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The orientation of CT toward the discovery of intramural growth explains the necessity of formulating more detailed computed tomographic semiotics, particularly for diffuse forms of gastric cancer. Above all, this depends on the possibility of estimating thickness of the stomach wall.

Using our methods, the symptoms of diffuse cancer are identical [38, 40, 47, 53]: ™ Thickening of the stomach wall to various degrees (7-45 mm) ™ Loss of wall elasticity at the site of tumor infiltration

As a rule, in addition to thickening of the stomach wall at the site of a blastomatous process, it is possible to reveal uneven (sometimes polygonal) contours, which persist after inflation of additional portions of air, suggesting rigidity of the wall (D Fig. 84). Intact portions of the wall remain elastic and their thickness is 1.52.5 mm on average, with distinct inner and outer contours, except in the prepyloric and cardiac parts of the stomach, where normal thickness is 5-6 mm (in conditions of adequate inflation) [160]. This is especially obvious when using pneumotomography.

D Fig. 84a-g. Patient P., age 58. Diagnosis: gastric cancer. a Stomach roentgenogram (vertical position, anterior projection): the sign of air redistribution in the bubble, which is elongated. b Stomach roentgenogram (tight filling, vertical position, anterior projection): the cavity volume decreased, the angular notch is straightened, the lesser curvature is shortened and depressed; its contours are uneven; the walls are rigid (arrows). c Stomach roentgenogram (double contrast, horizontal position, anterior projection): diffuse thickening of the walls due to intramural infiltration (arrows). Conclusion: Infiltrative cancer of the stomach. d, e, f, g Consecutive computed tomograms of the stomach (dosed stomach inflation with air, supine position): the walls are rigid and thickened over the entire length, the inner contours are polygonal. Retroperitoneal lymph nodes are enlarged, a hypodense stripe of irregular character is seen between the stomach wall and the pancreas over the entire length; commissure of the anterior wall with the parietal peritoneum is seen (arrows)

While assessing the results of using computed tomography for the diagnosis of stomach tumors, especially its infiltrative forms, it is necessary to note that CT sometimes not only gives additional information on the intramural growth of tumors, but also helps discover a thickened wall over a short distance, which considerably facilitates the differential diagnosis of early forms of gastric cancer.

At the same time, computed tomography is used in its earlier known capacity to the full extent, giving information on the possible spread of tumor into the neighboring organs and tissues. One of the most important problems is verification of involvement of the pancreas in the blastomatous process. In the absence of invasion between the pancreas and the stomach wall, a hypodense stripe of parapancre-atic cellular tissue is distinctly seen over the entire

length, which is easily identifiable owing to CT densitometry parameters that are characteristic of fatty tissue (D Fig. 85). As gastric tumor grows into the pancreas, this stripe is not differentiated either partly or over the entire length (D Fig. 86). But it is necessary to note that in patients with cachexia due to cancer, parapancreatic cellular tissue may be absent on CT images of an intact pancreas. This should be kept in mind when interpreting the results of the study. According to Kim et al., CT evidence of tumor invasion of the pancreas should not be regarded as a contraindication to surgical treatment, because the results of their studies indicated a low sensitivity of CT in determining involvement of the pancreas proper (60%) and of the perigastric lymph nodes [3, 121, 167].

□ Fig. 85a-j. Patient L., age 64. Diagnosis: gastric cancer. a Stomach roentgenogram (tight filling, vertical position, anterior projection): uneven contours of the lesser curvature (arrow). b Stomach roentgenogram (double contrast, horizontal position, anterior projection): thickening of the lesser curvature due to intramural infiltration (arrows). In order to verify spread of the tumor to the adjacent anatomical structures, the patient was examined by computed tomography. c, d, e, f, g Consecutive computed tomograms of the stomach (tight filling with E-Z-CAT DRY, supine position, at the level of the upper part and the body of the stomach): the posterior wall is thickened due to intramural infiltration. Distinctly differentiated is the hypodense stripe of cellular fat tissue between the infiltrated wall of the stomach and the intact pancreas at the level of its tail and body (arrow). h, i, j Computed tomograms of the stomach (tight filling with E-Z-CAT DRY, position on the right side, the level of the antral and pyloric parts of the stomach): the posterior wall is thickened due to intramural infiltration. Distinctly differentiated is the hypodense stripe of cellular fat tissue between the stomach wall and intact pancreas at the level of its body and head (arrows). Conclusion: Infiltrative cancer of the stomach body. The patient was operated. Histologically, adenocarcinoma.

□ Fig. 86a-f. Female patient V., age 56. Diagnosis: gastric cancer. a Stomach roentgenogram (tight filling, vertical position, anterior projection): the antral part is narrowed and curved, the walls are rigid, the contour of the greater curvature is uneven (arrow), the stomach sinus sags. b Stomach roentgenogram (double contrast, horizontal position, anterior projection): the antral part is irregularly and circularly narrowed due to intramural infiltration; the walls are rigid (arrows); the duodenal loop is straightened. In order to verify the spread of the tumor to the adjacent anatomical structures, the patient was examined by computed tomography. c Computed tomogram of the stomach (tight filling with E-Z-CAT DRY, supine position, the level of the body and the distal part of the stomach): the walls are thickened unevenly due to circular intramural infiltration (white arrow indicates site of the maximum thickening). The hypodense stripe of a fat layer between the infiltrated stomach wall and the pancreas body is absent (black arrow). d, e, f Computed tomograms (tight filling with E-Z-CAT DRY, supine position, at the level of the body and the distal part of the stomach): the walls are thickened due to intramural infiltration. The hypodense stripe of fatty tissue between the infiltrated stomach wall and the pancreas head is irregular (arrow). Conclusion: Infiltrative cancer of the antral part of the stomach with invasion of the pancreas

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