2.4.1. Transrectal ultrasonography
TRU was performed using an easi-scan™ ultrasonic
scanner (BCF Technology Ltd., Livingston, United Kingdom)
and an HS-101V ultrasonic device (Honda Electronics Co.,
Ltd., Toyohashi, Japan) with a 5 MHz linear ultrasonic
transducer. After the removal of feces, the probe was
inserted into the rectum and positioned dorsal to the
cervix. The probe was passed along the cervix and each
uterine horn to analyze the cross and longitudinal sections.
A positive TRU result was defined as the presence of
intrauterine fluid and an embryo with a detectable
heartbeat. Questionable results included cases with
intrauterine fluid without an embryo or with an embryo
without a detectable heartbeat, and a negative result was
defined as a uterus with no accompanying fluid.