Virtual colonoscopy

Definition

虚拟结肠镜检查(VC)是一种寻找癌症的成像或x射线检查， polyps或大肠(结肠)的其他疾病. The medical name of this test is CT colonography.

Alternative Names

Colonoscopy - virtual; CT colonography; Computed tomographic colonography; Colography - virtual

How the Test is Performed

VC is different from regular colonoscopy. Regular colonoscopy uses a long, 一种被称为结肠镜的轻便工具，它被插入直肠和大肠.

VC是在十大赌博平台排行榜或医疗中心的放射科进行的. 不需要镇静剂，不使用结肠镜.

The exam is done as follows:

• 你左侧侧卧在一张狭窄的桌子上，桌子连接着一个 MRI or CT machine.
• Your knees are drawn up toward your chest.
• 将一根小而柔软的管子插入直肠. 空气通过管子输送，使结肠更大，更容易被看到.
• You then lie on your back.
• 桌子滑进CT或MRI机器的一个大隧道. X-rays of your colon are taken.
• x光片也是在你趴着的时候拍的.
• 在这个过程中你必须保持静止，因为移动会模糊x光片. 每次拍x光片时，你可能会被要求屏住呼吸.

计算机将所有的图像组合成结肠的三维图像. 十大赌博平台排行榜可以在视频监视器上查看图像.

How to Prepare for the Test

为了检查，你的肠子需要完全清空和清洁. 如果你的肠道没有被清理干净，你的大肠中需要治疗的问题可能会被忽视.

你的十大赌博平台排行榜会告诉你清洁肠道的步骤. This is called bowel preparation. Steps may include:

• Using enemas
• 测试前1 - 3天不吃固体食物
• Taking laxatives

你需要在测试前1到3天喝大量的透明液体. Examples of clear liquids are:

• Clear coffee or tea
• Fat-free bouillon or broth
• Gelatin
• Sports drinks
• Strained fruit juices
• Water

坚持服药，除非你的十大赌博平台排行榜告诉你不要服药.

你需要在测试前几天询问你的十大赌博平台排行榜你是否需要停止服用铁药片或液体, 除非你的十大赌博平台排行榜告诉你可以继续. Iron can make your stool dark black. 这使得十大赌博平台排行榜更难观察到你的肠道内部.

CT and MRI scanners are very sensitive to metals. Do not wear jewelry the day of your exam. 在手术过程中，你会被要求脱掉你的便服，穿一件病号服.

How the Test will Feel

The x-rays are painless. 将空气注入结肠可能会导致痉挛或气痛.

After the exam:

• 你可能会感到腹胀，有轻微的腹部痉挛，并排出大量气体.
• 你应该能够恢复正常的活动.

Why the Test is Performed

VC may be done for the following reasons:

• Follow-up on colon cancer or polyps
• 腹痛、排便改变或体重减轻
• Anemia due to low iron
• Blood in the stool or black, tarry stools
• 检查结肠癌或直肠癌(每5年做一次)

你的十大赌博平台排行榜可能会建议常规结肠镜检查而不是VC. 原因是VC不允许移除组织样本或息肉.

有时，如果不能完成常规结肠镜检查，则进行VC.

Normal Results

正常表现为健康的肠道图像.

What Abnormal Results Mean

检测结果异常可能意味着以下任何一种情况:

• Colorectal cancer
• 肠壁上的异常小袋，叫做 diverticulosis
• Colitis (a swollen and inflamed intestine) due to Crohn disease, ulcerative colitis, infection, or lack of blood flow
• Lower gastrointestinal (GI) bleeding
• Polyps
• Tumor

如果有下列情况，可在VC术后(另一天)进行常规结肠镜检查:

• 没有发现出血或其他症状的原因. VC can miss some smaller problems in the colon.
• Problems that need a biopsy were seen on a VC.

Risks

Risks of VC include:

• Exposure to radiation from the CT scan
• 恶心，呕吐，腹胀，或直肠刺激，由药物准备测试
• 当插入泵气管时肠穿孔(极不可能).

Considerations

虚拟结肠镜检查与传统结肠镜检查的区别包括:

• VC can view the colon from many different angles. This is not as easy with regular colonoscopy.
• VC does not require sedation. 你通常可以在测试后立即回到你的正常活动. 常规结肠镜检查使用镇定剂，通常会损失一天的工作时间.
• VC using CT scanners expose you to radiation.
• 常规结肠镜检查导致肠穿孔的风险很小(造成小撕裂)。. There is almost no such risk from VC.
• VC通常不能检测到小于10mm的息肉. 常规结肠镜检查可以发现各种大小的息肉.

References

Garber JJ, Chung DC. Colonic polyps and polyposis syndromes. In: Feldman M, Friedman LS, Brandt LJ, eds. Sleisenger和Fordtran的胃肠和肝脏疾病. 11th ed. Philadelphia, PA: Elsevier; 2021:chap 126.

Kim DH, Pickhardt PJ. 计算机断层结肠镜检查和结肠评估. In: Gore RM, Levine MS, eds. Textbook of Gastrointestinal Radiology. 5th ed. Philadelphia, PA: Elsevier; 2021:chap 38.

Lawler M, Johnston B, Van Schaeybroeck S, et al. Colorectal cancer. In: Niederhuber JE, Armitage JO, Kastan MB, Doroshow JH, Tepper JE，编. Abeloff' Clinical Oncology. 6th ed. Philadelphia, PA: Elsevier; 2020:chap 74.

Shaukat A, Kahi CJ, Burke CA, Rabeneck L, Sauer BG, Rex DK. ACG临床指南:2021年大肠癌筛查. Am J Gastroenterol. 2021;116(3):458-479. PMID: 33657038 pubmed.ncbi.nlm.nih.gov/33657038/.

US Preventive Services Task Force website. Final recommendation statement. Colorectal cancer: screening. www.uspreventiveservicestaskforce.org/uspstf/recommendation/colorectal-cancer-screening. Published May 18, 2021. Accessed March 28, 2023.