Ectopic pregnancy (EP) is one of the most common acute abdominal diseases in gynecology. Once the condition of EP is delayed, it may lead to massive hemorrhage, shock, and even death in a short time, seriously threatening the patient’s life. Early diagnosis is the key to preventing and improving the prognosis of EP. Transabdominal ultrasound (TAS) and transvaginal ultrasound (TVS) are the main diagnostic methods for abdominal diseases. The purpose of this study is to explore the application value and effect of TAS and TVS in the diagnosis of EP, hoping to provide more valuable references for the diagnosis of EP.

To explore the application value of TAS and TVS in the diagnosis of EP and to improve the level of clinical diagnosis.

A total of 140 patients with EP admitted to our hospital from July 2018 to July 2020 were selected for this study. All patients were divided into two groups according to the examination methods. 63 patients who underwent abdominal ultrasound examination were set as the TAS group, while 77 patients who underwent TVS examination were set as the TVS group. We compared the diagnostic accuracy and misdiagnosis rates between the two types of ultrasound examinations, as well as the postoperative pathological results of the two diagnostic methods for different types of ectopic pregnancies. We also analyzed the sonograms for the presence of mixed ectopic masses, adnexal masses, ectopic gestational sacs, the presence or absence of visible embryo and fetal heart in the ectopic sac shadow, and the detection of fluid in the rectal fossa of the uterus, such as the adnexal area, yolk sac, and embryo, etc. In addition, the diagnosis time, days of gestational sac appearance, operation time, endometrial thickness, and blood flow resistance index were compared as well.

After performing both types of ultrasound examinations in 140 patients with EP, we found that the diagnostic accuracy of TVS was significantly higher than that of TAS, and the misdiagnosis rate was significantly lower than that of TAS. The differences were statistically significant (P < 0.05). In addition, the detection rate of TVS was better than that of TAS for the presence of mixed masses, adnexal masses, ectopic gestational sacs, the presence or absence of visible embryo and fetal heart in the shadow of the ectopic sac, and sonograms such as the adnexal area, yolk sac, and embryo, etc. The coincidence rate of its postoperative pathological examination results was significantly higher than those of TAS. The diagnosis time and the days of gestational sac appearance by TVS were significantly shorter than that by TAS, and the operation time was earlier than that by TAS. What’s more, the detection rates of the endometrial thickness £ 1.5 mm and blood flow resistance £ 0.5 were significantly higher in TVS diagnosis of EP than in TAS. All differences were statistically significant (P < 0.05).

Compared with TAS, TVS has the advantages of high detection accuracy and good sonogram performance.

Ectopic pregnancy (EP) is one of the common acute abdominal diseases in gynecology, which mainly refers to the implantation of fertilized eggs outside the uterine cavity[1,2]. There are many causes of EP, such as pelvic inflammation, pelvic effusion, fallopian tube abnormalities, etc[3]. EP can be divided into tubal pregnancy, ovarian pregnancy, and cervical pregnancy according to the different locations of fertilized eggs implanted outside the uterine cavity, among which EP accounts for more than 95%[4]. Menopause, abdominal pain, and vaginal bleeding are the typical clinical manifestations of EP, especially tubal pregnancy. As a result of acute intra-abdominal bleeding and severe abdominal pain, mild cases of fainting can lead to shock and even death in severe cases, seriously threatening the lives of patients[5,6]. Therefore, improving the diagnostic accuracy of EP can help patients get timely treatment and effectively guarantee their prognosis.

At present, there are many methods to diagnose EP, such as pregnancy test, ultrasound diagnosis, posterior fornix puncture, laparoscopy, endometrial pathology examination, etc.[7], among which transabdominal ultrasound (TAS) has become a common clinical examination method because of its convenience and quick operation. However, due to factors such as the thickness of human abdominal sebum and the low frequency of the probe, misdiagnosis and missed diagnosis of abdominal ultrasound is inevitable. Therefore, it is very important to find a more efficient and accurate method for the diagnosis of EP. Transvaginal ultrasound (TVS) is a kind of intracavitary ultrasound, which requires a special vaginal probe to be placed directly in the vagina for an ultrasound examination. As a technological breakthrough in the application of obstetrical and gynecological ultrasound in recent years, compared with traditional TAS, it can clearly show the internal organ and tissue structure of the female pelvic cavity without filling the bladder. It has early and accurate characteristics for the diagnosis of normal and abnormal pregnancies and gynecological diseases[8]. Previous studies have found that TVS examination of EP can improve diagnostic accuracy and ensure the timely treatment of patients[9]. In addition, studies by Mei et al[10] have shown that TAS and TVS are the main diagnostic methods for abdominal diseases, especially in the early diagnosis of EP[11-12].

Based on this, this study aims to explore the application value and effect of TAS and TVS in the diagnosis of EP through retrospective analysis of clinical data of patients with EP, hoping to provide more valuable references for the diagnosis of EP.

In normal pregnancy, the fertilized eggs are deposited in the uterine cavity, whereas in EP, the fertilized eggs are deposited outside the uterine cavity and grow and develop[19-21]. In the early stage of EP, there is no obvious clinical manifestation, some patients present with menopause, abdominal pain, and a small amount of vaginal bleeding. Patients often suffer from acute severe abdominal pain, and recurrent episodes, and are more painful at the onset. However, there are still some patients with EP who do not have typical clinical symptoms, and the diagnosis rate is low at the early stage, which undoubtedly increases the difficulty of clinical diagnosis. And once the condition is delayed, it may lead to hemorrhage, even shock, and death in a short period[22-24]. Therefore, the principle of treatment for EP is early diagnosis and early treatment.

At present, EP is mainly treated clinically by surgery, which presupposes scientific and accurate clinical judgment[25,26]. It has been reported that ultrasound diagnosis has become the main method for early diagnosis of patients with EP because of its convenience, noninvasiveness, and freedom from the pain of diagnostic curettage and fornix puncture[27]. TAS was an earlier method of clinical diagnosis. EP is diagnosed when the diagnostic TAS image shows an increase in the thickness of the endometrium, the absence of a gestational sac in the uterine cavity, a mixed mass with uneven echogenic borders on the side of the uterus, or even a mass of gestational sac, embryo or even primitive ventricular pulsation on the side of the uterine cavity in some patients[28,29]. But TAS requires the patient to have a full bladder, and it is far away from the uterus and fallopian tube, which makes lesion detection unclear or incomplete and also prone to misdiagnosis. As a result, the application of TAS is not very ideal, and cannot improve the detection rate of clinical diagnosis.

With the development of clinical diagnosis technology and the improvement of the medical level, ultrasonic equipment and examination technology have also developed. Transvaginal ultrasonography is gradually being used in the diagnosis of various clinical fields[30,31]. Studies have shown that TVS has a higher sensitivity in the diagnosis of EP (especially in the early stage of tubal pregnancy, where there is little internal bleeding and the non-echogenic area is confined to the rectum fossa and around the uterus)[32]. TVS allows the probe to be placed into the vagina, which is closer to the pelvic tissues and organs, and can significantly reduce the interference of gas and fatty tissue in the abdominal cavity, making the uterus and ovaries appear clearer[33,34]. Calì et al[35] also found that TVS does not require the patient to have a full bladder during the diagnosis, which is suitable for the examination of gynecological emergencies, thus saving time for patients with ruptured EP-type hemorrhage. Based on this, this study aimed to compare the value of TAS and TVS in the diagnosis of EP, hoping to provide some help for the early diagnosis and treatment of EP.

In this study, TAS and TVS were performed on 140 patients with EP. The diagnostic accuracy of TVS was 97.40%, which was significantly higher than the 88.89% accuracy of TAS, and its misdiagnosis rate was significantly lower than that of TAS. In addition, a comparative sonogram analysis revealed that a transvaginal Doppler sonography was able to show more clearly the ectopic gestational sac shadow, mixed masses, and the presence of fetal heart and embryo in the ectopic sac shadow. The main reason may be that the resolution of the TVS probe is higher than that of TAS, and the penetration of the probe is stronger, which can clearly show the changes in the uterine cavity and endometrium, and accurately reflect the situation of adnexal masses. In addition, the TVS probe is directly placed into the patient’s vagina and is closer to the uterus, which is less likely to be affected by other factors[36]. In contrast, the abdominal ultrasound probe has a lower frequency and is at a certain distance from the gestational sac, so it is easy to be interfered with by factors such as the filling bladder, abdominal fat, abdominal wall invasive bowel contents, and the bowel wall, etc., thus reducing the accuracy of diagnosis[37,38].

Previous studies have shown that when there is no specificity in the sonogram of adnexal masses, special trophoblast blood flow can be formed after implantation with the help of color Doppler flow imaging, and low resistance flow can be detected in nonspecific adnexal masses that separate from the ovary, thus improving the sensitivity and specificity of EP diagnosis[39,40]. In this study, by comparing and analyzing the diagnostic time and the days of gestational sac appearance between TAS and vaginal ultrasound, it was also found that the diagnostic time of TVS for EP and the days of showing the gestational sac were significantly shorter than that of TAS, and the operation time was significantly earlier than that of TAS. This may be related to the fact that TAS requires more than 5 wk of menopause for detection, whereas TVS can detect the gestational sac within 3-30 d of menopause[41]. This suggests that TVS is more accurate and sensitive in detecting EP compared to TAS, which is consistent with the study by Ramanan et al[42]. That is to say, TVS can detect EP more accurately and its diagnostic time and days of gestational sac appearance are shorter, allowing for earlier surgical treatment options. Timely diagnosis and surgery can enhance the outcome of treatment and reduce the risk of postoperative hemorrhage, which undoubtedly increases the value of TVS and makes it more suitable for use in the diagnosis of gynecologic emergencies. In addition, our results showed that the postoperative pathological findings are more consistent with TVS than with TAS and that its postoperative diagnosis of tubal pregnancy is particularly typical, which may be related to the fact that tubal pregnancy accounts for more than 95% of ectopic pregnancies[43].

It has been found that ultrasound sonograms can reflect cyclic changes in the thickness of endometrial morphology from linear and progressive thickening in the early stages of hyperplasia to 7-10 mm in the late stages of secretion. Since the blood supply and chorionic villus development vary depending on the location of the implanted egg, making differences in the corresponding hormones and the thickness of the endometrium which directly influenced by them. Thus, a combination of endometrial thickness detection can predict the site of pregnancy and improve the accuracy of EP[44,45]. The resistance encountered by blood as it flows through the blood vessels is called blood flow resistance. Blood flow resistance is reported to be caused by energy consumption due to friction during blood flow, and increased blood flow resistance is mainly due to the influence of blood viscosity. Any factor that increases the viscosity of blood has a high potential to increase peripheral resistance and increase blood pressure, thus increasing cardiac burden. Therefore, monitoring the mass flow resistance index may improve diagnostic rates[46,47]. Based on this, we compared the endometrial thickness and blood flow resistance under two different ultrasound diagnoses. It was found that the detection rates of endometrial thickness ≤ 1.5 mm and blood flow resistance ≤ 0.5 were significantly higher in TVS diagnosis of EP than in TAS diagnosis, which is also consistent with previous studies[48]. That is to say, TVS can more accurately predict the location of the pregnancy, identify the blood flow resistance index, and improve the diagnostic rate of EP. This is related to the higher resolution and better penetration of the TVS probe, which allows for clearer visualization of the uterine cavity, endometrial changes, and blood flow. Our research also has certain limitations, the included sample size was limited, and the findings still need more multicentered studies with large samples for further confirmation. In addition, this is a retrospective study, a prospective study using these two scans for pregnant women is the next step to be undertaken.

To sum up, compared with TAS, TVS has higher diagnostic accuracy, clearer image quality, higher accuracy, and specificity in the diagnosis of EP, and is worthy of widespread promotion in the clinical setting. Of course, abdominal ultrasound also has its advantages, but it should be avoided especially for clinical use in patients with combined vaginal and intrauterine inflammation to further avoid infection aggravation. Therefore, the clinical diagnosis of EP needs to be tailored to the patient’s actual situation so that the most suitable detection method can be adopted. As for the effect of combined treatment on the positive diagnosis rate, we will further explore this in the follow-up study.