Pancreatolithiasis

Japanese: 膵石症 - すいせきしょう（英語表記）Pancreatolithiasis

What is the disease?

Pancreatic stones are Intrapancreatic duct ( Sorry ) These are stones (calculi) that have formed in the Chronic pancreatitis ( Full-body water ) It is seen in approximately 40% of patients diagnosed with chronic pancreatitis. The frequency of this complication increases as chronic pancreatitis progresses.

In typical patients, they begin to appear about 5 years after the first attack of pancreatitis. Pancreatic stones are whitish, hard, and irregular in appearance, and range in size from small stones less than 5 mm to large stones over 10 mm.

Pancreatic stones formed in the pancreatic duct cause obstruction of the outflow of pancreatic juice, which is thought to be one of the causes of abdominal pain attacks and acute inflammation. When pancreatic stones cause abdominal pain, fever, and inflammatory symptoms, the condition is called pancreatic lithiasis.

Things that can be confused with pancreatic stones include pancreatic blood vessel walls and pancreatic lesions ( Pancreatic tumors ( Supplementary ) These are calcium deposits that occur within the pancreatic duct. Unlike intraductal stones, these do not often cause any symptoms, and are strictly distinguished from pancreatic stones.

What is the cause?

The main component of pancreatic stones is calcium carbonate. The mechanism by which pancreatic stones are formed is not fully understood, but it is thought that they are formed when changes in the properties of pancreatic juice or stagnation of pancreatic juice cause proteins in the pancreatic juice to precipitate (come out as crystals) (protein plugs), and calcium deposits on them.

The causes of pancreatic lithiasis are almost the same as those of chronic pancreatitis. Hyperparathyroidism ( Fukukojo Sengen no Koushin ) etc.), Pancreatic duct malformation ( Water quality control ) In addition to pancreatitis caused by malnutrition, pancreatitis of unknown cause ( Idiopathic pancreatitis ( Special water facility ) ) can also cause pancreatic stones.

It is known that the morphology and distribution of pancreatic stones differs depending on the cause. For example, in cases of alcoholic pancreatitis, small stones are often distributed throughout the pancreas, whereas in cases of idiopathic pancreatitis of unknown cause, relatively large pancreatic stones are often found in limited areas.

How symptoms manifest

The pain of chronic pancreatitis is caused by increased pressure in the pancreatic duct and pancreatic tissue, production of pain-related substances, nerve degeneration, Pancreatic pseudocyst ( Watermelon production method ) Formation of Bile duct stricture ( Tankan Kyosaku ) It is believed that the pain is caused by a combination of various factors such as the above. In the case of pancreatic lithiasis, the main cause of pain is thought to be the obstruction of pancreatic juice outflow caused by pancreatic stones getting stuck in the pancreatic duct. Typical patients experience abdominal pain and back pain after drinking or eating.

The abdominal pain associated with pancreatic lithiasis is said to be a relatively constant pain with little fluctuation. Forward bending position ( National ) In many cases, abdominal pain is relieved by leaning forward, so patients tend to lean forward when abdominal pain intensifies. Other symptoms include nausea, vomiting, loss of appetite, and weight loss.

In chronic pancreatitis, repeated attacks of pancreatitis cause the impairment of the exocrine and endocrine functions of the pancreas. As chronic pancreatitis progresses and the exocrine and endocrine functions of the pancreas are impaired, abdominal pain symptoms become milder and instead Impaired glucose tolerance ( Illness in the Philippines ) Nutritional disorders due to impaired digestion and absorption may occur.

Traditionally, pancreatic lithiasis was thought to be a pathological condition seen in the terminal stage of chronic pancreatitis, but as mentioned in "What kind of disease is it?", there are cases in which pancreatic stones are thought to be the cause of acute inflammation, and the appearance of pancreatic stones is not necessarily a sign that abdominal pain will subside.

In addition, patients with chronic pancreatitis are considered to be at high risk of developing pancreatic cancer. The incidence of cancer arising from pancreatic lithiasis is particularly high, said to be 20 to 30 times that of healthy people (approximately 1% per year). Therefore, it is also important to be careful about abdominal pain and weight loss due to pancreatic cancer.

Testing and diagnosis

Since most pancreatic stones are accompanied by calcification, they can be diagnosed with a plain abdominal X-ray. However, ultrasound or CT scans are required to accurately determine their position relative to the pancreas.

Of these, ultrasound examinations are advantageous in that they can be easily performed in an outpatient setting, are less stressful on the body, and provide images in real time (instantaneous). However, they are easily affected by the skill of the doctor (technologist) performing the examination, the physique (obesity) of the patient undergoing the examination, and digestive gas, and do not necessarily image the entire pancreas. In this respect, CT examinations have the problem of exposure to X-rays, but they have the advantage of being able to sensitively image even minute calcifications and not being affected by physique or digestive gas.

In recent years, MRCP (magnetic resonance cholangiopancreatography) examinations have become common, using an MRI device to visualize pancreatic juice components in the pancreatic duct to draw images of the pancreatic duct. In MRCP examinations, pancreatic juice components are highlighted in white, while pancreatic stones have no signal (do not turn white), so compared to CT examinations, MRCP examinations are inferior in diagnosing pancreatic stones themselves, but they are useful for evaluating pancreatic juice stasis, such as dilation or narrowing of the pancreatic duct and pseudocysts.

In addition, detailed examinations to obtain information on the pancreatic duct containing pancreatic stones include Endoscopic retrograde cholangiopancreatography ( Neither-Kyoto Prefectural Government Employment Agency ) There are two types of ERCP: endoscopic pancreatic duct imaging (ERCP). ERCP is an examination that uses an endoscope to image the pancreatic duct, injecting a contrast agent directly into the pancreatic duct from the duodenal papilla using a contrast catheter, and taking an X-ray image of the pancreatic duct. Since the contrast agent does not penetrate into the area where the pancreatic stones are present, the stones are depicted as a missing image of the contrast agent. Recently, as the accuracy of MRCP has improved, ERCP for the purpose of diagnosing pancreatic stones is becoming less common. On the other hand, as described below, it is possible to perform treatment to remove pancreatic stones following ERCP, and ERCP for the purpose of treating pancreatic stones is becoming more common.

Treatment methods

The basics are abstinence from alcohol, dietary therapy, and drug therapy. Even when symptoms are stable, try to eat a low-fat diet that does not stimulate pancreatic secretion. When abdominal pain is severe, stop eating to protect the pancreas and replenish nutrition through intravenous drip or high-calorie infusion. Pancreatic enzymes ( Aquarium ) Acute inflammation is suppressed with trypsin inhibitors and analgesics. If abdominal pain persists or does not stabilize despite these treatments, treatment for pancreatic stones is considered.

Pancreatic stones that are the target of treatment are those that are located in the main pancreatic duct and are thought to be obstructing the outflow of pancreatic juice. The main pancreatic duct here refers to the thickest of the ducts (pancreatic ducts) that carry pancreatic juice to the duodenum, which begins at the tail of the pancreas and reaches the main duodenal papilla.

Usually, when there is an obstruction to the outflow of pancreatic juice, the main pancreatic duct upstream of that area becomes thicker. This is just like the phenomenon that occurs with the pancreatic duct when water is flowing from a hose and the outlet is narrowed, causing the pressure in the front part of the hose (the faucet side) to rise and the entire hose to swell. In this condition, abdominal pain is often present.

Pancreatic stone treatment is performed after hospitalization and acute inflammation has subsided. Currently, only surgery is covered by health insurance in Japan, but other treatments are becoming more common and are actually recommended as useful treatments in guidelines.

① Extracorporeal shock wave lithotripsy (ESWL)

ESWL is a treatment method that uses shock waves to break stones into small pieces (fragmentation) from outside the body. Urinary stones ( Nyoro Kesseki ) It was first introduced to treat pancreatic stones, and then applied to the treatment of gallstones. Currently, many facilities consider it the first choice for the treatment of pancreatic stones.

In actual treatment, the patient lies on a treatment table that is integrated with a shock wave generator, and shock waves are aimed at the pancreatic stones under X-ray or ultrasound imaging to break them up. Each treatment takes about an hour, and painkillers are used as needed to ensure sufficient breakage.

If there is no abdominal pain after treatment, it is possible to eat on the same day or the next day. A simple abdominal X-ray examination the day after treatment is performed to confirm the effect of crushing the pancreatic stones, and the treatment is repeated two or three times a week until the stones disappear or are crushed into small pieces of about 3 mm. On average, four or five treatments are required. Although about 5% of patients experience an exacerbation of pancreatitis due to treatment, most cases are mild, and serious complications are rare.

In patients with pancreatic lithiasis, the main pancreatic duct downstream (duodenal side) of the site where the pancreatic stones are located is often narrowed (stenosis) due to inflammation, so the treatment effect (stone removal) of ESWL alone may not always be sufficient. In such cases, endoscopic treatment, described below, is used in combination.

②Endoscopic treatment

Endoscopic treatment is performed following the ERCP mentioned above. A wire is inserted into a tube and expands into a basket shape when pushed out. Grasping forceps ( Time ) This is a treatment in which a basket is inserted into the pancreatic duct from the duodenal papilla in place of a contrast catheter, and the pancreatic stones are placed into a basket and pulled out into the duodenum.

Small pancreatic stones can be removed with one or two endoscopic treatments, making it an excellent method in terms of treatment efficiency. However, the size of pancreatic stones that can be treated with an endoscope alone is limited to those that are within the range that the treatment tool can reach and that can be held. For this reason, a synergistic effect can be achieved by combining it with ESWL to break down the pancreatic stones into small fragments.

In addition, methods such as inflating the narrowed part of the pancreatic duct with a balloon catheter (endoscopic balloon dilation) and endoscopic incision to widen the opening of the pancreatic duct at the duodenal papilla (pancreatic duct orifice incision) are performed to assist in the expulsion of pancreatic stones. In addition, when the pancreatic duct is severely narrowed, a plastic cylindrical tube called a stent may be placed to secure the lumen.

3) Surgery

Surgical procedures include pancreatic resection, which removes the most inflamed areas, and pancreatic duct decompression, which minimizes the amount of resection and connects the pancreatic duct to the small intestine, and are considered to have the same effect on pain. Compared to ESWL and endoscopic treatment, the surgery itself places a greater burden on the body, but the postoperative course, especially the recurrence of pain, is less likely, and it can be a good treatment when ESWL and endoscopic treatment are not effective.

What to do if you notice an illness

Patients with pancreatic stones should first strictly abstain from alcohol, and undergo dietary and drug therapy. In many cases, these treatments will improve abdominal pain symptoms, but if symptoms persist or recur, pancreatic stone treatment will be considered.

There are various options for treating pancreatic stones. Even if you have no symptoms, pancreatic stones can lead to pancreatic cancer, so regular checkups are necessary. We recommend that you first consult a medical facility with a pancreatic specialist.

Naoki Sasahira

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

Japanese:

どんな病気か

　膵石は膵管内(すいかんない)に形成された石（結石）のことで、慢性膵炎(まんせいすいえん)と診断された患者さんの約40％にみられます。慢性膵炎の進行に伴って合併する頻度が高くなります。

　典型的な患者さんでは、初回の膵炎発作から約5年の経過で現れ始めます。膵石の外観は白色調で硬く、表面が不整で、大きさは5㎜以下の小結石から10㎜を超える大結石までさまざまです。

　膵管内に形成された膵石は膵液の流出障害を引き起こし、腹痛発作や急性炎症の一因になると考えられています。膵石が原因となって腹痛症状や発熱、炎症症状が引き起こされた場合を膵石症といいます。

　膵石とまぎらわしいものに、膵臓の血管壁や膵病変（膵腫瘍(すいしゅよう)）内に生じた石灰（カルシウム）の沈着があります。これらは膵管内膵石と違って症状には直接結びつかないことが多く、厳密には膵石と区別されます。

原因は何か

　膵石の主成分は炭酸カルシウムです。膵石が形成される機序（仕組み）は十分にわかってはいませんが、膵液の性状の変化や、膵液のうっ滞などが原因になって膵液中の蛋白質が析出（結晶として出てくる）し（蛋白栓）、それにカルシウムが沈着して作られると考えられています。

　膵石症の成因は、慢性膵炎の成因とほぼ同じです。アルコールの多飲、高カルシウム血症（副甲状腺機能亢進症(ふくこうじょうせんきのうこうしんしょう)など）、膵管奇形(すいかんきけい)、低栄養によるもののほか、原因がはっきりしない膵炎（特発性膵炎(とくはつせいすいえん)）によっても、膵石は生じます。

　この成因の違いにより、膵石の形態や分布にも特徴があることがわかっています。たとえば、アルコール性の場合には膵全体に小結石が分布することが多く、一方、原因不明の特発性膵炎の場合には比較的大きい膵石が限られた部位に認められることが多いとされています。

症状の現れ方

　慢性膵炎の痛みは、膵管や膵組織内圧の上昇、疼痛関連物質の産生、神経の変性、膵仮性嚢胞(すいかせいのうほう)の形成、胆管狭窄(たんかんきょうさく)などの要因が、さまざまに組み合わさって生じると考えられています。このうち膵石症の場合は、膵石が膵管内にはまり込むことによる膵液の流出障害が痛みの主な原因と考えられています。典型的な患者さんでは、飲酒後や食事後の腹痛、背部痛として現れます。

　膵石症に伴う腹痛は、比較的起伏に乏しい持続性の痛みであることが多いとされています。痛みは前屈位(ぜんくつい)（前かがみ）で軽くなることが多いため、腹痛増強時には独特の前かがみ姿勢をとる傾向があります。このほか、吐き気、嘔吐、食欲不振、体重の減少などがみられます。

　慢性膵炎では、膵炎発作を繰り返すことにより膵外分泌機能、膵内分泌機能の障害が進行します。慢性膵炎が進行して膵外分泌機能、膵内分泌機能が損なわれてくると腹痛症状は軽くなり、代わりに耐糖能障害(たいとうのうしょうがい)や消化吸収障害に伴う栄養障害が現れてきます。

　従来、膵石症は慢性膵炎の終末像にみられる病態と考えられていましたが、「どんな病気か」でも述べたように、膵石が急性炎症の原因と考えられる場合もあり、膵石が現れたからといって必ずしも腹痛がおさまる兆候とはいえないところがあります。

　また、慢性膵炎は膵がんの高危険群とされていますが、とくに膵石症からの発がんの頻度は高く、健常人の20～30倍（年率1％程度）といわれていますので、膵がんによる腹痛や体重減少などにも注意が必要です。

検査と診断

　膵石の多くは石灰化を伴っているため、腹部単純X線検査でも診断することができます。ただし、膵臓との位置関係を正確に把握するためには、超音波検査やCT検査が必要です。

　このうち超音波検査は外来で簡便に受けられ、体への負担が少なくリアルタイム（即時）に画像が得られる点で優れています。しかし、検査する医師（技師）の技量、検査を受ける患者さんの体格（肥満）や消化管ガスの影響を受けやすく、必ずしも膵全体が描き出せるとはかぎりません。その点、CT検査はX線被曝の問題はありますが、微小な石灰化であっても鋭敏に描出が可能であり、体格や消化管ガスに左右されないという特長があります。

　近年では、MRI装置を用いて膵管内の膵液成分を画像化することにより、膵管像を描き出すMRCP（MR胆管膵管造影）検査が広く行われています。MRCP検査では、膵液成分が白く強調される反面、膵石は無信号となる（白くならない）ため、CT検査と比べると膵石そのものの診断には劣りますが、膵管の拡張や狭窄、仮性嚢胞など、膵液うっ滞の評価に有用です。

　このほか、膵石のある膵管の情報を得る精密検査として内視鏡的逆行性膵胆管造影(ないしきょうてきぎゃっこうせいすいたんかんぞうえい)（ERCP）があります。ERCPは内視鏡を用いて膵管を造影する検査で、十二指腸の乳頭から造影カテーテルを用いて直接膵管内に造影剤を注入し、膵管像をX線撮影する検査です。膵石のある部位には造影剤が入り込まないため、膵石は造影剤の欠損像として描き出されます。最近ではMRCPの精度が高くなってきたので、膵石の診断を目的としたERCPはあまり行われなくなりつつあります。一方で、後述のように、ERCPに引き続き、膵石の除去治療を行うことが可能であり、膵石治療を目的としたERCPが盛んに行われるようになっています。

治療の方法

　基本は、禁酒と食事療法、そして薬物療法です。症状が落ち着いてる時でも、膵液分泌刺激の少ない低脂肪食を心がけます。腹痛症状の強い時には、膵臓を守るために食事を止め、点滴もしくは高カロリー輸液で栄養を補給し、膵酵素(すいこうそ)（トリプシン）の阻害薬や鎮痛薬などにより急性炎症を抑えます。これらの治療によっても腹痛症状が長引いたり安定しない場合には、膵石に対する治療が検討されます。

　治療の対象になる膵石は、主膵管内にあり、膵液の流出障害になっていると考えられる場合です。ここで主膵管というのは、膵液を十二指腸に運ぶ導管（膵管）のうち、膵臓の尾部に始まり、十二指腸主乳頭に至る最も太い膵管のことです。

　通常、膵液の流出障害があると、その部位より上流の主膵管が太くなります。ちょうどホースから水を流しているときに出口近くを狭めると、ホースの手前部分（蛇口側）の圧が上がってホース全体がふくらんでくるのと同じ現象が膵管にも起こります。このような状態では、多くの場合腹痛症状を伴っています。

　膵石治療は入院したうえで、急性炎症がおさまってから行います。現在、日本で保険診療として認められているのは手術のみですが、その他の治療についても普及しつつあり、実際に、ガイドラインでも有用な治療法として推奨されています。

①体外衝撃波結石破砕療法(たいがいしょうげきはけっせきはさいりょうほう)（ESWL）

　ESWLとは、体外から結石に対して衝撃波を当てて細かく砕く（破砕）治療法です。臨床的には尿路結石(にょうろけっせき)の治療にまず導入され、次いで胆石の治療に応用されました。現在では膵石治療の第一選択と位置づける施設が多くなっています。

　治療の実際は、衝撃波発生装置と一体化した治療テーブルの上に寝た状態で、X線透視もしくは超音波映像下に膵石に照準を合わせて衝撃波を当てて破砕します。1回の治療時間は約1時間で、十分な破砕効果を得るために適宜、鎮痛薬を使用します。

　治療後は、腹痛がなければ、当日ないし翌日から食事をすることが可能です。治療翌日の腹部単純X線検査で膵石の破砕効果を確認し、消失ないし3㎜程度に小さく破砕されるまで週2、3回のペースで繰り返し行われます。平均4、5回の治療が必要です。治療に伴う膵炎の増悪を5％程度に認めますが、ほとんどが軽症で、重い合併症は少ないとされています。

　膵石症の患者さんの場合、膵石がある部位よりも下流（十二指腸側）の主膵管が炎症により狭くなっている（狭窄）ことが多いため、ESWL単独での治療（排石）効果は必ずしも十分でないことがあります。そのような場合には次に述べる内視鏡治療を併用します。

②内視鏡治療

　内視鏡治療は、前述したERCPに引き続き行います。押し出すとバスケット型に広がるワイヤーをチューブ内に格納したバスケット把持鉗子(はじかんし)を、造影カテーテルの代わりに十二指腸乳頭から膵管内に挿入し、膵石をバスケットのなかに入れて十二指腸内に引っ張り出す治療法です。

　小さな膵石であれば、1、2回の内視鏡治療で排石できるので、治療効率の面からは優れた方法といえます。ただし、内視鏡単独で治療できる膵石は処置具が到達できる範囲内にあり、かつ保持できる大きさに限られます。このため、ESWLと組み合わせて膵石を細かい破砕片とすることにより相乗効果が得られます。

　このほか、膵管が狭くなっている部位をバルーンカテーテルでふくらませる方法（内視鏡的バルーン拡張術）や、十二指腸乳頭の膵管開口部を広げるため内視鏡的に切開する方法（膵管口切開術）などが、膵石の排石を補助する目的で行われます。また、膵管の狭窄が強い場合には、内腔を確保すべく、ステントと呼ばれるプラスチックの筒状の管を留置することもあります。

③外科手術

　外科手術には、炎症の強い部分を切除する膵切除術のほかに、切除を最小限にとどめ、膵管と小腸をつなぎ合わせる膵管減圧術などがあり、痛みに対する効果は同等とされています。ESWLや内視鏡治療と比べ、手術そのものの体への負担は大きいものの、術後の経過、とくに痛みの再発は少なく、ESWLや内視鏡治療でうまくいかない場合には、良い治療となりえます。