Diagnosis and management of cystic lesions of the liver
Authors
Arie Regev, MD
K Rajender Reddy, MD Section Editor
Sanjiv Chopra, MD Deputy Editor
Peter A L Bonis, MD
Last literature review version 17.1: January 2009 | This topic last updated: November 13, 2008 (More)
INTRODUCTION — Cystic lesions of the liver represent a heterogeneous group of disorders, which differ in etiology, prevalence, and clinical manifestations (show table 1). Most liver cysts are found incidentally on imaging studies and tend to have a benign course. A minority can cause symptoms, and rarely may be associated with serious morbidity and mortality [1,2] . Larger cysts are more likely to be symptomatic and cause complications such as spontaneous hemorrhage [3] , rupture into the peritoneal cavity or bile duct [4] , infection [5] , and compression of the biliary tree [2] . Specific types of cysts may have unique complications such as malignant transformation in case of a cystadenoma, or anaphylactic shock due to a hydatid cyst. Some of these complications may occasionally mandate surgical intervention.
Considerable controversy still exists regarding the definition and classification of cystic lesions of the liver (show table 1). Furthermore, consensus has not been achieved on the optimal treatment of patients with symptomatic cysts, although a number of therapeutic approaches have been described [6,7] . This topic review will provide an overview of the diagnosis and management of cystic lesions in the liver. Detailed discussions on some of the individual causes of cysts are provided on the corresponding topic reviews.
SIMPLE CYST — Simple cysts of the liver are cystic formations containing clear fluid that do not communicate with the intrahepatic biliary tree. Although simple cysts are found in approximately 1 percent of necropsied adults, very few become large, and even fewer cause symptoms. Their size ranges from a few millimeters to massive lesions occupying large volumes of the upper abdomen; the largest reported cyst contained 17 liters of fluid [8] .
Simple cysts tend to occur more commonly in the right lobe, and are more prevalent in women. The female-to-male ratio is approximately 1.5:1 among those with asymptomatic simple cysts while it is 9:1 in those with symptomatic or complicated simple cysts [1] . Huge cysts are found almost exclusively in women over 50.
Symptomatic patients may present with abdominal discomfort, pain, or nausea. As a general rule, cysts in symptomatic patients are larger than those in asymptomatic ones [7,9] . Large cysts can produce atrophy of the adjacent hepatic tissue while huge cysts can cause complete atrophy of an hepatic lobe with compensatory hypertrophy of the other lobe. Complications (such as spontaneous hemorrhage, bacterial infection, torsion of pedunculated cyst, or biliary obstruction) are more common in large cysts [2-5] .
Diagnosis — The distinction between a simple cyst, cystadenoma, cystadenocarcinoma, and echinococcal cyst can be difficult. However, the distinction is extremely important since these lesions have different clinical significance.
Imaging studies — Ultrasonography is probably the most helpful initial test since it can usually differentiate a simple cyst from other cystic lesions. It should also be used for follow-up studies. Simple cysts appear as an anechoic unilocular fluid filled space with imperceptible walls, and with posterior acoustic enhancement [10,11] . Clinical features combined with the sonographic findings are usually sufficient to distinguish simple cysts from other lesions that can appear cystic such as a liver abscess, necrotic malignant tumor, hemangioma, and hamartoma.
On a CT scan a simple cyst is defined as a well-demarcated water attenuation lesion that does not enhance following the administration of intravenous contrast (show figure 1). Uncomplicated simple cysts are virtually never septated. However, hemorrhage into a simple cyst can lead to confusion in the sonographic differentiation from a cystadenoma or cystadenocarcinoma [3,12] . In one report, hemorrhage was associated with the appearance of septa in 2 of 57 patients (3.5 percent) with large simple cysts (≥ 4 cm) [13] . Hemorrhage is much less frequent in smaller cysts.
Magnetic resonance imaging (MRI) demonstrates a well-defined water-attenuation lesion that does not enhance following the administration of intravenous Gadolinium. On T1-weighted images the cyst shows a low signal, whereas a very high intensity signal is shown on T2-weighted images (show figure 1).
Differential diagnosis — The differential diagnosis of a simple cyst includes a variety of hepatic lesions that can have a cystic appearance, such as an abscess, a necrotic malignant tumor, hemangioma, and hamartoma (show table 2). As mentioned above, the distinction can usually be made based upon the clinical setting and radiographic findings. A rare exception is an hepatic metastasis from a neuroendocrine tumor, which can be asymptomatic and can have a sharply-defined necrotic area [1] .
Histology and needle aspiration — Histological examination is seldom needed for establishing the diagnosis. However, when histology is available, the following criteria can be used for a definitive diagnosis: An outer layer of a thin dense fibrous tissue An inner epithelial lining consisting of a single layer of cuboidal or columnar epithelium; this layer is found in most but not in all simple cysts Lack of mesenchymal stroma or cellular atypia
Aspiration is usually not required for diagnosing cysts that have a typical sonographic appearance. When it is performed, the aspirated fluid is always sterile and cytologically negative. It may vary from clear straw color to brown.
Treatment — The majority of simple cysts do not require treatment. However, it may be prudent to monitor large cysts (≥ 4 cm in diameter) periodically with ultrasonography to assure that they have remained stable. We suggest an initial follow-up study in three months after the diagnosis and then again at 6 to 12 months. Further monitoring is usually unnecessary if the cyst remains unchanged for two to three years.
The presence of symptoms related to the cyst or increasing size should raise concern that the lesion could be a cystadenoma or a cystadenocarcinoma since simple cysts tend to remain stable in size. Such patients may require surgical intervention. The causal relationship between abdominal pain or discomfort and a simple cyst must be admitted with caution, and accepted only if the cyst is large, and other possible causes of the symptoms have been excluded. These include cholelithiasis, gastroesophageal reflux disease, gastric dysmotility, and peptic ulcer disease. Percutaneous aspiration has been advocated as a diagnostic test for relief of symptoms [14] . However, this test is not without risk, and has not been widely accepted.
Several therapeutic approaches have been described for symptomatic, large simple cysts including needle aspiration with or without injection of sclerosing solution [15-17] , internal drainage with cystojejunostomy [18] , wide unroofing [19-22] , and varying degrees of liver resection [23] . In most series, needle aspiration was associated with a high failure rate and rapid recurrence. On the other hand, wide unroofing or cyst resection has been associated with a relatively low incidence of cyst recurrence or complications [13,19-21,24] . The laparoscopic approach has proven to be safe, achieving a wide unroofing or resection without the need for a debilitating incision [13,21,22,25-31] .
Several centers have reported recurrence rates ranging from 0 to 14.3 percent and morbidity rates of 0 to 15 percent after laparoscopic unroofing of solitary simple cysts [21,25-27] . These results support the notion that surgical therapy is the only definitive treatment for symptomatic simple cysts, and that laparoscopic unroofing should be the procedure of choice for accessible cysts. Potential complications of laparoscopic unroofing include wound infection, chest infection, bile leak, subphrenic hematoma, and prolonged postoperative drainage through abdominal drain (>three days) [21,22,27] . Laparoscopic unroofing may not be possible in patients with a superior or posterior location of the cyst.
CYSTADENOMA — Hepatobiliary cystadenomas is a rare cystic tumor that occurs within the liver parenchyma or, less frequently, in the extrahepatic bile ducts. The published experience with these lesions is limited to single case reports and small series [13,32-34] . These reports suggest that cystadenomas occur in adults, more often in women. The tumors occurred more often in the right lobe than in the left in one report [32] , while two other series reported frequent involvement of the left lobe [13,33] . The tumors grew to a large size and required surgical intervention in most reports.
Clinical manifestations — The most commonly reported presenting symptoms were a sensation of an upper abdominal mass, abdominal discomfort or pain, and anorexia. These symptoms had been present for several years prior to diagnosis in several patients. However, many patients were asymptomatic, and the lesions were found incidentally on abdominal imaging studies.
Diagnosis — Histologic examination is required for definitive diagnosis, although the lesion may be suspected on imaging studies. The differential diagnosis includes cystadenocarcinoma, echinococcal cyst, and a simple cyst. Simple cysts can usually be distinguished because of the absence of septations and papillary projections and the presence of serous cystic fluid. Echinoccocal cysts are frequently associated with calcifications and patients will have positive serology. (See "Clinical manifestations and diagnosis of cystic and alveolar echinococcosis").
Imaging studies — The appearance of cystadenoma on ultrasonography can usually differentiate it from a simple cyst (show figure 2). On ultrasonography, a cystadenoma typically appears as an hypoechoic lesion with thickened irregular walls and occasional internal echoes representing debris and wall nodularity. These findings are generally indicative of a complicated cyst, which may represent a simple cyst with previous bleeding, a neoplastic cyst such as a cystadenoma, cystadenocarcinoma, or rarely a metastasis. On a CT scan a cystadenoma appears as a low attenuated mass, which may be uni- or multilocular, or may have septations (show figure 2). The cyst wall is usually thickened and/or irregular. This is in contrast to a simple cyst, which is typically devoid of septations and has imperceptible walls.
Histopathology — A cystadenoma is usually a multilocular cystic lesion with a smooth external surface, and a thin wall with smooth internal lining [32,33] . The cyst frequently contains blood or chocolate-colored material. Histology is essential for the diagnosis and is usually obtained during or after resection of a suspicious cyst. Microscopically, cystadenomas are lined by biliary type mucus-secreting cuboidal or columnar epithelium, supported by dense cellular (mesenchymal) fibrous stroma resembling ovarian tissue (show figure 2). The lining is surrounded by a loose and less cellular layer of collagen. It has been suggested that hepatobiliary cystadenoma may be composed of two distinct groups that differ in the presence or absence of a mesenchymal stroma surrounding the epithelial lining of the cyst [33] .
Treatment — The preferred treatment for cystadenomas is resection, which should be performed whenever possible since malignant transformation of the cyst lining has been described in as many as 15 percent of patients [35] . Removal of the cyst can be accomplished by enucleating it from the surrounding liver. Partial excision is invariably associated with recurrence and with worse prognosis compared to complete resection [21,24,28] . Aspiration is also associated with rapid recurrence of fluid and symptoms [13] .
CYSTADENOCARCINOMA — Cystadenocarcinomas probably arise from malignant transformation of a cystadenoma. This tumor is usually found in the elderly, although it has been reported in patients in their thirties [32] . While the tumors can invade adjacent tissues and metastasize, their prognosis has generally been better than that associated with cholangiocarcinoma [32] . (See "Treatment of cholangiocarcinoma").
Diagnosis — The distinction between a cystadenoma and cystadenocarcinoma can be difficult to make based upon clinical, radiologic, and histological evidence (show figure 3) [36] . Cystadenocarcinomas are usually multilocular and resemble cystadenomas. Malignant changes are typically found in the inner epithelial lining (show figure 3).
Macroscopically, cystadenoma, and cystadenocarcinomas have a smooth external surface. However, internally, cystadenomas have varying degrees of thickness in the wall, although infrequently they may have a thin wall with a smooth lining. Cystadenocarcinomas generally have a thick wall that may show large tissue masses protruding from the internal cyst lining [32,33] . Cystadenocarcinomas have occasionally been identified preoperatively by aspiration and examination of the contents of the cyst, but this procedure carries the risk of peritoneal seeding of the tumor [37] .
Treatment — In contrast to a cystadenoma, if cystadenocarcinoma is suspected, treatment should consist of a formal liver resection [38] . Enucleation is not recommended since it may be associated with an increased risk of recurrence. The lesion is potentially curable by complete excision. The effect of nonsurgical therapy (eg, radiation or chemotherapy) is unknown.
ECHINOCOCCAL CYST — Echinococcal (hydatid) cysts of the liver are caused by the larval form of Echinococcus granulosus, which is usually acquired from infected dogs. These are fluid-filled structures limited by a parasite-derived membrane, which contains germinal epithelium (show figure 4). Hydatid cysts of the liver are uncommonly encountered in the United States. (See "Clinical manifestations and diagnosis of cystic and alveolar echinococcosis").
Patients are often asymptomatic. When symptoms do occur, they are usually due to the mass effect of an enlarging cyst or complications such as intraperitoneal leakage, infection, or biliary obstruction. E. granulosus cysts can rupture into the biliary tree and produce biliary colic, obstructive jaundice, cholangitis, or pancreatitis. (See "Endoscopic diagnosis and management of biliary parasitosis"). Pressure or mass effects on the bile ducts, portal and hepatic veins, or on the inferior vena cava can result in cholestasis, portal hypertension, venous obstruction, or the Budd-Chiari syndrome. (See "Etiology of the Budd-Chiari syndrome"). Liver cysts can also rupture into the peritoneum causing peritonitis, or transdiaphragmatically into the bronchial tree causing pulmonary hydatidosis or a bronchial fistula. Secondary bacterial infection of the cysts can result in liver abscesses. (See "Pyogenic liver abscess").
Detailed discussion on the clinical manifestations, diagnosis, and treatment of echinococcis are presented separately. (See "Clinical manifestations and diagnosis of cystic and alveolar echinococcosis" and see "Treatment and prevention of echinococcosis").
OTHER CYSTIC LESIONS OF THE LIVER — A variety of other cystic lesions of the liver have been described the clinical significance of which are variable.
Ciliated hepatic foregut cyst — A ciliated foregut cyst is a rare, benign solitary cyst consisting of ciliated pseudostratified columnar epithelium, subepithelial connective tissue, a smooth muscle layer, and an outer fibrous capsule. Unlike simple solitary cysts, they occur more frequently in men, and are found most commonly in the left lobe [39] . There are about 60 reported cases of ciliated foregut cyst, the size of which ranged from 0.4 to 9.0 cm. There are no cases reported of malignant transformation. The clinical importance of its diagnosis lies in the distinction from other potentially malignant hepatic lesions.
Primary squamous cell carcinoma — There are several reports of primary squamous cell carcinoma arising in hepatic cysts lined predominantly by stratified squamous epithelium. These lesions appear to have a poor prognosis, although the information in the literature is sparse [40,41] .
Liver metastases — Rarely, certain liver metastases may appear as cystic lesions, usually due to the occurrence of central necrosis. These include metastases from ovarian carcinoma, pancreas, colon, kidney, and neuroendocrine tumors.
Polycystic liver disease — Polycystic liver disease most often occurs in patients with polycystic kidney disease. The incidence of hepatic cysts in polycystic kidney disease increases with age from approximately 10 percent below the age of 30 to greater than 50 percent over the age of 60. The cysts, which appear to be derived from biliary epithelium, are more commonly observed in patients with advanced renal disease. (See "Extrarenal manifestations of autosomal dominant polycystic kidney disease", section on Hepatic cysts).
A less common disorder, autosomal dominant polycystic liver disease, is distinct from polycystic kidney disease, since it is not associated with kidney involvement or cerebral aneurysms. Two mutations have been found to cause this disorder: a mutation in the PRKCSH gene that encodes a protein called hepatocystin [42] , and a mutation in the SEC63 gene that encodes for a component of the protein translocation machinery in the endoplasmic reticulum [43] .
Biliary cysts — Biliary cysts are cystic dilatations, which may occur singly or in multiples throughout the bile ducts. They were originally termed choledochal cysts (involving the extrahepatic bile duct) but the clinical classification was revised in 1977 to include intrahepatic cysts. Infants with biliary cysts commonly present with conjugated hyperbilirubinemia (80 percent), failure to thrive, or an abdominal mass (30 to 60 percent). The triad of pain, jaundice, and abdominal mass is found in 11 to 63 percent. In contrast, chronic and intermittent abdominal pain appears to be the most common presenting symptom (50 to 96 percent) in patients older than two. (See "Biliary cysts").
SUMMARY AND RECOMMENDATIONS — Cystic lesions of the liver may pose a diagnostic and therapeutic dilemma. Simple cysts are by far the most common lesions encountered. Clinical features combined with typical sonographic findings are usually sufficient to distinguish simple cysts from other cystic lesions (show table 1). Needle aspiration is usually not required for diagnosis. On the other hand, certain clinical and radiologic features should raise suspicion for an alternative diagnosis such as cystadenoma, cystadenocarcinoma, or hydatid cyst (show table 2).
Large asymptomatic, non-complicated simple cysts should be monitored by periodic ultrasonography for the first two to three years following diagnosis. Significant growth, progressive symptoms, or any suspicion of neoplastic cyst mandate surgical intervention. In symptomatic patients, the possibility of coexisting pathology must be excluded. (See "Clinical manifestations and diagnosis of cystic and alveolar echinococcosis"). When symptoms are the only indication for surgery, selection of patients with truly symptomatic cysts is crucial before considering any intervention. The procedure of choice for simple cysts is laparoscopic wide unroofing. Percutaneous aspiration is ineffective and should be avoided. Prior to surgery, echinococcal cysts should be ruled out. On opening the cyst roof, close inspection of the interior for neoplastic components is extremely important. Any suspicion regarding underlying malignancy (eg, solid or thickened cyst wall, nodules, etc.) mandates a biopsy for frozen section histopathology.
Laparoscopic unroofing is usually curative for simple cysts. Enucleation may be sufficient for a cystadenoma, whereas formal hepatic resection is indicated for cystadenocarcinomas.
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Last literature review version 16.3: September 2008 | This topic last updated: April 10, 2007 (More)
INTRODUCTION — Cystic lesions of the liver represent a heterogeneous group of disorders, which differ in etiology, prevalence, and clinical manifestations (show table 1). Most liver cysts are found incidentally on imaging studies and tend to have a benign course. A minority can cause symptoms, and rarely may be associated with serious morbidity and mortality [1,2] . Larger cysts are more likely to be symptomatic and cause complications such as spontaneous hemorrhage [3] , rupture into the peritoneal cavity or bile duct [4] , infection [5] , and compression of the biliary tree [2] . Specific types of cysts may have unique complications such as malignant transformation in case of a cystadenoma, or anaphylactic shock due to a hydatid cyst. Some of these complications may occasionally mandate surgical intervention.
Considerable controversy still exists regarding the definition and classification of cystic lesions of the liver (show table 1). Furthermore, consensus has not been achieved on the optimal treatment of patients with symptomatic cysts, although a number of therapeutic approaches have been described [6,7] . This topic review will provide an overview of the diagnosis and management of cystic lesions in the liver. Detailed discussions on some of the individual causes of cysts are provided on the corresponding topic reviews.
SIMPLE CYST — Simple cysts of the liver are cystic formations containing clear fluid that do not communicate with the intrahepatic biliary tree. Although simple cysts are found in approximately 1 percent of necropsied adults, very few become large, and even fewer cause symptoms. Their size ranges from a few millimeters to massive lesions occupying large volumes of the upper abdomen; the largest reported cyst contained 17 liters of fluid [8] .
Simple cysts tend to occur more commonly in the right lobe, and are more prevalent in women. The female-to-male ratio is approximately 1.5:1 among those with asymptomatic simple cysts while it is 9:1 in those with symptomatic or complicated simple cysts [1] . Huge cysts are found almost exclusively in women over 50.
Symptomatic patients may present with abdominal discomfort, pain, or nausea. As a general rule, cysts in symptomatic patients are larger than those in asymptomatic ones [7,9] . Large cysts can produce atrophy of the adjacent hepatic tissue while huge cysts can cause complete atrophy of an hepatic lobe with compensatory hypertrophy of the other lobe. Complications (such as spontaneous hemorrhage, bacterial infection, torsion of pedunculated cyst, or biliary obstruction) are more common in large cysts [2-5] .
Diagnosis — The distinction between a simple cyst, cystadenoma, cystadenocarcinoma, and echinococcal cyst can be difficult. However, the distinction is extremely important since these lesions have different clinical significance.
Imaging studies — Ultrasonography is probably the most helpful initial test since it can usually differentiate a simple cyst from other cystic lesions. It should also be used for follow-up studies. Simple cysts appear as an anechoic unilocular fluid filled space with imperceptible walls, and with posterior acoustic enhancement [10,11] . Clinical features combined with the sonographic findings are usually sufficient to distinguish simple cysts from other lesions that can appear cystic such as a liver abscess, necrotic malignant tumor, hemangioma, and hamartoma.
On a CT scan a simple cyst is defined as a well-demarcated water attenuation lesion that does not enhance following the administration of intravenous contrast (show figure 1). Uncomplicated simple cysts are virtually never septated. However, hemorrhage into a simple cyst can lead to confusion in the sonographic differentiation from a cystadenoma or cystadenocarcinoma [3,12] . In one report, hemorrhage was associated with the appearance of septa in 2 of 57 patients (3.5 percent) with large simple cysts (≥ 4 cm) [13] . Hemorrhage is much less frequent in smaller cysts.
Magnetic resonance imaging (MRI) demonstrates a well-defined water-attenuation lesion that does not enhance following the administration of intravenous Gadolinium. On T1-weighted images the cyst shows a low signal, whereas a very high intensity signal is shown on T2-weighted images (show figure 1).
Differential diagnosis — The differential diagnosis of a simple cyst includes a variety of hepatic lesions that can have a cystic appearance, such as an abscess, a necrotic malignant tumor, hemangioma, and hamartoma (show table 2). As mentioned above, the distinction can usually be made based upon the clinical setting and radiographic findings. A rare exception is an hepatic metastasis from a neuroendocrine tumor, which can be asymptomatic and can have a sharply-defined necrotic area [1] .
Histology and needle aspiration — Histological examination is seldom needed for establishing the diagnosis. However, when histology is available, the following criteria can be used for a definitive diagnosis: An outer layer of a thin dense fibrous tissue An inner epithelial lining consisting of a single layer of cuboidal or columnar epithelium; this layer is found in most but not in all simple cysts Lack of mesenchymal stroma or cellular atypia
Aspiration is usually not required for diagnosing cysts that have a typical sonographic appearance. When it is performed, the aspirated fluid is always sterile and cytologically negative. It may vary from clear straw color to brown.
Treatment — The majority of simple cysts do not require treatment. However, it may be prudent to monitor large cysts (≥ 4 cm in diameter) periodically with ultrasonography to assure that they have remained stable. We suggest an initial follow-up study in three months after the diagnosis and then again at 6 to 12 months. Further monitoring is usually unnecessary if the cyst remains unchanged for two to three years.
The presence of symptoms related to the cyst or increasing size should raise concern that the lesion could be a cystadenoma or a cystadenocarcinoma since simple cysts tend to remain stable in size. Such patients may require surgical intervention. The causal relationship between abdominal pain or discomfort and a simple cyst must be admitted with caution, and accepted only if the cyst is large, and other possible causes of the symptoms have been excluded. These include cholelithiasis, gastroesophageal reflux disease, gastric dysmotility, and peptic ulcer disease. Percutaneous aspiration has been advocated as a diagnostic test for relief of symptoms [14] . However, this test is not without risk, and has not been widely accepted.
Several therapeutic approaches have been described for symptomatic, large simple cysts including needle aspiration with or without injection of sclerosing solution [15-17] , internal drainage with cystojejunostomy [18] , wide unroofing [19-22] , and varying degrees of liver resection [23] . In most series, needle aspiration was associated with a high failure rate and rapid recurrence. On the other hand, wide unroofing or cyst resection has been associated with a relatively low incidence of cyst recurrence or complications [13,19-21,24] . The laparoscopic approach has proven to be safe, achieving a wide unroofing without the need for a debilitating incision [13,21,22,25-30] .
Several centers have reported recurrence rates ranging from 0 to 14.3 percent and morbidity rates of 0 to 15 percent after laparoscopic unroofing of solitary simple cysts [21,25-27] . These results support the notion that surgical therapy is the only definitive treatment for symptomatic simple cysts, and that laparoscopic unroofing should be the procedure of choice for accessible cysts. Potential complications of laparoscopic unroofing include wound infection, chest infection, bile leak, subphrenic hematoma, and prolonged postoperative drainage through abdominal drain (>three days) [21,22,27] . Laparoscopic unroofing may not be possible in patients with a superior or posterior location of the cyst.
CYSTADENOMA — Hepatobiliary cystadenomas is a rare cystic tumor that occurs within the liver parenchyma or, less frequently, in the extrahepatic bile ducts. The published experience with these lesions is limited to single case reports and small series [13,31-33] . These reports suggest that cystadenomas occur in adults, more often in women. The tumors occurred more often in the right lobe than in the left in one report [31] , while two other series reported frequent involvement of the left lobe [13,32] . The tumors grew to a large size and required surgical intervention in most reports.
Clinical manifestations — The most commonly reported presenting symptoms were a sensation of an upper abdominal mass, abdominal discomfort or pain, and anorexia. These symptoms had been present for several years prior to diagnosis in several patients. However, many patients were asymptomatic, and the lesions were found incidentally on abdominal imaging studies.
Diagnosis — Histologic examination is required for definitive diagnosis, although the lesion may be suspected on imaging studies. The differential diagnosis includes cystadenocarcinoma, echinococcal cyst, and a simple cyst. Simple cysts can usually be distinguished because of the absence of septations and papillary projections and the presence of serous cystic fluid. Echinoccocal cysts are frequently associated with calcifications and patients will have positive serology. (See "Clinical manifestations and diagnosis of cystic and alveolar echinococcosis").
Imaging studies — The appearance of cystadenoma on ultrasonography can usually differentiate it from a simple cyst (show figure 2). On ultrasonography, a cystadenoma typically appears as an hypoechoic lesion with thickened irregular walls and occasional internal echoes representing debris and wall nodularity. These findings are generally indicative of a complicated cyst, which may represent a simple cyst with previous bleeding, a neoplastic cyst such as a cystadenoma, cystadenocarcinoma, or rarely a metastasis. On a CT scan a cystadenoma appears as a low attenuated mass, which may be uni- or multilocular, or may have septations (show figure 2). The cyst wall is usually thickened and/or irregular. This is in contrast to a simple cyst, which is typically devoid of septations and has imperceptible walls.
Histopathology — A cystadenoma is usually a multilocular cystic lesion with a smooth external surface, and a thin wall with smooth internal lining [31,32] . The cyst frequently contains blood or chocolate-colored material. Histology is essential for the diagnosis and is usually obtained during or after resection of a suspicious cyst. Microscopically, cystadenomas are lined by biliary type mucus-secreting cuboidal or columnar epithelium, supported by dense cellular (mesenchymal) fibrous stroma resembling ovarian tissue (show figure 2). The lining is surrounded by a loose and less cellular layer of collagen. It has been suggested that hepatobiliary cystadenoma may be composed of two distinct groups that differ in the presence or absence of a mesenchymal stroma surrounding the epithelial lining of the cyst [32] .
Treatment — The preferred treatment for cystadenomas is resection, which should be performed whenever possible since malignant transformation of the cyst lining has been described in as many as 15 percent of patients [34] . Removal of the cyst can be accomplished by enucleating it from the surrounding liver. Partial excision is invariably associated with recurrence and with worse prognosis compared to complete resection [21,24,28] . Aspiration is also associated with rapid recurrence of fluid and symptoms [13] .
CYSTADENOCARCINOMA — Cystadenocarcinomas probably arise from malignant transformation of a cystadenoma. This tumor is usually found in the elderly, although it has been reported in patients in their thirties [31] . While the tumors can invade adjacent tissues and metastasize, their prognosis has generally been better than that associated with cholangiocarcinoma [31] . (See "Treatment of cholangiocarcinoma").
Diagnosis — The distinction between a cystadenoma and cystadenocarcinoma can be difficult to make based upon clinical, radiologic, and histological evidence (show figure 3) [35] . Cystadenocarcinomas are usually multilocular and resemble cystadenomas. Malignant changes are typically found in the inner epithelial lining (show figure 3).
Macroscopically, cystadenoma, and cystadenocarcinomas have a smooth external surface. However, internally, cystadenomas have varying degrees of thickness in the wall, although infrequently they may have a thin wall with a smooth lining. Cystadenocarcinomas generally have a thick wall that may show large tissue masses protruding from the internal cyst lining [31,32] . Cystadenocarcinomas have occasionally been identified preoperatively by aspiration and examination of the contents of the cyst, but this procedure carries the risk of peritoneal seeding of the tumor [36] .
Treatment — In contrast to a cystadenoma, if cystadenocarcinoma is suspected, treatment should consist of a formal liver resection [37] . Enucleation is not recommended since it may be associated with an increased risk of recurrence. The lesion is potentially curable by complete excision. The effect of nonsurgical therapy (eg, radiation or chemotherapy) is unknown.
ECHINOCOCCAL CYST — Echinococcal (hydatid) cysts of the liver are caused by the larval form of Echinococcus granulosus, which is usually acquired from infected dogs. These are fluid-filled structures limited by a parasite-derived membrane, which contains germinal epithelium (show figure 4). Hydatid cysts of the liver are uncommonly encountered in the United States. (See "Clinical manifestations and diagnosis of cystic and alveolar echinococcosis").
Patients are often asymptomatic. When symptoms do occur, they are usually due to the mass effect of an enlarging cyst or complications such as intraperitoneal leakage, infection, or biliary obstruction. E. granulosus cysts can rupture into the biliary tree and produce biliary colic, obstructive jaundice, cholangitis, or pancreatitis. (See "Endoscopic diagnosis and management of biliary parasitosis"). Pressure or mass effects on the bile ducts, portal and hepatic veins, or on the inferior vena cava can result in cholestasis, portal hypertension, venous obstruction, or the Budd-Chiari syndrome. (See "Etiology of the Budd-Chiari syndrome"). Liver cysts can also rupture into the peritoneum causing peritonitis, or transdiaphragmatically into the bronchial tree causing pulmonary hydatidosis or a bronchial fistula. Secondary bacterial infection of the cysts can result in liver abscesses. (See "Pyogenic liver abscess").
Detailed discussion on the clinical manifestations, diagnosis, and treatment of echinococcis are presented separately. (See "Clinical manifestations and diagnosis of cystic and alveolar echinococcosis" and see "Treatment and prevention of echinococcosis").
OTHER CYSTIC LESIONS OF THE LIVER — A variety of other cystic lesions of the liver have been described the clinical significance of which are variable.
Ciliated hepatic foregut cyst — A ciliated foregut cyst is a rare, benign solitary cyst consisting of ciliated pseudostratified columnar epithelium, subepithelial connective tissue, a smooth muscle layer, and an outer fibrous capsule. Unlike simple solitary cysts, they occur more frequently in men, and are found most commonly in the left lobe [38] . There are about 60 reported cases of ciliated foregut cyst, the size of which ranged from 0.4 to 9.0 cm. There are no cases reported of malignant transformation. The clinical importance of its diagnosis lies in the distinction from other potentially malignant hepatic lesions.
Primary squamous cell carcinoma — There are several reports of primary squamous cell carcinoma arising in hepatic cysts lined predominantly by stratified squamous epithelium. These lesions appear to have a poor prognosis, although the information in the literature is sparse [39,40] .
Liver metastases — Rarely, certain liver metastases may appear as cystic lesions, usually due to the occurrence of central necrosis. These include metastases from ovarian carcinoma, pancreas, colon, kidney, and neuroendocrine tumors.
Polycystic liver disease — Polycystic liver disease most often occurs in patients with polycystic kidney disease. The incidence of hepatic cysts in polycystic kidney disease increases with age from approximately 10 percent below the age of 30 to greater than 50 percent over the age of 60. The cysts, which appear to be derived from biliary epithelium, are more commonly observed in patients with advanced renal disease. (See "Extrarenal manifestations of autosomal dominant polycystic kidney disease", section on Hepatic cysts).
A less common disorder, autosomal dominant polycystic liver disease, is distinct from polycystic kidney disease, since it is not associated with kidney involvement or cerebral aneurysms. Two mutations have been found to cause this disorder: a mutation in the PRKCSH gene that encodes a protein called hepatocystin [41] , and a mutation in the SEC63 gene that encodes for a component of the protein translocation machinery in the endoplasmic reticulum [42] .
Biliary cysts — Biliary cysts are cystic dilatations, which may occur singly or in multiples throughout the bile ducts. They were originally termed choledochal cysts (involving the extrahepatic bile duct) but the clinical classification was revised in 1977 to include intrahepatic cysts. Infants with biliary cysts commonly present with conjugated hyperbilirubinemia (80 percent), failure to thrive, or an abdominal mass (30 to 60 percent). The triad of pain, jaundice, and abdominal mass is found in 11 to 63 percent. In contrast, chronic and intermittent abdominal pain appears to be the most common presenting symptom (50 to 96 percent) in patients older than two. (See "Biliary cysts").
SUMMARY AND RECOMMENDATIONS — Cystic lesions of the liver may pose a diagnostic and therapeutic dilemma. Simple cysts are by far the most common lesions encountered. Clinical features combined with typical sonographic findings are usually sufficient to distinguish simple cysts from other cystic lesions (show table 1). Needle aspiration is usually not required for diagnosis. On the other hand, certain clinical and radiologic features should raise suspicion for an alternative diagnosis such as cystadenoma, cystadenocarcinoma, or hydatid cyst (show table 2).
Large asymptomatic, non-complicated simple cysts should be monitored by periodic ultrasonography for the first two to three years following diagnosis. Significant growth, progressive symptoms, or any suspicion of neoplastic cyst mandate surgical intervention. In symptomatic patients, the possibility of coexisting pathology must be excluded. (See "Clinical manifestations and diagnosis of cystic and alveolar echinococcosis"). When symptoms are the only indication for surgery, selection of patients with truly symptomatic cysts is crucial before considering any intervention. The procedure of choice for simple cysts is laparoscopic wide unroofing. Percutaneous aspiration is ineffective and should be avoided. Prior to surgery, echinococcal cysts should be ruled out. On opening the cyst roof, close inspection of the interior for neoplastic components is extremely important. Any suspicion regarding underlying malignancy (eg, solid or thickened cyst wall, nodules, etc.) mandates a biopsy for frozen section histopathology.
Laparoscopic unroofing is usually curative for simple cysts. Enucleation may be sufficient for a cystadenoma, whereas formal hepatic resection is indicated for cystadenocarcinomas.
INTRODUCTION — Cystic lesions of the liver represent a heterogeneous group of disorders, which differ in etiology, prevalence, and clinical manifestations (show table 1). Most liver cysts are found incidentally on imaging studies and tend to have a benign course. A minority can cause symptoms, and rarely may be associated with serious morbidity and mortality [1,2] . Larger cysts are more likely to be symptomatic and cause complications such as spontaneous hemorrhage [3] , rupture into the peritoneal cavity or bile duct [4] , infection [5] , and compression of the biliary tree [2] . Specific types of cysts may have unique complications such as malignant transformation in case of a cystadenoma, or anaphylactic shock due to a hydatid cyst. Some of these complications may occasionally mandate surgical intervention.
Considerable controversy still exists regarding the definition and classification of cystic lesions of the liver (show table 1). Furthermore, consensus has not been achieved on the optimal treatment of patients with symptomatic cysts, although a number of therapeutic approaches have been described [6,7] . This topic review will provide an overview of the diagnosis and management of cystic lesions in the liver. Detailed discussions on some of the individual causes of cysts are provided on the corresponding topic reviews.
SIMPLE CYST — Simple cysts of the liver are cystic formations containing clear fluid that do not communicate with the intrahepatic biliary tree. Although simple cysts are found in approximately 1 percent of necropsied adults, very few become large, and even fewer cause symptoms. Their size ranges from a few millimeters to massive lesions occupying large volumes of the upper abdomen; the largest reported cyst contained 17 liters of fluid [8] .
Simple cysts tend to occur more commonly in the right lobe, and are more prevalent in women. The female-to-male ratio is approximately 1.5:1 among those with asymptomatic simple cysts while it is 9:1 in those with symptomatic or complicated simple cysts [1] . Huge cysts are found almost exclusively in women over 50.
Symptomatic patients may present with abdominal discomfort, pain, or nausea. As a general rule, cysts in symptomatic patients are larger than those in asymptomatic ones [7,9] . Large cysts can produce atrophy of the adjacent hepatic tissue while huge cysts can cause complete atrophy of an hepatic lobe with compensatory hypertrophy of the other lobe. Complications (such as spontaneous hemorrhage, bacterial infection, torsion of pedunculated cyst, or biliary obstruction) are more common in large cysts [2-5] .
Diagnosis — The distinction between a simple cyst, cystadenoma, cystadenocarcinoma, and echinococcal cyst can be difficult. However, the distinction is extremely important since these lesions have different clinical significance.
Imaging studies — Ultrasonography is probably the most helpful initial test since it can usually differentiate a simple cyst from other cystic lesions. It should also be used for follow-up studies. Simple cysts appear as an anechoic unilocular fluid filled space with imperceptible walls, and with posterior acoustic enhancement [10,11] . Clinical features combined with the sonographic findings are usually sufficient to distinguish simple cysts from other lesions that can appear cystic such as a liver abscess, necrotic malignant tumor, hemangioma, and hamartoma.
On a CT scan a simple cyst is defined as a well-demarcated water attenuation lesion that does not enhance following the administration of intravenous contrast (show figure 1). Uncomplicated simple cysts are virtually never septated. However, hemorrhage into a simple cyst can lead to confusion in the sonographic differentiation from a cystadenoma or cystadenocarcinoma [3,12] . In one report, hemorrhage was associated with the appearance of septa in 2 of 57 patients (3.5 percent) with large simple cysts (≥ 4 cm) [13] . Hemorrhage is much less frequent in smaller cysts.
Magnetic resonance imaging (MRI) demonstrates a well-defined water-attenuation lesion that does not enhance following the administration of intravenous Gadolinium. On T1-weighted images the cyst shows a low signal, whereas a very high intensity signal is shown on T2-weighted images (show figure 1).
Differential diagnosis — The differential diagnosis of a simple cyst includes a variety of hepatic lesions that can have a cystic appearance, such as an abscess, a necrotic malignant tumor, hemangioma, and hamartoma (show table 2). As mentioned above, the distinction can usually be made based upon the clinical setting and radiographic findings. A rare exception is an hepatic metastasis from a neuroendocrine tumor, which can be asymptomatic and can have a sharply-defined necrotic area [1] .
Histology and needle aspiration — Histological examination is seldom needed for establishing the diagnosis. However, when histology is available, the following criteria can be used for a definitive diagnosis: An outer layer of a thin dense fibrous tissue An inner epithelial lining consisting of a single layer of cuboidal or columnar epithelium; this layer is found in most but not in all simple cysts Lack of mesenchymal stroma or cellular atypia
Aspiration is usually not required for diagnosing cysts that have a typical sonographic appearance. When it is performed, the aspirated fluid is always sterile and cytologically negative. It may vary from clear straw color to brown.
Treatment — The majority of simple cysts do not require treatment. However, it may be prudent to monitor large cysts (≥ 4 cm in diameter) periodically with ultrasonography to assure that they have remained stable. We suggest an initial follow-up study in three months after the diagnosis and then again at 6 to 12 months. Further monitoring is usually unnecessary if the cyst remains unchanged for two to three years.
The presence of symptoms related to the cyst or increasing size should raise concern that the lesion could be a cystadenoma or a cystadenocarcinoma since simple cysts tend to remain stable in size. Such patients may require surgical intervention. The causal relationship between abdominal pain or discomfort and a simple cyst must be admitted with caution, and accepted only if the cyst is large, and other possible causes of the symptoms have been excluded. These include cholelithiasis, gastroesophageal reflux disease, gastric dysmotility, and peptic ulcer disease. Percutaneous aspiration has been advocated as a diagnostic test for relief of symptoms [14] . However, this test is not without risk, and has not been widely accepted.
Several therapeutic approaches have been described for symptomatic, large simple cysts including needle aspiration with or without injection of sclerosing solution [15-17] , internal drainage with cystojejunostomy [18] , wide unroofing [19-22] , and varying degrees of liver resection [23] . In most series, needle aspiration was associated with a high failure rate and rapid recurrence. On the other hand, wide unroofing or cyst resection has been associated with a relatively low incidence of cyst recurrence or complications [13,19-21,24] . The laparoscopic approach has proven to be safe, achieving a wide unroofing without the need for a debilitating incision [13,21,22,25-30] .
Several centers have reported recurrence rates ranging from 0 to 14.3 percent and morbidity rates of 0 to 15 percent after laparoscopic unroofing of solitary simple cysts [21,25-27] . These results support the notion that surgical therapy is the only definitive treatment for symptomatic simple cysts, and that laparoscopic unroofing should be the procedure of choice for accessible cysts. Potential complications of laparoscopic unroofing include wound infection, chest infection, bile leak, subphrenic hematoma, and prolonged postoperative drainage through abdominal drain (>three days) [21,22,27] . Laparoscopic unroofing may not be possible in patients with a superior or posterior location of the cyst.
CYSTADENOMA — Hepatobiliary cystadenomas is a rare cystic tumor that occurs within the liver parenchyma or, less frequently, in the extrahepatic bile ducts. The published experience with these lesions is limited to single case reports and small series [13,31-33] . These reports suggest that cystadenomas occur in adults, more often in women. The tumors occurred more often in the right lobe than in the left in one report [31] , while two other series reported frequent involvement of the left lobe [13,32] . The tumors grew to a large size and required surgical intervention in most reports.
Clinical manifestations — The most commonly reported presenting symptoms were a sensation of an upper abdominal mass, abdominal discomfort or pain, and anorexia. These symptoms had been present for several years prior to diagnosis in several patients. However, many patients were asymptomatic, and the lesions were found incidentally on abdominal imaging studies.
Diagnosis — Histologic examination is required for definitive diagnosis, although the lesion may be suspected on imaging studies. The differential diagnosis includes cystadenocarcinoma, echinococcal cyst, and a simple cyst. Simple cysts can usually be distinguished because of the absence of septations and papillary projections and the presence of serous cystic fluid. Echinoccocal cysts are frequently associated with calcifications and patients will have positive serology. (See "Clinical manifestations and diagnosis of cystic and alveolar echinococcosis").
Imaging studies — The appearance of cystadenoma on ultrasonography can usually differentiate it from a simple cyst (show figure 2). On ultrasonography, a cystadenoma typically appears as an hypoechoic lesion with thickened irregular walls and occasional internal echoes representing debris and wall nodularity. These findings are generally indicative of a complicated cyst, which may represent a simple cyst with previous bleeding, a neoplastic cyst such as a cystadenoma, cystadenocarcinoma, or rarely a metastasis. On a CT scan a cystadenoma appears as a low attenuated mass, which may be uni- or multilocular, or may have septations (show figure 2). The cyst wall is usually thickened and/or irregular. This is in contrast to a simple cyst, which is typically devoid of septations and has imperceptible walls.
Histopathology — A cystadenoma is usually a multilocular cystic lesion with a smooth external surface, and a thin wall with smooth internal lining [31,32] . The cyst frequently contains blood or chocolate-colored material. Histology is essential for the diagnosis and is usually obtained during or after resection of a suspicious cyst. Microscopically, cystadenomas are lined by biliary type mucus-secreting cuboidal or columnar epithelium, supported by dense cellular (mesenchymal) fibrous stroma resembling ovarian tissue (show figure 2). The lining is surrounded by a loose and less cellular layer of collagen. It has been suggested that hepatobiliary cystadenoma may be composed of two distinct groups that differ in the presence or absence of a mesenchymal stroma surrounding the epithelial lining of the cyst [32] .
Treatment — The preferred treatment for cystadenomas is resection, which should be performed whenever possible since malignant transformation of the cyst lining has been described in as many as 15 percent of patients [34] . Removal of the cyst can be accomplished by enucleating it from the surrounding liver. Partial excision is invariably associated with recurrence and with worse prognosis compared to complete resection [21,24,28] . Aspiration is also associated with rapid recurrence of fluid and symptoms [13] .
CYSTADENOCARCINOMA — Cystadenocarcinomas probably arise from malignant transformation of a cystadenoma. This tumor is usually found in the elderly, although it has been reported in patients in their thirties [31] . While the tumors can invade adjacent tissues and metastasize, their prognosis has generally been better than that associated with cholangiocarcinoma [31] . (See "Treatment of cholangiocarcinoma").
Diagnosis — The distinction between a cystadenoma and cystadenocarcinoma can be difficult to make based upon clinical, radiologic, and histological evidence (show figure 3) [35] . Cystadenocarcinomas are usually multilocular and resemble cystadenomas. Malignant changes are typically found in the inner epithelial lining (show figure 3).
Macroscopically, cystadenoma, and cystadenocarcinomas have a smooth external surface. However, internally, cystadenomas have varying degrees of thickness in the wall, although infrequently they may have a thin wall with a smooth lining. Cystadenocarcinomas generally have a thick wall that may show large tissue masses protruding from the internal cyst lining [31,32] . Cystadenocarcinomas have occasionally been identified preoperatively by aspiration and examination of the contents of the cyst, but this procedure carries the risk of peritoneal seeding of the tumor [36] .
Treatment — In contrast to a cystadenoma, if cystadenocarcinoma is suspected, treatment should consist of a formal liver resection [37] . Enucleation is not recommended since it may be associated with an increased risk of recurrence. The lesion is potentially curable by complete excision. The effect of nonsurgical therapy (eg, radiation or chemotherapy) is unknown.
ECHINOCOCCAL CYST — Echinococcal (hydatid) cysts of the liver are caused by the larval form of Echinococcus granulosus, which is usually acquired from infected dogs. These are fluid-filled structures limited by a parasite-derived membrane, which contains germinal epithelium (show figure 4). Hydatid cysts of the liver are uncommonly encountered in the United States. (See "Clinical manifestations and diagnosis of cystic and alveolar echinococcosis").
Patients are often asymptomatic. When symptoms do occur, they are usually due to the mass effect of an enlarging cyst or complications such as intraperitoneal leakage, infection, or biliary obstruction. E. granulosus cysts can rupture into the biliary tree and produce biliary colic, obstructive jaundice, cholangitis, or pancreatitis. (See "Endoscopic diagnosis and management of biliary parasitosis"). Pressure or mass effects on the bile ducts, portal and hepatic veins, or on the inferior vena cava can result in cholestasis, portal hypertension, venous obstruction, or the Budd-Chiari syndrome. (See "Etiology of the Budd-Chiari syndrome"). Liver cysts can also rupture into the peritoneum causing peritonitis, or transdiaphragmatically into the bronchial tree causing pulmonary hydatidosis or a bronchial fistula. Secondary bacterial infection of the cysts can result in liver abscesses. (See "Pyogenic liver abscess").
Detailed discussion on the clinical manifestations, diagnosis, and treatment of echinococcis are presented separately. (See "Clinical manifestations and diagnosis of cystic and alveolar echinococcosis" and see "Treatment and prevention of echinococcosis").
OTHER CYSTIC LESIONS OF THE LIVER — A variety of other cystic lesions of the liver have been described the clinical significance of which are variable.
Ciliated hepatic foregut cyst — A ciliated foregut cyst is a rare, benign solitary cyst consisting of ciliated pseudostratified columnar epithelium, subepithelial connective tissue, a smooth muscle layer, and an outer fibrous capsule. Unlike simple solitary cysts, they occur more frequently in men, and are found most commonly in the left lobe [38] . There are about 60 reported cases of ciliated foregut cyst, the size of which ranged from 0.4 to 9.0 cm. There are no cases reported of malignant transformation. The clinical importance of its diagnosis lies in the distinction from other potentially malignant hepatic lesions.
Primary squamous cell carcinoma — There are several reports of primary squamous cell carcinoma arising in hepatic cysts lined predominantly by stratified squamous epithelium. These lesions appear to have a poor prognosis, although the information in the literature is sparse [39,40] .
Liver metastases — Rarely, certain liver metastases may appear as cystic lesions, usually due to the occurrence of central necrosis. These include metastases from ovarian carcinoma, pancreas, colon, kidney, and neuroendocrine tumors.
Polycystic liver disease — Polycystic liver disease most often occurs in patients with polycystic kidney disease. The incidence of hepatic cysts in polycystic kidney disease increases with age from approximately 10 percent below the age of 30 to greater than 50 percent over the age of 60. The cysts, which appear to be derived from biliary epithelium, are more commonly observed in patients with advanced renal disease. (See "Extrarenal manifestations of autosomal dominant polycystic kidney disease", section on Hepatic cysts).
A less common disorder, autosomal dominant polycystic liver disease, is distinct from polycystic kidney disease, since it is not associated with kidney involvement or cerebral aneurysms. Two mutations have been found to cause this disorder: a mutation in the PRKCSH gene that encodes a protein called hepatocystin [41] , and a mutation in the SEC63 gene that encodes for a component of the protein translocation machinery in the endoplasmic reticulum [42] .
Biliary cysts — Biliary cysts are cystic dilatations, which may occur singly or in multiples throughout the bile ducts. They were originally termed choledochal cysts (involving the extrahepatic bile duct) but the clinical classification was revised in 1977 to include intrahepatic cysts. Infants with biliary cysts commonly present with conjugated hyperbilirubinemia (80 percent), failure to thrive, or an abdominal mass (30 to 60 percent). The triad of pain, jaundice, and abdominal mass is found in 11 to 63 percent. In contrast, chronic and intermittent abdominal pain appears to be the most common presenting symptom (50 to 96 percent) in patients older than two. (See "Biliary cysts").
SUMMARY AND RECOMMENDATIONS — Cystic lesions of the liver may pose a diagnostic and therapeutic dilemma. Simple cysts are by far the most common lesions encountered. Clinical features combined with typical sonographic findings are usually sufficient to distinguish simple cysts from other cystic lesions (show table 1). Needle aspiration is usually not required for diagnosis. On the other hand, certain clinical and radiologic features should raise suspicion for an alternative diagnosis such as cystadenoma, cystadenocarcinoma, or hydatid cyst (show table 2).
Large asymptomatic, non-complicated simple cysts should be monitored by periodic ultrasonography for the first two to three years following diagnosis. Significant growth, progressive symptoms, or any suspicion of neoplastic cyst mandate surgical intervention. In symptomatic patients, the possibility of coexisting pathology must be excluded. (See "Clinical manifestations and diagnosis of cystic and alveolar echinococcosis"). When symptoms are the only indication for surgery, selection of patients with truly symptomatic cysts is crucial before considering any intervention. The procedure of choice for simple cysts is laparoscopic wide unroofing. Percutaneous aspiration is ineffective and should be avoided. Prior to surgery, echinococcal cysts should be ruled out. On opening the cyst roof, close inspection of the interior for neoplastic components is extremely important. Any suspicion regarding underlying malignancy (eg, solid or thickened cyst wall, nodules, etc.) mandates a biopsy for frozen section histopathology.
Laparoscopic unroofing is usually curative for simple cysts. Enucleation may be sufficient for a cystadenoma, whereas formal hepatic resection is indicated for cystadenocarcinomas.
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