Ileus

Japanese: イレウス

Concept A condition in which the propulsion of intestinal contents is severely impaired, resulting in symptoms such as abdominal distension and abdominal pain. Also known as intestinal obstruction.
Based on classification and causative mechanism, ileus can be divided into functional ileus and mechanical ileus (Table 8-5-23).
1) Functional ileus:
A condition in which the propulsion of intestinal contents is severely impaired despite the absence of organic obstruction to passage. Most cases are paralytic ileus.
a) Paralytic ileus: This occurs as a result of impaired intestinal motility due to various causes. Causes include prolonged bed rest, central nervous system disease, psychiatric disease, peritonitis, post-surgery, post-trauma, systemic sclerosis, pseudo-intestinal obstruction, and Ogilvie syndrome [⇨8-5-16)]. Other causes include drugs such as ergot alkaloids, narcotics, anticholinergics, and psychotropic drugs.
b) Spastic ileus: The intestines contract strongly due to causes such as those in Table 8-5-23, causing severe abdominal pain and obstruction to passage. This is rarely seen.
c) Congenital: Hirschsprung disease [⇨8-5-1)].
2) Mechanical ileus (Table 8-5-23):
It occurs when the propulsion of intestinal contents is physically obstructed due to an organic disease. It is also widely divided into small intestinal ileus and large intestinal ileus based on the site of the causative disease; small intestinal ileus is often caused by adhesions or internal/external hernias, while large intestinal ileus is often caused by colon cancer.
a) Simple ileus: Mechanical ileus that is not accompanied by severe intestinal blood flow disorder. Most cases are caused by adhesions following abdominal surgery. Other causes include external and internal hernias, endometriosis, post-abdominal inflammation such as cholecystitis and appendicitis, obstruction due to malignant tumors, gallstone ileus, foreign body ileus, intestinal malrotation, Crohn's disease, post-radiation therapy, and severe constipation. In newborns, it is seen in congenital intestinal atresia.
b) Complicated (strangulated) ileus: A type of mechanical ileus that is accompanied by impaired intestinal blood flow. It can be caused by intraperitoneal adhesions, external or internal hernias, intussusception, or gastrointestinal volvulus, and is a serious condition that requires emergency treatment. Intussusception in infants can sometimes be treated with an enema.
Pathophysiology: When intestinal obstruction occurs, contents accumulate in the digestive tract upstream, and digestive fluids secreted from upstream also add to the pressure, causing the intestine to expand. This results in abdominal distension, abdominal pain, and vomiting. Furthermore, as the obstruction progresses, intestinal bacteria proliferate, causing bacteria and toxins to leak into the bloodstream (bacterial translocation), and bacteremia. However, downstream of the obstruction, there is no stagnation of contents or expansion of the intestine. The accumulation of a large amount of digestive fluids in the intestine reduces the circulating plasma volume, which can lead to hypovolemic shock. In complicated ileus, symptoms are even more severe, with intestinal necrosis leading to perforation and generalized peritonitis, accompanied by aspects of endotoxic shock, and if left untreated, death can occur.
Clinical manifestations
1) Symptoms:
In mechanical ileus, symptoms such as cessation of defecation and gas passage, abdominal pain, vomiting, and abdominal distension occur acutely or subacutely. In simple ileus, abdominal pain initially appears as a colic that worsens and subsides repeatedly, but as the condition progresses, it becomes persistent. In complicated ileus, there is often strong, persistent pain from the beginning. The onset of vomiting depends on the location of the obstruction, with vomiting occurring later in the lower part of the digestive tract. Vomitus is mixed with bile, and over time it begins to smell like feces. In paralytic ileus, the progression is slower and milder. In most cases, defecation and gas passage cease, but in cases of intussusception or volvulus, a small amount of blood in the stool may be seen.
2) Objective symptoms:
In ileus, flatulence is observed to a greater or lesser extent. In mechanical ileus, bowel sounds are increased and produce a metallic sound, and increased peristalsis can sometimes be confirmed by visual inspection, but it should be noted that these are not evident on examination after the administration of antispasmodics as emergency treatment. In simple ileus, tenderness is present but peritoneal irritation symptoms are absent, whereas in complicated ileus, subjective symptoms are strong and accompanied by peritoneal irritation symptoms. Furthermore, in complex ileus, bowel sounds also decrease as the condition progresses.
inspection
Results Plain abdominal X-rays are the most important, as they allow for the diagnosis of the presence of ileus and a rough estimate of the site of obstruction (Figure 8-5-32). X-rays are taken in the supine and upright positions, but if upright positioning is difficult, the lateral position can be used. The intestine upstream of the obstruction is dilated, and the formation of a niveau can be seen. The distinguishing feature of intestinal gas images is that the small intestine has fine Kerckring folds (ring-shaped folds seen in the small intestine, particularly noticeable in the upper small intestine), but the large intestine does not. However, in complex ileus, the niveau may not be clear. In paralytic ileus, the intestine is dilated overall.
Abdominal ultrasound, CT, and MRI are also very useful. Ultrasound can reveal the keyboard sign, which shows Kerckring folds in the small intestine filled with intestinal fluid, and the to-and-fro sign, which shows the intestinal contents moving back and forth. If a moderate or large amount of ascites is present, the possibility of complicated ileus should be considered. CT and MRI can also be used to evaluate the presence of ileus, identify the site and cause of obstruction, and determine whether strangulation is present.
Conventional colonoscopy or barium enema is rarely performed for ileus, but in intussusception, the characteristic crab-claw-like appearance of a barium enema can provide a clear diagnosis and may also be a treatment. Sigmoid volvulus is treated by reduction using a colonoscope. Advances in small intestinal endoscopy in the 21st century have made it possible to observe the deep parts of the small intestine with double-balloon endoscopy, making preoperative diagnosis of ileus and endoscopic treatment of strictures much easier.
Blood tests show an increase in white blood cells and platelets in the early stages, but as the disease progresses, increases in Hb and BUN due to dehydration, decreases in K ⁺ and ^C1- due to vomiting and loss into the intestinal tract, and metabolic alkalosis. In cases of strangulated ileus, metabolic acidosis and elevated CPK levels are also seen. Caution is required as increases in inflammatory responses such as CRP cannot be confirmed in the early stages of the disease.
Diagnosis It is necessary to determine whether the ileus is functional or mechanical, whether it is simple or complex, and the cause.
Treatment, course, and prognosis: In the case of functional ileus, first symptomatic treatment is performed as necessary (fasting and fluid replacement, decompression through a tube, etc.), and then treatment is performed according to the cause. As with mechanical ileus, systemic administration of antibiotics is often necessary, so it is important to determine whether or not it is a complicated ileus. In the case of complicated ileus, immediate treatment is required. [Matsuhashi Nobuyuki]

Table 8-5-23
Classification of ileus ">

Table 8-5-23

Source : Internal Medicine, 10th Edition About Internal Medicine, 10th Edition Information

Japanese:

概念
　腸内容の推進が高度に障害され腹部膨満，腹痛などの症状をきたすにいたった状態．腸閉塞ともいう．
分類・原因
　機序の上から機能的イレウスと機械的イレウスに分けられる（表8-5-23）．
1）機能的イレウス：
器質的な通過障害がないのに腸内容の推進が高度に障害されたもの．大部分は麻痺性イレウスである．
a）麻痺性イレウス：種々の原因で腸の運動能が障害された結果起こる．長期臥床，中枢神経疾患，精神疾患，腹膜炎，術後，外傷後，全身性硬化症，偽性腸閉塞，Ogilvie症候群【⇨8-5-16）】などが原因となる．麦角アルカロイド，麻薬，抗コリン薬，向精神薬などの薬物も原因となる．
b）痙攣性イレウス：表8-5-23のような原因で腸が強く収縮し，強い腹痛と通過障害をきたす．まれにしかみられない．
c）先天性：Hirschsprung病【⇨8-5-1）】．
2）機械的イレウス（表8-5-23）：
器質的疾患のため腸内容の推進が物理的に阻害されて起こる．原因疾患の部位から小腸イレウスと大腸イレウスに分けることも広く行われ，小腸イレウスでは癒着や内・外ヘルニア，大腸イレウスでは大腸癌が多い．
　a）単純性イレウス：機械的イレウスのうち，腸の高度の血流障害を伴っていないもの．多いのは腹部術後の癒着によるもの．ほかに外ヘルニアや内ヘルニア，子宮内膜症，胆囊炎や虫垂炎などの腹腔内炎症後，悪性腫瘍による通過障害，胆石性イレウス，異物性イレウス，腸回転異常，Crohn病，放射線照射後，高度の便秘など多くのものが原因となる．新生児では先天性の腸管閉鎖でみられる．
　b）複雑性（絞扼性）イレウス：機械的イレウスのうち，腸の血流障害を伴うもの．腹腔内癒着，外ヘルニアや内ヘルニアの陥嵌，腸重積，消化管軸捻症などが原因となり，重篤であり緊急の対処を要する．乳児の腸重積では注腸での治療も可能なことがある．
病態生理
　腸管に通過障害が発生するとそこより上流の消化管内に内容物がたまり，さらに上流から分泌された消化液も加わって圧力が高まり腸管が拡張する．このため腹部膨満，腹痛，嘔吐をきたす．さらには停滞に伴って腸内細菌が繁殖して血中へ菌や毒素が流出し（細菌移行），菌血症も起こす．一方，通過障害部位より下流では内容の停滞や腸管の拡張はみられない．腸内に多量の消化液が貯留した結果循環血漿量が減少し，ひいては血液量減少性ショックに至ることもある．複雑性イレウスでは，さらに症状が激しく，腸管壊死から穿孔，汎発性腹膜炎をきたしてエンドトキシンショックの側面も伴い，無治療では死に至る．
臨床症状
1）自覚症状：
機械的イレウスでは排便・排ガスの停止，腹痛，嘔吐，腹部膨満などの症状が急性ないし亜急性に発症する．単純性イレウスでの腹痛は発症当初は増悪，緩和を繰り返す疝痛だが進行すると持続性になってくる．複雑性イレウスでは当初から強い持続痛のことが多い．嘔吐の発生時期は閉塞の部位により，消化管の下部であるほど発生時期が遅くなる．吐物は胆汁をまじえ，時間がたつと糞臭を伴ってくる．麻痺性イレウスでは経過はより緩徐かつ軽度である．ほとんどの場合排便・排ガスが止まるが，腸重積や軸捻症では少量の血便がみられることがある．
2）他覚症状：
イレウスでは多かれ少なかれ鼓腸がみられる．機械的イレウスでは腸音が亢進して金属音を呈し，ときに視診で亢進した蠕動が確認できるが，救急処置で鎮痙薬を投与した後の診察ではそれらがはっきりしなくなることに注意する必要がある．単純性イレウスでは圧痛はあっても腹膜刺激症状を欠くが，複雑性イレウスでは自覚症状が強い上に腹膜刺激症状を伴ってくる．また，腸音も，複雑性イレウスでは進行すると逆に減弱していく．
検査
成績
　腹部単純X線写真が最も重要で，イレウスの存在診断と閉塞部位のおおまかな推定ができる（図8-5-32）．臥位と立位で撮影するが，立位困難なときは側臥位でよい．閉塞部より上流の腸管が拡張し，ニボーの形成がみられる．腸管ガス像は，小腸では細かいKerckringひだ（小腸にみられる輪状のひだ構造，とくに上部小腸で目立つ）があるのに大腸ではそれがないのが区別のポイントになる．ただし，複雑性イレウスではニボーがはっきりしないこともある．麻痺性イレウスでは腸が全体に拡張する．
　腹部エコーやCT，MRIも非常に有用である．エコーでは腸液で満たされた小腸にKerckringひだがみえるキーボードサイン（keyboard sign）や，腸内容が前後に動くto-and-fro signがみられる．中等量以上の腹水が出現している場合は複雑性イレウスの可能性を考える．CTやMRIではイレウスの存在，閉塞部位や原因の同定，絞扼の有無なども評価可能である．
　イレウスでは通常の大腸内視鏡や注腸造影が行われることは少ないが，腸重積では注腸で特徴的なカニの爪状の所見で診断がはっきりするとともに治療にもなりうる．S状結腸軸捻では大腸内視鏡による整復が治療として行われる．21世紀になって小腸内視鏡が進歩し，ダブルバルーン内視鏡で小腸深部の観察が可能になり，イレウスでも術前診断や狭窄の内視鏡治療が大幅に可能になってきた．
　血液検査では，初期には白血球・血小板の増加，進行すると脱水に伴うHbやBUNの増加，K^＋やC1⁻の嘔吐や腸管内への喪失による低下，代謝性アルカローシスがみられる．絞扼性イレウスでは代謝性アシドーシスやCPK上昇もみられる．CRPなどの炎症反応は発症初期には上昇が確認できないので注意が必要である．
診断
　イレウスであることの診断，機能性か機械的かの診断，単純性か複雑性かの診断，原因の確定が必要である．
治療・経過・予後
　機能性イレウスではまずは必要に応じた対症療法（絶食補液，チューブによる減圧など）を行った上で原因に応じた処置を行う．機械的イレウスでも同様だが抗菌薬の全身投与が必要なことが多く，複雑性イレウスでないかの見極めが重要である．複雑性イレウスでは早急な対処が必要となる．［松橋信行］

表8-5-23
イレウスの分類">

表8-5-23

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