Skip to main contentLast updated: 08-Nov-2026
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Dr Harsh Shah
MS, MCh (Surgical Gastroenterology), DrNB (Surgical Gastroenterology)
Registered with Gujarat Medical Council, Reg. No. G-38738
Gastro & Cancer Surgeon
Dr. Jivraj Mehta Hospital, Vasna, Ahmedabad · 18 years of experience
In short
Bile duct cysts are present from birth. Most form where the bile and pancreas ducts join too early, outside the bowel wall.
Doctors sort cysts into five types, called Todani types I to V. The type is read from your MRCP scan.
The type tells the surgeon which operation fits, and how closely you will need check-ups afterwards.
This post explains where the types come from. For the whole journey of a bile duct cyst, from first scan to treatment, see our choledochal cyst and Caroli treatment page.
A bile duct cyst is a swelling of the duct that is there from birth. It is not caused by anything the mother or child did.
Doctors know of two separate ways it can start. The first affects the ducts outside the liver. The second affects the small ducts inside the liver. Most cysts you will meet in the clinic come from the first way.
A cyst can be found before birth on an antenatal scan. It can also show up in a baby with yellow eyes, or in an adult with repeated belly pain. The age at which it shows up does not change how it began. The cyst was formed long before.
The bile duct and the pancreas duct normally meet inside the bowel wall. In many cysts they meet too early, outside it.
Inside the bowel wall, a small muscle ring controls both ducts. When the two ducts join outside it, that control is lost. The doctor calls this an anomalous pancreaticobiliary junction, or APBJ.
The pancreas makes juice at a higher pressure than the liver makes bile. So the juice can flow backwards into the bile duct. Over the years it irritates the duct wall, makes it weak, and lets it balloon out into a cyst.
This idea does not explain every case. Some cysts are seen on scans before the pancreas is working, and some have no early joining. In those, a narrowing at the lower end of the duct is also thought to play a part. So doctors treat the backflow idea as the main cause, not the only one.
Todani’s system has five types. Types I and IV involve the ducts outside the liver. Type V sits inside it.
| Type | What it looks like | How common it is |
|---|---|---|
| I | The main bile duct outside the liver swells like a bag or a sausage | The most frequent kind |
| II | A small pouch hangs off the side of a normal duct | Rare |
| III | A swelling at the end of the duct, inside the bowel wall (a choledochocele) | Rare |
| IVa | Cysts both outside and inside the liver | Second most frequent |
| IVb | Several cysts, all outside the liver | Uncommon |
| V | Cysts only inside the liver (Caroli disease) | Uncommon |
The system began in 1959 with three types by Alonso-Lej. Todani added the liver ducts in 1977 and gave us the five types used today. Type V is a different disease in how it forms. Read about it in our post on Caroli disease.
Each type has its own usual operation. Getting the type right at the first scan keeps you from too little surgery or too much.
| Type | Usual plan |
|---|---|
| I and IVb | Remove the whole cyst and gallbladder, then join the liver duct to a loop of bowel |
| II | Cut out the pouch and keep the duct |
| III | Often an endoscopic cut, or a short operation through the bowel |
| IVa | Remove the outside cyst and rebuild; treat the liver part by how far it spreads |
| V | Plan around the liver: part of the liver, or rarely a transplant |
The steps of the common operation are described in our post on cyst removal and the new bile duct join. Types II and III are the exceptions. They rarely need the full rebuild, so they should not be treated like type I by habit.
Not always. A narrow lower duct can push bile back and widen the ducts above, which settle after surgery. A true type IVa stays cystic.
This is the most important call in the whole classification. If the liver ducts are widened only by back-pressure, removing the outside cyst lets them shrink to normal. If they are truly cystic, they will not.
A wrong call costs a lot. The surgeon may take out part of a healthy liver for no reason. Or a pocket of diseased duct stays behind and goes on making stones and infection.
Types I and IV carry the highest lifetime risk of cancer in the duct lining. They need the closest check-ups after surgery.
The lining of an unremoved cyst can change slowly over the years, and that change can turn into cancer. The risk is highest in types I and IV. It is lower in types II and III, which are mostly settled by their small operations.
Type IVa also behaves like a long-term liver duct disease. Even after a well-done operation, the remaining liver ducts can still form stones and cause infection. Some people with IVa will later need a liver operation. A person with type V may have liver scarring as well. For that reason, the type decides how long and how closely you are followed.
Our post on check-ups after choledochal cyst surgery lists what each visit covers.
Ask which Todani type your MRCP shows, whether the junction is abnormal, and whether the liver ducts are truly cystic.
If the scan was done elsewhere, bring the actual images on a disc, not only the report. The type is drawn from the pictures.
It is the group your cyst belongs to, from I to V. The group tells the surgeon the shape of the cyst and which operation usually fits.
Most form when the bile and pancreas ducts join too early, outside the bowel wall. Pancreatic juice then flows back and slowly widens the duct.
Yes. Some are seen on an antenatal scan. Others show up later as yellow eyes, belly pain or repeated infection.
The lining of an unremoved cyst can change over many years. The risk is highest in types I and IV, which is why removal is advised.
It is a swelling at the end of the bile duct, inside the bowel wall. It is type III and is often treated through an endoscope.
From an MRCP scan, which pictures the bile ducts without a needle or dye injection. Some adults need extra scans to confirm the junction.
Yes, as type V, but it forms differently. It starts inside the liver and may come with liver scarring or kidney cysts.
No. The type describes how the cyst was before the operation. It stays in your record and guides how long you are followed.
For questions before you travel, call +91-63555-64601. The pages below cover the next steps.
Dr Harsh Shah — Dr. Jivraj Mehta Hospital, Vasna, Ahmedabad
Dr. Jivraj Mehta Hospital, Dr Jivraj Mehta Marg, Vasna, Ahmedabad 380007.
Consultations, review of reports and scans, operations and follow-up. OPD Monday to Saturday, 9 am to 5 pm.
Appointments: +91-63555-64601 · +91-63590-11009 · Hospital 079-2663 6363
Directions to the hospital · WhatsApp +91-63555-64601
Has a scan report called your child's or your own bile duct cyst "type I" or "type IVa" and left you unsure what that means? The type is not just a label. It shapes the whole plan. Dr Harsh Shah goes through your MRCP with you, names the type, and explains why it points to one operation and not another. Call, or message us on WhatsApp. Call +91-63555-64601 Ask on WhatsApp
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