In a diagnostic laparotomy, the nature of the disease is unknown, and laparotomy is deemed the best way to identify the cause. In therapeutic laparotomy, a cause has been identified (e.g. peptic ulcer, colon cancer) and laparotomy is required for its therapy. Usually, only diagnostic laparotomy is referred to as a surgical operation by itself; and when a specific operation is already planned, laparotomy is considered merely the first step of the procedure.
Depending on incision placement, it may give access to any abdominal organ or space, and is the first step in any major diagnostic or therapeutic surgical procedure of these organs, which include the lower part of the digestive tract (the stomach, duodenum, jejunum, ileum and colon), the liver, pancreas and spleen, the bladder, the female reproductive organs (the uterus and ovaries) and the retroperitoneum (the kidneys, the aorta, abdominal lymph nodes)
The most common incision for laparotomy is the midline incision, a vertical incision which follows the linea alba. The upper midline incision usually extends from the xiphoid process to the umbilicus, while a typical lower midline incision is limited by the umbilicus superiorly and by the pubic symphysis inferiorly. Sometimes a single incision extending from xiphoid process to pubic symphysis is employed, especially in trauma surgery. Midline incisions are particularly favored in diagnostic laparotomy, as they allow wide access to most of the abdominal cavity.