Differential Diagnoses for Irregular Uterus with Hypodensities and Calcifications Post-Endometrial Ablation
In a patient with prior endometrial ablation presenting with an irregular uterus containing hypodensities and calcifications on CT, the primary differentials include post-ablation changes (necrotic debris, fibrosis, hematometra), adenomyosis, uterine fibroids (leiomyomas) with degeneration or calcification, and less commonly, retained necrotic tissue or complications such as cornual hematometra.
Expected Post-Ablation Changes
The CT findings may represent normal sequelae of endometrial ablation rather than pathology:
Ablative necrosis and fibrosis are common findings that can persist for months after the procedure, appearing as hypodense material within the uterine cavity and dense fibrosis/hyalinization of the endometrial surface 1, 2.
Calcifications can develop as part of the healing process, particularly in areas of necrotic tissue or chronic inflammation 1.
Hysterectomies performed within the first year post-ablation demonstrate necrosis, fibrosis, and vascular changes, with abundant necrotic tissue of myometrial origin found in 28% of cases 1.
The time interval from ablation matters: hysterectomies performed earlier (mean 5 months) show more prominent fibrosis compared to those performed later (mean 22 months), which show less fibrosis 1.
Adenomyosis
This is a critical differential given its high prevalence in ablation patients:
Adenomyosis is found in 40% of post-endometrial ablation hysterectomy specimens and is significantly associated with continued bleeding after ablation 1, 2.
Adenomyosis can cause an irregular, heterogeneous myometrial appearance on CT and may contribute to treatment failure 2, 3.
The presence of adenomyosis may explain persistent symptoms and the irregular uterine contour, as endometrial tissue within the myometrium can regenerate and cause bleeding 2.
Uterine Fibroids (Leiomyomas)
Fibroids are common and may coexist with prior ablation:
Extensive leiomyomas or diffuse leiomyomatosis were found in 12% of post-ablation hysterectomy specimens 1.
Calcified fibroids are particularly well-visualized on CT and can appear as hyperdense calcifications within hypodense masses 4.
CT is helpful when calcified masses cause shadowing that limits ultrasound visualization 4.
Fibroids may undergo degeneration, necrosis, or torsion, appearing as hypodense areas with diminished contrast enhancement 4.
Hematometra and Post-Ablation Complications
Long-term complications specific to endometrial ablation should be considered:
Central or cornual hematometra can develop when intrauterine scarring obstructs bleeding from persistent or regenerating endometrium behind the scar 5.
Post-ablation tubal sterilization syndrome may occur, particularly in patients with prior tubal ligation, causing obstructed menstrual flow and hematometra 5, 2.
These complications are likely underdiagnosed because many radiologists are not educated about the specific findings of cornual hematometra and post-ablation syndrome 5.
Residual endometrium in the cornual regions is a common finding that can lead to continued bleeding and fluid accumulation 2.
Incomplete Ablation
Ablation changes present only in the lower uterine segment with sparing of the fundus or cornual regions can result in persistent endometrium and continued bleeding 2.
Residual endometrium is found more frequently in hysterectomies performed later (mean 13 months) compared to those performed earlier (mean 2 months) 1.
Vascular Abnormalities
The uterine cavity may be lined by superficial, large, congested, patent blood vessels with atherosis following ablation 2.
Patients with these superficial abnormal vessels have a shorter ablation-to-hysterectomy interval (median 2 months vs. 18 months without such vessels) 2.
Less Common Considerations
Endometrial cancer should always be considered, though the ablation procedure itself makes diagnosis more challenging due to scarring and obstruction 5.
Tubal endometriosis after prior tubal ligation can contribute to pelvic pain 2.
Recommended Next Steps
MRI pelvis provides superior soft-tissue detail compared to CT and is the problem-solving modality of choice for evaluating post-ablation complications, adenomyosis, and fibroid characterization 4.
Transvaginal ultrasound should be performed if not already done, as it is the first-line imaging modality for uterine pathology 6.
Clinical correlation is essential: the presence of symptoms (bleeding, pain) versus incidental findings will guide management 1, 2.