Materials and Methods
One hundred eighty-nine consecutive patients who presented to the Pelvic Floor Dysfunction Clinic at the Duke University Medical Center between January 1997 and September 1998 were included in the study. Patients were examined at their initial visit in the dorsal lithotomy position, and a clinical assessment for pelvic organ prolapse was performed using the International Continence Society's POPQ system5 (Figure 1). Six sites of pelvic organ prolapse quantification are located with reference to the plane of the hymen and are measured in centimeters above or proximal to the hymen (negative number) or below or distal to the hymen (positive number) with the plane of the hymen defined as zero. The anterior and posterior points A (Aa, Ap) are located on the midline vaginal wall 3 cm proximal to the hymen (range ±3 cm). The anterior and posterior points B (Ba, Bp) represent the maximum extent of prolapse of the anterior and posterior vaginal wall (range −3 cm to total vaginal length [tvl]). Point C represents the position of the cervix or vaginal cuff, and point D, the posterior fornix. The genital hiatus (gh) is measured from the external urethral meatus to the posterior midline hymen, and the perineal body (pb) is measured from the posterior midline hymen to the midanal opening. At a second clinic visit, subjects were examined while sitting 45° upright in a birthing chair and a second clinical assessment for pelvic organ prolapse was performed using POPQ. Both examinations are part of the standard comprehensive evaluation of all patients who present to our Pelvic Floor Dysfunction Clinic.
Other than patient position, the supine and upright examinations were performed in the same fashion. All examinations were done or supervised by the senior author (RCB). Patients were asked to empty their bladder before both examinations. Before the upright examination, but not the supine examination, a catheter was placed to determine postvoid residual. During each examination, patients were asked to strain forcefully and measurements were made when the patient was performing maximum Valsalva maneuver. Before each examination in the birthing chair, the 45° position was determined using a level and a protractor. Instruments used for the determination of the nine quantitative POPQ measurements included a standard bivalve vaginal speculum; a ring forceps with measuring grooves engraved at 1, 2, 3, 4, 5, 7.5, and 10 cm; and a 15-cm clear plastic ruler. Before any manipulation, the first measurements obtained were the genital hiatus and perineal body measurements using the plastic ruler. If prolapse beyond the hymen was present, measurements of the external sites were obtained first. If no external prolapse was present, the bivalve speculum was inserted into the vagina and slowly withdrawn as the patient strained down. The points of maximal descent of the cervix or vaginal cuff (point C) and, in patients with a cervix, the posterior fornix (point D) were measured with the graduated ring forceps. The bivalve speculum was then separated in half and the anterior and posterior points A and B (points Aa, Ba, Ap, and Bp) were measured using the graduated ring forceps with the half speculum retracting the opposite vaginal wall. Total vaginal length was measured by digitally replacing the vaginal apex to its normal anatomic position and measuring the maximum depth with the ring forceps. All nine measurements, with the exception of total vaginal length, were taken with the patient performing maximum Valsalva.
After each examination, patients were assigned to one of five ordinal stages of prolapse (0–IV) in accordance with the POPQ system. Subjects were also subgrouped according to which portion of the lower genital tract was the most distal part of the prolapse during maximal strain, as previously described.5,6 All methods, definitions, and descriptions conformed to the standards recommended by the International Continence Society.
The nine POPQ measurements and the stage of prolapse obtained from examination in the supine position were compared with those from the examination in the upright sitting position by using paired Wilcoxon signed-rank test and the nonparametric correlation coefficient, Spearman rho. A clinically important change in a POPQ value was defined a priori as an increase of 2 cm or more. Logistic regression analysis was done to identify patient characteristics that were independently associated with a clinically important increase in POPQ value with a change in examination position. A second logistic regression analysis was done to identify patient characteristics that were independently associated with an increase in stage of pelvic organ prolapse with change in examination position. All values of continuous variables are expressed as the mean ± standard deviation (range). Ordinal variables, such as stage of prolapse, are expressed as median (range). Statistical analysis was performed using SAS 6.12 (SAS Institute Inc., Cary, NC).
The mean age of the study subjects was 61 ± 13.5 years (range 30–85 years), the median parity was two (range 0–14), and the mean weight 74 ± 16 kg (range 43–160 kg). One hundred eighty-three women (94%) were white, and 167 (87%) were either premenopausal or using estrogen replacement therapy. One hundred thirty women (67%) had a previous hysterectomy, and 89 (44%) had previous urogynecologic or pelvic reconstructive surgery.
Table 1 shows the relationship between stage of pelvic organ prolapse in the supine position compared with reexamination in the upright sitting position. When examined in the upright position, 133 patients (70%) had the same stage of prolapse, whereas 49 (26%) had a higher stage of prolapse and seven (4%) had a lower stage of prolapse. Of the patients who were stage 0 or I when examined supine, 23 (36%) were stage II or greater when examined sitting upright. Similarly, of patients who were stage II when supine, 17 (23%) were stage III when examined upright. Nine patients (23%) who were stage III on supine examination were stage IV when examined upright.
The mean values for the nine POPQ measurements for each examination position are shown in Table 2. There was a statistically significant increase in the magnitude of prolapse at all eight POPQ sites but not in the measurement of total vaginal length. The median change for each site ranged from a low of 0.25 cm at site Ap to a high of 1.0 cm at the genital hiatus and point C. Over 15% of measurements at sites Ba and Bp and over 20% of measurements at sites C and the genital hiatus increased 2 cm or more when patients were examined upright. In all, 91 patients (48%) had at least one POPQ measurement increase by 2 cm or greater when examined in the upright position.
Logistic regression analysis was used to identify variables that might be independently associated with an increase in at least one POPQ measurement by 2 cm or more when a patient was examined upright. A second regression analysis was used to identify variables that might be independently associated with an increase in prolapse stage when a patient was examined upright. Variables considered included age, race, parity, weight, height, estrogen status, history of hysterectomy, history of urogynecologic or pelvic reconstructive surgery, the genital hiatus measurement in lithotomy position, and stage of prolapse in lithotomy position. None of those variables was significantly associated with either outcome variable.
In this study we compared quantification of pelvic organ prolapse in the most common examination position, dorsal lithotomy, with examination upright in a birthing chair, a position designed to maximize the magnitude of prolapse while allowing the access to the vagina and perineum necessary for precise measurements. Overall, the average values for each measurement increased when patients were examined upright, but only by a relatively small amount. There was moderate to good correlation between the POPQ measurements made in each position. Importantly, however, there was a subset of patients whose prolapse increased substantially when examined in the birthing chair. Over one quarter of patients in our study had a higher stage of prolapse and almost half of our subjects had at least one POPQ measurement increase by 2 cm or more when examined upright. Our findings are consistent with those of two smaller studies that evaluated quantification of pelvic organ prolapse in both dorsal lithotomy position and sitting upright.6 Both studies found a greater stage of prolapse when patients were in the upright sitting position.
Swift and Herring11 directly compared POPQ measurements in the standing position with measurements in the dorsal lithotomy position. They found a high degree of correlation between the values obtained in the two positions and no significant differences in stage of prolapse. They postulated that they did not find an effect of patient position on prolapse quantification because the standing position does not provide the same degree of pelvic tilt that is provided by the sitting position. They likened sitting in a birthing chair to McRoberts maneuver, in which maximum hip flexion straightens out and opens up the pelvis. Certainly, the birthing chair is designed to open the pelvic outlet and maximize the effect of pushing in order to facilitate vaginal birth. In contrast, we found a significantly larger mean genital hiatus measurement in the upright sitting position than in dorsal lithotomy position. This finding is consistent with the concept that sitting upright in a birthing chair opens the pelvic outlet thereby allowing the pelvic organs to protrude to a greater extent than examination in the lithotomy position in some patients. Although a standing examination is advocated by many as a means of demonstrating the maximal extent of pelvic organ prolapse, an examination in a birthing chair might be superior because of the mechanics of the pelvis and pelvic floor. Regardless of examination position, we should remember that the patient is an important resource in the clinical evaluation of pelvic organ prolapse and she should be asked whether the examination is demonstrating the maximum extent of prolapse that she has noted.
One confounding factor that could have influenced the results of this study was the difference in urine volume in the bladder at the time of each examination. Bladder catheterization was done routinely before the upright examination, to determine the postvoid residual urine volume, but not before the supine examination. In the proportion of patients who had voiding dysfunction that resulted in an elevated postvoid residual urine volume, an accentuation of anterior vaginal prolapse might have occurred during the supine examination. Had we catheterized patients before both examinations, we might have seen a larger increase in anterior vaginal prolapse with upright examination than was observed in this study.
It is standard at our clinic for a new patient referred for pelvic floor dysfunction to have a comprehensive pelvic floor evaluation, which includes two examinations, one supine and one upright in a birthing chair. Clinical decisions are not made until both examinations have occurred. Consequently, we cannot reliably determine the proportion of patients whose clinical treatment was changed because of the upright examination. Future studies that evaluate the effect of patient position on the clinical evaluation of pelvic organ prolapse should attempt to accurately determine the effect of examination position on clinical decision making.
The POPQ system has proved to be reliable and reproducible in several studies. It has been advocated by both national and international professional societies interested in the study of pelvic floor dysfunction. Consequently, it has the potential of improving scientific and clinical communications about pelvic organ prolapse. Several variables, including examination position, can affect POPQ values and the stage of pelvic organ prolapse. Various examination positions have been advocated, and each has its relative advantages and disadvantages. The severity of pelvic organ prolapse that can be demonstrated when an examination is performed upright in a birthing chair is greater in many patients than can be demonstrated in lithotomy position even with maximum straining. However, birthing chairs are not universally available, and a standardized examination position has not been and should not be specified. This highlights the importance of clearly specifying patient position when describing pelvic organ prolapse and of performing studies such as this one that elucidate the relationship that differences in examination technique have on the clinical evaluation of pelvic floor dysfunction.
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