Sigmoid Perforation

The sigmoid colon lies below the limits of the cone of renal fascia where it is in anatomic continuity with both the anterior and posterior pararenal spaces (Fig. 8-215). Gas from a sigmoid perforation may therefore enter either or both compartments.

Studies by Meyers et al.269,270 have confirmed that only one of the four rows of colonic diverticula faces the peritoneal cavity and that fully 75% of sigmoid di-verticula are related to the extraperitoneal tissues. Ex-traperitoneal gas associated with perforated sigmoid di-verticulitis typically progresses up the left side. The gas may extend medially over the psoas muscle in the form of mottled radiolucencies (Fig. 8-212), but extension into the posterior compartment often dominates the radiologic findings. The gas may enter the properitoneal

Diverticulitis Sigmoid

Fig. 8-212. Perforated sigmoid diverticulitis.

Extraperitoneal gas (arrows) extends anterior to the psoas muscle toward the spine within the anterior pararenal space. Superiorly, the gas extends within the posterior pararenal space outlining the adrenal gland (A) and the posteromedial border of the spleen, the medial crus of the diaphragm (crossed arrows), and segments of the extraperitoneal subdiaphragmatic tissue (large white arrows). Note that the latter do not follow the highest plane of the diaphragm, in contradistinction to free intraperitoneal air. (Reproduced from Meyers.9)

Fig. 8-212. Perforated sigmoid diverticulitis.

Extraperitoneal gas (arrows) extends anterior to the psoas muscle toward the spine within the anterior pararenal space. Superiorly, the gas extends within the posterior pararenal space outlining the adrenal gland (A) and the posteromedial border of the spleen, the medial crus of the diaphragm (crossed arrows), and segments of the extraperitoneal subdiaphragmatic tissue (large white arrows). Note that the latter do not follow the highest plane of the diaphragm, in contradistinction to free intraperitoneal air. (Reproduced from Meyers.9)

flank fat directly, but superiorly is characterized by its outlining of the left adrenal gland and upper renal pole, the medial crus of the diaphragm, the medial contour of the posterior aspect of the spleen, and the extraperitoneal subdiaphragmatic plane (Fig. 8-212). The relationships of these localizations are lucidly displayed by computed tomography (Fig. 8-216).

Only if the sigmoid perforation occurs between the leaves of the mesocolon does the extraperitoneal gas rise bilaterally within the anterior pararenal spaces9 (Fig. 8217).

Essentials of Human Physiology

Essentials of Human Physiology

This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.

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