Male fetal pig lower urinary tract function in mid second and early third trimester of gestation

Purpose: Routine use of ultrasound during pregnancy has emphasized the need for greater knowledge about normal and abnormal voiding function during fe tal live. We describe the developmental changes in lower urinary tract func tion from the middle of the second to the early third trimester of gestatio n. Materials and Methods: The study included 22 male fetal pigs of 13 pregnant Goettingen minipigs (gestational period 111 to 115 days) with 11 fetuses i n the middle of the second (median 61.5 days, 0.55 of term) and 11 fetuses in the beginning of the third trimester of gestation (median 80 days, 0.72 of term). With the sow under isoflurane anesthesia catheters were placed in the bladder, rectum and amniotic cavity of the fetuses, and a flow probe w as placed around the distal urethra. After the sow was at light sleep ureth ral flow, amniotic pressure, abdominal pressure and bladder pressure were r ecorded a median of 241 minutes. Results: The recordings of 14 fetuses were evaluable. In the middle of the second trimester the fetuses showed an almost constant dribbling with a med ian flow of 0.2 mi. per minute and a median of 4 concomitant bladder contra ctions per minute of median 3.5 cm. H2O (detrusor pressure). At the beginni ng of the third trimester the fetuses had periods of staccato flow (median 0.2 mi. per minute, staccato frequency 1 to 2 Hz.) on top of contractions ( median 4 contractions per minute, median detrusor pressure 5.5 cm. H2O) wit h no flow between voidings. Conclusions: Development of storage and voiding function in male pigs occur s between the mid-second and early third trimester of gestation, together w ith emergence of striated sphincter bursting activity, which interrupts flo w in the urethra during the voiding phase.