腸阻塞 | 醫學影像學習園地

腸阻塞‭ ‬Ileus‭


‭/‬家翔‭ ‬佳茵‭ ‬柏安‭ ‬韋愷


觀念剖析

腸阻塞是指腸內容物不能正常運行及順利通過腸道,是外科常見病症,腸阻塞不但可引起腸管本身解剖與功能上的改變,並可導致全身性生理上的紊亂。

定義

腸阻塞的定義是腸內含物部份或完全沒法順利到達肛門。

分類

發病的基本原因分類:
機械性阻塞(mechanical obstruction):一般所指的腸阻塞
麻痺性腸塞(paralyticileus):並無真正的阻塞,只是腸子不蠕動,失去推進食物的能力。

病因

Adhesions
Malignancy
Hernias
Strictures
Small intestinal tumors
Early postoperative obstruction
Trauma
Intussusception
Bezoars
Gallstone ileus
Superior mesenteric artery syndrome

臨床症狀

各類腸阻塞在臨床上最易出現四大症狀:
1.
腹痛(abdominal pain )
大多數會合併腹鳴症狀出現,這種症狀大都因小腸阻塞而造成。典型的腸阻塞造成的腹痛為間歇性絞痛(intermittent cramping pain)。
2.
腹脹(abdominal distension)
越往下位的阻塞,尤其是結腸部位的阻塞,腹脹更趨明顯。
3.
嘔吐(vomiting)
若為上段小腸阻塞,通常會在早期即出現墨綠色的嘔吐物。越上段的小腸阻塞,嘔吐越明顯,而且很快會有虛脫現象。
若為下段小腸或結腸阻塞,則會在幾天後才出現上段現象,之後則會慢慢轉變為黃褐色的嘔吐物。若阻塞部位在迴腸末端,則嘔吐較不明顯,虛脫現像較遲緩。大腸的阻塞甚至不會產生嘔吐,而主要是以腹脹表現。
4.
停止排便排氣
腸道受阻,內含物沒法到達肛門,因此典型的完全阻塞的病人,不只沒有排便,也不會排氣。


影像學檢查

腹部X光(
KUB)的檢查是簡單且重要的診斷工具。腸管的氣液平面是腸阻塞特有的 X 線檢查表現。
小腸阻塞者一般顯示小腸擴張積氣 ,並有大小不等的階梯狀液平面;小腸高位阻塞者,空腸黏膜環狀皺襞常呈魚骨刺樣;結腸阻塞者,盲腸、升結腸膨脹顯著。小腸的縐褶(Valvulae conniventes)橫貫整個腸腔徑,因此小腸阻塞會形成所謂“stack of coin sign”
區別大腸阻塞引起的大腸擴張是看到大腸縐褶(haustral folds)並沒有橫貫整個腸腔徑。當麻痹性腸阻塞時大腸、小腸皆廣泛擴張。當懷疑腸套疊、乙狀結腸扭轉或結腸腫瘤時,應作鋇劑灌腸,可見鋇劑通過受阻,呈杯口型、鳥嘴型、狹窄等不同特徵。
在區分腸腔是否阻塞進而造成擴大的情形,可以用腸腔的直徑來分辨:
1.
小腸:正常小腸直徑應該小於2CM。而大於3CM時代表有脹大的情況。
2.
大腸:正常大腸直徑應該小於5CM。而大於6CM時代表有脹大的情況。

治療

除了少數例外,大部份的腸阻塞都應儘早手術(urgent operation)。手術方式則視腸阻塞原因及嚴重程度而定。

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案例探討

案例一
‭: ‬機械性阻塞mechanical obstruction (糞石阻塞Bezoar obstruction)
KUB(
1)

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Abdomen CT:
(
2)

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(
3)
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(
4)
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鑑別診斷

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1‭.‬‭ ‬
麻痺性腸塞(paralytic ileus)
λ Commom causes: Post-surgery, medications, post-injury, ischemia
λ Dilated small bowel and large bowel loops with no transition point, aperistaltic fluid levels
λ Absence of obstruction on CT

2‭.‬‭ ‬
缺血性腸炎‭ ‬(Ischemic bowel)
KUB
Multiple air-fluid levels; ileus pattern
Thickening of valvulae conniventes
Linear distribution of gas (pneumatosis intestinalis)
CT
Segmental thickening of bowel wall (>3mm); average 8mm,
20mm
Clot or reduced lumen in SMA, SMV or other mesenteric vessels.
Emboli usually observed at origin of SMA or 3-10 cm from SMA distal to middle colic artery.
“Misty mesentery”: Mesenteric fat infiltrated by edema; more common with venous thrombosis.
3‭. ‬
急性胰臟炎(Acute pancreatitis)
KUB
Duodenal ileus
Sentinel loop:mildly dilated,gas-filled segment of small bowel or air-fluid levels
“Colon cutoff” sign:markedly distended transverse colon with air,absence of gas distal to splenic flexure due to functional colonic spasm(spread of pancreatic inflammation to proximal descending colon)
CT
Focal or diffuse pancreatic enlargement
Rim enhancement of acute fluid collection, abscesses, and pseudocysts
infiltration of peripancreatic fat; gallstones

4‭.‬‭ ‬
闌尾破裂‭(‬appendix rupture‭)‬
KUB
Appendicolith in 5-10% of patient
Air-fluid level within bowel in RLQ
Splinting
Loss of right psoas margin
Free peritoneal air very uncommon
With perforation:small bowel obstruction,RLQ extraluminal gas,displacement of bowel loops from RLQ
CT
With perforation:SBO,inflammatory fluid collections demonstrating mass effect,most commonly in RLQ or dependent pelvis(cul-de-sac)

參考資料

1. 台北榮民總醫院‭ ‬一般外科主治醫師‭ ‬石宜銘‭ ‬「腸阻塞」一文
2. Harrison's Principles of Internal Medicine 17th Edition
3. UpToDate
4. Diagnostic Imaging Abdomen 2nd Edition
5. Robbins and Cotran Pathology Basis of Disease 8th Edition