Objective:To measure the distance between the fetal bladder neck and the rectal end using prenatal MRI and analyze the developmental patterns of this distance and the gender differences in the second and third trimesters of pregnancy.Methods:This retrospective cohort study involved fetuses born at Guangzhou Women and Children's Medical Center, Guangzhou Medical University after regular prenatal examinations from January 2019 to December 2022 and confirmed to have typical anorectal structures after birth. These fetuses had undergone prenatal MRI examinations for reasons other than abdominal issues. The morphology of the fetuses' colons, rectums, and bladders was observed, and the vertical distance between the bladder neck and the rectal end was measured on sagittal T1weighted imaging. Differences in the distance between male and female fetuses were analyzed. The fetuses were divided into five groups based on their gestational age at the time of MRI examination (23-24 weeks, >24-26 weeks, >26-28 weeks, >28- 30 weeks, and >30-32 weeks), and the changes in the distance with gestational age were analyzed. Statistical analysis was performed using t-test, Kruskal-Wallis test, and Spearman correlation analysis. Pairwise comparisons among multiple groups were conducted using the Bonferroni method. Results:(1) A total of 142 fetuses were included in this study, all of which were singletons, with 73 males (51.4%) and 69 females (48.6%). The gestational age at the MRI examination was 28 weeks (26-30 weeks). (2) All fetuses had meconium filling the entire rectum and colon, with the rectal end located 0.570-2.610 cm below the bladder neck. (3) The distance between the bladder neck and the rectal end was shorter in male fetuses than in female fetuses [(1.140±0.261) vs. (1.519±0.405) cm, t=－6.58, P<0.001]. (4) In female fetuses, four pairs of groups showed statistically significant differences in the distance (23-24 weeks group vs. >26-28 weeks, >28- 30 weeks, and >30-32 weeks groups, and >24-26 weeks group vs. >30-32 weeks group). However, only two groups of male fetuses (23-24 weeks group vs. >28-30 weeks group) had statistically significant differences in the distance (all P<0.005). (5) The distance was moderately correlated with gestational age in male fetuses ( r=0.42, P<0.001), but they were strongly correlated in female fetuses ( r=0.66, P<0.001). Conclusions:The distance between the bladder neck and the rectal end in fetuses shows certain developmental patterns and gender differences in pregnancy's second and third trimesters. The correlation between the value and gestational age is stronger in female fetuses.

Objective:To measure the distance between the fetal bladder neck and the rectal end using prenatal MRI and analyze the developmental patterns of this distance and the gender differences in the second and third trimesters of pregnancy.Methods:This retrospective cohort study involved fetuses born at Guangzhou Women and Children's Medical Center, Guangzhou Medical University after regular prenatal examinations from January 2019 to December 2022 and confirmed to have typical anorectal structures after birth. These fetuses had undergone prenatal MRI examinations for reasons other than abdominal issues. The morphology of the fetuses' colons, rectums, and bladders was observed, and the vertical distance between the bladder neck and the rectal end was measured on sagittal T1weighted imaging. Differences in the distance between male and female fetuses were analyzed. The fetuses were divided into five groups based on their gestational age at the time of MRI examination (23-24 weeks, >24-26 weeks, >26-28 weeks, >28- 30 weeks, and >30-32 weeks), and the changes in the distance with gestational age were analyzed. Statistical analysis was performed using t-test, Kruskal-Wallis test, and Spearman correlation analysis. Pairwise comparisons among multiple groups were conducted using the Bonferroni method. Results:(1) A total of 142 fetuses were included in this study, all of which were singletons, with 73 males (51.4%) and 69 females (48.6%). The gestational age at the MRI examination was 28 weeks (26-30 weeks). (2) All fetuses had meconium filling the entire rectum and colon, with the rectal end located 0.570-2.610 cm below the bladder neck. (3) The distance between the bladder neck and the rectal end was shorter in male fetuses than in female fetuses [(1.140±0.261) vs. (1.519±0.405) cm, t=－6.58, P<0.001]. (4) In female fetuses, four pairs of groups showed statistically significant differences in the distance (23-24 weeks group vs. >26-28 weeks, >28- 30 weeks, and >30-32 weeks groups, and >24-26 weeks group vs. >30-32 weeks group). However, only two groups of male fetuses (23-24 weeks group vs. >28-30 weeks group) had statistically significant differences in the distance (all P<0.005). (5) The distance was moderately correlated with gestational age in male fetuses ( r=0.42, P<0.001), but they were strongly correlated in female fetuses ( r=0.66, P<0.001). Conclusions:The distance between the bladder neck and the rectal end in fetuses shows certain developmental patterns and gender differences in pregnancy's second and third trimesters. The correlation between the value and gestational age is stronger in female fetuses.

Objective:To evaluate the value of MRI in the diagnosis of jejunal and ileal atresia in fetus.Methods:This study included thirteen neonates with surgically and pathologically confirmed jejunal or ileal atresia without other gastrointestinal diseases treated in our institution between January 1, 2010 and December 31, 2018. MRI was performed on all fetuses subsequent to routine prenatal sonographic examinations indicated bowel dilation or ascites. MR images were analyzed by two radiologists,and MRI diagnosis was compared with surgical and pathological results.Results:On prenatal MRI, eight fetuses exhibited single or multiple dilated small bowel loops, one of them exhibited a cystic mass in the abdomen; five fetuses exhibited massive ascites, and collected bowels. On final surgical and pathological diagnosis, nine fetuses had ileal atresia, five of them had intestinal perforation; four fetuses had jejunal atresia, one of them had intestinal perforation and a meconium pseudocyst. Among the 7 cases without intestinal perforation, the atresia location was diagnosed correctly in 5 cases. The 6 fetuses with intestinal perforation were diagnosed as intestinal atresia and meconium peritonitis by prenatal MRI, but the location of atresia could not be determined.Conclusions:Jejunal and ileal atresia have their characteristic manifestations on prenatal MRI. The location of atresia can be inferred from the distribution of amniotic fluid and meconium in the intestine. Prenatal MRI has a complementary role in the assessment of fetal bowel abnormalities after standard obstetric ultrasound.

Objective To explore the value of MRI in diagnosis of fetal meconium peritonitis.Methods Seven meconium peritonitis fetuses proved by surgery and pathology were enrolled.The prenatal MRI findings and clinical data were analyzed retrospectively.Results Six fetuses showed a large amount of ascites,intestinal tube floating in the abdomen,small intestine gathered together.One fetus showed a giant abdominal cystic mass,with bowel compressed,displaced and uneven dilated.Four fetuses showed small colon and rectum,or without meconium signal.Two fetuses were accompanied by bilateral hydrocele.Amniotic fluid increased in 3 cases.After the neonates were born,1 case of them died from sudden heart rate decline during operation,1 case died from severe pulmonary edema after operation,and 5 cases survived after operation.Conclusion MRI has some features in the prenatal diagnosis of meconium peritonitis,which can provide an important basis for postpartum treatment and evaluation of prognosis.