Gastrointestinal tract images Perforation: Previously performed watersoluble contrast enema has been replaced by CT. Computed tomography readily identifies these mostly advanced tumors, with a majority being associated with an abscess near the tumor. An occasional carcinoma perforates into adjacent soft tissues and leads to extraintestinal gas or subcutaneous emphysema. At times unusual fistulas form. Technetium-99m- DTPA renography in a patient with hematuria revealed sigmoid colon radioactivity extending to the transverse colon; a sigmoid adenocarcinoma had invaded the bladder and formed a colovesical fistula. Do patients with a perforating colon carcinoma have a worse prognosis than those without a perforation? Comparing perforating cancers and obstructing cancers undergoing emergency surgery, no significant difference in survival or disease progression was evident between these two groups.
Radiology images of Perforated right colon carcinoma (arrows) in a patient suspected to have acute appendicitis. Soft tissue gas in the necrotic tumor mimics an appendiceal abscess.
Obstruction: The size of colon cancers when first detected have decreased during the last several decades, yet it is still common in most practices to see a patient first present withcolonic obstruction due to a large, bulky tumor. These patients first undergo proximal colon decompression and only later have definitive cancer resection.A sufficiently tight obstruction obviates both a complete barium enema and colonoscopy, studies not only defining an obstructing tumor but also detecting any synchronous neoplasm. In such a setting, preoperative CT colonography is very useful to evaluate the proximal colon. In 19 patients with distal occlusive colorectal carcinomas, preoperative CT colonography identified all occlusive cancers and also detected synchronous lesions—two cancers and 20 other polyps, findings confirmed by other studies.
Expandable intraluminal stents are useful in malignant colonic obstructions. A pretherapy stent placed through an obstruction provides decompression, allows a bowel-cleansing regimen to be employed, and thus obviates a preliminary colostomy. After decompression, these patients undergo tumor staging, and a decision is made whether to proceed to cancer resection or whether successful stenting is to be the primary palliative therapy. The success rate in stent placement varies but typically is about 90%; thus stent placement was successful in 88% of 80 patients and bowel obstruction resolved in 67%. A multicenter study of 71 patients with acute malignant obstruction found self-expandable metallic stent placement to be technically successful in 90%, but it was not possible to advance across the obstruction in 3% and the prostheses was poorly positioned in 7%. Stent complications include perforation and stent dislocation. Completely covered stents tended to migrate more than uncovered stents.
This is radiology images of Obstructing carcinoma (arrow). CT colonography can also study the proximal colon. Sagittal images are helpful in surgical planning.