340.Rectosigmoid carcinoma
每天朗读一段医学影像学英语文章
Clinical Presentation：
A 44-year-old woman presents with abdominal pain and distension.
Imaging Findings：
(A) Abdominal radiograph shows colonic dilatation (large arrowhead) terminating in the pelvis (arrow) and multiple air-filled ileal loops that are abnormal in caliber (small arrowhead).
(B) Single-contrast barium enema shows an irregularly marginated stricture (arrows) of the rectosigmoid colon.
(C) Pelvic computed tomography (CT) shows marked attenuation of the rectal lumen (arrow) leading to a critical stenosis (arrowhead) due to a circumferential infiltrating soft-tissue mass.
Diagnosis
Rectosigmoid carcinoma: This is the most worrisome diagnosis and should be at the top of the list for distal colonic obstruction.
Differential Diagnosis：
· Rectosigmoid carcinoma: This is the most worrisome diagnosis and should be at the top of the list for distal colonic obstruction.
· Intraluminal material: Impacted feces or foreign bodies may cause distal obstruction. Fecal impaction is typically bubbly, but not always.
· Inflammation or infection: A third possibility, this can cause complete obstruction. Consider diverticulitis, inflammatory bowel disease, and proctocolitis due to lymphogranuloma venereum or tuberculosis.
· Extrinsic causes: These include pelvic tumor, abscess, adhesions, and bladder distension and are also worthy of consideration.
· Inguinal hernia: This can cause sigmoid obstruction.
Other Imaging Findings：
Ultrasound (transrectal) provides an accurate staging of rectal carcinoma by assessing the depth of penetration of the mass into the bowel wall.
Pearls & image Pitfalls
·Intussusception causing colonic obstruction has a neoplastic lead point in the majority of cases but more commonly occurs in the ascending colon rather than in the rectosigmoid.
·Sigmoid volvulus is unlikely in this case as the classic signs such as the “coffee bean” sign and double loop obstruction are not present.
·Obstruction of the ileocecal valve by a markedly distended cecum may cause a pattern of dilated small and large bowel in cases of colonic obstruction, suggesting a generalized ileus and confusing the picture.
·Toxic megacolon is a clinical diagnosis based on colonic distension in the setting of an increased sedimentation rate, fever, leukocytosis, anemia, and bloody diarrhea.
·Pneumatosis, pneumoperitoneum, portal venous gas, and toxic megacolon are contraindications for barium enema.
· This case reviews the nonspecific radiographic finding of distal colonic obstruction. Paradoxically, distal colonic obstruction tends to cause maximal colonic distension in the cecum and more proximal colon.
· Colonic diameter of 6 cm (and cecal diameter of 10 cm) heralds impending rupture.
· Most neoplasms causing colonic obstruction occur in the rectosigmoid colon, but neoplasms occur about equally within the right and left colon.
· Colorectal carcinoma can occur as an infiltrating, annular mass (“apple-core”), as in this case, a polypoid mass, or an ulcerated mural mass.
· Competency of the ileocecal valve determines the bowel gas pattern on abdominal radiographs of colonic obstruction.
· Competent: no small-bowel dilatation
· Incompetent: small-bowel dilatation
Notes:
rectosigmoid /rɛkto'sɪgmɔɪd/ 直肠乙状结肠
distension /dɪ'stɛnʃən/ n. 膨胀，扩张
dilatation /ˌdaɪlə'teʃən/ n. (中空器官或空洞)扩张;膨胀
ileal /'ɪlɪəl/ adj. 肠阻塞的,回肠的
caliber /'kæləbɚ/ n. 口径
stenosis /stɪ'nosɪs/ n. （器官）狭窄
distal /'dɪstl/ adj. [解]末梢的，末端的
luminal /'lju:minəl/ n. 鲁米那（一种镇静剂）adj. 腔的；细胞腔的
diverticulitis /ˌdaɪvɚtɪkjʊ'laɪtɪs/ 憩室炎
lymphogranuloma /'lɪmfəʊ,ɡrænjʊ'ləʊmə/ n. 淋巴肉芽肿
tuberculosis /tʊ'bɝkjə'losɪs/ n. 肺结核
inguinal /'ɪŋgwɪnl/ adj. [医]腹股沟的
volvulus /'vɑlvjələs/ n. 肠扭转,肠扭结
cecum /'sikəm/ n. 盲肠
sedimentation /ˌsɛdɪmɛn'teʃən/ n. 沉淀,沉降
leukocytosis /ˌlʊkosaɪ'tosɪs/ n. 白细胞增多,白细胞增多
anemia /əˈnimiə/ n. [医]贫血；贫血症
diarrhea /ˌdaɪə'riə/ n. 腹泻，痢疾
pneumatosis /ˌnju:mə'təusis/ n. 气肿
pneumoperitoneum /'nju:mə,peritə'niəm/ n. 气腹
megacolon /ˌmeɡə'kəulən/ n. 巨结肠(症)
contraindication /ˌkɑntrəˌɪndɪˈkeʃən/ n. 禁忌症
enema /'ɛnəmə/ n. [医]灌肠剂（复数enemas）
paradoxically /ˌpærə'dɑksɪkl/ 自相矛盾的
proximal /'prɑksɪməl/ adj. 最接近的，邻近的
herald /'hɛrəld/ n. 预报
annular /'ænjəlɚ/ adj. 环形的
ulcerated /'ʌlsəreitid/ 成为溃疡的;形成溃疡的
ileocecal /ˌiliəu'sekəl/ adj. 回盲的
来源：每天朗读一段医学影像学英语文章
圈主
深圳市人民医院放射科副主任医师杨敏洁