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FEATURE CT


PERITONEAL COMPARTMENTS The major barrier dividing the peritoneal cavity is the transverse mesocolon forming two compartments:  Supramesocolic  Inframesocolic


SUPRAMESOCOLIC COMPARTMENT Left peritoneal space  Left anterior perihepatic space  Left posterior perihepatic space  Left anterior sub-phrenic space  Left posterior sub-phrenic space


Right peritoneal space  Right perihepatic space • Right sub-phrenic space • Right sub-hepatic space • Morrison’s pouch


 Lesser sac The falciform ligament separates the left and right subphrenic spaces. Both perihepatic spaces are divided into the subphrenic space and the subhepatic space by the triangular ligament, and these spaces communicate freely (see figures


 The hydrostatic pressure under the diaphragm is normally


subatmospheric


1, 2). The lesser omentum forms the boundary between the right subhepatic space and the lesser sac, and the lesser sac is connected to the main peritoneal space by the epiploic foramen. The hydrostatic pressure under the


diaphragm is normally subatmospheric, and it further decreases during inspiration. This is explained by the lateral movement of the ribs during inspiration, which enlarges the space in the upper abdomen more than it is decreased by the descent of the diaphragm.


PATHOLOGICAL CONDITIONS AFFECTING PERITONEAL SPACES  Conditions producing air attenuation  Conditions producing fat attenuation  Perihepatic fluid collections  Perihepatic infections  Peritoneal tumours 


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 Figure 1: Hepatic ligaments dividing the peritoneal spaces. The liver is covered by visceral peritoneum except at the bare area, bed of the gallbladder, and portahepatis  Figure 2: Hepatic ligaments dividing the peritoneal spaces  Figure 3: Perforation of an intraperitoneal hollow viscus result in air often found anterior to the liver but can be seen anywhere.  Figure 4: At CT, it appears as a well-circumscribed nodule on the liver surface with a centre of fat or soft-tissue attenuation  Figure 5: Juxtacaval fat is a focal collection of fat that is typically observed medially and adjacent to the lumen of the inferior vena cava, near the hepatic venous confluence  Figure 6:The changes in the intraperitoneal hydrostatic pressure and the anatomic arrangement of the peritoneal recesses result in transcelomic migration of fluid toward the undersurface of the diaphragm.  Figure 7: The frequency of subhepatic and subphrenic abscesses on the right side is two to three times greater than on the left side  Figure 8: Actinomycosis on CT may be seen as an infiltrative mass with unusual aggressiveness. Abundant granulation and dense fibrous tissues in the solid components of this mass may cause marked enhancement after infusion of contrast material.  Figure 9: CT scan showing smooth or nodular peritoneal thickening and enhancement  Figure 10: Thickening of the right hemidiaphragm by tumour plaque, omental implants, and ascites  Figure 11: CT criteria for pseudomyxoma peritonei are scalloping of the visceral surfaces (particularly the liver), septated ascites or ascites with attenuation slightly higher than that of water, and hypoattenuating peritoneal implants that may cause extrinsic pressure on the bowel loops


Imaging & Diagnostics Issue 4 2011 13 5 11


FIGS 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 A


1 7 8 2 9 3 10 4


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