The falciform ligament sign of pneumoperitoneum.

Sir,

A 84-year-old bed-ridden man presented with an acute onset of abdominal pain. The abdomen was diffusely tender with rebound; bowel sounds were absent. Laboratory tests showed increased white blood cell count of 21,600/mm3. A supine radiograph showed the presence of air in the bilateral subphrenic spaces and a linear density on the ventral surface of the liver (arrows), known as the falciform ligament sign [Figure 1]. A computed tomography (CT) scan disclosed the falciform ligament (arrow), outlined by intraperitoneal free air [Figure 2]. Laparotomy disclosed the perforated diverticulitis of the sigmoid colon, which was treated with colostomy leading to an uneventful recovery.

Figure 1

The supine abdominal radiograph of the patient showing the presence of air in the bilateral subphrenic spaces and a linear density on the ventral surface of the liver (arrows), known as the falciform ligament sign

Figure 2

The computed tomography scan of the abdomen of the patient showing the falciform ligament (arrow), outlined by intraperitoneal free air

Pneumoperitoneum can be an indicator of underlying serious disorders, which may require emergent surgical interventions. Upright chest radiographs and abdominal radiographs in the left lateral decubitus position have been sensitive indicators for pneumoperitoneum; however, only supine radiographs can be often obtained in critically ill patients. The falciform ligament, the embryological remnant of the umbilical artery, connects the anterior abdominal wall to the anterosuperior surface of the liver. It is invisible under normal situations, however; when surrounded by intraperitoneal free air it may become visible as a vertical band of soft tissue parallel to the right border of the spine.[1] The falciform ligament sign refers also to the CT evaluation. Although the CT-falciform ligament sign has been more frequent in the proximal gastrointestinal perforation,[2] extensive quantity of free air from the distal gastrointestinal perforation may disclose the sign like our case.

Other signs of pneumoperitoneum in supine radiographs include the right-upper-quadrant gas sign (localized extraluminal gas in the right upper quadrant) and the Rigler sign, also known as double-wall sign (gas on both sides of the bowel wall).[34] Proper evaluation of above signs of pneumoperitoneum on supine radiographs should lead to further more accurate diagnostic techniques in this life-threatening disorder.