Putting POP-Q to the test: does C - D = cervical length?

We investigated the correlation between calculated cervical length (CCL) and gross specimen cervical length (GCL) after total vaginal hysterectomy (TVH) at the time of surgery for pelvic organ prolapse (POP).

This was a retrospective chart review of patients who had undergone TVH with reconstructive surgery for POP between 2013 and 2015. Patients without an intact specimen or documented cervical length in the pathology report were excluded. CCL was defined as the absolute difference between Pelvic Organ Prolapse Quantification (POP-Q) points C and D. GCL was obtained from the pathology report as the distance from the external to the internal os. The Bland-Altman method was used to assess the accuracy of POP-Q measurements with a priori ranges. Symptom severity was evaluated using the PFDI-20 questionnaire. Analysis of variance was used to model both GCL and CCL as a function of prolapse stage and the leading compartment.

The final analysis included 202 subjects. Of the CCL measurements, 56.93% were within ±2 cm of GCL, while 36.14% were within ±1 cm. POP stage was significantly associated with GCL (P < 0.0024). CCL was significantly longer in patients with stage 4 POP (3.57 cm, 95% CI 3.13-4.00) than in those with stage 2 POP (P < 0.0017; mean 2.68 cm, 95% CI 2.45-2.92) and stage 3 POP (P < 0.0300; mean 2.94 cm, 95% CI 2.73-3.15). There were no significant correlations between PFDI scores and CCL or GCL.

The agreement between POP-Q CCL (|C - D|) and GCL decreases with increasing POP-Q stage. There was no correlation between POP symptom severity and GCL or CCL. GCL significantly increased with increasing POP stage.