What are the complications of Focal Nodular Hyperplasia (FNH)?

Complications of Focal Nodular Hyperplasia

Focal nodular hyperplasia has an extremely low complication rate, with spontaneous rupture being exceedingly rare (only one case reported in the literature) and no routine monitoring required during pregnancy or with oral contraceptive use. 1, 2

Primary Complications

Spontaneous Rupture and Hemorrhage

• Rupture is the most serious but exceptionally rare complication, with only one case of hepatic rupture documented in contemporary literature 1, 2
• Historical data from 1975-2007 identified only five cases of spontaneous rupture and bleeding 3
• Size appears to correlate with rupture risk, with large lesions (>5 cm) potentially warranting consideration for intervention even when asymptomatic 3
• When rupture occurs, it can present as acute abdomen requiring emergency evaluation 3

Pain and Discomfort

• Epigastric or right upper quadrant pain represents the most common symptomatic presentation when complications occur 4, 5
• Pain is an indication for potential intervention only when no other identifiable cause exists and symptoms are clearly attributable to FNH 4
• In conservative management series, patients with FNH-related pain did not experience worsening of symptoms over time 6

Compression of Adjacent Structures

• Large lesions can cause mass effect on nearby anatomical structures including the hepatic vein, stomach, and biliary system 4
• This complication is size-dependent and typically occurs only with substantial lesions 4

Lesion Growth

• Progressive enlargement during follow-up occurs rarely and may necessitate intervention 6
• In one series, only 1 of 54 patients (1.9%) required treatment for lesion growth during mean follow-up of 35.5 months 6
• During pregnancy specifically, FNH size remained constant or decreased in most patients with no FNH-related complications 2

Coexisting Conditions

• FNH coexists with other vascular hepatic lesions (particularly hepatic hemangiomas) in up to 20% of cases 1, 2
• Prevalence is 100-fold greater in patients with hereditary hemorrhagic telangiectasia compared to the general population 2
• Rare association with multiple hepatic adenomas has been reported 3

Critical Clinical Pitfalls

Misdiagnosis Risk

• FNH can be mistaken for hepatocellular carcinoma, particularly when the liver appears nodular or when atypical imaging features are present 2, 3
• The prime differential diagnoses include hepatocellular adenoma (which carries significant rupture risk), hepatocellular carcinoma, and hypervascular metastases 7
• Misdiagnosis can lead to unnecessary surgical intervention, as occurred in a reported case where FNH with multiple adenomas was misdiagnosed as ruptured HCC with intrahepatic spreading 3

Pregnancy and Hormonal Considerations

• Unlike hepatic adenomas, FNH does not require monitoring during pregnancy regardless of size 1, 2
• Pregnancy is not contraindicated, and vaginal delivery carries no increased risk 2
• The association with oral contraceptives is not well established, and current guidelines do not consider hormonal exposure causally related to FNH development or growth 2

Management Implications

Conservative management is effective in 94.4% of cases, with only 5.5% requiring any therapeutic intervention 6

Indications for Intervention

• Persistent pain with no other identifiable cause 4
• Large or progressively growing lesions with risk of causing complications 4
• Lesions >5 cm that are symptomatic may warrant consideration for resection, though this remains controversial 3

Treatment Options When Needed

• Surgical resection 4
• Radiofrequency ablation 4
• Arterial embolization 4

The key distinction from hepatic adenomas is critical: while adenomas ≥5 cm require prophylactic treatment before pregnancy due to rupture risk, FNH of any size requires no special surveillance or pre-pregnancy intervention 1, 2