Cystic Lesions of Liver

DEFINITION
Simple cysts
Complex cysts
Polycystic liver disease
Traumatic cysts
Ciliated hepatic foregut cyst
Also see hydatid disease

[Exam imaging classification for liver lesions
Consider / classify as hypervascular or hypovascular]
--> aids rapid differential

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EPIDEMIOLOGY

Varies by cause
Overall a common finding.
- often incidental posing difficult decisions for surgeons.

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AETIOLOGY

Classification
Several schemes proposed.
True vs false
- true = congenital and acquired cysts
- false = abscesses and posttraumatic haematoma or biloma.

Congenital
- simple cysts (up to 5% incidence)
- polycystic diseases
- either associated with AD PCKD
- or autosomal-dominant polycystic liver disease without renal cysts
- bile-duct related; Caroli disease, bile duct duplication, peribiliary cysts

Acquired
- Infective, e.g. echinococcal
- Tumour;
--> primary, e.g. cystadenoma, cystadenocarcinoma, other (cystic sarcoma, SCC)
--> secondary; e.g. metastatic mucinous neoplasms from pancreas, ovary
--> or cystic degeneration of metastases from colon, pancreas, neuroendocrine tumours.
Trauma
- hematomas and bilomas
--> can be seen years after trauma; may have resulted from blood or bile leak.
--> gen. manage conservatively unless biliary complications

Ciliated Hepatic Foregut Cysts
Oddball; extremely rare.
detachment and migration of resp epithelium during embryogenesis; segment IV us.
Ciliated pseudo-stratified columnar epithelium.
Benign but with malignant potential; resect.


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BIOLOGICAL BEHAVIOUR

Pathogenesis
Simple cysts
Probably abnormal embryonal development of intrahepatic biliary ducts
- which lack a connection to their extrahepatic counterparts
Histologically = single layer of columnar or cuboidal epithelium with minimal stroma.
- contains straw-colored serous fluid without bile; similar to serum.
Can be single or several.
Polycystic
No widely accepted way to differentiate multiple simple cysts from polycystic disease.
Generally diffuse hepatic involvement, familial pattern, several organs.
Genetic basis has 2 disorders
- AD PCKD and AD PCLD (without renal involvement)
- in 40-90% of PCKD, probably all if lived long enough (variable penetrance)
- PCLD rarer cf PCKD cause
Cysts are thought to result from bile duct overgrowth and failure of intralobular to connect with extralobular ducts.
--> biliary microhamartomas called von Meyenburg complexes
--> cell proliferation and fluid secretion lead to cyst formation.

Pathophysiology

Simple cysts
Almost always asymptomatic
Size from 5-20cm

Polycystic
Asymptomatic until advanced disease develops
- then develop abdo pain and fullness in RUQ
Hepatic failure rare (unlike kidneys in polycystic renal disease)
- then in rare circumstances needs transplant
But mass effect can be serious.
- obstruction of IVC, with lower limb oedema or Budd Chiari
- portal vein with ascites, portal hypertension
- jaundice
- cyst infection is uncommon but potentially very serious.
Associated with PCKD and intracranial aneurysms.

Cystadenomas
Rare.
Predominantly asymptomatic, benign cysts but with malignant potential (--> cystadenocarcinoma).
Often detected incidentally on imaging.
Slow growing, multilocular; can grow as much as 20cm
Lined by cuboidal / columnar epithelium, surrounded by thickened stroma
Mesenchymal tissue secures diagnosis

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MANIFESTATIONS

Simple
Vast majority asymptomatic
Symptomas can result from large cysts mass effect
RUQ pain, early satiety and abdo fullness
- us. when lesions >8cm
Haemorrhage into a cyst can cause pain.

Cystadenoma
If large, RUQ fullness
Mass effect can be on GI or biliary tract

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INVESTIGATIONS

Imaging

USS

Simple cysts = thin walled, non-enhancing, hypodense, no septations, normal CEA CA 19-9 in fluid, may contain blood or bile
Neoplastic cysts = thick, irregular, papillary projections, multilocular, higher density, mucinous fluid; elevated CEA or CA 19-9 in fluid.
Can delineate cyst complications.

CT
Very useful for cysts; go triple phase.
Anatomy, complications / relationships.
Hepatic cysts are non-enhancing on CT, should show well defined borders and no wall or cyst content.
Simple cysts contain low-density fluid (<10HU) that is homogenous.
Suspicious cysts show higher density fluid (>10HU) inhomogenous fluid and irrefular wall, septations and papillary projections.

MRI
MRI very useful for complex lesions.
Contrast 'primovist' useful; taken up by hepatocytes and secreted into bile ducts, making a useful additional tool
Simple cysts are hypointense on T1 and hyperintense on T2
Haemorrhage into a cyst can increase T1 signal, as can mucinous material.
MRCP for delineating biliary anatomy.
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MANAGEMENT

Conservative

Simple cysts
Simple small cysts need no Rx
Rule out serious disease
In poor operative candidates, aspirated and injected with sclerosing agent.
Aspiration without sclerosing agent = 100% recurrence rate
Sclerosing agents include ethanol, hypertonic saline, with comparable results.
- us. 25% of the cyst volume, max 100mL is instilled.  Drained after 10min of periodically changing position to get fluid in contact with whole cyst wall.
- complications are usually minor, include pain, fever nausea and vomiting.
- recurrence then only 5-10%

Operative
Simple cysts
Surgical Rx highly effective; reserved for patients with symptoms or recurrent complex cysts.
Surgery should be first line treatment for these options.
E.g. symptomatic cysts >5cm:
- laparoscopic or open cyst unroofing.
- unroofing, fenestration and marsupialization all refer to basically the same thing.
--> take large portion of cyst wall; fluid drains into cavity to be reabsorbed by the peritoneum.
- examine cyst wall carefully for malignant nodules or irregularities
- if contents bilious, explore, identify communication with biliary system and ligate
- optimal results when cyst opened widely, much of wall resected or ablated, but be careful not to damage healthy liver.
- laparoscopic approach is possible and usually allows excellent visualization.
Enucleation and formal resection associated with much higher morbidity.

Polycystic liver disease
Used to be treated at end stage; poor outcomes due to high morbidity; now advocated that an earlier aggressive approach advisable.
Drugs that reduce secretin release (somatostatin) may help but remain unsupported by evidence.
Combination of fenestration and resection may be appropriate.
- higher morbidity but more durable results in terms or relapse and symptoms.
Transplantation gaining acceptance for sever disease.

Cystadenomas
Consider surgery, especially if growth.
Remove in entirety as risk of malignant transformation; do not unroof.
Enucleation ok, but formal resection if malignancy considered possible.
Careful pathologic evaluation should include examination for intestinal metaplasia.
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REFERENCES
Cameron 10th