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1.The report suggest there is a mass lesion in the left adnexa / lumbar region.
2.The most possible cause i would think of depend on type of
hysterectomy ( including ovaries or excluding) if ovaries were left one can think in terms of ovarian /
adnexal mass lesions.
3.Other possible causes could be
lymph nodal mass lesions or bowel mass as mentioned.
4.Howevere the confirmatory diagnosis will be
biopsy. The dilated pelvis and calyx with prominent
ureter is due to the distal obstruction / pressure effect causing by the mass lesion.
5.Rest of all scan appears normal. In this case i would recommend to get an biopsy, treated accordingly.
Good luck.
Hope i have answered your query,
any thing to ask ? do not hesitate to ask.
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