Rudimentary Uterine Horn Presenting as a Tubal Mass
A Papneja1*, BSc, MD Candidate 2014 & A Murji2, MD
1
2
University of Toronto
Department of Obstetrics and Gynecology, University of Toronto
*anjali.papneja@utoronto.ca
A 33-year-old nulligravida woman was referred for an incidental ultrasound finding of a
1 x 3 cm solid mass with increased vascularity in the right fallopian tube. The patient
was asymptomatic. Physical exam revealed unremarkable external genitalia, normal
cervix and non-tender, mobile, right adnexal mass. The differential diagnosis at this point
included: ectopic pregnancy, fibroid, tubal carcinoma, mullerian anomaly. To rule out an
ectopic pregnancy, Beta-HCG was ordered and was subsequently negative. MRI
demonstrated a 2.3 x 1.6 cm solid mass in the infundibular/ampullar portion of the right
fallopian tube (Figure 1, arrow) consistent with either tubal leiomyoma or carcinoma.
Laparoscopy (Figure 2) revealed a unicornuate uterus (U) with non-communicating right
uterine horn (arrow), normal bilateral ovaries and tubes. Subsequently, renal ultrasound
was obtained and was normal. No further treatment was offered. The patient was
advised to have an early ultrasound in the event of pregnancy due to the literature
reporting ectopic pregnancies in non-communicating rudimentary horns. [1]
Female embryological development is dictated by the absence of a Y chromosome. The
SRY gene on the Y chromosome codes for Testis Determining Factor and in its absence
the undifferentiated gonads become ovaries. With insufficient levels of testosterone, the
Wolffian (mesonephric) ducts regress, while the Mullerian (paramesonephric) ducts
continue to develop. As the Mullerian ducts migrate caudally toward the urogenital sinus,
the two inferior ends fuse to form the uterovaginal canal [2]. The uterovaginal canal
further differentiates into the uterus, cervix and upper portion of the vagina (Figure 3).
Mullerian anomalies generally result from either a defect in Mullerian agenesis or an
error in fusion of the Mullerian ducts. Our patient has a unicornuate uterus with a
rudimentary horn, which is the result of abnormal development of one of the two
Mullerian ducts. Approximately two-thirds of all unicornuate uteri occur with a
rudimentary horn, indicating partial development of the contralateral Mullerian system.
Approximately half of such non-communicating rudimentary horns contain functioning
endometrium (Figure 4) and commonly present in adolescence with progressive
dysmenorrhea. Ectopic pregnancy in rudimentary horns has also been described and
occurs due to trans-peritoneal embryo migration [3]. A unicornuate uterus poses certain
reproductive risks including, recurrent pregnancy loss, preterm labor and delivery, intrauterine fetal growth restriction and abnormal presentation. Finally, women with
Mullerian anomalies have a strong association with renal anomalies (renal agenesis,
pelvic or horseshoe kidney) and must be investigated appropriately [5].
Key Learning Points:
 Ectopic pregnancy must be ruled out women of reproductive age presenting
with a pelvic mass.
 A unicornuate uterus results from a failure of one Mullerian duct to develop
or elongate.
 Women with a unicornuate uterus is at risk for: obstructed rudimentary
horn, ectopic pregnancy and adverse pregnancy outcomes,
 Mullerian anomalies have a 30% association with renal anomalies
necessitating ultrasound investigation.
References
[1] Jayasinghe Y, Rane A, Stalewski H, Grover S. The Presentation and Early Diagnosis
of the Rudimentary Uterine Horn. Obstet Gynecol 2005; 105(6):1456-67.
[2] Emans, S. Jean Herriot; Laufer, Marc R.; Goldstein, Donald P. 2005. Pediatric and
Adolescent Gynecology. Philadelphia: Lippincott Williams & Wilkins.
[3] Shulman, Lee P. Mullerian Anomalies. Clinical Obstetrics and Gynecology 2008;
51(1):214-22
[4] The American Fertility Society classifications of adnexal adhesions, distal tubal
obstruction, tubal occlusion secondary to tubal ligation, tubal pregnancies, mullerian
anomalies and intrauterine adhesions. Fertil Steril 1988; 49:944-95
[5] Li S, Alya Quayyum FV, Hricak Cand H. Journal of Computer Assisted
Tomography. 2000;24:829-834
Figures
Consent to publish these images was obtained from the patient.
U
Figure 1: MRI image
demonstrating a 2.3 x 1.6 cm
solid mass in the
infundibular/ampullar portion of
the right fallopian tube.
Figure 2: Laparoscopic image
revealing unicornuate uterus (U)
with non-communicating right
uterine horn (arrow), normal
bilateral ovaries and tubes.
Figure 3: Embryological development of the female genital tract. [2]
Figure 4: Anatomical and functional
variations of a unicornuate uterus
anomaly. [4]