Introduction

Today there is a significant increase of ectopic pregnancies worldwide. The incidence of ectopic pregnancies ranges between 1-2% of all gestations. However, nearly 96% are located in the fallopian tube, mainly in the isthmo-ampullary part [1, 2]. Only 2-4% of all ectopic pregnancies develop in the interstitial part of the fallopian tube. Interstitial or cornual pregnancy implants exactly in the interstitial region of the fallopian tube where it passes through the uterine wall (Fig. 2). This location leads to two major problems. First, interstitial pregnancy is often diagnosed later in the run of the gestation. Second, it is directly located in the “delta” of the ramus ascendens of the uterine artery. These special factors explain the significant higher risk of hemorrhage in contrast to classical tubal pregnancy. Moreover, interstitial pregnancy accounts for approximately 20% of the deaths attributed to ectopic gestation in the United States [5]. Overall, interstitial pregnancy is diagnosed once every 2500–5000 live birth [3, 4].Traditionally the surgical treatment of choice was primary laparotomy performing cornual resection or hysterectomy. In the past 20 years due to tremendous processes in the development of endoscopic surgery and the therapeutic option of methotrexate minimal invasive management is of striking importance. The surgical basics of laparoscopic treatment are cornuale incision, extraction of the conceptus and sufficient hemostasis. Today there is no standard procedure, no “gold standard” in managing ectopic interstitial pregnancy established. Therefore, every doctor dealing with women’s health should be aware of the problems associated with this ectopic condition.

Results

Diagnosis

The risk factors for interstitial pregnancy do not differ from those of classical tubal pregnancy. Pathogenetically the most important risk factor is an impaired tubal function. All conditions leading to an impaired tubal function, namely chronic pelvic inflammation, endometriosis or tubal surgery are leading to an increased risk of ectopic pregnancy. Table 1 gives an informative overview of risk factors [6].

Table 1 Risk factors for ectopic pregnancy [6]
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In the past, diagnosis of ectopic pregnancy was made by clinical examination in addition to culdocentesis. A diagnostic procedure which is nearly forgotten worldwide and only older collegues still know about this examination. Nowadays, a more sophisticated preoperative diagnosis could be made using sensitive pregnancy tests and transvaginal ultrasound. Unfortunately, there is no sufficient diagnostic procedure to reliably differentiate between interstitial or tubal pregnancy. Moreover, the differentiation between interstitial or other ectopic pregnancies can be very difficult. Only in a few cases slight differences might be detectable. These diagnostic problems lead to the unfavourable situation that almost all cases of interstitial pregancy are diagnosed after the patient is symptomatic [6]. The most frequent symptoms are abdominal pains, abnormal vaginal bleedings, amenorrhea and shock resulting from the hemorrhage of uterine rupture. In laboratory, urine and blood samples will be tested positive for hCG. For hCG testing in blood samples there exists a useful cut-off level improving diagnostic safety; if hCG levels exceed 1500 mU/ml the pregnancy or the gestational sac must be seen in the uterus sonographically; if not suspect of ectopic pregnancy must arise leading to further therapeutic consequences [1, 7]. Due to favourable technical equipment in our department we lowered this cut-off level to 800–1000 mU/ml leading to further improvement of diagnostic and therapeutic safety.

In interstitial pregancies, due to of later time of diagnosis higher serum hCG levels can be detected. In unpublished data we found a two- to threefold increase of serum hCG levels in interstitial pregnancy compared to tubal gestation. These remarkably higher serum hCG levels must increase the attention in vaginal ultrasound examination. Typical sonographic signs for ectopic pregnancy are given in Table 2. The vaginal ultrasound examination in ectopic tubal pregnancy shows rather unspecific signs and it must be emphasized that in only ten percent proper diagnosis of ectopic pregnancy can be made. This means that in 90% of the cases diagnosis has to be made by carefully examining three parts. The diagnostic “puzzle” includes clinical signs and symptoms, laboratory procedures and vaginal ultrasound.

Table 2 Sonographic findings in classical tubal pregancy (transvaginally)
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Sonographic findings in interstitial gestation will be similiar to those of tubal pregnancy. The major finding is the empty uterus covered with a thick layer of endometrium; but this is not the whole truth. In interstitial pregnancy a far excentric location of the gestational sac can be detected. Typically, the excentric gestational sac is surrounded by a thin layer of myometrium. The detection of these ultrasound findings will further emphasize the possibility of an interstitial ectopic pregnancy (Fig. 1).

Fig. 1
figure 1

Sonographic picture of an ectopic interstitial pregnancy

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Therapy

In the past, routine laparotomy performing cornual resection or hysterectomy was commonly used in the management of ectopic interstitial pregnancies (Fig. 2). Today, due to advances in endoscopic operative technology minimally invasive treatment is possible. The operative procedure in laparoscopic surgery must not differ from open surgery regarding safety and quality aspects for the patients. The operative strategy is similiar in both routes. The basics of laparoscopic treatment are the cornual incision, extraction of the conceptus and a sufficient hemostasis. In interstitial pregnancy because of the far higher risk of hemorrhage a safe hemostasis is of striking importance. Every surgeon should avoid using the same operative procedure in interstitial and tubal pregnancy. In interstitial pregnancy this operative management could cause severe intraoperative hemorrhage leading to a high percentage of emergency laparotomies. Noteworthy in this context that interstitial pregnancy is still one of the leading causes of death associated with ectopic pregnancies [5]. For safety reasons, modification in operative treatment is needed. Many successful laparoscopic managements for early interstitial pregnancy have been reported [8–14]. In previous reports most authors used electric cauterization for bleeding control and cornual incision [10, 14, 15]; also cornual excision was performed by others [11, 13]. In our opinion, an easy and safe laparoscopic method is discribed by Moon et al. [9]. We made favorable experiences in modifying these operative methods leading to sufficient bleeding control. First, we perform an encircling endoscopic suture around the base of the interstitial pregnancy. Second, the encircling suture must tied producing a tourniquet effect. Third, while keeping the tension on the knot cornual incision can be made and the conceptus can be removed (Fig. 3). For ensuring safe hemostasis we lie an endoloop around the knot (Fig. 4). This procedure leads to secure hemostasis. However, this procedure interrupts the fallopian tube (Fig. 5). In general, after surgery several determinations of serum hCG levels should be performed ensuring efficacy of the therapy.

Fig. 2
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Left-sided interstitial ectopic pregnancy

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Fig. 3
figure 3

Encircling suture around the base and incision of the interstital part of the fallopian tube

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Fig. 4
figure 4

Endoloop procedure for ensuring hemostasis

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Fig. 5
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Final situs

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Discussion

Interstitial ectopic pregnancy represents nearly 3% of all ectopic gestations. The major problem in this clinical presentation is the significant higher risk of severe hemorrhage due to the mostly later time of diagnosis and the development in the interstitial part of the fallopian tube. The diagnostic problem preoperatively leads to the unfavorable fact that most cases will be first diagnosed during surgery. However, the same operative handling of tubal and interstitial pregnancy should be avoided thus leading to major life threatening complications in a high percentage.

Resolving the problem of sufficient hemostasis different operative approaches are discribed. In reviewing the literature some collegues prefer electric cauterization before incision of the cornual part [10, 11, 13–15]; also cornual resection is discribed. Moon and collegues found the combination of vasopressin-injections and cauterization in early ectopic pregnancies with an gestational sac of 7 mm helpful [9]. Managing more advanced pregnancies by this approach seems to be critical and riskful leading to significant blood loss in some cases [9]. Confino and Gleicher had positive results concerning bleeding control when performing severel ligatures around the base of the pregnancy before cornual incision was made [8]. Using this operative procedure blood loss could be minimized. A modified method for safe hemostasis is discribed by Moon et al comparing three different operative techniques [9]. They obtained favourable hemostasis by using endoloop technique or an encircling suture around the base of cornual pregnancy before incision and extraction of the conceptus was performed. Moon et al performed the encircling suture technique when the size or shape of the ectopic pregnancy did not allow a successful application of the endoloop [9]. Every surgeon familiar with laparoscopy knows about the critical part of endoloops. They tend to slip; mainly in those cases little tissue is available to ensure closure. Exactly this is the problem in some cases when performing laparoscopic surgery in interstitial pregnancy. We therefore tend to combine encircling suture and endoloop technique in interstitial pregnancies. In the study of Moon et al, the endoloop and the encircling suture technique was more effective in bleeding control compared to the application of vasopressin and electric cauterization. Blood loss differed significantly between the groups. Moreover, the duration of surgery using endoloop or encircling suture was significantly shorter reflecting the simplicity of these operative methods [9].

Fortunately, interstitial pregnancy is a rare event; due to this fact little is known about the treatment of choice. In the study of Moon et al discribing a considerable amount of 24 patients with interstitial pregnancy only 3 patients were treated by encircling suture; whereas 15 patients obtained endoloop technique. Therefore, general guidelines are still missing. Alternatively to surgery medical management for the treatment of interstitial ectopic pregnancy has been applied [16–21]. Mostly methotrexate is used; but administering methotrexate several problems must be considered; a close medical follow-up has to be performed after application of methotrexate. According to actual literature after a single-shot methotrexate a 15% decline of serum hCG measured day 4 and day 7 should be reached [22]. Noteworthy, that a regular decline of serum hCG levels is not always associated with the resolution of ectopic pregnancy. Rupture of the ectopic pregnancy can still occur resulting in severe intraabdominal hemorrhage. Especially in interstitial pregnancy a life threatening event [23–25]. It is a clinical experience that after application of methotrexate diffuse self-limiting abdominal pain can occur imitating rupture of ectopic pregnancy [26]. Furthermore, there exists a medical report concerning uterine rupture on future pregnancy [27]. For these reasons combined with the knowledge of possible life-threatening hemorrhages we prefer planned surgical treatment in the management of interstitial ectopic pregnancy. In our laparoscopic department we perform a combination of discribed endoscopic techniques. We made favorable experiences concerning effective and safe bleeding control in interstitial pregnancies. First, we perform an encircling suture around the base of the pregnancy. Second, we ensure hemostasis by an endoloop. Some collegues may not agree that the combination of both, suture and endoloop, is necessary. In our opinion, every suture or endoloop that can avoid major bleeding complications - even in rare cases - is helpful and necessary.