Keywords

Unicornuate uterus, rudimentary horn pregnancy, pre-rupture diagnosis

The incidence of mullerian duct anomalies in general population is found to be 3.2%. Unicornuate uterus occurs in 1 in 4,020 women in the general population and a rudimentary horn is present in about 84% of the cases.1 Most of these rudimentary horns are noncommunicating. Ectopic pregnancy occurring in a noncommunicating rudimentary horn has an estimated incidence of 1 per 1,00,000 to 1,40,000 pregnancies.2 Pregnancy in the rudimentary horn usually culminates in rupture during second trimester in about 90% of the cases. Pre-rupture diagnosis is unusual and challenging but possible with high index of suspicion in the early pregnancy.

Abdominal pregnancy is an extremely rare and serious form of extrauterine gestation with an incidence of 1 per 10,000 births.3 Abdominal pregnancies account for almost 1% of ectopic pregnancies.4 It has a reported incidence of 1 in 2,200 to 1 in 10,200 of all pregnancies.5 The gestational sac is implanted outside the uterus, ovaries and fallopian tubes. The maternal mortality rate can be as high as 20%.5 This is primarily because of the risk of massive hemorrhage from partial or total placental separation. The placenta can be attached to the uterine wall, bowel, mesentery, liver, spleen, bladder and ligaments. It can detach at any time during pregnancy leading to torrential blood loss.6 It is thought that abdominal pregnancy is more common in developing countries, probably because of the high frequency of pelvic inflammatory disease in these areas.7 Abdominal pregnancy is classified as primary or secondary according to Studdiford’s criteria.8 In these criteria, the diagnosis of primary abdominal pregnancy is based on the following anatomic conditions: 1) Normal tubes and ovaries, 2) absence of an uteroplacental fistula and 3) attachment exclusively to a peritoneal surface early enough in gestation to eliminate the likelihood of secondary implantation. We report a case of a secondary abdominal pregnancy following rupture of rudimentary horn who presented in the second trimester.

CASE REPORT

A 28-year-old, multipara was admitted to Shyam Shah Medical College (SSMC), Rewa, Madhya Pradesh on 12/01/14 in emergency hours. She was referred from a private practitioner. She presented with complaints of 3 months amenorrhea, pain abdomen since 15 days, bleeding per vaginum and weakness since 3 days and one fainting episode 1 day back. She had history of medical termination of pregnancy (MTP) followed by laparoscopic tubectomy (LTT) at a camp on 28/11/2013 (about 45 days back) at a primary healthcare center. On examination, she had average general condition with pulse rate of 120 beats/minute, good volume and regular, blood pressure 110/70 mmHg and pallor, generalized tenderness present on lower abdomen. On P/V examination uterus was 8-10 weeks, anteverted, fullness and tenderness in both fornices and no cervical motion tenderness. There was slight vaginal bleeding. Her hemoglobin on admission was 7.2 gm% and other laboratory parameters were within normal limits. She came with USG report of 13 weeks fetus lying within uterine cavity. A provisional diagnosis of septic abortion with peritonitis was made. Antibiotics were given and patient was managed conservatively. USG whole abdomen and pelvis was done, which revealed: 1) Dilated bowel loops with fluid and gas, 2) free fluid with internal septation was seen in peritoneal cavity and 3) uterus with a normal endometrial thickness of 12 mm. Even after antibiotic coverage, there was no symptomatic improvement, so the decision was taken for laparotomy. Under spinal anesthesia, laparotomy was performed and 1.5 liters of hemoperitoneum was found. Old ruptured rudimentary horn of uterus was found on left side. It had placenta with the cord attached (Fig. 1). The ruptured rudimentary horn was excised. Uterus was bulky, deviated to right, with normal right ovary and right fallopian tube. Left ovary was normal, left fallopian tube was healthy and attached to rudimentary horn. Omentum was plastered with clots, clots were removed and umbilical cord was seen going towards right hypochondrium, it was reaching the mesentery of transverse colon. The adjacent areas were cleaned, which lead us to visualize the fetus embedded in the mesentery. Fetus was removed, hemostasis achieved. Peritoneal cavity was washed with normal saline. Patient received 1 unit blood intraoperatively. Her postop period was uneventful and she was discharged on 7th post-op day.

DISCUSSION

Unicornuate uterus results from the failure in the development of one of the paramesonephric ducts, either partially or completely. Partial development of one of the duct gives rise to a rudimentary uterine horn. As per revised classification for Mullerian anomalies given by American Society of Reproductive Medicine, unicornuate uterus is a type 2 classification with unilateral hypoplasia or agenesis. It can be further subclassified into communicating, noncommunicating, no cavity and no horn. Pregnancy in a noncommunicating rudimentary horn occurs through the transperitoneal migration of the spermatozoa or the fertilized ovum, as evidenced by the 8% prevalence of a corpus luteum on the side contralateral to the rudimentary horn containing the pregnancy.2 In most of the cases, the pregnancy in the rudimentary horn leads to spontaneous abortion, preterm labor, intrauterine growth restriction or fetal demise. The most dreaded complication is the massive intraperitoneal hemorrhage due to rupture of the horn, which can be life-threatening to the mother. Rarely, embryo is expelled into abdomen and remains attached to the horn and embryo continues to live and grow, which is referred as “secondary abdominal pregnancy”. The usual outcome of the rudimentary horn pregnancy is rupture in the second trimester in about 90% of the cases with fetal demise, which can be catastrophic.2 Unlike tubal ectopic pregnancy, bleeding is more severe in rupture of the rudimentary horn, the uterine wall is much thicker and more vascular. The uterine rupture associated with rudimentary horn was first reported in 1669 by Mauriceau.9 The timing of rupture varies from 5 to 35 weeks depending on the horn musculature and its ability to hypertrophy and dilate. Maternal mortality due to rupture was 47.6% before 1900, but no case of maternal death has been reported since 1960.10 Few cases of pregnancies with late or false diagnosis progressing to third trimester resulting in live births have been reported.11 Among these, neonatal survivability was only 6%.11 Patient with abdominal pregnancy typically presents with constant abdominal pain, progressive anemia and sudden loss of fetal movements.12

As the consequences of rupture can cause significant mortality and morbidity, early diagnosis is essential for management. However, the pre-rupture diagnosis of rudimentary horn pregnancy is challenging. If an ultrasound is done in the first trimester with a high index suspicion, then one should be able to make a diagnosis of pregnancy in the rudimentary horn. Ultrasound examination is the usual diagnostic procedure of choice, but the findings are sometimes questionable. They are dependent on the examiner’s experience and the quality of the ultrasound. Transvaginal ultrasound is superior to transabdominal ultrasound in the evaluation of ectopic pregnancy, since it allows a better view of the adnexa and uterine cavity. Tsafrir et al, have proposed a set of criteria for diagnosing pregnancy in the rudimentary horn: 1) A pseudo pattern of asymmetrical bicornuate uterus, 2) absent visual continuity with the tissue surrounding the gestation sac and the uterine cervix and 3) presence of myometrial tissue surrounding the gestational sac.13 The sensitivity of ultrasound is only 26% and sensitivity decreases as the pregnancy advances.14 In such cases, magnetic resonance imaging (MRI) is very useful not only in confirming the diagnosis, but it also helps to plan the surgery.15 Tubal pregnancy, cornual pregnancy and abdominal pregnancy are common sonographic and clinical misdiagnosis. It is very difficult to establish diagnosis in second trimester due to lack of definitive clinical criteria. The traditional and established treatment for rudimentary horn pregnancy is surgical removal of the pregnant horn even in unruptured case to prevent rupture and recurrent rudimentary horn pregnancy. In this case, laparotomy was performed and excision of the rudimentary horn was done successfully. Laparoscopic excision of the rudimentary horn pregnancy prior to rupture has been done successfully, since last two decades.16 Renal anomalies are found in 36% of cases; hence, it is mandatory to assess renal anomalies by scan.

CONCLUSION

Rudimentary horn pregnancy is a rare complication, which carries grave risk to the mother. More than 90% of the cases present in second trimester with intraperitoneal hemorrhage due to rupture of the horn. Diagnosis prior to rupture should be the concern in early pregnancy with either ultrasound or MRI to prevent life-threatening complications. The recent trend is to do laparoscopic excision of the rudimentary horn; laparotomy is still an option when the patient has developed abundant hemoperitoneum or is in shock.

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