Uterine rupture in the setting of pyometra is a rare occasion, with an incidence of less than 0.5%. The clinical manifestation of a perforated pyometra is non-specific; therefore, it can mimic many other causes of acute abdomen, such as perforated viscus, acute appendicitis, or diverticulitis, which poses unique challenges to diagnosis solely based on clinical information. We reviewed a case of an elderly postmenopausal lady who presented with a sudden onset of generalized abdominal pain, preceded by fever and vomiting. Physical examination revealed a distended abdomen with clinical signs of peritonism. She was initially diagnosed with possible obstructed gastrointestinal carcinoma by clinical examination, with the differential diagnosis of diverticular abscess. Eventually, further abdominal and pelvic contrast-enhanced computed tomography (CECT) study revealed a pyometra with uterine rupture, complicated with pneumoretroperitoneum and pneumoperitoneum. This case emphasizes the value of a CT scan in establishing an accurate diagnosis and early detection of life-threatening complications, such as uterine rupture, as in this case.