Best investigation for air in peritoneal cavity is -: (A) USG, (B) Laparotomy, (C) Laparoscopy, (D) X-ray abdomen-erect view
Answer is D. Not given in the option but free gas under the diaphragm is best shown on an erect chest x-ray. If the patient is too ill for an erect film, a lateral decubitus film is done.