Ill Defined Periduodenal Lucency

Another anterior collection of free air but situated more inferiorly, ill-defined periduodenal lucency appears as an agglomeration of bubbles or slitlike lucency in the per-iduodenal region. It is more difficult to detect than the anterior superior bubble due to nearby duodenal and colonic gas. It also may resemble localized retroperito-neal gas collections.6

Fig. 7—33. Anterior superior bubble.

Free air is aggregated as a small lucency ventral to the liver (curved arrow) on a supine digital radiograph (a) and on a corresponding CT section (b).

Fig. 7—33. Anterior superior bubble.

Free air is aggregated as a small lucency ventral to the liver (curved arrow) on a supine digital radiograph (a) and on a corresponding CT section (b).

Pneumoperitoneum Supine

Fig. 7—34. Anterior superior bubble.

A small pneumoperitoneum (curved arrow) visualized on both a supine film (a) and on a CT scan (b) in a patient with small bowel obstruction and perforation. The anterior superior bubble is the only plain film sign of free air. There is also air trapped within the fissure for the ligamentum venosum demonstrated on CT, but not discerned on the plain film.

Fig. 7—34. Anterior superior bubble.

A small pneumoperitoneum (curved arrow) visualized on both a supine film (a) and on a CT scan (b) in a patient with small bowel obstruction and perforation. The anterior superior bubble is the only plain film sign of free air. There is also air trapped within the fissure for the ligamentum venosum demonstrated on CT, but not discerned on the plain film.

Fissure For Ligamentum Venosum

Fig. 7-35. Pneumoperitoneum less than 1 mL.

(a) A digital radiograph reveals three tiny air collections. The most medial air bubble (arrow) is in volume a less than 0.5 mL deposit of free air in the fissure for the ligamentum teres. The lucency lateral and cephalad to it (arrowhead) is a less than 1 mL anterior superior bubble, and the oblique slit inferolaterally (open arrow) is in the posterior subhepatic space, Morison's pouch. It, too, is less than 1 mL.

(b) CT at the level of the fissure for the ligamentum teres. Air in the fissure (arrow) and a separate bubble of free air anteriorly (arrowhead) correspond to the plain film lucencies.

(c) CT section 3 cm caudad reveals a tiny amount of air trapped between the liver and the kidney (open arrow), corresponding to the oblique slit seen on the digital scout. The amount of air is so small it occupies only a portion of Morison's pouch. Therefore, it appears as an atypical lucency and not the expected triangular doge's cap configuration.

(From Baker and Cho.6)

Fig. 7-35. Pneumoperitoneum less than 1 mL.

(a) A digital radiograph reveals three tiny air collections. The most medial air bubble (arrow) is in volume a less than 0.5 mL deposit of free air in the fissure for the ligamentum teres. The lucency lateral and cephalad to it (arrowhead) is a less than 1 mL anterior superior bubble, and the oblique slit inferolaterally (open arrow) is in the posterior subhepatic space, Morison's pouch. It, too, is less than 1 mL.

(b) CT at the level of the fissure for the ligamentum teres. Air in the fissure (arrow) and a separate bubble of free air anteriorly (arrowhead) correspond to the plain film lucencies.

(c) CT section 3 cm caudad reveals a tiny amount of air trapped between the liver and the kidney (open arrow), corresponding to the oblique slit seen on the digital scout. The amount of air is so small it occupies only a portion of Morison's pouch. Therefore, it appears as an atypical lucency and not the expected triangular doge's cap configuration.

(From Baker and Cho.6)

Essentials of Human Physiology

Essentials of Human Physiology

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