(for example, head or chest CT); in these cases abdominal CT can be performed at the same time without wasting time in patient care. CT is able to detect 76% of hollow viscous injuries so people who have negative scans are often observed and rechecked if they deteriorate. However, CT has been demonstrated to be useful in screening people with certain forms of abdominal trauma in order to avoid unnecessary laparotomies, which can significantly increase the cost and length of hospitalizations. A meta-analysis of CT use in penetrating abdominal traumas demonstrated sensitivity, specificity and accuracy >= 95%, with a PPV of 85% and an NPV of 98%. This suggests that CT is excellent for avoiding unnecessary laparotomies but must be augmented by other clinical criteria to determine the need for surgical exploration (23.37 positive likelihood ratio, 0.05 negative likelihood ratio). Peritoneal lavage Diagnostic peritoneal lavage is a controversial technique but can be used to detect injury to abdominal organs: a catheter is placed in the peritoneal cavity, and if fluid is present, it is aspirated and examined for blood or evidence of organ rupture. If this does not reveal evidence of injury, sterile saline is infused into the cavity and evacuated and examined for blood or other material. While peritoneal lavage is an accurate way to test for bleeding, it carries a risk of injuring the abdominal organs, may be difficult to perform, and may lead to unnecessary surgery; thus it has largely been replaced by ultrasound in Europe and North America. Classification Abdominal trauma is divided into blunt and penetrating types. While penetrating abdominal trauma (PAT) is usually diagnosed based on clinical signs, diagnosis of blunt abdominal trauma is more likely to be delayed or altogether missed because clinical signs are less obvious. Blunt injuries predominate in rural areas, while penetrating ones are more frequent in urban settings. Penetrating trauma is further subdivided into stab wounds and gunshot wounds, which require different methods of treatment. Treatment Abdominal trauma requires urgent medical attention and sometimes requires hospitalization. The initial treatment involves stabilizing the person enough to ensure adequate airway, breathing, and circulation, and identifying other injuries. Surgery may be needed to repair injured organs. Surgical exploration may be necessary for people with penetrating injuries and signs of peritonitis or shock. Laparotomy is often performed in blunt abdominal trauma, and is urgently required if an abdominal injury causes a large, potentially