What is a septated cyst?

What is a Septated Cyst?

A septated cyst is a fluid-filled sac that contains one or more internal dividing walls (septa) that create multiple compartments within the cyst. According to the Ovarian-Adnexal Reporting and Data System (O-RADS), these are classified as multilocular cysts, defined as "cystic lesions with more than one compartment (at least one complete septum)" 1.

Characteristics of Septated Cysts

Anatomical Features

• Structure: Contains internal dividing walls (septa) that create multiple compartments
• Appearance on imaging: Shows internal lines or walls dividing the cyst into sections
• Classification: Multilocular when containing multiple compartments

Imaging Findings

• Ultrasound: Most sensitive for detecting septations 2

  • Appears as linear structures crossing the cystic space
  • Septations may be thin (<2mm) or thick (≥2mm)
  • May show blood flow within septations on color Doppler

• MRI: Provides detailed characterization

  • Can show varying signal intensities in different compartments
  • Helpful in distinguishing hemorrhagic content from other materials

• CT: Less sensitive than ultrasound for detecting thin septations 2

  • May show enhancement of septations with contrast

Clinical Significance

Risk Assessment

The presence and characteristics of septations help determine the risk of malignancy:

• Thin septations (<3mm): Generally considered benign 1
• Thick septations (≥0.5mm): Higher risk of malignancy, especially when combined with other concerning features 3
• Number of septations: Multiple septations without papillary projections are unlikely to be malignant 1

According to the O-RADS risk stratification system, septations are considered in the overall assessment:

• Thin septations alone are a minor worrisome feature
• Thick septations are a major worrisome feature 1

Common Types of Septated Cysts

1. Ovarian septated cysts:

   • Most common location for septated cysts in women
   • Often benign, especially with thin septations
   • Low risk of malignancy (1% in one study of 2,870 septated ovarian cysts) 4

2. Hepatic septated cysts:

   • May represent simple cysts with hemorrhage
   • Can be mucinous cystic neoplasms (MCNs) when combined with other features 1

3. Other locations:

   • Pancreatic cystic lymphangioma 5
   • Thoracic duct cysts 6
   • Breast cysts 3

Septations Due to Hemorrhage

Septations can sometimes form temporarily after hemorrhage into a cyst:

• Hemorrhagic cysts may show "thin mobile septations" on ultrasound 1
• These septations represent blood clots and typically do not enhance on contrast imaging
• On MRI, hemorrhagic septations appear hyperintense on T1-weighted images 1

Management Considerations

Management depends on:

1. Location of the cyst
2. Thickness of septations
3. Presence of other concerning features
4. Patient symptoms

For ovarian septated cysts:

• Simple septated cysts without solid components can often be followed with imaging surveillance 4
• Thick septations (≥2mm) may warrant closer follow-up or consideration of surgical evaluation

For hepatic septated cysts:

• MRI is recommended to characterize cysts with worrisome features 1
• Combination of thick septations with other features (nodularity, upstream biliary dilatation) raises concern for mucinous cystic neoplasm 1

Potential Pitfalls

• Hemorrhagic cysts can mimic neoplastic septated cysts due to blood clot formation
• Ultrasound is more sensitive than CT for detecting septations 2
• Septations alone should not trigger immediate intervention without considering other features
• Complicated cysts (with hemorrhage or infection) may present with imaging findings that mimic neoplastic cysts 1

In summary, septated cysts are fluid-filled structures containing internal dividing walls that create multiple compartments. Their clinical significance varies based on location, septation characteristics, and associated features, with management ranging from observation to surgical intervention depending on the overall risk assessment.