INTRODUCTION
A diverticulum is caused by a change in the structure and the resistance of the colonic wall muscular layer as a result of colon movement disorder or lack of dietary fiber, and its incidence tends to increase with age. In Korea, the number of cases of diverticulitis has increased due to the increase in the prevalence of diverticulosis due to the higher average age of the population and the westernization of eating habits [
1]. Because the cause and the tendency of diverticulosis have much in common with those of colon cancer, the causal relationship between the two diseases has been investigated. However, any correlation remains controversial [
2,
3]. Although abdominal computed tomography (CT) is the most accurate method for diagnosing acute diverticulitis, its differentiation from colon cancer in the presence of complications, such as abscess and perforation, is difficult [
4]. Thus, whether a follow-up colonoscopy should be performed to detect colon cancer after treatment for acute diverticulitis, as well as whether such an investigation should be routine, remains controversial [
5].
Here, we report three cases of colon cancer, along with a literature review of patients diagnosed with colon cancer following an initial diagnosis of acute diverticulitis based on abdominal CT findings and clinical opinion. Colon cancer was diagnosed based on a biopsy specimen obtained during either colonoscopy or surgery.
DISCUSSION
The incidences of diverticular disease of the colon and colon cancer in the West are high, but these diseases are relatively rare in the East. However, their incidence is increasing in Korea due to changes in eating habits such as reduction in dietary fiber intake, extended life expectancy, aging of the population, and advances in diagnostic methods such as CT and colonoscopy [
6].
Diverticular disease and colon cancer have many epidemiological similarities; therefore, the correlation between these diseases has been investigated. However, any correlation remains controversial. Stefansson et al. [
7,
8] reported that diverticulitis in the sigmoid colon could increase the occurrence of left colon cancer and proposed a mechanism in which the high concentration of intestinal bacteria in the left colon facilitates the decomposition of feces, resulting in the generation of carcinogenic compounds which are, in turn, trapped inside the diverticulum and constantly irritate the mucous membranes, causing chronic inflammation and cancerous changes. In addition, Kikuchi et al. [
9] reported that concurrent chronic inflammation in diverticula could result in cancerous changes and metaplasia, increasing the risk of colon cancer. Meanwhile, some researchers, such as Soran et al. [
3] and Loffeld et al. [
10], reported that the prevalences of colon cancer and diverticulosis in diverticulitis patients were lower than they were in normal individuals and that no correlation existed between the two diseases [
11]. Recent studies showed no significant difference between the prevalence of colon cancer detected during colonoscopy after diverticulitis treatment to the prevalence of colon cancer in ordinary people. For reasons of cost, this has raised questions regarding the need for routine follow-up colonoscopy after treatment of acute diverticulitis [
2,
12].
Accordingly, controversy regarding the correlation between diverticulitis and colon cancer remains. However, the diverticulitis treatment recommendations published in 2006 by the American Society of Colon and Rectal Surgeons include follow-up colonoscopy for the differentiation of colon cancer, ischemia, and inflammatory bowel diseases after recovery from acute diverticulitis.
Early endoscopy, which is performed during in-patient treatment, has a high probability of perforation, pain and inflammatory stenosis, resulting in a cecum arrival rate as low as 75% to 82%. Therefore, colonoscopy is recommended approximately six weeks after diverticulitis treatment [
13,
14]. The authors of the present study typically perform colonoscopy six weeks after diverticulitis treatment.
Although abdominal ultrasound with barium enema may be useful for diagnosing acute diverticulitis, abdominal CT has high specificity and sensitivity and a low false-negative rate and so can identify complications with high precision. For this reason, abdominal CT is considered the best method for the diagnosis of diverticulitis [
1,
5,
12]. However, in some cases, CT cannot differentiate other abdominal inflammatory diseases, infectious diseases, colon cancer, etc., due to technical error in the shooting, the anatomical state of the contracted colon, and nonspecific concurrent complications in the abdominal cavity, retroperitoneal organs, or abdominal wall [
4].
Mesenteric fluid collection and hyperemia of adjacent mesenteric blood vessels indicate diverticulitis when the stenosis transition is gradual and the intestinal wall thickness is <1 cm. Conversely, lymph node enlargement around the intestine indicates colon cancer. However, when both findings are present, differentiation of diverticulitis and colon cancer is difficult in cases in which cancer infiltration into the intestinal wall is concurrent with fat infiltration; in this situation, biopsy during colonoscopy is necessary [
4,
15].
These cases are patients who were suspected of having diverticulitis based on CT findings at their initial visit to the hospital and who were discharged with clinical improvement in symptoms after treatment with antibiotics and fluid therapy. The patients were subsequently diagnosed with colon cancer based on the pathology results of specimens obtained during follow-up colonoscopy or surgery. The lesion in all three cases was in the right ascending colon, and there were no findings suggestive of cancer, such as weight loss before admittance, persistent abdominal pain, melena, sudden constipation, etc. Additionally, the patients had no history of undergoing a colonoscopy (
Table 1). In case 1, who was diagnosed with a mucinous adenocarcinoma based on pathologic result, there is a possibility that the diverticulitis and colonic mucinous adenocarcinoma were concurrent at the time of diverticulitis diagnosis; the follow-up CT showed an increase in cystic lesions due to filling of the diverticulum with mucus as a result of the improvement in wall thickening after treatment of inflammation. In case 2, the diverticulitis was concurrent with the focal wall thickening around the diverticulum, peripheral fat infiltration and inflammation. Because of the possibility of concurrent diverticulitis and colon cancer due to the lymph node enlargement around the ileum, a follow-up colonoscopy was performed, and the patient was diagnosed with colon cancer. In case 3, abscess formation due to diverticulitis perforation was suspected based on CT, but colon cancer could not be excluded because centripetal colonic wall thickening was concurrent. A follow-up colonoscopy was recommended after diverticulitis treatment. However, the patient was not followed up after discharge from the hospital. The colonoscopy was performed two years later, and the patient was diagnosed with cancer at that time. If the colonoscopy had been performed as scheduled after the diverticulitis treatment, the cancer would have been detected earlier and so a better prognosis would have been expected. Although the complications differed, focal colonic wall thickening was concurrent in all three cases based on the abdominal CT findings at the time of diverticulitis diagnosis. Follow-up CT after diverticulitis treatment showed that wall thickening remained or had increased in all three cases in spite of the improvement of inflammation around the diverticulum. Accordingly, although the follow-up CT after diverticulitis treatment showed an improvement in inflammation, if focal wall thickening persists, examination of the lesion by colonoscopy is important for differentiation from colon cancer.
This report evaluated only three patients; therefore, the results should be interpreted with caution. However, follow-up colonoscopy is necessary to observe progress, detect any recurrence, and differentiate diverticulitis from colon cancer after diverticulitis treatment. In particular, colonoscopy is considered necessary if local wall thickening is observed consistently in spite of an improvement in inflammation on the follow-up CT. The importance of follow-up care should be emphasized to patients or guardians both at the time of diagnosis and during diverticulitis treatment.