Intraovarian Blood Flow Research Articles

Doppler study of arterial and venous intraovarian blood flow in stimulated cycles.

To evaluate arterial and venous intraovarian blood flow in follicle stimulating hormone-stimulated cycles. This was a prospective study of 76 follicle stimulating hormone-stimulated cycles carried out in 39 infertile patients who were included in a timed intercourse or intrauterine insemination program in a referral center for assisted reproduction. Transvaginal color and pulsed Doppler measurements of the follicular and luteal phase resistance index, pulsatility index, peak systolic velocity and maximum venous velocity were made and serum progesterone levels during the mid-luteal phase were recorded. Velocimetric parameters were established and then used to classify ovarian function as having a normal ovulatory cycle, or a cycle in which there was either luteal phase deficiency or a luteinized unruptured follicle. In 52 normal ovulatory cycles, the luteal phase peak systolic and maximum venous velocities were significantly higher and resistance and pulsatility indices were significantly lower than those found in the follicular phase. In 15 women with luteal phase deficiency we did not find any differences in arterial velocimetric parameters when compared with normal ovulatory cycles. However, luteal phase maximum venous velocities were lower in the luteal phase deficiency cycles and there was a significant correlation between luteal phase maximum venous velocity and serum progesterone levels (r = 0.36). Luteinized unruptured follicle cycles (n = 9) did not show significant changes during the ovarian cycle and no 'luteal conversion' of the Doppler signal was identified. Follicle stimulating hormone-stimulated cycles in infertile patients can have a high percentage of abnormal functional responses that can be diagnosed only by sonographic assessment, Doppler and the appropriate hormonal follow-up. Arterial and venous intraovarian blood flow remain unaltered during luteinized unruptured follicle cycles and serum progesterone levels correlated with luteal phase maximum venous velocity, which makes Doppler a potentially useful non-invasive test to assess ovulation and luteal function.

A Doppler ultrasonographic study of cyclic changes of ovarian perfusion in the Beagle bitch

Changes in intraovarian arterial blood flow were monitored by means of colour-coded and pulsed Doppler ultrasonography in Beagle bitches during the normal oestrous cycle (n = 11) and pregnancy (n = 3), and at PGF(2alpha)-induced luteolysis (n = 4). The ultrasonographic findings were related to the reproductive stage of the bitch, as determined by vaginoscopical and cytological criteria, and by the concentrations of oestradiol, LH and progesterone in peripheral blood plasma. Colour-coded Doppler ultrasonography was used to visualize and estimate intraovarian vascularization, and pulsed Doppler ultrasonography was used to measure the arterial blood flow. The systolic and diastolic peak velocities, the end-diastolic velocity, and the pulsatility index and resistance index were calculated for quantitative analysis of the Doppler waveforms. Intraovarian perfusion increased gradually during pro-oestrus. A marked enhancement of intraovarian colouring and blood flow velocities, and a decline in the indices for pulsatility and resistance were observed in the preovulatory period. Maximum perfusion was observed at ovulation and during the early luteal phase. Significant differences (P < 0.05) were detected for the values of all calculated Doppler parameters 2 days before and 2 days after ovulation. Intraovarian blood flow decreased gradually in accordance with luteal regression. Treatment with PGF(2alpha) caused a distinct decline in luteal activity and a concomitant reduction in intraovarian perfusion. The values of blood flow parameters found during the luteal phase of pregnant bitches were comparable to those of the normocyclic bitches. Doppler ultrasonography of the intraovarian arteries in bitches provides complementary information about cyclic changes of ovarian function.

A Doppler ultrasonographic study of cyclic changes of ovarian perfusion in the Beagle bitch

Changes in intraovarian arterial blood flow were monitored by means of colour-coded and pulsed Doppler ultrasonography in Beagle bitches during the normal oestrous cycle (n = 11) and pregnancy (n = 3), and at PGF(2alpha)-induced luteolysis (n = 4). The ultrasonographic findings were related to the reproductive stage of the bitch, as determined by vaginoscopical and cytological criteria, and by the concentrations of oestradiol, LH and progesterone in peripheral blood plasma. Colour-coded Doppler ultrasonography was used to visualize and estimate intraovarian vascularization, and pulsed Doppler ultrasonography was used to measure the arterial blood flow. The systolic and diastolic peak velocities, the end-diastolic velocity, and the pulsatility index and resistance index were calculated for quantitative analysis of the Doppler waveforms. Intraovarian perfusion increased gradually during pro-oestrus. A marked enhancement of intraovarian colouring and blood flow velocities, and a decline in the indices for pulsatility and resistance were observed in the preovulatory period. Maximum perfusion was observed at ovulation and during the early luteal phase. Significant differences (P < 0.05) were detected for the values of all calculated Doppler parameters 2 days before and 2 days after ovulation. Intraovarian blood flow decreased gradually in accordance with luteal regression. Treatment with PGF(2alpha) caused a distinct decline in luteal activity and a concomitant reduction in intraovarian perfusion. The values of blood flow parameters found during the luteal phase of pregnant bitches were comparable to those of the normocyclic bitches. Doppler ultrasonography of the intraovarian arteries in bitches provides complementary information about cyclic changes of ovarian function.

Subtorsion of the ovary: sonographic features and clinical management.

To define the sonographic imaging criteria of ovarian subtorsion. Fourteen women 16 to 35 years of age with suspected unilateral twisted ovaries were sonographically evaluated in a tertiary care center before laparoscopy. Transvaginal sonography was performed to determine the longest ovarian dimension, diameter of the periovarian vessels, and degree of intraovarian blood flow and to evaluate ovarian morphology. Laparoscopy was performed to verify the sonographic findings and to perform detorsion. All ovaries with subtorsion were of normal size, although still significantly longer than the contralateral, normal ovaries (47.5 and 29.6 mm, respectively; P = .001). The mean diameter of the periovarian vessels was significantly greater for the ovaries with subtorsion than the normal ovaries (29.9 and 19.2 mm, respectively; P= .0001). At laparoscopy, the ovary was twisted less than 180 degrees in 9 patients and 180 degrees to 360 degrees in 5. The degree of twisting correlated significantly with the size of the ovary (P = .016) and diameter of the periovarian vessels (P = .046). The 3-month sonographic follow-up after detorsion revealed bilateral normal ovarian dimensions with proper follicular growth. Congestion of the periovarian vessels with normal ovarian morphology and persistent blood flow on sonography, combined with the presence of appropriate clinical signs, may be indicative of ovarian subtorsion.

Polycystic ovary syndrome: relationship between insulin sensitivity ,sex hormone levels and ovarian stromal blood flow

Polycystic ovary syndrome (PCOS) is the most common cause of menstrual disorders ,and is characterized by chronic anovulation ,hyperandrogenism and infertility. In recent years ,it has become apparent thatPCOS is also associated with hyperinsulinemia that is probably central to the pathogenesis of PCOS. As a peculiar vascular pattern has been reported to be present in PCOS ,the aim of this study was to investigateintraovarian stromal vascularization in PCOS patients and its possible correlation with sex hormones ,gonadotropins and insulin levels.Twenty-eight oligomenorrheic or amenorrheic patients with PCOSand 14 eumenorrheic women with a PCOS-like ovarian pattern undergoing endocrine screening and ultrasound color Doppler intraovarian blood flow were recruited to the study. Ten healthy women with regularmenses represented the control group.Hormonal assays (follicle-stimulating hormone (FSH) ,luteinizing hormone (LH) ,androstenedione ,testosterone ,sex hormone-binding globulin (SHBG) and estradiol),oral glucose tolerance test (OGTT) ,baseline and glucose-induced insulin levels ,and transvaginal ultrasonographic and color Doppler analysis (pulsatility index (PI) ,resistance index (RI) and velocity(Vmax) of ovarian stromal flow) were performed in all participants in the early proliferative phase. Endocrine values showed significant differences in PCOS patients compared with PCOS-like womenand controls ,while PI and RI indices were significantly higher in controls. PCOS patients were divided into hyperinsulinemic (n = 16) and normoinsulinemic (n = 12). Androstenedione was significantlyhigher (p < 0.01) in the hyperinsulinemic than in the normoinsulinemic patients and controls ,while SHBG was significantly (p < 0.01) lower in the hyperinsulinemic group. Analysis ofcolor Doppler intraovarian vascularization showed a significantly lower RI and a higher Vmax in the hyperinsulinemic subjects than in the normoinsulinemic PCOS patients and controls.An increasedstromal blood flow was observed in the PCOS and PCOS-like patients by transvaginal color Doppler evaluation ,but this technique is not able to differentiate these two similar ovarian patterns. However,hyperinsulinemic PCOS patients had an increased vascularity of the ovarian stroma. A strong correlation between hyperinsulinemia ,hyperandrogenism and low SHBG levels was evidenced ,and a hyperinsulinemia-inducedmechanism for ovarian stromal angiogenesis is discussed.

WS03‐02Doppler assessment of the ovarian blood flow

BackgroundThe aim of this study was to evaluate arterial and venous intraovarian blood flow in infertile patients.MethodsSeventy‐six FSH stimulated cycles in 39 patients participating in a timed intercourse or iui program were studied. Transvaginal color and pulsed Doppler measurement of the dominant follicle and corpus luteum resistance index (RI), pulsatility index (PI), peak systolic velocity (PSV), maximum venous velocity (MVV) and serum p levels during mesoluteal phase were recorded. Velocimetric parameters were established and then used to classify ovarian function in normal ovulatory cycle (NOV; n = 52), luteal phase defect (LPD; n = 15) and luteinized unruptured follicle (LUF; n = 9).ResultsThe luteal PSV and MVV in the nov and LPD cycles were significantly higher (NOV: 24.3 ± 12.2 vs. 13.1 ± 6.5 and 8.1 ± 3.30 vs. 3.6 ± 1.1; LPD: 29.8 ± 10.3 vs. 14.4 ± 4.8 and 5.7 ± 1.5 vs. 4.3 ± 1.2) and luteal RI and PI were significantly lower (NOV: 0.45 ± 0.06 vs. 0.55 ± 0.08 and 0.62 ± 0.15 vs. 0.83 ± 0.22; LPD: 0.46 ± 0.05 vs. 0.54 ± 0.06 and 0.62 ± 0.10 vs. 0.81 ± 0.15) than follicular ones. LUF cycles did not show significant changes during the ovarian cycle (follicular vs. luteal PSV; MVV; RI and PI: 14.4 ± 4.8 vs. 14.9 ± 7.3; 4.3 ± 1.2 vs. 4.2 ± 2.1; 0.47 ± 0.07 vs. 0.58 ± 0.12 and 0.66 ± 0.12 vs. 0.89 ± 0.29) and no ‘luteal conversion’ of the Doppler signal was identified. There was significant correlation between luteal MVV and serum p (r = 0.36).ConclusionsArterial and venous intraovarian blood flow remain unaltered during LUF cycles and P levels correlate with luteal MVV. This makes Doppler an effective noninvasive test to assess ovulation and luteal function.

Conservative management of adnexal torsion in premenarchal girls

Study Objective. To evaluate treatment of premenarchal girls with torsion of the adnexa. Design. Retrospective review of medical records (Canadian Task Force classification II-2). Setting. Tertiary care, university-affiliated hospital. Patients. Eight premenarchal girls (age range 3–12 yrs) with twisted adnexa. Intervention. Laparoscopic detorsion and follow-up with B scan and Doppler ultrasound imaging. Measurements and Main Results. Duration of complaints ranged from 8 to 72 hours (mean 34.6 hrs) and the interval from admission to surgery ranged from 6 to 24 hours (mean 18.7 hrs). Four patients had torsion of normalappearing adnexa. The other four had ovarian neoplasms. Two had cystic mature teratomas (dermoid cysts) and one a serous cystadenoma that required additional operation. The fourth girl had a simple ovarian cyst that was aspirated laparoscopically. Seven girls (87%) had normal-appearing ovaries on follow-up ultrasound. In one patient, a small ovary was seen, with no intraovarian blood flow on color Doppler. Conclusion. Although the diagnosis of torsion of the adnexa in premenarchal girls is difficult and usually delayed, laparoscopic detorsion seems to be an effective adnexa-sparing approach. We suggest that laparoscopy should be the treatment of choice and that detorsion, rather than adnexectomy, be performed more often in these patients.

Comparison of Transvaginal Color Doppler Imaging and Color Doppler Energy for Assessment of Intraovarian Blood Flow

Objective: To investigate any systematic differences in the analysis of blood flow velocity waveforms derived by color Doppler imaging and color Doppler energy examination of corpora lutea and adnexal tumors, to test whether the accuracy for diagnosing ovarian malignancy differs between end points derived by color Doppler imaging and color Doppler energy, and to compare the reproducibility of flow velocity waveform analysis obtained by both methods.Methods: Fifty-six asymptomatic women with presumed corpora lutea and 67 women with known adnexal masses were included in the study. They all were examined using transvaginal sonography with color Doppler imaging and color Doppler energy. Pulsed Doppler sonography was used to obtain flow velocity waveforms to determine the pulsatility index (PI), resistance index (RI), peak systolic velocity, and time-averaged maximum velocity. The tumors were classified retrospectively according to histologic criteria.Results: There were 52 women with benign, three with borderline, and 12 with malignant ovarian tumors. Repeated-measures analysis of variance revealed no systematic differences in the values of all four measurements performed under color Doppler imaging and color Doppler energy for all cases of corpora lutea and adnexal tumors (PI: P = .153, RI: P = .197, peak systolic velocity: P = .355, time-averaged maximum velocity: P = .159). All cases of borderline and malignant tumors had detectable pulsatile blood flow with color Doppler imaging and color Doppler energy. Forty-two (80.8%) of the benign tumors had flow detectable with color Doppler imaging, compared with 40 (76.9%) with color Doppler energy (P = .480). Analysis of receiver operating characteristic curves showed a marginal but nonsignificant improvement in diagnostic performance with color Doppler energy compared with color Doppler imaging for all four measurements (PI: P = .182, RI: P = .178, peak systolic velocity: P = .254, time-averaged maximum velocity: P = .238). The intraclass correlation coefficients for all four measurements were superior with color Doppler imaging compared with color Doppler energy.Conclusion: Flow velocity waveform analysis and diagnostic accuracy for ovarian malignancy are not significantly different between color Doppler imaging and color Doppler energy. Examinations with color Doppler imaging appear to be more reproducible than those with color Doppler energy.

Comparison of Transvaginal Color Doppler Imaging and Color Doppler Energy for Assessment of Intraovarian Blood Flow

Comparison of Transvaginal Color Doppler Imaging and Color Doppler Energy for Assessment of Intraovarian Blood Flow

Low intraovarian vascular resistance: a marker for severe ovarian hyperstimulation syndrome

Objective: To assess intraovarian blood flow in relation to the severity of ovarian hyperstimulation syndrome (OHSS) after controlled ovarian hyperstimulation. Design: A prospective study. Setting: Monash IVF, Clayton, Victoria, Australia. Patient(s): Thirty patients with OHSS after embryo or gamete transfer who also had sonographic evidence of ascites. Main Outcome Measure(s): The resistance to blood flow within the ovaries of 11 patients with severe OHSS and 19 patients with mild OHSS was measured by using transabdominal ultrasonography with color flow and pulsed Doppler imaging. Result(s): The pulsatility index (PI), resistance index (RI), and the S-D ratio, all measures of downstream vascular impedance, were significantly lower in those patients with severe OHSS. In cases with RI < 0.48, more than two thirds of the patients had a pleural effusion, whereas patients with either PI < 0.75 or S-D < 1.92 had pleural effusion in over one half of the cases. It was notable that blood flow velocity did not differ significantly between the two groups despite the changes in vascular impedance. Conclusion(s):There appears to be a close correlation between the severity of OHSS and the resistance to blood flow within the stimulated ovaries. Measurement of intraovarian vascular resistance before gamete transfer or ET in patients undergoing controlled ovarian hyperstimulation may help in predicting those patients at particular risk of developing severe OHSS.

Color Doppler analysis in oligo-and amenorrheic women with polycystic ovary syndrome

The objective of this study was to determine whether amenorrheic women have more severe blood flow variations and clinical-endocrinological patterns in comparison with oligomenorrhea polycystic ovary syndrome (PCOS) patients. Twenty oligomenorrhea women (cycle length > 35 days; Group I), and 20 amenorrheic women (no vaginal bleeding for at least 6 months; Group II) were submitted to ultrasonographic evaluation of ovarian volume, follicle distribution, number and diameter, color Doppler analysis of uterine and intraovarian blood flow, hormonal assay of different compartments, and plasma evaluation of lipid profile.The number of subcapsular small-sized follicles, and the ovarian volume, androstenedione and luteinizing hormone (LH) plasma levels, and the LH/follicle-stimulating hormone (FSH) ratio were significantly higher in the amenorrheic group compared with the oligomenorrhea patients. Furthermore, significantly lower high-density lipoprotein (HDL) and HDL/total cholesterol ratio were observed in Group II compared with Group I. In addition, in Group II, higher resistance in the uterine arteries and lower impedance to blood flow in the intraovarian arteries have been shown.The assessment of ovarian morphology by transvaginal ultrasound and Doppler flow analysis of both intraovarian and uterine arteries in patients with PCOS may provide an insight into the pathological state and the degree of progression of the disease.

Intraovarian blood flow during spontaneous and stimulated cycles.

This study was undertaken to investigate intraovarian blood flow during the early follicular, periovulatory and mid-luteal phases, during spontaneous and stimulated ovarian cycles. Transvaginal ultrasonography with colour flow imaging was used to measure the pulsatility index in eight patients with spontaneous cycles, 20 patients undergoing induction of ovulation with clomiphene citrate and 11 patients undergoing controlled ovarian hyperstimulation for in-vitro fertilization (IVF)-embryo transfer with gonadotrophin-releasing hormone analogue, human menopausal gonadotrophin, human chorionic gonadotrophin. All patients were studied during the early follicular, periovulatory and mid-luteal phase. Intraovarian blood flow velocity waveforms were found in 20% of cases at the early follicular phase, in 56% during the periovulatory phase and in 85% during the mid-luteal phase (P < 0.001). Pulsatility index at the early follicular phase was found to be 1.05 +/- 0.22, during the periovulatory phase 0.99 +/- 0.22 and during the mid-luteal phase 0.85 +/- 0.22. The appearance of intraovarian flow velocity waveforms may suggest either ovarian neovascularization or final follicular maturation or luteinization, which can be detected or measured by Doppler technology.

Relationship of ovarian stromal blood flow at the baseline ultrasound scan to subsequent follicular response in an in vitro fertilization program

To assess whether Doppler indices of intraovarian blood flow are related to the subsequent follicular response in an in vitro fertilization (IVF) program. One hundred five women underwent ultrasonographic assessment of ovarian morphology, transvaginal color Doppler measurement of intraovarian blood flow and immunoassay of serum FSH during the early follicular phase of an IVF cycle. The subsequent follicular response was related to the Doppler data. Mean ovarian stromal peak systolic blood flow velocity was significantly correlated with the follicular response (P = .001), even after adjusting for the age of patient, type of ovary (polycystic or normal), total number of human menopausal gonadotropin ampules used, and serum FSH. Mean ovarian stromal pulsatility index was not related to the follicular response. Mean ovarian stromal peak systolic blood flow velocity was significantly lower (P = .007) in the poor-response group. The adjusted odds of a poor response increased significantly by an estimated 22% per cm/second decrease in velocity (P = .02). Ovarian stromal blood flow at the baseline ultrasound scan is correlated with subsequent follicular response and may be a new indicator for predicting ovarian responsiveness in an IVF program.

Human follicular nitric oxide pathway: relationship to follicular size, oestradiol concentrations and ovarian blood flow.

Nitric oxide (NO) has been suggested to be involved in ovarian physiology. Our aim was to study follicular nitrite and nitrate (NO3/NO2) levels in women undergoing in-vitro fertilization (IVF), and to examine their relationship to follicular size, oestradiol concentrations, and ovarian artery and intra-ovarian blood flow as measured by Doppler ultrasound. A total of 15 patients from the IVF programme of Hadassah University Hospital, Mt Scopus, Israel, participated in the study. Detailed transvaginal ultrasonographic examination was performed before ovum collection, and ovarian artery and intra-ovarian blood flow were measured. While aspirating the follicles, the content of two to four of the follicles in each ovary was collected individually, the volume of follicular fluid measured, and NO3/NO2 concentrations were determined. A statistically significant positive correlation was found between follicular fluid NO3/NO2 concentrations and follicular volume (r = 0.76), as well as between NO3/NO2 concentrations and oestradiol concentrations (r = 0.63). A statistically significant negative correlation was found between follicular fluid NO3/NO2 concentrations and ovarian flow parameters as well as between NO3/NO2 concentrations in follicles containing 4-5 ml and ovarian artery pulsatility index.

Blood flow changes in the ovarian and uterine arteries during the normal menstrual cycle

OBJECTIVE: Our purpose was to study the hemodynamic changes in the uterine and intraovarian vessels during the normal menstrual cycle and to relate the vascular changes to hormonal index values. STUDY DESIGN: Seven women who had bilateral tubal patency, a normal pelvis on laparoscopy, and regular ovulatory cycles underwent serial transvaginal ultrasonography on menstrual cycle day 2, daily from estimated day of ovulation –6, hourly from estimated day of ovulation –2, or when the mean follicular diameter was >16 mm (whichever was earlier) until 6 hours after follicular rupture and once 7 days after follicular rupture. At each scan uterine and intraovarian blood flow was assessed with transvaginal color Doppler ultrasonography and serum concentrations of follicle-stimulating hormone, luteinizing hormone, estradiol, and progesterone assessed by fluoroimmunoassay. RESULTS: In one case there was evidence of a luteinized unruptured follicle and the patient was therefore excluded from analysis. In the other six women there was spontaneous ovulation at a mean of 39 hours after the onset of the luteinizing hormone surge. On the side with the dominant follicle, follicular and ovarian stromal peak systolic blood flow velocity rose significantly during the menstrual cycle with no significant change in pulsatility index. The changes in blood flow velocity correlated significantly with changes in serum follicle-stimulating hormone, luteinizing hormone and progesterone concentrations. There were no significant changes in either blood flow velocity or pulsatility index in the contralateral ovary. Uterine artery time-averaged maximum velocity on the side of the developing ovarian follicle increased during the menstrual cycle with no significant change in the contralateral vessel. Uterine artery pulsatility index on the side of the developing follicle declined during the midluteal phase and was significantly lower than on the contralateral side. The changes in time-averaged maximum velocity correlated with the changes in serum estradiol and progesterone concentrations. CONCLUSION: The vascular changes in the wall of the dominant ovarian follicle and ovarian stroma during the menstrual cycle are consistent with activity of angiogenic-like factors. The decline in uterine artery resistance during the midluteal phase may reflect optimal vascularity for implantation of the blastocyst. (Am J Obstet Gynecol 1996;175:625-31.)

Color Doppler analysis in lean and obese women with polycystic ovary syndrome.

The objective of this study was to determine whether obese patients with polycystic ovary syndrome (PCOS) show different ovarian and uterine blood flow patterns in comparison with lean patients. Sixteen obese (body mass index: BMI = 31.4 +/- 3.6 kg/m2) and 22 lean (BMI = 21.1 +/- 1.3 kg/m2) PCOS patients underwent, in the early follicular phase if oligomenorrheic or randomly if amenorrheic, ultrasonographic evaluation of ovarian volume, echodensity and follicle number; transvaginal color Doppler evaluation of uterine and intraovarian blood flow; and radioimmunological assay of luteinizing hormone, follicle stimulating hormone, growth hormone, estradiol, progesterone, testosterone, androstenedione, insulin, insulin-like growth factor I, and other hormonal parameters. Hematocrit, plasma glucose, total cholesterol, high density lipoprotein and triglycerides were also evaluated. Insulin levels were significantly higher in the obese group, whereas levels of growth hormone were significantly lower. Moreover, a more adverse lipid profile was observed in overweight patients. This was associated with higher hematocrit values. At Doppler analysis, a significantly higher mean uterine artery pulsatility index (PI) was observed in the obese group. Furthermore, the PI was inversely correlated with high density lipoprotein values (r = -0.4820; p < 0.05). In both groups, androstenedione was correlated with the uterine PI. The above findings may, in part, explain the increased risk in women with PCOS of developing cardiovascular diseases, and emphasize that obesity may further increase the risk.

Blood flow changes in the intraovarian arteries during the periovulatory period: relationship to the time of day.

Intraovarian blood flow was assessed by transvaginal color and pulsed Doppler ultrasound prospectively in six women during the periovulatory period. All patients had regular ovulatory menstrual cycles and a mid-luteal serum progesterone level consistent with spontaneous ovulation in the preceding cycle. Each patient underwent serial transvaginal ultrasound examination and Doppler assessment of blood flow in the ovarian stroma and in the wall of the dominant follicle or corpus luteum. When the mean follicular diameter was > 16 mm or day -2 from the estimated day of ovulation was reached, patients were scanned at 6-h intervals at 06.00, 12.00, 18.00 and 24.00 until follicular rupture, to investigate the presence of circadian rhythms. The pulsatility index (PI) and the maximum peak systolic blood flow velocity (Vmax) were calculated as Doppler indices of impedance to blood flow and velocity, respectively. A venous blood sample was taken at each visit for subsequent hormonal analysis. There was no significant circadian fluctuation in either mean follicular Vmax or mean follicular PI before or after the luteinizing hormone (LH) surge. Similarly, mean Vmax and mean PI in the non-dominant ovarian stroma did not show any significant fluctuation over the same periods. The mean PI in the dominant ovarian stroma showed daily fluctuations with the highest values occurring most commonly at 06.00 and the nadir in the afternoon and late evening. This fluctuation was the reverse of the circadian variation previously demonstrated in the uterine artery. However, in contrast to the uterine artery, comparison between the mean PI values in the dominant ovarian stroma at 06.00 and 18.00 only approached significance after the LH surge. The dominant ovarian stroma Vmax tended to rise during the day, although the differences between 06.00 and 18.00 were also not significant. Although there are fluctuations in Doppler blood flow indices in the dominant ovarian stroma, further studies are necessary to demonstrate whether this represents a significant circadian rhythm.

Physiological and Immunocytochemical Evidence for a New Concept of Blood Flow Regulation in the Corpus Luteum1

To explain the high rate of blood flow in the corpus luteum, we hypothesize that luteal blood vessels offer minimal resistance to flow and are incapable of vasomotion. This hypothesis was tested in rabbits at mid-pseudopregnancy by measuring blood flow in the corpus luteum and ovarian stroma with tracer-labeled microspheres at three levels of arterial blood pressure, which was manipulated by constricting the aorta above the ovarian artery. In addition, the distribution of vascular smooth muscle in the ovary was evaluated with morphological and immunocytochemical techniques. Decreases in arterial pressure were paralleled by reductions in blood flow in the corpus luteum, whereas ovarian stromal blood flow was unchanged. Consistent with our hypothesis, there was no change in the low level of vascular resistance offered by blood vessels in the corpus luteum, supporting the view that they are maximally dilated and incapable of autoregulation. Morphologically, the vessels within the corpus luteum appeared as large sinusoidal capillaries without smooth muscle, providing an anatomical explanation for the lack of vasomotor control demonstrated physiologically. The absence of vascular smooth muscle was confirmed with immunocytochemistry using an antibody against the muscle-specific intermediate filament, desmin. The fluorescein-labeled antibody decorated arteries and arterioles within the ovarian stroma and near the capsule of the corpus luteum, but did not decorate vessels in the corpus luteum of pseudopregnancy, providing additional evidence that the vessels of the corpus luteum lack the smooth muscle investment necessary to change vascular caliber. From these findings, we have proposed a novel scheme to explain intraovarian blood flow regulation. Vascular resistance in the ovarian stroma, as in most tissues, is acutely regulated by dilation or constriction of intratissue arterioles. In contrast, vascular resistance within the corpus luteum is modeled as a relatively invariable parameter, fixed at a low level by the morphological characteristics of the luteal vasculature. Therefore, the corpus luteum operates on a linear (maximally "vasodilated") pressure-flow curve, does not actively regulate intratissue blood flow, and is subject to acute regulation of perfusion only through changes in extra-luteal vessels.