Crohn's Disease - Crohn's Disease

Japanese: クローン病 - くろーんびょう（英語表記）Crohn Disease

[What kind of disease is it?]
It was named after the American doctor Dr. Crohn and his colleagues who first reported it in 1932. It is an inflammatory disease that affects the entire digestive tract from the oral cavity to the anus, and is characterized by the formation of a certain type of granuloma (a raised lesion).
It is mainly seen in young people in their late teens to twenties, and ulcers form in any part of the digestive tract, accompanied by abdominal pain, diarrhea, and bloody stools. Environmental factors and diet are deeply involved in the onset of the disease, and it is thought that people who consume a lot of animal protein and fat are more likely to get it.
The prevalence rate in Japan is about 8 people per 100,000 people, which is lower than in Europe and the United States, but the number of patients has been increasing rapidly recently. This is thought to be due to the Westernization of dietary habits, increased fat intake, and advances in diagnostic methods.
[Cause]
There are theories that genetic factors are involved, that it is caused by infection with bacteria similar to tuberculosis bacteria or the measles virus, and that food components cause abnormalities in the intestinal mucosa, but none of these have been clearly proven.
Recently, abnormal reactions of cells responsible for the immune system, such as certain lymphocytes, have been discovered, and it is believed that this may be caused by abnormal responses of the immune system to the invasion of foreign antigens such as food components, foreign substances, and pathogens.
[Symptoms]
Symptoms vary from case to case. Also, depending on the part of the body affected, it is classified as small intestine type (approximately 45%), small intestine and large intestine type (approximately 34%), and large intestine type (approximately 13%).
The most characteristic symptoms are abdominal pain and diarrhea, which are seen in more than half of cases. In addition, fever, bloody stool, abdominal masses, weight loss due to malabsorption, general fatigue, and anemia are also often seen. Anal lesions such as anal fistulas also occur frequently. Systemic complications include arthritis, iritis, and erythema nodosum, as well as local complications of the digestive tract such as internal and external fistulas and stenosis.
[Testing and diagnosis]
Diagnosis is based on a medical history, general blood and fecal tests, X-rays (contrast tests) including the small intestine, and endoscopic examinations. Blood tests are used to check inflammatory reactions such as erythrocyte sedimentation rate and CRP (C-reactive protein), the degree of anemia, and nutritional status.
In stool tests, trace amounts of blood in the stool are detected by using the immune reaction to human hemoglobin, and a culture test is used to differentiate it from bacterial enteritis.
In a barium enema X-ray examination, barium and air are injected into the large intestine and X-rays are taken to examine the condition of the mucosa, the presence or absence of ulcers, strictures, fistulas, and the extent of lesions. In a small intestine X-ray examination, barium is sent to the small intestine and X-rays are taken to examine lesions in the small intestine.
In endoscopy, a colonoscope is inserted through the anus to observe the appendix or terminal ileum, and a biopsy is taken to detect lesions and to diagnose pathology. In addition, a gastroscopy may be performed to check for lesions in the esophagus or stomach.
The diagnosis is confirmed if these tests reveal longitudinal ulcers, cobblestone lesions, or a special type of granuloma called non-caseating epithelioid cell granuloma.
[Treatment]
Because the cause is unknown, there is no fundamental treatment; however, by correctly understanding and treating the disease, it is becoming possible to put the disease into remission (a state in which the symptoms are alleviated) and maintain this state.
The basic approach is to suppress intestinal inflammation to alleviate symptoms and improve nutritional status, with medical treatment mainly consisting of a combination of nutritional therapy and drug therapy.
Nutritional therapy aims to improve nutritional disorders, keep the intestines at rest, and prevent the intestines from being exposed to antigen-stimulating proteins and fats. Nutritional therapy is broadly divided into enteral nutrition (elemental nutrition) and total parenteral nutrition (total parenteral nutrition) (Column: Nutritional therapy for Crohn's disease).
Once the condition goes into remission, in addition to drug therapy, a low-residue, low-fat diet will be started and the amount of food eaten will be gradually increased. After discharge, elemental nutrition therapy will be continued at home to prevent recurrence.
Drug therapy: Anti-inflammatory drugs to suppress localized inflammation in the intestinal tract and immunosuppressants to correct abnormal responses of the immune system are generally used in combination. Antidiarrheal drugs, antispasmodics, and sedatives are also used as supplementary drugs.
The anti-inflammatory drug salazosulfapyridine (salazopyrin) is broken down into 5-ASA and sulfapyridine by intestinal bacteria in the large intestine. 5-ASA is an active ingredient that acts locally in the intestinal tract to suppress inflammation, but sulfapyridine is thought to cause side effects such as digestive symptoms and hypersensitivity.
Salazopyrin is not expected to be effective for small intestinal Crohn's disease, but the recently developed enteric-coated 5-ASA sustained-release formulation (mesalazine) has been shown to be effective for small intestinal and small intestinal/large intestinal Crohn's disease.
Adrenal cortex hormones (steroids) also have a strong anti-inflammatory effect and are effective. They are used in combination with nutritional therapy for small intestinal lesions, and in cases of severe inflammation.
Recently, new types of steroids that have less impact on the whole body have been developed, but they are not yet commercially available in Japan. In difficult cases, immunosuppressants such as azathioprine and 6-MP are also used.
●Surgery treatment Surgery is indicated when there is severe stenosis, fistula, or lesion in the anal area. In the past, extensive intestinal resection was performed, but because of the high recurrence rate, the current mainstream method is to minimize the resection area as much as possible, or to perform stricture formation without resection. Furthermore, less invasive (physically stressful) surgical methods using laparoscopes are also becoming more common.
The prognosis for treatment varies greatly from person to person. The majority of people are able to resume social life to some extent, but there are also cases where the condition becomes chronic and relapses multiple times.
[Precautions in daily life]
Eat low-fat, low-residue foods that are easy to digest and absorb. Avoid spicy foods, carbonated drinks, and alcohol as much as possible. There are many foods that some people can eat without any problems, so it is important to find foods that suit each person. Smoking is strictly prohibited as it often worsens Crohn's disease.
Stress and fatigue can also cause symptoms to worsen, so be sure to get plenty of rest and sleep.
If you become pregnant during remission, most births will be normal, and the incidence of miscarriage and congenital malformations is no different from that of healthy people, so there is no need to worry.

Source: Shogakukan Home Medical Library Information

Japanese:

[どんな病気か]
　1932年に、アメリカのクローン博士らによって初めて報告されたためにこの名があります。口腔（こうくう）から肛門（こうもん）までの全消化管をおかす炎症性疾患で、ある種の肉芽腫（にくげしゅ）（病変の盛り上がり）ができるのが特徴です。
　おもに10歳代後半から20歳代の若年層にみられ、消化管のあらゆる部分に潰瘍（かいよう）ができ、腹痛や下痢（げり）、血便をともないます。発症には環境因子、食生活が深くかかわっており、動物性たんぱく質や脂肪を多くとるとかかりやすくなると考えられています。
　日本人の有病率は人口10万人あたり約8人で、欧米に比べて少ないのですが、最近患者数が急増しています。これは食生活の欧米化で、脂肪摂取量が増加したことと診断方法が進歩したことによると考えられています。
[原因]
　遺伝的な要因が関与するという説、結核菌（けっかくきん）に類似した細菌や麻疹（ましん）ウイルスの感染によるという説、食物の成分が腸管粘膜（ちょうかんねんまく）に異常をひきおこすという説などがありますが、いずれもはっきり証明されていません。
　最近では、ある種のリンパ球など、免疫（めんえき）を担う細胞の反応異常が明らかにされ、食物成分や異物、病原体などの外来抗原（こうげん）の侵入に対する免疫系の反応異常が原因ではないかとされています。
[症状]
　症状は多彩で、各症例によって異なります。また、おかされる部位により、小腸（しょうちょう）型（約45％）、小腸・大腸（だいちょう）型（約34％）、大腸型（約13％）と分類されています。
　もっとも特徴的な症状は腹痛と下痢で、症例の半数以上にみられます。さらに発熱、下血（げけつ）、腹部腫瘤（しゅりゅう）、吸収障害にともなう体重減少、全身倦怠感（けんたいかん）、貧血（ひんけつ）などもしばしばみられます。痔瘻（じろう）などの肛門病変もよくおこります。関節炎、虹彩炎（こうさいえん）、結節性紅斑（けっせつせいこうはん）などの全身的合併症や、内瘻（ないろう）、外瘻（がいろう）、狭窄（きょうさく）などの消化管の局所合併症もあります。
[検査と診断]
　診断は、病歴の聴取や一般的な血液、糞便（ふんべん）検査、小腸を含むＸ線検査（造影検査）、内視鏡検査をふまえて行なわれます。血液検査では血沈（けっちん）、ＣＲＰ（Ｃ反応たんぱく質）などの炎症反応、貧血の程度や栄養状態などが調べられます。
　糞便検査では、ヒトヘモグロビンに対する免疫反応（めんえきはんのう）を利用して、便の中の微量の出血が調べられ、培養検査で細菌性腸炎との鑑別が行なわれます。
　注腸Ｘ線検査ではバリウムと空気を大腸に注入してＸ線撮影を行ない、粘膜の状態、潰瘍、狭窄、瘻孔（ろうこう）の有無、病変の広がりなどを調べます。小腸Ｘ線検査はバリウムを小腸まで送ってＸ線撮影し、小腸の病変を調べます。
　内視鏡検査は肛門から大腸内視鏡を挿入し、盲腸（もうちょう）あるいは終末回腸までを観察し、病変とともに病理診断のための生検を行ないます。さらに、食道や胃の病変を調べるため、胃内視鏡検査が行なわれることもあります。
　これらの検査をして、縦走する潰瘍、敷石のような像、非乾酪性類上皮細胞肉芽腫（ひかんらくせいるいじょうひさいぼうにくげしゅ）という特殊な肉芽腫が見つかれば診断が確定します。
[治療]
　原因不明のため、根本的な治療はありませんが、病態を正しく把握して治療することで、寛解（かんかい）（病状の緩和状態）にいたり、その維持が可能になりつつあります。
　基本方針は、腸管の炎症を抑えて症状の軽減をはかり、栄養状態を改善させることで、栄養療法と薬物療法を組み合わせた内科的治療が主体です。
●栄養療法
　栄養障害の改善、腸管の安静、抗原刺激となるたんぱく質と脂肪に腸管がさらされないようにすることを目的とします。経腸栄養法（成分栄養法）と中心静脈栄養法（完全静脈栄養）とに大別されます（コラム「クローン病の栄養療法」）。
　病状が寛解したら薬物療法に加えて低残渣（ざんさ）・低脂肪食を開始し、徐々に食事量を増やします。退院後も家庭で成分栄養療法を行ない、再燃を予防します。
●薬物療法
　腸管局所の炎症を抑える抗炎症薬と、免疫系の異常反応を是正するための免疫抑制薬の併用が一般的です。止痢薬や鎮痙薬（ちんけいやく）、安定薬なども補助的に用いられます。
　抗炎症薬のサラゾスルファピリジン（サラゾピリン）は大腸の腸内細菌によって5‐ＡＳＡとスルファピリジンに分解されます。5‐ＡＳＡは腸管内で局所的に作用し炎症を抑える有効成分ですが、スルファピリジンは消化器症状や過敏症などの副作用をおこすことがあると考えられています。
　サラゾピリンは小腸型クローン病では効果が期待できませんが、最近開発された腸溶（ちょうよう）5‐ＡＳＡ徐放剤（じょほうざい）（メサラジン）は、小腸型、小腸・大腸型クローン病への効果が認められています。
　副腎皮質（ふくじんひしつ）ホルモン（ステロイド）も、強力な抗炎症作用があり、有効です。小腸病変に対する栄養療法と併用したり、炎症の強い例などに用いられます。
　最近は全身への影響が少ない新しい種類のステロイドも開発されていますが、日本ではまだ市販されていません。難治例ではアザチオプリンや6‐ＭＰという免疫抑制薬も使われます。
●手術療法
　強度の狭窄（きょうさく）や瘻孔（ろうこう）があったり肛門部に病変がある場合が手術対象となります。以前は広範囲な腸切除が行なわれましたが、再発率が高いため、現在では切除範囲をできるだけ小さくするか、切除しない狭窄形成術などが主流になっています。さらに、腹腔鏡（ふくくうきょう）を用いた侵襲（しんしゅう）（身体的負担）の少ない手術法も普及し始めています。
　治療予後（経過）には大きな個人差があります。大多数はある程度社会生活を再開できるようになりますが、慢性化して何度も再燃する例もあります。
[日常生活の注意]
　食事は低脂肪、低残渣食とし、消化吸収のよいものをとります。香辛料（こうしんりょう）や炭酸飲料、アルコール類はなるべく避けましょう。人によっては食べても問題ないものも多いため、それぞれに合った食物を見つけてゆくことが大事です。喫煙はしばしばクローン病を悪化させるので厳禁です。
　また、ストレスや疲労も症状悪化の誘因になります。十分な休養と睡眠をとりましょう。
　なお、寛解期に妊娠した場合、正常産がもっとも多く、流産や先天性形態異常の発生率は健康人と変わりありませんから心配いりません。

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