Factors influencing magnetic resonance imaging finding of endopelvic fascial edema after ultrasound-guided high-intensity focused ultrasound ablation of uterine fibroids

Figures & data

Figure 1. MRI sagittal view of a patient with uterine fibroid. (a) the distance from ventral surface of the fibroid to skin, (b) the distance from dorsal surface of the fibroid to sacrum, (c) thickness of abdominal wall.

Figure 2. The location of the endopelvic fascial edema. (a-d) MR images before USgHIFU ablation. (e) Anterior wall fascial edema; (f) posterior wall fascial, right lateral wall fascial, peri-vesical fascial, and perirectal fascial edema; (g) posterior wall fascial, left lateral wall fascial edema; (h) peri-uterine fascial, posterior wall fascial, and perirectal fascial edema.

Figure 3. A 44 years old patient with fibroid. (a-d) MRI images before USgHIFU ablation. (e-h) MRI images after USgHIFU ablation. (a) Pre-USgHIFU a sagittal T2WI image showed a posterior wall fibroid that is almost hyperintense on T2WI. (e-f) Fascial edema was shown as a high-intensity signal on T2WI and diffusion-weighted imaging (arrow).

Figure 4. Violin plot analysis of each quantitative parameter between the edema and non-edema groups (a–i). White dash lines represent median values. TD: therapeutic dose; EEF: energy efficiency factor

Table 1. Univariate analysis to evaluate the relationship between the endopelvic fascial edema and fibroid features.

Characteristics	edema group	non-edema group	p value
Number of patients (%)	556 (83.2)	112 (16.8)
Age, years (range)	42 (35–46)	40 (33–45)	0.173^a
Distance of ventral surface of the fibroid to skin in mm (range)	44.44 (33.09–61.95)	38.65 (31.22–52.85)	0.013^a
Distance of dorsal surface of the fibroid to sacrum in mm (range)	21.74 (12.69–36.17)	35.34 (19.87–53.00)	0.000^a
Thickness of abdominal wall in mm	26.36 ± 7.68	26.62 ± 7.28	0.743^b
Maximal diameter in cm (range)	6.32 (5.22–7.44)	5.65 (4.84–7.38)	0.011^a
Fibroid volume in cm^3 (range)	93.32 (55.59–171.74)	78.24 (41.63–150.93)	0.028^a
Number of ablated fibroids (range)	2 (1-3)	2 (1-3)	0.461^a
Position of uterine, n (%)			0.113^c
Anteverted and anteflexed	257 (38.5)	59 (8.8)
Anteverted and retroflexed	198 (29.6)	27 (4.0)
Retroverted and anteflexed	78 (11.7)	19 (2.8)
Retroverted and retroflexed	23 (3.4)	7 (1.0)
Location of fibroids, n (%)			0.000^c
Anterior wall	190 (28.4)	56 (8.4)
Posterior wall	180 (26.9)	13 (1.9)
Lateral wall	152 (22.8)	29 (4.3)
Fundus	34 (5.1)	14 (2.1)
Lateral location of fibroids, (n%)			0.868^c
Right	256 (38.3)	50 (7.5)
Mid-position	107 (16.0)	24 (3.6)
Left	193 (28.9)	38 (5.7)
Type of fibroids, n (%)			0.021^c
Submucosal	30 (4.5)	12 (1.8)
Intramural	449 (67.2)	78 (11.7)
Subserosal	77 (11.5)	22 (3.3)
T2WI, n (%)			0.003^c
Hypointense	111 (16.6)	30 (4.5)
Isointense	221 (33.1)	55 (8.2)
Hyperintense	224 (33.5)	27 (4.0)
Degree of enhancement, n (%)			0.000^c
Slight	199 (29.8)	64 (9.6)
Moderate	235 (35.2)	35 (5.2)
Significant	122 (18.3)	13 (1.9)

T2WI = T2-weighted imaging; n = number of patients.

^aFrom the Mann − Whitney U-test.

^bFrom the independent t-test.

^cFrom the χ² test.

Table 2. Univariate analysis to evaluate the relationship between the endopelvic fascial edema and ultrasound ablation parameters.

Variables	edema group (n = 556)	non-edema group (n = 112)	p value
Sonication power (W)	400 (400-400)	400 (400-400)	0.920^a
Sonication time (s)	1050 (727–1518)	682 (450–1000)	0.000^a
Treatment time (min)	108 (78–147)	81 (55–111)	0.000^a
Treatment intensity (s/h)	610.66 ± 157.35	533.85 ± 161.79	0.000^b
TD (J)	412575 (280000–60000)	260850 (176500–398100)	0.000^a
EEF (J/mm^3)	4.58 (3.29–6.18)	3.00 (2.27–4.71)	0.000^a
NPV (cm^3)	64.10 (36.84–121.05)	54.27 (30.74–93.20)	0.060^a
NPV ratio (%)	0.76 (0.63–0.86)	0.78 (0.67–0.87)	0.114^a

TD, therapeutic dose; EEF, energy efficiency factor; NPV, non-perfused volume; NPV ratio, the ratio (%) of NPV-to-fibroid volume.

In each category, numbers in the parentheses indicate the range.

^aFrom the Mann − Whitney U-test.

^bFrom the independent t-test.

Table 3. Multivariable binary logistic regression analysis to evaluate the correlation of fascial edema with the significant factors of univariate analysis.

Variables	B	SE	Wald	p value	Ors [Exp(B)]	95%CI		Collinearity statistics
						Lower	Upper	Tolerance	VIF
EEF	0.256	0.061	17.655	0.000	1.292	1.147	1.457	0.488	2.048
Location of fibroids								0.915	1.092
Anterior wall*			8.788	0.032
Posterior wall	0.707	0.358	3.888	0.049	2.028	1.004	4.094
Lateral wall	0.068	0.275	0.061	0.805	1.070	0.625	1.834
Fundus	−0.616	0.386	2.543	0.111	0.540	0.253	1.152
Dorsal surface of the fibroid to sacrum	−0.028	0.006	19.544	0.000	0.972	0.960	0.984	0.655	1.528
Degree of enhancement								0.859	1.164
Slight*			8.893	0.012
Moderate	0.618	0.247	6.252	0.012	1.856	1.143	3.013
Significant	0.779	0.344	5.125	0.024	2.179	1.110	4.278
constant	0.927	0.393	5.560	0.018	2.526

EEF, energy efficiency factor; B, regression coefficient; SE, standard error; Ors, odds ratios; VIF, variance inflation factor.

*indicates the contrast in binary logistic regression analysis.

Table 4. Summary of postprocedural adverse events.

SIR classification	Adverse events	Edema group (n = 556)	Non-edema group (n = 112)	p value
Class A	Vaginal discharge	150 (27.0%)	30 (26.8%)	0.967^a
	Lower abdominal pain	44 (7.9%)	8 (7.1%)	0.781^a
	Sacrococcygeal pain	26 (4.7%)	3 (2.7%)	0.489^a
	Odynuria	9 (1.6%)	3 (2.7%)	0.704^a
	Lower limb numbness /pain	7 (1.3%)	1 (0.9%)	1.000^a
	Erythema on skin	7 (1.3%)	1 (0.9%)	1.000^a
	Nausea and vomiting	3 (0.5%)	3 (2.7%)	0.062^b
	proctalgia	1 (0.2%)	0	1.000^b
Class B	Lower abdominal pain	49 (8.8%)	12 (10.7%)	0.524^a
	Sacrococcygeal pain	16 (2.9%)	2 (1.8%)	0.740^a
	Lower limb numbness /pain	15 (2.7%)	0	0.159^a
	Nausea and vomiting	10 (1.8%)	1 (0.9%)	0.779^a
	Erythema on skin	4 (0.7%)	0	1.000^b
Class C	Urinary retention	3 (0.5%)	0	0.996^b
Class D&E&F	–	0	0	–

^aFrom the χ² test.

^bFrom the Fisher’s exact test.

Table 5. Relationship between the pain-related adverse events and location of endopelvic fascial edema.

adverse events	Anterior fascia (n = 217)	Posterior fascia (n = 496)	Left lateral fascia (n = 200)	Right lateral fascia (n = 264)	Peri-vesical fascia (n = 113)	Peri-uterine fascia (n = 51)	Perirectal fascia (n = 78)
Lower abdominal pain	54 (24.9%)	89 (17.9%)	35 (17.5%)	50 (18.9%)	26 (23.0%)	9 (17.6%)	14 (17.9%)
Sacrococcygeal pain	6 (2.8%)	44 (8.9%)	19 (9.5%)	24 (9.1%)	4 (3.5%)	5 (9.8%)	17 (21.8%)
lower limb numbness/pain	6 (2.8%)	20 (4.0%)	8 (4.0%)	17 (6.4%)	6 (5.3%)	3 (5.9%)	6 (7.7%)
Odynuria	3 (1.4%)	7 (1.4%)	5 (2.5%)	4 (1.5%)	2 (1.8%)	2 (3.9%)	1 (1.3%)
proctalgia	0	1 (0.2%)	0	1 (0.4%)	0	0	1 (1.3%)

In the analysis of the correlation between pain-related adverse events and each location of endopelvic fascial edema, χ² test showed correlations of anterior fascia edema to lower abdominal pain, χ²=14.52, p = 0.000; anterior fascia edema to sacrococcygeal pain, χ²=8.96, p = 0.003; posterior fascia edema to sacrococcygeal pain, χ²=9.91, p = 0.001; perirectal fascia to sacrococcygeal pain, χ²=27.65, p = 0.000; right lateral fascia to lower limb numbness/pain, χ²=11.79, p = 0.001.

Detailed statistical test results are provided in the Supplementary Material.

Table 6. Relationship between the lateral location of fibroids and parietal fascial edema/lower limb discomfort.

	Right lateral fascial (present = 264/668)			Left lateral fascial (present = 200/668)			Lower limb numbness/pain (present = 23/668)
	With edema	Without edema	p value	With edema	Without edema	p value	With	Without	p value
Lateral location of fibroids, n (%)			0.000			0.000			0.016
Right	172 (65.1)	134 (33.2)		63 (31.5)	243 (51.9)		17 (73.9)	289 (44.8)
Left	48 (18.2)	183 (45.3)		109 (54.5)	122 (26.1)		3 (13.0)	228 (35.3)
Mid-position	44 (16.7)	87 (21.5)		28 (14.0)	103 (22.0)		3 (13.0)	128 (19.8)

From the χ² test.

Data availability statement

The data that support the findings of this study are available from the corresponding author, Furong Lv and Zhibo Xiao, upon reasonable request.