performed, which surprisingly showed free intraperitoneal air (FIA) located along the ascending colon. The patient had no signs indicative of peritonitis and the spontaneous pneumoperitoneum was suspected. Pneumoperitoneum is often associated with severe intraabdominal pathology, such as perforation of the gastrointestinal tract, requiring acute surgical intervention. In ~10% of all cases of FIA, the cause is related to conditions not requiring prompt surgical intervention. Doctors need to recognize the rare condition of spontaneous pneumoperitoneum and correlate these findings to patient complaints to be able to choose the correct conservative strategy and to avoid unnecessary surgical procedures and risks for the patient.