Rudimentary Horn Pregnancy: Diagnosis and Management
Rudimentary horn pregnancy (RHP) (figure 1) is a rare form of pregnancy in a rudimentary uterine horn with a reported incidence of 1 in 76,000–1 in 150,000 [1, 2]. RHP results in rupture in 80–90 % of cases during the second or third trimester due to poorly developed musculature that cannot stretch and the increased reported presence of placenta percreta in cases of RHP due to the above mentioned poor musculature and the presence of thin or nonfunctional endometrium and scant decidualization resulting in life-threatening hemorrhage [2-6 ].
The maternal mortality rate associated with RHP has reduced from 18 % in the nineteenth century to 0.5% now with very few reported cases of fetal survival [7-11]. Delayed diagnosis of RHP until it rupturs in second or third trimester is the main factor contributing to the high maternal mortality rate in comparison to that for tubal ectopic pregnancies.
The American Society of Reproductive Medicine developed one of the most commonly used classification system for Müllerian duct anomalies (MDA) .
Despite improvements in the diagnosis and treatment of RHP, 50% are diagnosed following uterine rupture in the second or third trimester and the morbidity associated with this condition remains very high . That is why every effort should be made to diagnose RHP at an early stage during the pregnancy.
1) a single interstitial portion of fallopian tube in the empty unicornuate uterine body; 2) a gestational sac, mobile, separate from the empty uterus and surrounded by myometrium; 3) a vascular pedicle adjoining the gestational sac to the unicornuate uterus . Other suggested findings including the presence of thin myometrium ring all around the gestational sac, absent continuity between the cervical canal and the lumen of the pregnant horn and hypervascularisation typical of placenta accreta may support the diagnosis [6,18].
Figure 3. Ultrasound findings of right Rudimentary horn pregnancy with fetal pole surrounded all around by myometrium (M) beside an empty uterus with prominent endometrium (E), Bladder (B) and a band of tissue connecting the rudimentary horn to the displaced empty unicornuate uterus is seen (arrow).
The differential diagnosis of an ultrasonographically suspected RHP is tubal pregnancy, interstitial pregnancy and a pregnancyin a bicornuate or septate uterus (Table 1). A tubal pregnancy will not show a ring of myometrium surrounding the gestational sac, but the differentiation between the 2 latter conditionsand RHP may be difficult . Interstitial pregnancy cannot be separated from the uterus (immobile gestational sac) and can be diagnosed by visualization of the interstitial line (echogenic line) adjoining the gestational sac and the lateral aspect of the uterine cavity and demonstrating the ipsilateral interstitial tube adjoining the uterine cavity and the gestational sac (figure 4) [10,19]. Variation in thickness of the myometrium in 2 horns and a marked distance between them favor the diagnosis of a RHP over that of pregnancy in a bicornuate uterus. In contrast to RHP, continuity between the endometrium lining the gestational sac and the other uterine horn is typical for a pregnancy in a bicornuate uterus .
In spite of the above, ultrasound sensitivity for diagnosis of rudimentary RHP ranges from 29 to 33 % only, that is why Magnetic Resonance Imaging (MRI) is recommended as a problem solving tool in cases of dilemma on ultrasonographic imaging for confirmation of RHP [8,16]. The main advantage of MRI as compared with ultrasound is the ability to visualize the whole uterus in one image plan, and thus identify the exact site of implantation. MRI provide images with high soft-tissue contrast, and multiplanar images which reveals both internal and external uterine structure, thus it is a very useful noninvasive tool for diagnosis of MDA, identifying communication between the uterine cavity and horn, and help to plan surgery by localizing the position of the horn attachment to the unicornate uterus and identifying whether this attachment is broad attachment or just a small fibrous band [20-23]. The contralateral dominant, or nonrudimentary unicornuate horn will be laterally displaced and has been described as a “banana-shaped uterus”[ 22,24]. In cases of RHP, coronal sagittal and axial planes are used for accurate assessment of uterine connection to the horn and either confirm or rule out communication with endometrial cavity or endocervical canal .
Table 1. Differential diagnosis of rudimentary horn pregnancy.
Surgery is the main line of management. Advanced RHP may rupture with little warning at any time, with significant risk to maternal health, hence early diagnosis can help in planning elective surgery before rupture [4,10, 22].
One paper reported that when the ipsilateral tube was preserved in two cases after elective removal of the non-gravid rudimentary horn, one of the patients subsequently developed ubal pregnancy in the preserved tube . In another report conservative treatment of RHP without removal of the pregnant rudimentary horn was followed by recurrence of RHP in the subsequent pregnancy . In view of the above surgery for RHP should involve excision of the rudimentary horn and ipsilateral salpingectomy with conservation of the ipsilateral ovary .
The excision of a RHP is not technically difficult in early pregnancy and the risk of complications is low if through evaluation of the rudimentary horn and any associated urological anomalies was done before embarking on the surgical excision [15,17, 21]. Laparoscopic excision increasingly becomes a better choice during the first trimester [10,17]. If a thick fibromuscular tissue connecting the RHP and the unicornuate uterus is present, laparoscopic removal is technically more challenging, requires a longer operation time, and closing the myometrium with laparoscopic sutures is recommended to avoid potential future uterine rupture. However, if only a thin fibrous band was present between the RHP and the unicornuate uterus no need to close the myometrium .
In advanced cases it is best to perform open surgery, although recently few case reports of laparoscopic management of RHP in second trimester have been reported. These cases undergone radiological evaluation of the rudimentary horn to determinethe feasibility of laparoscopic excision and received preoperative potassium chloride to induce feticide and reduce the size of the pregnancy which facilitated the removal of the excised pregnant horn with the help of morcellator and endoscopic bag though small abdominal incision [21,26].
Medical management of a viable RHP with methotrexate and intracardiac potassium chloride followed by gonadotropin-releasing hormone injections has also been used pre-operatively to reduce both size of pregnancy and the blood loss from associated placenta accreta before interval excision of the rudimentary horn 6 weeks later [10,21, 27].
Missed miscarriage in a rudimentary horn has been managed expectantly with serial β-hCG measurement until resolution of the pregnancy. However, recurrence of RHP can occur again if the rudimentary horn is not removed electively after the onservative
or medical treatment .
Prognosis and Future Pregnancy
After excision of RHP woman should be investigated to check of any associated renal tract anomalies if this was not done before surgery.
Women with a unicornuate uterus with or without rudimentary horn are at a higher risk of obstetric complications, such as first and second trimester miscarriage, preterm delivery, breech presentation, pregnancy induced hypertension (in women with associated unilateral renal agenesis), intrauterine growth restriction, intrauterine fetal demise and increased caesarean section rate [5, 28]. This risk will obviously persist after excision of the RHP and women should be informed about this risk.
Consideration for prophylactic resection of a non-communicating rudimentary horn in women with MDA has been advocated by some authors to prevent endometriosis and possible future RHP .
A case series of the reproductive and obstetric outcome after laparoscopic excision of non-pregnant functional,non-communicating broadly attached rudimentary horn showed no negative effect from the surgery on subsequent fertility and no reported case of uterine rupture during subsequent pregnancy in the remaining unicornuate uterus after the rudimentary horn excision . However, all cases in this series delivery by caesarean sections five for obstetrics reasons and two elective sections.
Women should be informed that there is lack of evidence-based data from well-designed studies addressing the issue of route of delivery in uncomplicated subsequent pregnancy after excision of RHP.
RHP is a rare form of pregnancy in a rudimentary uterine horn, if not diagnosed 80–90 % of the cases may rupture during the second or third trimester causing significant maternal morbidity and mortality. Early diagnosis during the first or early second trimester allows the safe planning for surgical excision through the most appropriate route before rupture of the pregnant horn.
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14.The American Fertility Society classifications of adnexal adhesions, distal tubal obstruction, tubal occlusions secondary to tubal ligation, tubal pregnancies, Müllerian anomalies and intrauterine adhesions. Fertil Steril. 1998,49: 944-955.
16.Chopra S, Keepanasseril A, Rohilla M, Bagga R, Kalra J, Jain V. Obstetric morbidity and the diagnostic dilemma in pregnancy in rudimentary horn: retrospective analysis. Arch Gynecol Obstet. 2009, 280: 907-910.
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24. Ozeren S, Caliskan E, Corakci A, Ozkan S, Demirci A. Magnetic resonance imaging and angiography for the prerupture diagnosis of rudimentary uterine horn pregnancy. Acta Radiol 2004, 45(8): 878-881.
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30.Pados G, Tsolakidis D, Athanatos D, Almaloglou K, Nikolaidis N, Tarlatzis B. Reproductive and obstetric outcome after laparoscopic excision of functional, non-communicating broadly attached rudimentary horn: a case series. European Journal of Obstetrics & Gynecology and Reproductive Biology. 2014, 182: 33–37.