A case is presented involving a patient with a history of pelvic fracture who experienced progressive difficulty in urination following the removal of a urethral catheter. Attempt to retain the catheter was unsuccessful, leading to an ultrasound-guided suprapubic puncture cystostomy. Subsequently, the patient developed persistent abdominal pain, distension, nausea, and vomiting. Analysis of turbid greyish-yellow thin purulent fluid obtained during abdominal paracentesis indicated the presence of peritonitis. Urgent surgical exploration revealed that the diversion tube had passed through the abdominal cavity and into the bladder. The entire abdominal cavity was filled with yellowish-thin purulent fluid. Intraoperatively, the patient presented with worsening hypotension, tachycardia, oliguria, and decreased skin temperature, suggestive of septic shock resulting from peritonitis. Prompt management, including antimicrobial therapy, hemodynamic support, and fluid resuscitation, successfully controlled the infectious symptoms, leading to complete recovery. In clinical practice, the emphasis is often placed on assessing injuries to intra-abdominal organs, whereas awareness and understanding of peritoneal injuries remain limited. As a result, postoperative peritonitis is frequently attributed solely to intra-abdominal organ damage, overlooking the potentially grave consequences of pure peritoneal injury. Therefore, it is imperative to enhance our recognition and knowledge regarding peritoneal injuries, enabling timely diagnosis and treatment to prevent the occurrence of complications.