1 Minimal Access Surgery Unit, Division of Gynaecologic Endocrinology & Reproductive Medicine, University Department of Obstetrics and Gynaecology, Waehringer Guertel 1820, A-1090 Vienna, and 2 Department of Medical Computer Sciences,University of Vienna, Waehringer Guertel 1820, A-1090 Vienna, Austria
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Abstract |
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Key words: flexible hysteroscope/optical properties/outpatient hysteroscopy/pain/rigid hysteroscope
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Introduction |
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In principle, there are two different types of hysteroscopes available: rigid and flexible. While some investigators prefer flexible hysteroscopy, most seem to favour rigid optics, the 5 mm instrument being the standard hysteroscope for a long time. With continuing improvements in technology, smaller diameter rigid hysteroscopes have been developed (Campo et al., 1999), and flexible ones have achieved increased popularity (Marty and Valle, 1995
; Coats et al., 1997
). However, there exist almost no objective data on this topic in the literature, and we have therefore carried out a clinical trial, comparing the two types of hysteroscopes in terms of optical properties and clinical feasibility using a prospective randomized design.
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Materials and methods |
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Procedure time (measured in seconds from insertion to removal of the hysteroscope) was defined as the primary outcome measure. Secondary endpoints included individual pain sensations experienced by patients at different times of the hysteroscopy, and optical properties of the two different hysteroscopes as assessed by surgeons. Sample size calculation was based on the assumption that a difference of 2 min in procedure time would be clinically relevant, especially in an outpatient setting; according to our previous study (Nagele et al., 1996), the SD of the procedure time was assumed to be 3.4 min. To detect such a difference with a power of 90% using a two-sided test and a 5% significance level, 62 patients were required on each treatment arm. Sample size calculation was based on the t-test using the software program STPLAN (Calculations for sample sizes and related problems, Version 2.0; Dept of Biomathematics, University of Texas MDACC, Houston, TX, USA).
At five different time-points during the investigation, each woman was asked to rank her individual pain sensations using a 10 cm visual analogue scale (VAS): immediately before the test, at insertion of the hysteroscope, during and immediately after the hysteroscopy, and at the time of endometrial biopsy. For this purpose a specially designed proforma was shown to the patient by a senior nurse, with the additional aim of relaxing and informing her about the ongoing procedure. The optical properties of the two different types of hysteroscopes were defined by the parameters intrauterine visibility (defined as the resolving power allowing for both brightness and sharpness of the image), hysteroscopic view (the quality of the panoramic overview inside the uterine cavity, responsible for quick identification of structural abnormalities), and diagnostic accuracy, and were judged by the individual surgeons immediately after the hysteroscopy using a 5-point verbal rating scale (1 = excellent, 2 = good, 3 = adequate, 4 = poor, 5 = insufficient). If the type of hysteroscope had to be changed due to visual and/or optical problems, the optical criteria were all scored as 5, the total procedure time was measured and for statistical analyses the patient remained in the group she was assigned to (intention to treat analysis).
Descriptive analyses of the relevant variables revealed clear violations of the normality assumptions. Therefore the non-parametric Wilcoxon rank-sum test was used for statistical comparisons of the two types of hysteroscopes, and results of P < 0.05 were considered statistically significant.
Assignment
Our outpatient hysteroscopy clinic is run once a week with one of four experienced surgeons being on duty. To ensure balanced treatment allocation for each surgeon and random assignments of patients to one of the two types of hysteroscopes, a computer-generated random permutation list was used with 36 blocks of length four. Consequently, the first four consecutive patients scheduled on every clinical day were included in this study. There were no major differences between the flexible and the rigid groups in terms of main indications for referrals, the most common being abnormal uterine bleeding (n = 64), subfertility (n = 39), and sonographically suspected intrauterine lesions or endometrial abnormalities (n = 25).
Technique of hysteroscopic examination
All procedures were performed according to an established protocol using either a 3.7 mm rigid standard hysteroscope with a 30° fore-oblique lens (WISAP, Munich, Germany) or a flexible hysteroscope with an outer diameter of 3.6 mm and a bending section of 100° both up and down (Olympus HYF Type P, Hamburg, Germany). Apart from the lidocaine spray, no premedication was given, but in cases of severe discomfort, intracervical-block anaesthesia was applied (Broadbent et al., 1992; Nagele et al., 1997
). The uterine cavity was distended with normal saline, installed from a 500 ml bag wrapped in a pressure bag connected to a manometer and pumped to 120200 mmHg (Nagele et al., 1996). All investigations were performed as panoramic hysteroscopies using a high resolution colour monitor and a chip camera and unusual lesions were recorded by video. The technique of outpatient hysteroscopy has been described in more detail elsewhere (Nagele et al., 1996c
). Endometrial biopsies were taken, if indicated, using a small metal curette.
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Results |
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Analysis of the VAS revealed that pain sensations at insertion of the endoscope and during the hysteroscopy itself were significantly worse with the use of rigid hysteroscopes (insertion: 1.7 versus 0.7, P = 0.003; during hysteroscopy: 3.1 versus 1.2, P < 0.001) (Figure 2). No major differences between the two groups were noted in patients' pre-operative anxiety and mood (flexible: median 0.8, lower-upper quartile 04.6; rigid: median 0.6, lower-upper quartile 02.6), and in pain scores assessed before (flexible: median 0, lower-upper quartile 00; rigid: median 0, lower-upper quartile 00), and immediately after the hysteroscopy, and at the time of endometrial biopsy.
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Discussion |
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Whereas the basic equipment for hysteroscopy provided by numerous companies is very similar, there are two completely different optical systems available, rigid and flexible endoscopes, the main technical difference being the mode of image transmission (Van der Pas and Vancaille, 1990). Rigid diagnostic hysteroscopes are
4 mm in outer diameter, and the type most commonly used has a 30° fore-oblique view, which facilitates visualization of the tubal cornua. Originally designed for bronchoscopy and gastroscopy, flexible endoscopes have recently gained popularity (Bradley and Widrich, 1995
); in general they have a 0° angle of view, and in addition to their distal steerability are fitted with a feature that allows the rounded tip to be bent according to need. These inherent differences between rigid and flexible instruments require a completely different surgical technique for successful, e.g. atraumatic, hysteroscopic investigation.
In order to compare the two types of hysteroscopes in terms of their optical properties, handling and patient acceptance, we have carried out what we believe to be the first randomized trial on this topic. The overall success rate in our series was almost 99%, a percentage comparable to the average outcome at our hysteroscopy clinic (Wieser et al., 1998). The outer diameter of the two types of endoscopes used in this study was almost identical (flexible and rigid: 3.6 and 3.7 mm respectively), although our findings still revealed several significant differences between the rigid and the flexible groups.
It is difficult to explain the apparently greater level of discomfort both at introduction of the scope and during inspection of the uterine cavity associated with the use of the rigid hysteroscope. The likeliest explanation for this finding is considerable differences in the external shape of the scopes, and even more important, in the technique of examination. Because the angle of the rigid hysteroscope view is offset from the axis by 30°, it is mandatory to correctly align the scope to the axis of the cervix. This can easily be controlled by the appearance of the cervical canal at the field of vision: if the uterus is anteverted and retroverted, it must be kept at the six and 12 o'clock positions, respectively (Taylor and Gordon, 1993). However, small up and down and side-to-side motions are eventually necessary during cervical passage, thus provoking discomfort. In addition, the angular tip of rigid hysteroscopes can cause painful trauma and damage to the mucosa when the scope is guided through the endocervical canal, even when the fore-oblique view is strictly taken into account (Valle, 1997
). The uterine cavity is then inspected by rotation of the scope, but again, slow motions and tilting in different directions against the axis of the cervix can cause pain at this stage of the examination. In contrast, the flexible hysteroscope is advanced with the rounded distal tip pointing straight ahead, and by doing so the image of the cervical canal is kept in the centre of the screen. As a consequence, undue pain during introduction of the scope rarely occurs. The uterine cavity is visualized by rotation of the hysteroscope, and by bending the distal end up and down which is activated by the angulation control lever close to the eyepiece of the instrument. Briefly, the fore-oblique vision is to rigid hysteroscopy what the swivel tip is to flexible hysteroscopy (Guedj and Valle, 1995
).
There is no doubt that the optical fibre pattern clearly seen in the image is an optical disadvantage associated with flexible endoscopes (Neis et al., 1994). For this reason the optical properties, in our study defined as intrauterine visibility, hysteroscopic view and diagnostic accuracy, were all judged to be significantly worse with the use of the flexible compared with the rigid hysteroscope. This factor, together with the more fastidious technique of hysteroscopic investigation, explains the >70% increase in procedure time associated with flexible hysteroscopy. Moreover, optical problems and the inability to negotiate the cervix accounted for the 12.5% (5/40) failure rate in the flexible group, a result consistent with findings recently reported (Kremer et al., 1998
).
Finally, at a time of considerable restrictions in the health system, cost is a major factor, and it must be pointed out that the flexible hysteroscope is more than twice the price of the rigid one (US$5420 versus 2540). From the nursing staff's point of view, an equally important fact is that instrument care and maintenance of flexible endoscopes is much more awkward, irrespective of whether simple disinfection or gas sterilization is applied.
In conclusion, our data show that outpatient hysteroscopy is more painful when using rigid compared with flexible endoscopes. This disadvantage is well balanced by the fact that rigid hysteroscopes provide superior optical qualities allowing for a more rapid examination at higher success rates, and at much lower instrument cost.
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Notes |
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References |
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Submitted on February 25, 2000; accepted on September 29, 2000.