Hepatic cysts usually refer to isolated nonparasitic liver cysts, also known as simple cysts. However, several other cystic lesions must be differentiated from true simple cysts. Cystic lesions of the liver include the following:
- Simple cysts
- Multiple cysts occurring in the context of polycystic liver disease (PCLD)
- Parasitic or hydatid (echinococcal) cysts
- Cystic tumors
- Abscesses
These conditions can be distinguished based on the patient’s symptoms, clinical history, and radiographic appearance of the lesion.
In patients with simple hepatic cysts, it is generally accepted that laparoscopic resection of the “roof” offers the best balance of efficacy and safety.
How patients with PCLD should be managed remains less clear, because failure rates for laparoscopic anterior wall resection are high. Hepatic resection, although more effective, carries higher risks.
The treatment of hydatid cysts remains controversial. As most experience is anecdotal, indications for PAIR (puncture, aspiration, injection, aspiration) versus surgery are described.
Pathophysiology and Etiology
Simple Cysts
The cause of simple hepatic cysts is unknown but is believed to be congenital. These cysts rarely contain bile. The cyst fluid is continuously secreted from the cyst wall. For this reason, needle aspiration of simple cysts is not curative, and recurrence is the norm.
Polycystic liver disease
Adult PCLD (AD-PCLD) is congenital and usually associated with autosomal dominant polycystic kidney disease (AD-PKD). Mutations in the PKD1 and PKD2 genes have been identified in these patients.
Neoplastic cysts
Liver tumors with central necrosis seen on imaging studies are often misdiagnosed as liver cysts. True intrahepatic neoplastic cysts are rare. The cause of cystadenomas and cystadenocarcinomas is unknown.
Cystadenoma is a premalignant lesion with neoplastic transformation to cystadenocarcinoma.
Hydroceles
Hydatid cysts are caused by infection with the parasite Echinococcus granulosus. This parasite is found worldwide but is particularly common in sheep and cattle farming areas.
The adult tapeworm lives in the digestive tract of carnivores, such as dogs or wolves. The eggs are released in the feces and are inadvertently ingested by intermediate hosts, such as sheep, cattle, or humans. The larvae of the eggs invade the intermediate host’s intestinal wall and mesenteric vessels, allowing circulation to the liver.
Liver abscesses
Liver abscesses can be of amoebic or bacterial origin.
Entamoeba histolytica is the causative agent of amoebic abscesses. It is acquired by ingesting food or water contaminated with the cyst stage of the parasite. Its only host is humans.
Pyogenic abscesses are most often caused by ascending cholangitis in the setting of biliary obstruction. The organisms isolated are usually intestinal flora. Other routes of infection include the portal vein and hepatic artery.
Patients with intra-abdominal infections may develop liver abscesses with bacterial extension through the portal vein system. Hematogenous spread via the hepatic artery in patients with bloodstream infection is rare.
Liver Cysts – Epidemiology
The exact incidence of liver cysts is unknown, as most are asymptomatic. However, liver cysts have been estimated to occur in 5% of the population. Only 10-15% of these patients have symptoms that bring the cyst to clinical attention. Hepatic cysts are usually discovered as an incidental finding on imaging or at the time of laparotomy.
History and Physical Examination
Simple Cysts
Simple cysts generally do not cause symptoms but may cause mild pain in the right upper quadrant of the abdomen if they are large. Patients with symptomatic simple hepatic cysts may also report abdominal distension and early satiety. Occasionally, a cyst is large enough to present with a palpable abdominal mass. Jaundice caused by bile duct obstruction is rare, as is cyst rupture. Patients with cyst torsion may present with an acute abdomen. When simple cysts rupture, secondary infection may develop, leading to a presentation similar to a liver abscess, with abdominal pain, fever, and leukocytosis.
Polycystic Liver Disease
Polycystic liver disease (PCLD) is a rare childhood condition. These cysts are first noticed during adolescence and increase in size in adulthood. They occur as part of a congenital disorder associated with polycystic kidney disease (PKD). Women are more commonly affected, and the increase in cyst size and number correlates with estrogen levels. Complications (e.g., rupture, bleeding, and infection) are rare. However, patients experience abdominal pain as the cysts enlarge.
Neoplastic Cysts
Cystadenoma occurs most frequently in middle-aged women. However, cystadenocarcinoma affects men and women equally. Most patients are asymptomatic or present with vague abdominal complaints, bloating, nausea, and fullness. These patients, like all those with hepatic cysts, eventually present with abdominal pain. They rarely present with evidence of biliary obstruction.
Hydroceles
Patients with hydroceles, like those with simple cysts, are most often asymptomatic, but pain may develop as the cyst grows. Larger lesions are usually more painful and are more likely to develop complications than simple cysts. On physical examination, patients generally have a palpable mass in the right upper quadrant of the abdomen.
The rupture of the cyst is the most serious complication of hydroceles.
As with simple cysts, patients with hydroceles may develop secondary infection and subsequent liver abscesses.
Liver Abscesses
Patients with liver abscesses present with abdominal pain, fever, and leukocytosis. Typically, symptoms are vague and relatively nonspecific, and as a result, diagnosis is often delayed. The clinical history is important because of the associated illnesses.
Pyogenic abscesses often present with cholangitis, abdominal infections, or sepsis. Rarely, abscesses will rupture.
Liver Cysts – Diagnosis
Evaluation of a patient with a simple liver cyst includes a careful history physical examination and imaging studies (e.g., abdominal computed tomography [CT] scan) to define the anatomy of the cyst.
Before the widespread availability of abdominal imaging techniques, including ultrasound and computed tomography, hepatic cysts were diagnosed only when they grew to enormous size and became apparent as an abdominal mass or as an incidental finding at laparotomy.
Today, imaging studies often reveal asymptomatic lesions incidentally.
Laboratory Studies
Little preoperative laboratory testing is required for these patients.
Liver function test results, such as transaminases or alkaline phosphatase (ALP), may be mildly abnormal, but bilirubin, prothrombin time (PT), and activated partial thromboplastin time (aPTT) are usually within normal ranges.
Patients with liver abscesses can usually be easily identified based on the clinical presentation. Leukocytosis is generally present.
Imaging Studies
The clinician has several options for imaging the liver in patients with liver cysts.
Ultrasound is readily available, noninvasive, and highly sensitive.
CT is also very sensitive and is easier for most clinicians to interpret, particularly concerning treatment planning.
Magnetic resonance imaging (MRI), nuclear medicine scanning, and hepatic angiography have a limited role in the evaluation of liver cysts.
Therapeutic Approach
Treatment of polycystic liver disease (PCLD) or isolated nonparasitic liver cysts is indicated only in symptomatic patients. Asymptomatic patients do not require treatment because the risk of complications related to the lesion is lower than the risk associated with treatment.
Patients with hydatid cysts should be treated to prevent complications related to cyst growth and rupture. If cysts on imaging studies show abnormalities suggestive of cystic masses, excision is indicated.
Abscesses should be treated at diagnosis, but percutaneous drainage and antibiotics are usually adequate treatment.
Contraindications to treatment of symptomatic hepatic cysts are primarily related to underlying comorbidities that increase surgical risk.
In particular, congestive heart failure and hepatic failure with portal hypertension and ascites increase surgical risk.
Conservative Treatment
Simple Cysts
No medical treatment is effective in reducing the size of simple hepatic cysts.
Ultrasound- or computed tomography (CT)-guided percutaneous aspiration is technically simple but has been abandoned because recurrence rates are nearly 100%.
Aspiration combined with sclerotherapy with alcohol or other agents has also been successful in some patients but has high failure and recurrence rates. Successful sclerotherapy depends on complete decompression of the cyst and positioning of the cyst walls. This is not possible if the cyst wall is thick or if the cyst is large.
Polycystic Liver Disease – Neoplastic Cysts
There are no options available for conservative treatment of PCLD or cystadenocarcinoma.
Due to the malignant potential of cystadenoma, there is also no role for conservative treatment for this lesion.
Hydroceles
Conservative treatment with anti-hydrocele agents (albendazole and mebendazole) is relatively ineffective. These drugs are used as adjunctive therapy but do not replace surgical or transdermal therapy.
Liver Cysts – Surgical Treatment
Simple Cysts
Most patients with simple cysts are asymptomatic and do not require treatment. When the cysts become large and cause symptoms, such as pain, surgical treatment is indicated.
Surgical treatment of simple liver cysts involves “de-sealing” the cyst by excision of the portion of the wall that extends to the surface of the liver. Excision of this portion of the cyst wall on the surface of the liver creates a dish-like appearance in the remaining cyst so that any fluid secreted by the remaining epithelium leaks into the peritoneal cavity where it can be absorbed.
Historically, treatment of symptomatic liver cysts required laparotomy, but today it can be successfully performed laparoscopically. Compared with laparotomy, this technique is associated with less postoperative pain, shorter hospital stays, and superior cosmetic outcomes.
Polycystic Liver Disease
In adult PCLD (AD-PCLD), liver enlargement occurs slowly and rarely compromises liver function. Only those patients with clearly severe pain should be considered for surgery.
Neoplastic Cysts
Several surgical methods have been described for the treatment of cystadenoma and cystadenocarcinoma. Regardless of the surgical technique, all surgical options should result in the complete removal of the tumor.
Hydroceles
All patients with hydroceles should be considered for percutaneous or surgical treatment because of the risk of life-threatening complications of the disease without treatment.
More complex cysts are best treated surgically.
Treatment of hydroceles is associated with two technical problems:
(1) risk of anaphylaxis from leakage of cyst fluid containing eggs and larvae into the peritoneal cavity and
(2) recurrence caused by residual eggs in incompletely removed germinal membranes.
To prevent these problems, most surgeons use a technique in which the cyst contents are aspirated and replaced with a hypertonic saline solution to kill residual daughter cysts in the blastocyst before removal of the “roof” and pericystectomy.
Attempts to resect the entire cyst wall or to perform a formal hepatectomy for hydatid cysts have been largely abandoned due to increased surgical morbidity.
Liver Abscesses
Abscesses are generally adequately treated with antibiotics and percutaneous drainage.
If abscesses persist despite attempts at percutaneous drainage, surgical drainage is indicated.
Other surgical indications include large cysts at risk of rupture and abscesses that are anatomically not amenable to percutaneous treatment.
