Many systems for staging prolapse have been described. Typically it is graded on a scale of 0 to 3 or 0 to 4, with the grade increasing with the severity of prolapse (22). Currently the system approved by the International Continence Society is the Pelvic Organ Prolapse Quantification system, or POP-Q (23). This standardized quantification system facilitates communication between physicians in practice and research and enables progression of these conditions to be followed accurately. In this system, anatomic descriptions of specific sites in the vagina are used in place of traditional terms. The system identifies nine locations in the vagina and vulva in centimeters relative to the hymen, which are used to assign a stage (from 0 to IV) of prolapse at its most advanced site (Fig. 27.9). Although probably more detailed than necessary for general practice, clinicians should be familiar with the POP-Q system because most published studies use it to describe research results. Its two most important advantages over previous grading systems are (i) it allows the use of a standardized technique with quantitative measurements at straining relative to a constant reference point (i.e., the hymen), and (ii) its ability to assess prolapse at multiple vaginal sites.
The classification uses six points along the vagina (two points on the anterior, middle, and posterior compartments) measured in relation to the hymen. The anatomic position of the six defined points should be measured in centimeters proximal to the hymen (negative number) or distal to the hymen (positive number), with the plane of the hymen representing zero. Three other measurements in the POP-Q examination include the genital hiatus, perineal body, and the total vaginal length (23).
Figure 27.9 Standardization of terminology for female pelvic organ prolapse (POP-Q) classification. This diagram demonstrates the anatomic position of the POP-Q sites, including six sites involving the anterior (Aa, Ba), middle (C, D), and posterior (Ap, Bp) compartments with the genital hiatus (gh), perineal body (pb), and total vaginal length (tvl). (From Bump RC, Mattiason A, Bo K, et al. The standardization of terminology of female pelvic organ prolapse and pelvic ﬂoor dysfunction. Am J Obstet Gynecol 1996;175:12, with permission.)
The genital hiatus is measured from the middle of the external urethral meatus to the posterior midline hymen. The perineal body is measured from the posterior margin of the genital hiatus to the midanal opening. The total vaginal length is the greatest depth of the vagina in centimeters when the vaginal apex is reduced to its full normal position. All measurements except the total vaginal length are measured during maximal straining.
The anterior vaginal wall measurements are termed Aa and Ba, with the Ba point moving depending on the amount of anterior compartment prolapse. Point Aa represents a point on the anterior vagina 3 cm proximal to the external urethral meatus, which corresponds to the bladder neck. By definition, the range of position of this point is −3to +3. Point Ba represents the most distal or dependent point of any portion of the anterior vaginal wall from point Aa to just anterior to the vaginal cuff or anterior lip of the cervix. This point can vary depending on the nature of the patient’s support defect. For example, point Ba is −3 in the absence of any prolapse (it is never less than −3) to a positive value equal to the total vaginal length in a patient with total eversion of the vagina.
The middle compartment consists of points C and D. Point C represents the most dependant edge of the cervix or vaginal cuff after hysterectomy. Point D is the location of the posterior fornix; it is omitted if the cervix is absent. This point represents the level of the attachment of the uterosacral ligament to the posterior cervix. It is intended to differentiate suspensory failure from cervical elongation.