Lung suppuration (Lung abscess)

Japanese: 肺化膿症（肺膿瘍） - はいかのうしょう（はいのうよう）（英語表記）Lung suppuration (Lung abscess)

What is the disease?

Lung abscess, like pneumonia, Alveoli ( Yes ) Bacteria grow in the blood, and inflammatory cells, mainly white blood cells, and infection defense substances in the body gather in response, causing inflammation. This is an infectious disease that can also cause tissue destruction ( Necrosis ( Replying to @sarah_mcdonald ) As a result, cavities in the lungs expand and liquid necrotic material accumulates in the cavities. In simple terms, a hole appears in the lungs and pus accumulates in the hole. Lungs gangrene ( Eso ) Also called a lung abscess.

What is the cause?

The extent of tissue destruction depends on the number and nature of the causative bacteria. Anaerobic bacteria ( Research ) , Staphylococcus aureus, Pseudomonas aeruginosa ( Power ) Bacteria that are likely to cause lung abscess include Klebsiella, Escherichia coli, and others. Mycobacterium tuberculosis ( Results ) may also be accompanied by cavities, so differential diagnosis is essential.

Anaerobic bacteria are abundant in the oral cavity, Aspiration ( Thank you ) They also enter the airways by causing abscess ( Use ) It can also spread from the bloodstream to the lungs (hematogenous infection). E. coli can also spread from the urinary tract or biliary tract, while Staphylococcus aureus can spread from the skin, soft tissue, or Endocarditis ( Shinnaikuen ) It reaches the lungs through the blood from these lesions.

How symptoms manifest

Like pneumonia, fever, cough ( cough ) Patients may have purulent sputum, as well as chest pain, which may indicate pleural inflammation. Physical examination may reveal increased respiratory rate and pulse rate. Severe cases may show dyspnea, cyanosis, and impaired consciousness, and require urgent treatment.

In the case of lung abscess due to aspiration, phlegm with a putrid odor is produced. However, symptoms may appear gradually. Fatigue ( Health test ) In some cases, the only symptom is weight loss, so caution is required for elderly people.

Staphylococcus aureus and gram-negative Bacillus ( Kankin ) In most cases of lung abscess caused by pulmonary tuberculosis, symptoms appear suddenly.

Testing and diagnosis

The most useful test is a chest x-ray, which shows a cavity and a horizontal surface (niveau) of liquid pus within the cavity, which characteristically moves due to gravity when the patient changes position (Figure 13).

Bacteriological testing is required if anaerobic bacteria are involved. sputum ( Conclusion ) Culture alone is of little value, and it is necessary to insert a needle through the chest wall into the lung, collect pus from inside the cavity, and culture it under anaerobic conditions. In cases of hematogenous infection, sputum cultures as well as blood cultures are useful.

In the case of aspiration pneumonia, it is necessary to search for the underlying disease that caused the aspiration (cerebrovascular disease, neurological disease, gastroesophageal reflux, lesions in the oral cavity, etc.), and if the underlying disease is not controlled, the condition will recur.

In the case of hematogenous infection, the bacteria are supplied from a distant source (the urinary tract, gall bladder ( Tannou ) It is also necessary to identify the location of the lesion (intraperitoneal, intrapelvic, bone, skin, catheter, etc.).

Treatment methods

Hospitalization is the rule. We will determine whether it is aspiration pneumonia or bloodstream infection.

In the case of aspiration pneumonia, considering the involvement of anaerobic bacteria, penicillin and β ( beta ) We recommend administering a combination drug with a lactamase inhibitor, clindamycin, or a carbapenem antibiotic. In the case of hematogenous infection, the primary lesion is estimated, and antibiotics are selected based on the results of blood cultures, etc. This requires a longer treatment period than general pneumonia. If the abscess is large, drainage via catheter or surgery may be considered.

What to do if you notice an illness

Similar to pneumonia, but in elderly people and those who are bedridden, symptoms may appear more slowly and they may only have vague symptoms such as fatigue, loss of appetite, and weight loss, so caution is required.

Kazunori Asano

Figure 13. Lung abscess caused by Staphylococcus aureus
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Figure 13 Staphylococcus aureus-induced hematogenous infection

Source: Houken “Sixth Edition Family Medicine Encyclopedia” Information about the Sixth Edition Family Medicine Encyclopedia

Japanese:

どんな病気か

　肺化膿症は、肺炎と同様に肺胞(はいほう)に細菌が増殖し、それに対して生体側の白血球を主とする炎症細胞や感染防御物質が集まり、炎症を起こした状態の感染症ですが、それに組織の破壊（壊死(えし)）を伴うのが特徴的な病態です。その結果、肺内に空洞が広がり、液状の壊死物質が空洞内にたまります。簡単にいうと肺に穴があき、その穴のなかにうみがたまった状態です。肺壊疽(えそ)や肺膿瘍とも呼ばれます。

原因は何か

　組織破壊の程度は、原因になる細菌の数や性状によって左右されます。嫌気性菌(けんきせいきん)、黄色ブドウ球菌、緑膿菌(りょくのうきん)、クレブシエラ、大腸菌などが肺化膿症を起こしやすい細菌です。結核菌(けっかくきん)も空洞を伴うことがあるので、必ず鑑別診断をしなければなりません。

　嫌気性菌は、口腔内にたくさん存在するために、誤嚥(ごえん)を起こすことによって気道から侵入してきます。また、骨盤腔内の膿瘍(のうよう)から血流に乗って肺に到達（血行性感染）することもあります。大腸菌も尿路、胆道などの感染病巣から、黄色ブドウ球菌は皮膚や軟部組織あるいは心内膜炎(しんないまくえん)などの病巣から血液を介して肺に到達します。

症状の現れ方

　肺炎同様、発熱、咳(せき)、膿性の痰がみられ、それに加えて胸痛が起こることもあり、この場合は胸膜への炎症の広がりを示唆しています。身体所見では、呼吸数や脈拍の増加がみられます。重症例では呼吸困難、チアノーゼ、意識障害がみられ、緊急に治療を開始する必要があります。

　誤嚥による肺化膿症では、腐敗臭のある痰を伴います。ただし、症状の発現がゆるやかな場合があり、倦怠感(けんたいかん)や体重の減少だけの場合もあるので、高齢者などでは注意が必要です。

　黄色ブドウ球菌やグラム陰性桿菌(かんきん)による肺化膿症では、多くは症状が急激に現れます。

検査と診断

　最も有用な検査は胸部X線です。X線像では、空洞と空洞内に液状のうみによる水平面（鏡面：ニボー）がみられ、体位を変換すると重力によってその水平面が動くのが特徴的です（図13）。

　細菌学的検査は、嫌気性菌が関係する場合は喀痰(かくたん)の培養だけでは有用性が低く、胸壁を通して肺に針を刺し、空洞内部の膿成分を採取し、嫌気状態での培養を行う必要があります。血行性感染の場合は、喀痰培養とともに血液培養が有用です。

　誤嚥性肺炎の場合は、誤嚥を来した基礎疾患（脳血管障害、神経疾患、胃食道逆流、口腔内の病変など）の検索も必要で、原因疾患をコントロールしなければ繰り返すことになります。

　血行性感染の場合は、細菌が供給される遠隔病巣（尿路、胆嚢(たんのう)、腹腔内、骨盤内、骨、皮膚、カテーテルなど）を特定することも必要です。

治療の方法

　入院治療が原則です。誤嚥性肺炎なのか、血行性感染なのかを推定します。

　誤嚥性肺炎の場合は、嫌気性菌の関与を考慮して、ペニシリン系とβ(ベータ)ラクタマーゼ阻害薬との配合薬、クリンダマイシン、カルバペネム系抗菌薬投与がすすめられます。血行性感染の場合は、原発の病巣を推定し、血液培養などの結果によって抗菌薬を選択します。一般の肺炎より長い治療期間を要します。膿瘍が大きければ、カテーテルによる排膿や外科手術も考慮します。