Overview

Mirizzi syndrome is a rare complication that may arise due to gallstone disease. Gallstones are hardened bile substances that accumulate in the gallbladder, frequently causing no symptoms in certain individuals. However, one complication they can cause is obstruction of the bile ducts, the passageways that lead from the gallbladder throughout the liver. 

Mirizzi syndrome causes a distinctive blockage in the bile ducts where gallstones can obstruct the flow of bile from the gallbladder to the small intestine through ducts. In Mirizzi syndrome, a gallstone in the gallbladder or duct can grow larger and compress a nearby duct externally.¹ 

This syndrome is named after Pablo Luis Mirizzi, an Argentine surgeon born in 1893 in Cordoba, Argentina, who graduated from the Medical Sciences School at the National University of Cordoba where he studied in 1915. A significant achievement in surgery was his execution of the initial intraoperative cholangiogram in 1931. The syndrome named after him was first detailed in a paper published in 1940.²

Epidemiology

Mirizzi syndrome is rare. Because it is uncommon and closely resembles other typical ailments, it is frequently unidentified until gallstone surgery is underway. Up to 2.5% of people having their gallbladder removed are found to have Mirizzi syndrome during surgery.¹

Risk factors

1. First, an atrophic gallbladder with either thick or thin walls, with impacted gallstones at the infundibulum or the Hartmann's pouch, is occasionally found firmly attached to the gallbladder wall
2. A cystic duct with low insertion into the common bile duct
3. A tortuous cystic duct³

Etiology

The exact cause of Mirizzi syndrome is unclear but is felt to be due to persistent and recurrent irritation of the area and chronic biliary stasis. 

Gallstones form when bile ingredients like cholesterol or bilirubin accumulate in the gallbladder due to infrequent emptying. These substances remain in the gallbladder for a long time and form crystals, which in turn form stones, ushering in discomfort in gallbladder ducts. 

The gallbladder has a cone shape with a round base, and its neck is a thin tube known as the cystic duct; it looks like a fig or a pear in shape. Gallstones may impact the last offshoot of the gallbladder, called the infundibulum, as well as the cystic duct if these passages are too narrow. 

The cystic duct branches into the common bile duct below and the common hepatic duct above. These two branches may also be situated near the cystic duct. An impacted gallstone or cluster of stones in the pouch, the neck, or the cystic duct can become swollen enough to compress the common bile duct or the common hepatic duct. That’s Mirizzi syndrome.¹. 

Mirizzi syndrome is categorized based on the types of gallstones that obstruct the bile duct

1. It is estimated that half of the population may eventually develop gallstones, which form from sharable, stagnant bile that can turn to sludge and eventually become stone-like. Other conditions that obstruct the bile flow, for instance, through the formation of strictures in the bile ducts or through other cancers, including pancreatic cancer, may equally lead to the formation of gallstones. Cholesterol gallstones form when cholesterol precipitates and crystallises²
2. Pigmented gallstones, a second type, develop from high bilirubin levels due to red blood cell breakdown
3. Gallstones are a mix of pigments that are black and contain substances like calcium carbonate or calcium phosphate, in addition to cholesterol and bile
4. Those made up mostly of calcium are frequently seen in patients with hypercalcemia, known as the fourth type

Heavy constant back pressure could cause chronic inflammation that may de-characterise layer space that forms the wall of the stone-stuck wall and the compressed wall like an ulcer to the biliary system. The abscess wall gets thinner due to inflammation, while the action of bile dissolves the tissue and leads to cell necrosis and fistula formation.¹

Classification

Management decisions depend on the type of Mirizzi syndrome. A few classification systems have been proposed.⁴ 

Csendes classification

• Type I: Extrinsic compression of the common hepatic duct (CHD)
• Type Ia: By impacted gallstone in the gallbladder neck or cystic duct
• Type Ib: If the cystic duct is absent
• Type II: Erosion of CHD wall and formation of cholecystocholedochal fistula (up to one-third of CHD wall circumference is involved)
• Type III: A cholecystocholedochal fistula can affect around two-thirds of the circumference of the CHD wall
• Type IV: A cholecystocholedochal fistula involves the entire wall of the common hepatic duct
• Type V: Any of the above with cholecysto-enteric fistula

Beltrán classification

• Type I: external compression of the bile duct
• Type II: cholecystobiliary fistula
• Type IIa: less than 50% of the diameter of the bile duct
• Type IIb: greater than 50% of the diameter of the bile duct
• Type III: cholecystobiliary fistula and cholecystoenteric fistula
• Type IIIa: without gallstone ileus
• Type IIIb: with gallstone ileus

Symptoms

Some of the common symptoms of Mirizzi syndrome include.²

1. Nausea and vomiting
2. Diarrhea
3. Pain in the upper right quadrant of the abdomen that radiates to the mid back or right scapular tip
4. Swollen abdomen
5. Jaundice (yellowing of the skin)
6. Increased bloating and flatulence
7. Fatty food ingestion
8. Dark-colored urine
9. Fever
10. Cholangitis (inflammation of the bile ducts)

Diagnosis

Mirizzi syndrome is diagnosed by the following tests¹:

1. Complete blood count (CBC)
2. Liver function tests
3. Ultrasound
4. CT scan
5. MRI
6. ERCP
7. A percutaneous transhepatic cholangiogram (PTHC)

Differential diagnosis

Many other conditions can mimic gallbladder disease. Patients who present with acute biliary colic are often worked up for cardiac issues. Other common conditions with similar presenting symptoms are:²

1. Peptic Ulcer Disease
2. Irritable bowel disease
3. Inflammatory bowel disease
4. Gastroesophageal reflux disease 
5. Pulmonary embolism 

Jaundice, along with other symptoms, is commonly misdiagnosed as other causes in cases of Mirizzi syndrome: 

1. Common bile duct stones
2. Ascending cholangitis 
3. Biliary cancer
4. Pancreatic tumors

Other medical conditions to consider that may mimic Mirizzi syndrome include:

1. Acute hepatitis 
2. Ischemic liver disease
3. Drug-induced hepatitis 

Treatment

The treatment for Mirizzi syndrome is cholecystectomy. Laparoscopic cholecystectomy is preferable, but a more involved surgery may be needed if the condition is advanced. An open cholecystectomy is an option. For advanced diseases, partial cholecystectomy may be an option. This procedure entails retaining Hartman's pouch while removing the gallbladder's body and gallstones. Decreasing the chance of harm to the porta hepatis and bile ducts is achieved with this method. If a fistula exists, performing an open cholecystectomy with bilioenteric anastomosis, potentially with a Roux-n-Y, has proven to be successful.²

Complications

The most common complication of Mirizzi syndrome is cholecystobiliary or cholecystoenteric fistula formation due to prolonged inflammation. Surgical complications with prolonged procedure time due to dense adhesions may also occur. These are, for example, bile duct injury and hemorrhage. Major Bleeding may be encountered in the course of dissection of the Calot’s triangle in some situations. This includes bile duct injury and hemorrhage. Deep hemorrhage can also occur during the excision of the Calot triangle during surgery including:²

1. Cutaneous fistula formation 
2. Secondary biliary cirrhosis 
3. Delayed Onset Biliary Strictures 

Prognosis

A delay in the timely diagnosis and treatment of Mirizzi syndrome can lead to disease progression. Inflammation may result in cutaneous fistula, secondary biliary cirrhosis, delayed biliary strictures, and potential fatality. 5% to 28% of patients develop gallbladder cancer post-cholecystectomy. Prolonged inflammation is believed to be the cause of both diseases rather than Mirizzi syndrome alone. Patients with fistula formation may require prolonged treatment with T-tube placement for small to moderate fistulas or biliary diversion procedures for larger ones. Prolonged surgical and hospital stays for fistula patients heighten their risk of complications and mortality. Elderly, high-risk patients should opt for less invasive treatments to reduce surgical morbidity.⁵

Summary

Mirizzi syndrome is a condition whereby gallstone enlarges and cause obstruction of the bile ducts, which is a rare complication of gallstones. It was named after the Argentinian surgeon Pablo Luis Mirizzi. Some of the risk factors include the cystic duct extending low into the common bile duct and a Torsion of the cystic duct. The signs may include stomach aches, skin turning yellow, high body temperature, and changes in bowel habits. Diagnosis can be done through blood tests, imaging tests, and ERCP. Cholecystectomy is the definitive therapy; the less invasive laparoscopic approach is preferred, but an open procedure might be appropriate for severe cases. Potential issues include fistulas, biliary cirrhosis, and delayed biliary strictures. Proper diagnosis and treatment are paramount to the prognosis of the disease, especially since any delay is likely to lead to more complications and possibly gallbladder cancer.