hysterectomy, pelvic organ prolapse, follow-up studies, urogynecology, kaplan-meier estimate
Hysterectomy is the most frequently performed major gynecological operation in Denmark with a rate of around 180/100,000 women per year . Long-term urogynecological complications such as pelvic organ prolapse (POP) have been described [2,3], but the epidemiology of these is so far not entirely clear.
In 2008 the lifetime risk of undergoing POP surgery for an 80-year-old woman was 18.7% , and another study found the cumulated incidence of POP surgery among hysterectomized women to be 12% after 32 years of follow-up .
The purpose of this study was to examine if regional difference was reflected in the incidence of POP surgery among hysterectomized women. To our knowledge, regional variances in POP surgery subsequent to hysterectomy has not been studied before.
Data were collected from the Danish National Patient Registry on all benign hysterectomies (n=168,474) and POP surgeries performed on women in Denmark from January 1, 1977 to December 31, 2009 . After exclusion of women with POP surgery preceding the hysterectomy (n=13,592), 154,882 hysterectomized women were included in the cohort for analyses. The hospitals performing the hysterectomies were grouped corresponding to today’s five regions in Denmark .
According to the compartment affected, POP operations subsequent to hysterectomy were classified into four groups using the ICD-8 and ICD-10 classifications : anterior compartment, apical compartment, posterior compartment, and unclassified. The unclassified operations were only recorded from 1996 onwards. Only the first incidence of POP surgery after hysterectomy for each woman was included in this study.
STATA 12.1 (Texas, USA) was used for data analyses. Patients were followed-up from hysterectomy to first POP surgery, death/emigration, or end of study period (December 31, 2009).
Some women had POP surgery in multiple compartments; when calculating proportions of first POP surgery in each compartment, all POP procedures for each woman were included. The Chi-square test of independency was used to test for association between compartment and region.
Cumulated incidence of women undergoing POP surgery for each region was depicted with Kaplan-Meier curves as failure (1- probability of survival without POP surgery). Differences in cumulated incidence were tested by log-rank test.
The study was approved by the Danish Data Protection Agency (reg no. 2010-41-4286).
154,882 women without previous POP surgery were hysterectomized on benign indications from 1977 to 2009. In all, 10,882 POP procedures were performed on 8,281 women after hysterectomy. During the study period, Central Denmark Region performed the highest number of hysterectomies (n=37,396) comprising 24.1% of all hysterectomies. Region of Southern Denmark performed 36,913 hysterectomies (23.8%), Region Zealand performed 32,709 hysterectomies (21.1%), Capital Region of Denmark performed 31,761 hysterectomies (20.5%), and North Denmark Region performed 16,103 hysterectomies (10.4%).
The compartmental surgical distribution of POP surgery revealed the following pattern: Anterior compartment 40% (39-41%), apical compartment 10% (9-11%), posterior compartment 50% (47-51%), and unclassified 1%. Capital Region Denmark deviated from this distribution; surgery in the anterior compartment comprised 35% and surgery in the apical compartment comprised 13%. A Chi Square test of independence (p=0.001) showed that region and compartment of POP were associated. This means that the deviation found in Capital Region Denmark was significantly different.
The cumulative incidence of POP surgery for each woman was plotted on a Kaplan-Meier curve (figure 1). After 32 years of follow-up Capital Region of Denmark had a cumulative incidence of 8.7% (95% confidence interval (CI): 8.1-9.3), which was significantly lower than the other regions (p=0.000). Region Zealand had a cumulative incidence of 11.0% (95% CI: 10.3-11.8), Region of South Denmark had a cumulative incidence of 11.9% (95% CI: 11.1-12.7), Central Denmark Region had a cumulative incidence of 12.4% (95% CI: 11.7-13.2), and North Denmark Region had a cumulative incidence of 13.0% (95% CI: 11.7-14.3)
One of the strengths of the study is the large number of women included and the long follow-up period. Further, all hysterectomized women without previous POP surgery in the study period were included in the study, thus the risks of selection bias were minimized.
In larger register based studies, there is always a risk that improper registrations by the clinicians may skew the results. The Danish National Patient Register has, however, been studied and found suitable for epidemiological studies [6,7]
A limitation to the study is the fact that only women operated for POP were included. Some women and probably clinicians prefer conservative treatment of POP (pelvic floor exercises, vaginal pessary treatment, etc.) Further, data for potential confounders such as parity, body mass index, smoking habits, etc. was not available. Women operated for POP before 1977 were not registered centrally. Hence some of the women hysterectomized early in the study period could have undergone POP surgery before the hysterectomy.
The distribution of POP surgery per compartment was different among hysterectomized women compared to the general Danish female population . POP surgery in the posterior compartment was predominant among hysterectomized women whereas POP surgery in the anterior compartment is predominant among the general population. This could be explained by a weakening of the rectovaginal fascia at hysterectomy. One could also suspect that the upper part of the rectovaginal fascia was never included in the closure of the vaginal cuff. The defect might therefore be categorized as part of an apical defect.
We found a significantly lower cumulated incidence of POP surgery for women hysterectomized in Capital Region of Denmark. This finding could either be explained by better operative technique at hysterectomy in Capital Region of Denmark, especially with regards to suspension of the vaginal cuff. It could also, however, be because of different diagnostic traditions or another treatment strategy.
In 2007 Capital Region of Denmark had one office gynecologist per 34,043 inhabitants whereas Region Zealand had one per 81,150, Region of Southern Denmark had one per 107,273, Central Denmark region had one per 133,333 inhabitants, and North Denmark Region had one per 289,000 inhabitants . These numbers are generally constant, as license to practice privately are tightly controlled in Denmark. Office gynecologists have limited surgical treatment possibilities and hence generally use conservative treatment. Conservative treatment is most feasible for POP in the anterior compartment. In regions with few office gynecologists, patients are often referred directly to a gynecologic department and thus have a more direct route to surgical treatment. This fact could explain the differences in cumulated incidence of POP surgery subsequent to hysterectomy: regions with lower number of inhabitants per office gynecologist had lower cumulated incidence. Also it could explain that Capital Region of Denmark had a lower proportion of POP surgery in the anterior compartment.
We recommend further studies to enlighten any regional inequality in treatment options for POP in hysterectomized women. These studies should ideally include data regarding conservative treatment.
The authors report no declarations of interest.
- Lykke R, Blaakær J, Ottesen B, Gimbel H (2013) Hysterectomy in Denmark 1977–2011: changes in rate, indications, and hospitalization. Eur J Obstet Gynecol Reprod Biol 171: 333–338. [Crossref]
- Shalom DF, Lin SN, O'Shaughnessy D, Lind LR, Winkler HA (2012) Effect of prior hysterectomy on the anterior and posterior vaginal compartments of women presenting with pelvic organ prolapse. Int J Gynecol Obstet 119: 274–276. [Crossref]
- Lukanovic A, Drazic K (2010) Risk factors for vaginal prolapse after hysterectomy. Int J Gynaecol Obstet 110: 27–30. [Crossref]
- Løwenstein E, Ottesen B, Gimbel H (2015) Incidence and lifetime risk of pelvic organ prolapse surgery in Denmark from 1977 to 2009. Int Urogynecol J 26: 49–55. [Crossref]
- Lykke R, Blaakær J, Ottesen B, Gimbel H (2015) Pelvic organ prolapse (POP) surgery among Danish women hysterectomized for benign conditions: age at hysterectomy, age at subsequent POP operation, and risk of POP after hysterectomy. Int Urogynecol J 26: 527–532. [Crossref]
- Lidegaard Ø, Hammerum MS (2002) The National Patient Registry as a tool for continuous production and quality control. Ugeskr Laeger 164: 4420–4423. [Crossref]
- M Ottesen (2009) Validity of the registration and reporting of vaginal prolapse surgery. Ugeskr Laeger 171: 404–408. [Crossref]
- D.H. Authority, Medicines (2007) Rapport for specialet: Gynækologi og obstetrik.