The uterine isthmus and its sphincter mechanism, a radiographic study

Cervical Insufficiency

“…Palmer and Liesse (1946) and Asplund (1952) demonstrated with hysterography that the internal 0 s is narrower in the secretory than in the proliferative phase of the normal menstrual cycle. These important findings were later confirmed by Youssef (1958), Viala and Loustau (1962) and, with other methods, by Bergman and Svennerud (1957). The cyclic changes in the width of the internal 0 s are easily demonstrated clinically when dilation and curettage or insertion of an IUD is performed in different phases of the cycle.…”

“…Around the 5th month (there are different opinions as to the exact time) the isthmus, including the internal os, unfolds and becomes a part of the lower uterine segment. According to some authors (Stieve, 1927;Asplund, 1952;Youssef, 1958), a new internal 0s is created lower down in the isthmus, which even here is rather muscular, and a new muscular sphincter is formed. According to Danforth (1947,1954), however, the whole isthmus takes part in the unfolding, which does not stop until the 'fibromuscular junction.…”

Vesicouterine fistula as a complication of forceps delivery: a case report

“…Youssef explains the lack of urinary loss via the uterus in this case by the fact that the isthmic sphincter may maintain sufficient pressure to prevent the escape of urine [10].…”

The Diameter of the Uterine Isthmus During the Menstrual Cycle, Pregnancy and the Puerperium

“…Unlike Asplund (1952) who found that the lumen seemed to become narrower at the time of ovulation, we found that, in the cross-sectional study, the lumen was if anything wider just preceding ovulation. These changes are probably under hormonal control, and both Asplund (1952) and Youssef (19586) have shown that the administration of a progestogen after oestrogen priming results in narrowing of the isthmus, while Youssef (1958b) found that in cases of anovular menstruation, isthmography performed one week before the period showed a dilated isthmus. Asplund (1952) studied 26 patients by hysterography in pregnancy, and observed that the isthmus was "often constricted".…”

“…This part of the uterus can probably be damaged with excessive or forceful dilatation, and it is believed that this isthmic region is important in the normal functions of nidation and maintenance of pregnancy (Youssef, 1958~). Among previous attempts to estimate the width of the uterine isthmus under different conditions, the two most comprehensive studies have been by Asplund (1952) and Youssef (1958aYoussef ( , 1958b, while Mann (1963) reported an extensive investigation of the uterus in primary dysmenorrhoea. Techniques used have included hysterography (Asplund, 1952;Rubovits et al, 1953) or "isthmography" (Youssef, 1958a), the injection of Lipoidol into the uterus by a colpotomy incision (Youssef, 1958a), percutaneous retrograde iliac arteriography combined with hysterography (Borell and Fernstrom, 1953), the attempted passage of Hegar dilators (Rubovits eta/., 1953), traction of a Foley catheter (Bergman and Svennerund, 1957) and the observation by cineradiography of the passage of an intra-uterine balloon filled with radio-opaque media (Mann, 1963).…”