National registry of thoracoamniotic shunting using a double-basket catheter: A post-marketing surveillance registry of 295 patients with fetal hydrothorax.

OBJECTIVE: We report on the 1-year outcomes of fetuses who underwent thoracoamniotic shunting (TAS) with a double-basket catheter for fetal hydrothorax (FHT) using a national post-marketing surveillance registry. METHODS: This surveillance study was conducted for cases enrolled between 2011 and 2019. Preoperative, operative, and postoperative findings and outcomes had to be reported through the national surveillance website. RESULTS: Forty-three institutes enrolled 295 patients. In 60 patients, associated abnormalities were diagnosed after birth. Among the 235 patients with isolated hydrothorax, the survival rate at 1 year of age was 70.5%. Among these patients, 89% did not require oxygen or other respiratory support. The 1-year survival rate in complicated cases was 27%. Trisomy 21 was the most common associated problem (40%). Catheter associated problems, including dislocation (25%), obstruction (24%), and preterm rupture of the membranes (6%) were observed, but there were no severe maternal complications. TAS before 29.5 weeks of gestation (odds ratio [OR] 0.16) and skin edema and ascites (OR 0.06) were risk factors for death at one year, whereas appropriate shunt location for >28 days (OR 4.2) was a protective factor. CONCLUSION: We report a favorable survival rate in fetuses with isolated FHT treated with this double-basket catheter.

Retrospective study of umbilical cord ulceration related to congenital intestinal atresia: A single-center report.

AIM: Umbilical cord ulceration (UCU) is a disease in which an ulcer forms in the umbilical cord in the pregnant uterus and is accompanied by hemorrhaging from the same site. UCU occurs in fetuses with congenital upper-intestinal atresia (CUIA); however, its onset mechanism remains unclear. Here, we report our investigation of cases of UCU in our hospital. METHODS: Among the 9825 deliveries performed between 2007 and 2016 at this hospital, 20 fetuses were diagnosed with CUIA, 4 (20%) of which had UCU. There was no difference in the backgrounds of the fetuses with UCU (UCU group: 4 fetuses) and those without (non-UCU group: 16 fetuses). RESULTS: There was no intergroup difference in gestational age at delivery. Four cases in the UCU group had maternal age 35 weeks (26-39), weeks of delivery 35 weeks (35-36) and weight 2178.5 g (1600-2640); three out of four fetuses were female; and the location of gastrointestinal obstruction was in the duodenum in one case and in the jejunum in three cases. Death occurred in three of four fetuses in the UCU group versus none in the non-UCU group. CONCLUSION: We performed a retrospective statistical investigation on the risk of UCU onset in cases from this hospital; however, we could not identify any prognostic factors for its onset. We investigated a total of 27 past reported UCU cases and the 4 cases in this study. Mean gestational age at onset was 33.3 ± 2.7 for all 27 cases. Various methods for the early discovery of UCU have been reported in the past; however, there is currently no gold standard. Based on this report and a review of past papers, for CUIA, it is desirable to perform in-hospital management from gestational week 30 onward and decide proper delivery timing on a case-by-case basis.

Study of the utility and problems of common iliac artery balloon occlusion for placenta previa with accreta.

AIMS: We investigated whether common iliac artery balloon occlusion (CIABO) was effective for decreasing blood loss during cesarean hysterectomy (CH) in patients with placenta previa with accreta and was safe for mothers and fetuses. METHODS: Of the 67 patients who underwent CH for placenta previa with accreta at our facility from 1985 to 2014, 57 patients were eligible for the study. The amount of intraoperative bleeding during CH was compared between three groups: surgery without blood flow occlusion (13 patients), internal iliac artery ligation (15 patients) and CIABO (29 patients). Additionally, multivariate analysis was performed to assess risk factors for massive bleeding during CH. RESULTS: The mean blood loss in the CIABO group (2027 ± 1638 mL) was significantly lower than in the other two groups (3787 ± 2936 mL in the no occlusion, 4175 ± 1921 mL in the internal iliac artery ligation group; P < 0.05). Multivariate analysis showed that spontaneous placental detachment during surgery (odds ratio [OR] 49.174, 95% confidence interval [CI] 4.98-1763.67), a history of ≥ 2 cesarean sections (OR 9.226, 95% CI 1.07-231.15) and no use of CIABO (OR 26.403, 95% CI 3.20-645.17) were significantly related to massive bleeding during surgery. There was no case of necrosis resulting from ischemia. The mean radiation dose during balloon placement never exceeded the threshold value for fetal exposure. CONCLUSION: Bleeding during CH for placenta previa with accreta can be decreased by CIABO. This study also confirmed the safety of CIABO in regard to maternal lower limb ischemia and fetal radiation exposure during balloon placement.

Diagnosis and potential management of gestational diabetes mellitus using the International association of diabetes and pregnancy study groups criteria.

AIM: Appropriate screening and plasma glucose control is important during pregnancy, but an international consensus has not been reached regarding the recommended method of screening and diagnosis of gestational diabetes mellitus (GDM). We investigated glucose intolerance in pregnant women diagnosed with GDM, applying stricter screening criteria. METHODS: The study involved 452 women with singleton pregnancies, who underwent a 2 h 75 g oral glucose tolerance test between January 2006 and December 2010. They had previously been screened for GDM using Japan Society of Obstetrics and Gynecology (JSOG) criteria. We retrospectively re-evaluated their status using International Association of Diabetes and Pregnancy Study Groups (IADPSG) criteria. The major differences between JSOG and IADPSG criteria are the number of applicable threshold values, and the threshold value for fasting glucose measured by the glucose tolerance test. The insulinogenic index and insulin resistance according to the homeostasis model assessment were compared among groups in the presence or absence of obesity. RESULTS: GDM was diagnosed in 56 (1.07%) and 133 (2.54%) women based on the JSOG and IADPSG criteria, respectively. Compared to non-GDM, non-obese women, those diagnosed with GDM according to IADPSG criteria had significantly higher insulin resistance, while those diagnosed with GDM exceeding two or more threshold values had significantly lower insulinogenic indexes. CONCLUSION: Adopting stricter diagnostic criteria increased the prevalence of GDM 2.37-fold, as women previously diagnosed with milder abnormalities in glucose levels were then diagnosed as having GDM.

Recent trend of acute appendicitis during pregnancy.

PURPOSE: We report the clinical presentation, management and outcomes of 33 patients who underwent surgery for acute appendicitis during pregnancy between April 1997 and March 2011. METHODS: Several variables were compared between these 33 patients (pregnant group, n = 33) and non-pregnant females aged 20-40 years who underwent an acute appendectomy during the same period (control group, n = 124). RESULTS: No significant differences were found between the two groups in terms of the type of anesthesia, operative method, duration of surgery, pathology, duration of antibiotic use, and incidence of surgical site infection, except for a higher frequency of pararectal incision performed and higher leukocyte counts in the pregnant group (P < 0.01). Tocolytic agents were administered to 17 patients (52%). Preterm labor occurred in 10 patients (30%), one of whom experienced preterm delivery. CONCLUSIONS: These results suggest that acute appendicitis during pregnancy can be managed successfully without fetal loss.

Thoracoscopy-assisted removal of a thoracoamniotic shunt double-basket catheter dislodged into the fetal thoracic cavity: report of three cases.

The indications for and timing of surgical removal of a dislodged thoracoamniotic shunt double-basket catheter are not established, and the side effects of the dislodged into the thoracic cavity remain controversial. The double-basket catheter was designed to reduce the incidence of catheter dislodgement; however, we have encountered four cases of thoracoamniotic shunt double-basket catheter dislodgement into the fetal thorax. The dislodged shunt catheters were removed safely with thoracoscopic assistance within several days of birth, when additional treatments for pleural effusion were needed, such as thoracic drainage tube insertion and adhesion treatment of the thorax. We report the clinical courses of three of these cases of thoracoamniotic shunt tube dislocation. By waiting several days postnatally for stabilization of respiratory and circulatory status and the effective use of thoracoscopic assistance, the dislodged catheter was safely removed from the neonatal thorax. The accumulation of case reports will help establish suitable treatments, and their indication, for a dislodged thoracoamniotic shunt catheter within the fetal thoracic cavity.

Efficacy of well-planned management in patients with incarcerated gravid uterus: A case series and literature review.

OBJECTIVE: Incarcerated gravid uterus is a condition in which uterine myoma and intraperitoneal adhesion lead to persistent uterine retroversion. Accurate diagnosis before cesarean section is crucial so that the procedure can be planned with regard to the spatial relationship between the uterine incision and other organs. This study investigated the effects of well-planned management on the outcome of cesarean sections. MATERIALS AND METHODS: Four patients with incarcerated gravid uterus who received well-planned management and preoperative magnetic resonance imaging were compared with three unexpected patients who were operated without preoperative diagnosis. RESULTS: In the preoperatively diagnosed group, compared with the non-preoperatively diagnosed group, the frequency of cervical canal damage tended to be lower (0% vs. 100%), blood loss tended to be less (1171 ± 290 mL vs. 2000 ± 300 mL), and surgery duration tended to be shorter (82 ± 17 min vs. 147 ± 84 min). None of the preoperatively diagnosed cases required allogeneic blood transfusion, and no organ damage was observed. CONCLUSION: The early detection of a suspected incarcerated uterus, and a thorough understanding of diagnostic methods and the use of preoperative magnetic resonance imaging and ultrasonography facilitate the safe performance of a cesarean section.

Limitations of internal iliac artery ligation for the reduction of intraoperative hemorrhage during cesarean hysterectomy in cases of placenta previa accreta.

AIM: Our purpose was to evaluate the effect of internal iliac ligation as a bleeding control during cesarean hysterectomy for placenta accreta. METHODS: We retrospectively reviewed the cases of placenta accreta receiving cesarean hysterectomy during the period of 1987-2006 in the Saitama Medical Center. The clinical outcomes of these patients either receiving or not receiving internal iliac artery ligation were compared in terms of bleeding amount, and length of hospitalization. The bleeding amounts in the variants of placenta accreta managed with internal iliac artery ligation were also analyzed to determine whether the different pathological findings would affect blood loss during cesarean hysterectomy. RESULTS: Among 23 cases, the mean blood loss during the operation and the length of hospitalization after the operation, with or without internal iliac artery ligation (IIAL) were not significantly different. There was no significant difference between the mean blood loss and the pathological findings of cases managed with IIAL. CONCLUSION: In cases of placenta previa accreta, ligation of the internal iliac artery did not significantly contribute to hemostasis during cesarean hysterectomy.

Late-onset ovarian hyperstimulation syndrome developing during ovarian stimulation in an ectopic pregnancy: a case report.

BACKGROUND: Ovarian hyperstimulation syndrome is normally induced by ovarian stimulation drugs. Severe cases of ovarian hyperstimulation syndrome involve complications such as renal failure and thrombosis. Evidence has recently been developed for a method to prevent ovarian hyperstimulation syndrome. Most cases of ovarian hyperstimulation syndrome are of an early-onset type, which occurs shortly after injection of human chorionic gonadotropin. However, late-onset ovarian hyperstimulation syndrome, which occurs in a pregnancy cycle, also requires caution. We report our experience in treating a woman who was transported to our hospital with a severe case of ovarian hyperstimulation syndrome occurring during ovarian stimulation and who was determined to have an ectopic pregnancy. CASE PRESENTATION: Assisted reproductive technology was planned for a 29-year-old nulligravida Japanese woman diagnosed with bilateral fallopian tube obstruction and right-sided hydrosalpinx. On day 1 of controlled ovarian stimulation, the result of her human chorionic gonadotropin urine test was negative, and her serum levels of luteinizing hormone, estradiol, and progesterone were normal. On day 11 of controlled ovarian stimulation, the levels of estradiol and progesterone had risen to 9679 pg/ml and 16 ng/ml, respectively, prompting suspension of controlled ovarian stimulation. Eleven days after controlled ovarian stimulation was suspended, the patient demonstrated ascites that did not improve despite administration of cabergoline, and she was transported to our hospital 2 days after. Late-onset ovarian hyperstimulation syndrome suggested that she was pregnant, and her serum human chorionic gonadotropin level was 27,778 IU/ml. She underwent laparoscopic bilateral salpingectomy and was diagnosed with right tubal pregnancy. CONCLUSION: In an ectopic pregnancy, human chorionic gonadotropin sometimes increases later than in an intrauterine pregnancy. In our patient's case, endogenous human chorionic gonadotropin following the start of controlled ovarian stimulation may have caused late-onset ovarian hyperstimulation syndrome. The key to early detection of similar cases may be to suspect pregnancy in the event of unexpectedly high progesterone levels during ovarian stimulation.

Modified underlying cardiac disease severity in twin-twin transfusion syndrome.

Twin-twin transfusion syndrome or related conditions affect fetal loading. We report monochorionic-diamniotic twins. Twin 1 had Ebstein anomaly with mild tricuspid regurgitation (TR) and slightly thickened tricuspid valve leaflets with plastering. Twin 2 had tricuspid valve dysplasia (with abnormal thickening but without plastering) with moderate TR and mild right atrial dilatation. After birth, the severity of TR was greatly reduced in the recipient but increased in the donor. Therefore, intravascular volume change which was due to twin-twin transfusion syndrome seemed to affect the severity of the valvar disease in fetuses. This case suggests that the intrinsic severity of fetal tricuspid valvular disease may be overestimated in the recipient and underestimated in the donor twin. These factors need to be taken into consideration in clinical decision-making.

Molecular cytogenetic analysis of a hydatidiform mole with coexistent fetus: a case report.

BACKGROUND: A hydatidiform mole with a coexisting fetus is a rare condition that commonly occurs as either a partial mole with fetus or a twin pregnancy comprising a complete mole and normal fetus. In the former case, the fetus is triploid, and in the latter case, the fetus is diploid with different alleles from those of the mole. Because there is a difference in the persistent trophoblastic disease incidence between the two, an accurate diagnosis is required. CASE PRESENTATION: We present a case of a 34-year-old Japanese woman who was pregnant with a hydatidiform mole and two coexisting fetuses. At 17 weeks of gestation, hemorrhage-induced progressive anemia in the mother prompted the decision to terminate the pregnancy, after which no complications occurred. Molecular cytogenetic analysis revealed that one of the fetuses was a normal diploid fetus with the same allele in the fetus and placenta. The hydatidiform mole was revealed to be a mosaic of two diploids, and the other coexisting fetus was a normal diploid that shared one of the mole alleles. CONCLUSIONS: This was presumed to be a rare case of twin pregnancy by triploid embryo formation, followed by loss of an allele due to postzygotic diploidization, development of a diploid fetus, and development of another fetus from a separate embryo. Because of the existence of cases such as this one with a diploid fetus, but without a normal pregnancy coexistent with a complete hydatidiform mole, diagnosis by genetic analysis is required for prognosis.

Kagami-Ogata syndrome in a fetus presenting with polyhydramnios, malformations, and preterm delivery: a case report.

BACKGROUND: Kagami-Ogata syndrome is also known as paternal uniparental disomy 14 and related disorders and is caused by abnormal genomic imprinting in the long arm of the chromosome 14q32.2 region. Its clinical manifestations include polyhydramnios in the fetal stage, respiratory insufficiency because of a small thorax, abdominal wall abnormalities, and peculiar facial features after birth. CASE PRESENTATION: A 38-year-old Japanese primigravida woman was referred to our hospital in the 19th week of pregnancy for suspected omphalocele. She had a history of hypothyroidism but was prescribed orally administered levothyroxine (50 µg/day) prior to conception and was euthyroid. Her ultrasound scan prior to visiting our hospital revealed fetal omphalocele, heavy for date, and polyhydramnios. The mother was advised to be admitted for observation from 28 weeks of gestation for threatened premature delivery. She required amniodrainage at 29 and 32 weeks of gestation. At 35 weeks of gestation, the fetal membrane prematurely ruptured and she gave birth after an emergency Cesarean section. The infant was a male child with a birth weight of 3188 g, and was suspected to have Kagami-Ogata syndrome after birth based on thoracic hypoplasia, swallowing function abnormalities, and peculiar facial features. A definitive diagnosis was established by performing genetic testing of the infant after obtaining informed written consent from both the parents; the results of the genetic testing revealed hypermethylated intergenic-differentially methylated region and maternally expressed gene 3-differentially methylated region in the corresponding chromosome 14 region. Both the parents were genetically tested after adequate genetic counseling, which revealed a de novo microdeletion in a differentially methylated region. CONCLUSION: Kagami-Ogata syndrome should have been suspected because of the presence of polyhydramnios and omphalocele during pregnancy. Respiratory insufficiency soon after birth, because of a small thorax, is expected in this disease and a diagnosis during pregnancy may have enabled appropriate care after birth.

Diagnosis of female 17α-hydroxylase deficiency after gonadectomy: a case report.

BACKGROUND: 17α-Hydroxylase deficiency is a recessively inherited autosomal disease caused by mutations in the CYP17A1 gene. It is a rare disease and accounts for approximately 1% of congenital adrenal cortex hyperplasias. Inhibition of 17α-hydroxylase causes low levels of cortisol and high levels of adrenocorticotropic hormone in the blood as well as excessive levels of mineralocorticoids that lead to hypertension and hypokalemia. Usually, the female patients are diagnosed with abnormality of the genitalia or extra genitalia, primary amenorrhea, or hypertension in puberty. We report a case of a 29-year-old woman who had undergone gonadectomy in her childhood due to complete androgen insensitivity syndrome and was diagnosed with 17α-hydroxylase deficiency in adulthood. CASE PRESENTATION: Our patient was a Japanese female diagnosed with androgen insensitivity syndrome, and both gonadectomy and episioplasty were performed at the age of 11 years at the University of Tsukuba Hospital. Thereafter, she was transferred to our hospital at the age of 21 years for vaginoplasty. At the age of 25 years, she presented with hypertension followed by complicated hypokalemia at the age of 28 years. The captopril loading test and adrenocorticotropic hormone loading test of her adrenal steroidogenesis revealed primary aldosteronism. After sufficient genetic counseling, a genetic test was performed that identified her as having CYP17A1 gene mutation. CONCLUSIONS: The differential diagnosis of disorders of sex development can be difficult at a young age without complete expression of the phenotype. However, diagnosis at a later age would change the treatment and prognosis of the disease; therefore, a genetic examination should be considered.

Differences in home blood pressure and pulse rates between singleton and twin pregnancies.

Objectives To evaluate home blood pressure (HBP) measurements during pregnancy and postpartum and investigate differences between singleton and twin pregnancies. Methods This prospective study involved normotensive, pregnant women who were planning to give birth at Saitama Medical Centre, Saitama, Japan between September 2013 and March 2017. HBP and pulse rate were measured twice daily and clinical blood pressure values were determined from patient records. Results HBP values were available from 101 participants; 69 women with singleton and 32 women with twin pregnancies. Systolic BP was statistically significantly higher in twin pregnancies from 23 weeks of gestation until 8 weeks after delivery compared with singleton pregnancies. Pulse rate was also statistically significantly higher between 11 and 30 weeks gestation in women with twin pregnancies compared with those with singleton pregnancies. Conclusions BP monitoring is important in the management of twin pregnancies, especially during the later gestational weeks and postpartum period and HBP would facilitate this monitoring.

Associations between the levels of soluble (pro)renin receptor in maternal and umbilical cord blood and hypertensive disorder of pregnancy.

INTRODUCTION: The prorenin (PR) receptor [(P)RR] contributes to the regulation of the tissue renin-angiotensin system (RAS) and Wnt signaling, which is involved in embryogenesis and the pathological progression of malignant tumors and diabetes mellitus. Placental (P)RR is significantly upregulated in placental tissues from preeclamptic women. However, because it cannot be examined during pregnancy, the chronological relationship between the acceleration of tissue RAS and the disease state of hypertensive disorder of pregnancy (HDP) has not been reported. In this study, we examined whether chronological changes in placental tissue RAS can be assessed by measuring soluble (P)RR [s(P)RR]. METHODS: We obtained maternal and umbilical cord blood samples from 517 pregnant women (441 singleton and 76 twin pregnancies). The concentrations of s(P)RR and prorenin (PR) were measured using enzyme-linked immunosorbent assays. RESULTS: Multivariate analysis showed that maternal serum s(P)RR levels were significantly higher in patients with HDP or fetal growth restriction (FGR) and were positively correlated with serum PR levels. Furthermore, the maternal s(P)RR level was significantly higher in HDP with severe hypertension and after the onset of HDP. However, maternal s(P)RR levels were not affected by the severity of proteinuria. Serum s(P)RR levels in umbilical cord blood of singleton pregnancies were significantly correlated with gestational week at delivery and PR level. DISCUSSION: Maternal serum s(P)RR concentrations may reflect acceleration of tissue RAS in the placenta and blood pressure severity; however, the umbilical serum s(P)RR concentration was not affected by maternal HDP.

Provisional criteria for the diagnosis of hypertension in pregnancy using home blood pressure measurements.

Most guidelines for the management of hypertension define it as a home blood pressure (HBP) value >135/85 mm Hg. However, there is no reference HBP value to diagnose hypertension in pregnant women. Therefore, in this study, we analyzed HBP measurements of pregnant women to determine whether it is appropriate to use the criteria for non-pregnant subjects for pregnant women. The participants of this study were 100 singleton pregnant women who visited our hospital between September 2013 and September 2016. We lent sphygmomanometers to the patients so they could measure their BP at home twice daily, and we measured their clinical BP when they visited the hospital. Six patients developed hypertensive disorders in pregnancy, whereas there were 63 women without hypertension or other complications that may affect BP. In the normotensive pregnant women, HBP values significantly correlated with the clinical BP values. HBP values equivalent to a clinical BP of 140/90 mm Hg, determined using the standard major axis method, were 120.8/83.5 mm Hg, 126.0/85.2 mm Hg and 136.3/89.3 mm Hg in the first, second and third trimesters, respectively. In normotensive pregnant women, HBP levels that indicate a risk of hypertensive disorder in pregnancy may be lower than 135/85 mm Hg before 28 weeks of gestation.

Can biparietal diameter-to-femur length ratio be a useful sonographic marker for screening thanatophoric dysplasia since the first trimester? A literature review of case reports and a retrospective study based on 10,293 routine fetal biometry measurements.

OBJECTIVE: The aim of the study was to determine whether the biparietal diameter/femur length (BPD/FL) ratio can be used to detect thanatophoric dysplasia in the first trimester of pregnancy. MATERIALS AND METHODS: Twenty-four reported cases of thanatophoric dysplasia diagnosed based on ultrasonographic results with molecular or radiographic diagnosis were included. All sonographic measurement records were extracted and reviewed, and the BPD/FL ratio was calculated for each gestational week. In addition, 10,293 routine fetal biometry measurements from 1395 cases of patients without skeletal dysplasia were compared. RESULTS: The BPD/FL ratio in the control group decreased to less than 3 prior to gestational week 13, and to less than 2 prior to week 18. Of the 27 BPD/FL ratios obtained from 24 cases of thanatophoric dysplasia, none was in the control range. CONCLUSION: The BPD/FL ratio may be used to detect lethal skeletal dysplasias such as thanatophoric dysplasia since the first trimester.

Methotrexate and actinomycin D chemotherapy in a patient with porphyria: a case report.

BACKGROUND: Despite their broadly recommended use as chemotherapeutic agents, the porphyrogenicity of methotrexate and actinomycin D have not been confirmed. Accordingly, it is not known whether these agents are safe for use in patients with porphyria. CASE PRESENTATION: In this report, we present a case of an invasive mole with lung metastasis in a 49-year-old Japanese woman who had previously been diagnosed with acute intermittent porphyria at 27 years of age but had no recent history of acute intermittent porphyria attacks. Her serum human chorionic gonadotropin level was elevated 1 month after hysterectomy, and she was referred to our center for chemotherapy. After she received 100 mg of methotrexate, drug eruptions were observed starting on day 3 and grew progressively worse. Erythema and mucosal erosion spread throughout her body, whereupon she was administered prednisolone. In addition, our patient experienced febrile neutropenia and required granulocyte colony- stimulating factor treatment. No changes in our patient's urinary coproporphyrin or uroporphyrin levels were detected during this entire episode. Methotrexate was replaced by actinomycin D (0.5 mg/body intravenously on days 1-5 every 2 weeks). After five uneventful cycles of actinomycin D, our patient achieved and maintained a normal serum human chorionic gonadotropin level for 3 years. CONCLUSIONS: Methotrexate and actinomycin D did not induce acute porphyric attacks in this patient with acute intermittent porphyria; however, severe adverse effects were noted with methotrexate. Although further investigation is required, our data suggest that these agents are nonporphyrinogenic and can therefore be used to treat patients with comorbid porphyria.

Ovarian mature cystic teratoma with fistula formation into the rectum: a case report.

BACKGROUND: While ovarian mature cystic teratomas are benign ovarian germ-cell tumors and the most common type of all ovarian tumors, the formation of fistulas into surrounding organs such as the bladder and the intestinal tract is extremely rare. This report documents a case of ovarian mature cystic teratoma with a rectal fistula, thought to be caused by local inflammation. CASE DESCRIPTION: A pelvic mass was diagnosed as an ovarian mature cystic teratoma of approximately 10 cm in diameter on transvaginal ultrasound and magnetic resonance examinations. Endoscopic examination of the lower gastrointestinal tract to investigate diarrhea revealed an ulcerative lesion with hair in the rectal wall adjacent to the ovarian cyst, and formation of a fistula from the ovarian teratoma into the rectum was suspected. Laparotomy revealed extensive inflammatory adhesions between a left ovarian tumor and the rectum. Left salpingo-oophorectomy and upper anterior resection of the rectum were performed. The final pathological diagnosis was ovarian mature cystic teratoma with no malignant findings, together with severe rectal inflammation and fistula formation with no structural disorders such as diverticulitis of the colon or malignant signs. DISCUSSION: The formation of fistulas and invasion into the neighboring organs are extremely rare complications for ovarian mature cystic teratomas. The invasion of malignant cells into neighboring organs due to malignant transformation of the tumor is reported as the cause of fistula formation into the neighboring organs. A review of 17 cases including the present case revealed that fistula formation due to malignant transformation comprised only 4 cases (23.5 %), with inflammation as the actual cause in the majority of cases (13 cases, 76.5 %). CONCLUSION: Although malignancy is the first consideration when fistula formation is observed between ovarian tumors and surrounding organs, in mature cystic teratoma, local inflammation is more likely than malignant transformation.