Mette Petri Lauritsen1 and Marianne Johansen2
The Fertility Clinic, Section 4071, Copenhagen University Hospital Rigshospitalet, Blegdamsvej 9, 2100 Copenhagen, Denmark
Department of Obstetrics, Copenhagen University Hospital Rigshospitalet, Blegdamsvej 9, 2100 Copenhagen, Denmark
Mette Petri Lauritsen (Corresponding author)
Rudimentary uterine horn pregnancyEctopic pregnancyUterine rupturePlacenta accretaHemorrhagic shockCongenital uterine malformationsMüllerian ductsRenal anomalies
This case report was previously published in Acta Obstet Gynecol Scand. 2010; 89:1111–1112 by Mette Petri Lauritsen, Elisabeth Clare Larsen and Marianne Johansen. Reprinted with permission.
A 34-year-old woman presented to the emergency department with severe abdominal pain of 1-h duration. She believed herself to be about 13 weeks pregnant. The pregnancy had been uneventful. That morning, she went to see a physician for the first time and the general practitioner reported that the uterine size was compatible with the gestational age. No ultrasound was performed. Past history revealed an emergency cesarean delivery at 29 weeks of gestation for her first child due to premature labor and fetal bradycardia followed by two normal deliveries at term.
On physical examination, the patient was pale and in severe pain. Blood pressure was 98/65 mm Hg and pulse rate initially 73 bpm. The hemoglobin was 6.0 mmol/l and serum hCG level was 22.252 iu/l. Her abdomen was soft with diffuse tenderness and a peritoneal reaction in the left iliac fossa. No intrauterine pregnancy could be seen on transvaginal ultrasound examination. Adjacent to the left ovary, a hyperechoic mass measuring 60 ⋅ 40 mm was seen. The right ovary appeared normal on ultrasound and minimal amount of free fluid was found in the posterior cul-de-sac. A transabdominal ultrasound examination was about to be performed when the patient’s condition suddenly deteriorated with confusion, hypotension, and loss of consciousness.
Diagnosis and Assessment
This case illustrates a potentially life-threatening condition that remains a diagnostic challenge. The clinical condition of this patient, levels of hCG, and an empty uterus on ultrasound was highly suggestive of an advanced, ruptured ectopic pregnancy . Even though a left-sided adnexal mass had been visualized on ultrasound, the location of the pregnancy and the fetus was unknown.
Due to the history of previous term deliveries, a uterine anomaly was not suspected. The adnexal mass could potentially represent a ruptured uterine horn but was not suspected on the first ultrasound examination. The recent pelvic examination performed by the general practitioner, indicating a normal pregnancy, was also a confounding factor.
Despite the fact that an ectopic pregnancy was clinically high on the agenda, other diagnoses also had to be considered. Sometimes, an intrauterine pregnancy can be difficult to diagnose by transvaginal ultrasound examination and in this case a transabdominal ultrasound examination, which is often a valid supplementary investigation, was not performed due to the emergency situation. The differential diagnoses at this time were adnexal torsion or rupture of a corpus luteum cyst. However, a ruptured tubal, cornual, or abdominal pregnancy was found to be a likely diagnosis.
Congenital uterine malformations occur in 1:200 to 1:600 women . The presence of a unicornuate uterus with a rudimentary horn is a result of an abnormal development of one of the Müllerian ducts . Uterine anomaly is often associated with renal anomalies due to the close embryologic relationship between the Müllerian and Wollfian ducts . A rudimentary uterine horn may be communicating or noncommunicating with the uterine cavity, and may or may not have a functional endometrial cavity (Fig. 20.1) . It is believed that 80–90 % of rudimentary uterine horn pregnancies arise in a noncommunicating horn due to transperitoneal migration of either fertilized ovum or spermatozoa  (Fig. 20.2). Rudimentary horn pregnancies are often diagnosed at a later stage in pregnancy than what is typically observed in ectopic gestations and most cases present with acute uterine rupture.
Variations of the unicorneate uterus: a communicating, b noncommunicating rudimentary horn, c rudimentary horn without a cavity, and d isolated unicorneate uterus 
Pregnancy in a noncommunicating rudimentary uterine horn arising due to transperitoneal migration of sperm
In a review of 568 cases of rudimentary uterine horn pregnancies from 1900 to 1999, a rupture rate of 50 % was found with 80 % occurring before the third trimester . The maternal mortality rate has fallen dramatically over time, from 23 % in the 1920s to currently less than 0.5 % as a result of improved diagnosis and early treatment. Only a few reports exist of rudimentary horn pregnancies proceeding to term .
Women with uterine malformation have an increased risk of miscarriages and obstetric complications including intrauterine growth retardation, abnormal presentations, and preterm labor . It is possible that uterine anomaly contributes to the preterm labor in our patient’s first pregnancy. Operative record of the cesarean delivery stated “a fibroma-like structure at the departure of the left salpinx.” Uterine anomalies can be classified according to the guidelines developed by the American Society of Reproductive Medicine , or according to a recent classification system for female genital anomalies developed by the European Society of Human Reproduction and Endocrinology (ESHRE) and European Society for Gynecological Endoscopy (ESGE) .
When a pregnant women presents with abdominal pain and symptoms of hemorrhagic shock , immediate surgical intervention should be performed. The choice of operative method depends on the condition of the patient and surgeon’s expertise and experience. Laparoscopy may be an alternative to laparotomy in the case of a hemodynamically stable patient. Surgery should include excision of the entire rudimentary horn. In addition to the morbidity associated with uterine rupture , a rudimentary horn pregnancy carries an increased risk of abnormal implantation of the placenta, such as placenta accreta or percreta. Thus, the clinician should be prepared for the potential massive intraabdominal hemorrhage.
Early detection of rudimentary uterine horn pregnancies remains a clinical challenge. Even though more women undergo a first trimester ultrasound examination, the sensitivity of ultrasound in diagnosing rudimentary horn pregnancies is only 29 % . Moreover, the diagnosis may be masked by a history of previous normal pregnancies, as in this case. On pelvic examination, the patient may have an adnexal mass, causing deviation of the uterus to one side. Ultrasound findings may be suggestive of the presence of a bicornuate uterus.
The rudimentary horn pregnancy may be detected by the lack of continuity between the cervical canal and the lumen of the uterine horn. In some cases, a well-defined placenta fitting into the confines of the rudimentary horn may differentiate a rudimentary horn pregnancy from an abdominal pregnancy . The diagnosis may be confirmed by magnetic resonance imaging. Once the diagnosis of rudimentary horn pregnancy is established, surgery should be performed including removal of the ipsilateral Fallopian tube to prevent future ectopic pregnancies . In rare cases, expectant management may be attempted , but this requires close monitoring of fetal growth and myometrial thickness and access for immediate operative intervention. If a rudimentary uterine horn is identified before conception, elective surgical removal by laparoscopy is recommended .
An emergency laparotomy was performed revealing a massive hemoperitoneum. On the left side of the uterus, a ruptured rudimentary horn containing the placenta was found. The fetus was found floating in the abdominal cavity. According to its crown–heel length, it was estimated to be 16 weeks of gestational age. There were no visible malformations. An excision of the rudimentary uterine horn along with the placenta and a left salpingectomy were performed. Estimated blood loss was 4.8 l and blood transfusions and fresh-frozen plasma were given. The woman recovered without complications and was discharged 4 days later.
When a pregnant woman presents with abdominal pain and hemorrhagic shock , a ruptured uterine horn pregnancy should be considered. This is despite the history of previous normal pregnancies.
· Pay special attention to women who have not attended any antenatal care.
· Rudimentary horn pregnancies can usually be differentiated from a tubal ectopic pregnancy by the more advanced gestation at the time of clinical presentation.
· When managing a ruptured rudimentary uterine horn pregnancy , massive hemorrhage due to abnormal implantation of the placenta should be expected.
· A history of recurrent pregnancy loss, abnormal fetal presentation, or preterm delivery should alert the physician to the possibility of uterine anomalies.
· Renal agenesis, urinary retention, or recurrent pyelonephritis may indicate a uterine anomaly.
· The presence of uterine anomalies should be carefully assessed when performing a cesarian section.
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