Colorectal carcinomas usually occur as a transformation within adenomatous polyps. Percutaneous sonography of the abdomen is usually performed as an exploratory examination of the abdomen (liver, ascites, gallstones) and also provides information on colon carcinomas that are growing beyond the organ. X-rays, CT or MRI are also used depending on the problem. The latter is currently the gold standard for local spread diagnostics.
Colorectal carcinoma is one of the three most common malignancies in the Western world, and is the second most common malignant tumor in women [1]. Around a third of these are found in the rectum. This corresponds to around 18,000 new cases per year [4]. 90-95% of the tumors are adenocarcinomas. The peak age is between 50 and 70 years. Men and women are affected in equal numbers. Many colorectal carcinomas develop from polyps. The symptoms develop relatively late. At the time of initial diagnosis, there is often tumor growth beyond the wall and metastases in around 25% of patients. The average 5-year survival rate is 50%. In stage Dukes A it is around 90%, in Dukes D 10%. Blood in the stool, alternating diarrhea and constipation and occasional tenesmus indicate a mass in the colon. Fever, night sweats, weight loss, reduced performance, fatigue and anemia sometimes occur.
The primary diagnostic procedure for detecting rectal or colon cancer is endoscopy. This allows precancerous lesions, such as mucosal polyps or adenomas, to be detected and removed at an early stage and manifest tumors to be diagnosed and histologically confirmed [6]. The recommendations for screening vary depending on the family history and hereditary risk. The risk factors are listed in Table 1.
Clinical examination allows the mobility of the tumor to be graded, while endoscopy allows the aboral tumor distance to the dentate line or anocutaneous line to be determined [5]. The magnetic resonance imaging findings are of great importance for treatment planning. In early carcinoma without risk factors, local excision can be performed, surgical resection with lymphadenectomy, minimally invasive or open surgery, is the standard therapy, combined with neoadjuvant treatment concepts. Complex therapy can lead to a post-resection syndrome (low anterior resection syndrome, LARS) in over 50% of patients. This includes limited continence, urge to defecate and frequent bowel movements.
X-rays of the thorax are part of the staging and clarification of pulmonary metastases [4].
Sonographically, endosonography is superior to abdominal ultrasonography, but should always be correlated with the findings of magnetic resonance imaging [5].
Computed tomography should be used for additional cross-sectional imaging in the case of unclear pulmonary or abdominal findings [4]. The local findings of rectal carcinoma may be conspicuous due to segmental wall thickening or polypous intraluminal masses [2]. Enlarged local lymph nodes, liver metastases and mesenteric and omental filiae can be detected. Inflammatory processes, such as diverticulitis or appendicitis, can simulate a malignancy [6].
CT colonography has become relatively quiet in recent years. FDG-PET-CT is a valuable diagnostic tool as a complementary imaging procedure for verifying metastasis-specific lesions.
Magnetic resonance imaging examinations are very well suited to differentiate carcinomas of the rectum. They have established themselves as the gold standard for local spread diagnostics. Polypous masses or wall thickening are suspicious, especially if there is a low signal in T1w and an intermediate signal in T2w [3,4]. After intravenous administration of Gd-DTPA, a clear increase in tumor signal is detectable. The size of the periproctal lymph nodes correlates with the degree of malignancy. Contrast enhancement of the mass is low.
Case study
Case example 1 (Fig. 1A to G) shows the course of a rectal carcinoma with pre- and postoperative imaging in a 70-year-old female patient. Originally there was a large rectal tumor. After radical tumor removal and creation of an anus praeter, postoperative computed tomography showed no residual or recurrent tumor. However, a suspicious lymph node was visible on the right iliac side.
Case 2 demonstrates (Fig. 2A, B and C) a circular stenosing carcinoma in the rectosigmoid junction with local fatty tissue infiltration and paracolic lymph nodes in a 61-year-old female patient. There was also extensive hepatic metastasis.
Take-Home-Messages
- Colorectal carcinoma is one of the three most common malignancies in the western world.
- Men and women are equally affected, with the disease peaking between the ages of 50 and 70.
- Adenocarcinomas make up the largest proportion with over 90%.
- The average 5-year survival rate is around 50%.
- Staging imaging is comprehensive and the treatment options are complex.
Literature:
- Beer AJ, Wieder HA, Stollfuss JC: Imaging staging of tumors of the digestive tract. Radiology up2date 1; 2007: 9-27.
- Burgener FA, et al: Differential diagnoses in computed tomography. 2nd, completely revised and expanded edition. Georg Thieme Verlag Stuttgart, New York 2013; pp. 824, 885.
- Burgener FA, et al: Differential diagnostics in MRI. Georg Thieme Verlag Stuttgart, New York 2002; pp. 612.
- Ghadimi M, et al: Multimodal therapy of rectal cancer. Dtsch Arztebl Int 2022; 119: 570-580.
- Isbert C, Germer CT: Importance of endoscopy and endosonography for local staging in rectal cancer. The Surgeon 2012: 83: 430-438.
- Rectal cancer: early detection and prevention. www.krebsgesellschaft.de/basis-informationen-krebs.html (last accessed 17.04.2024).
InFo ONKOLOGIE & HÄMATOLOGIE 2024; 12(4): 22–24
