Hysteroscopic Surgery in Gynaecological Practice

INTRODUCTION
Hysteroscopy is a vital surgical technique for diagnosing and treating intrauterine pathology. The procedure can be divided into diagnostic and operative hysteroscopy.

DIAGNOSTIC HYSTEROSCOPY
Diagnostic hysteroscopy (rigid or flexible hysteroscopy) is regularly performed to evaluate the uterine cavity and treat menstrual disorders and fertility conditions. Detection of polyps, fibroids, endometrial cancer, and endometrial hyperplasia remains to be the key for patients with menorrhagia or abnormal menstruation. Transvaginal ultrasound (TVS), with or without the use of saline infusion sonography (SIS), is commonly used in the diagnosis of uterine abnormalities. However, sensitivity and specificity of TVS, including the use of SIS, is lower than that of a diagnostic hysteroscopy (Table 1).¹



Imaging alone cannot detect the presence of endometrial cancer or hyperplasia. In women below age 40, endometrial cancer is rare however its incidence rises steeply beyond ages 45–50+.¹ Up to 10% of women with post-menstrual bleeding (PMB) will have endometrial cancer.² Diagnostic hysteroscopy with endometrial sampling provide the most accurate investigation available for such diagnosis (Table 2).



Asherman’s syndrome, intrauterine adhesions, endometrial polyps, fibroids, and congenital abnormality of the genital tract may present with amenorrhoea, irregular bleeding, or failure to conceive. Diagnostic hysteroscopy can accurately confirm the presence, location, and extensiveness of the scarring, as well as diagnose other congenital abnormalities.

OPERATIVE HYSTEROSCOPY
Operative hysteroscopy involves procedures performed under the guidance of a hysteroscope. These procedures usually involve a rigid hysteroscope and working channels (conventional hysteroscope or resectoscope) to allow for continuous flow of distending media. The working channel generally incorporates a working element using either a monopolar or bipolar electric energy through diathermy loop, tip, or rollerball. Newer techniques may incorporate tissue morcellation or removal using electric motor cutting blades where tissues are simultaneously cut and aspirated from the uterine cavity.

Hysteroscopic resection of submucosal fibroid
Resection of submucosal fibroid involves the use of an operating hysteroscope. With complete removal, improvement of menorrhagia can be as high as 94.1%.³

Traditionally, it is performed using a diathermy loop which passes through the resectoscope. Monopolar or bipolar energy can be used, and the procedure is completed with a progressive slicing of the intracavity portion of the submucous myomas, a subsequent “cold loop” pushing of the intramural part (to preserve the pseudocapsule), and finally, a slicing resection of it.

The availability of Hysteroscopic Tissue Removal systems (HTRs) opened a new era.⁴ Multiple devices (TRUCLEAR, MyoSure, BIGATTI shaver), all share similar techniques. Under the guidance of a hysteroscope and after distension of the uterus, a specially designed morcellator is introduced through the hysteroscope to cut and aspirate the morcellated tissue which is then collected for histological analysis⁵ (Figure 1).



Several studies have evaluated the efficacy and safety of HTRs compared with conventional operative hysteroscopy.

A randomized controlled trial (RCT) by van Dongen, et al, reported mean operative times of 11 and 17 minutes (p=0.008) for HTRs and conventional hysteroscopic resection, respectively,⁶ while similar fluid deficit of 409 and 545 mL (p=0.224) were found. Emmanuel, et al, reported operative times of 16 and 42 minutes respectively, with a mean fluid deficit of 660 and 742 mL with no statistical significant.⁷ Both studies suggested significant reductions in operative time associated with HTRs but there was no difference in fluid deficit.

According to the Manufacture and User Facility Device Experience (MAUDE) database,⁸ adverse events associated with hysteroscopic morcellation is less than 0.1%, which is less than conventional hysteroscopic surgery. Although limited to case reports, major complications (eg, intubation and admission to intensive care unit, bowel damage, hysterectomy, and death) have been reported.⁵ Minor events reported include uterine perforation requiring no other treatment, uncomplicated fluid overload, postoperative bleeding, and pelvic infections.

Systematic review by Vitale, et al,⁴ showed that overall complete fibroid resection rates between HTRs and conventional procedures were comparable. Although Lee and Matsuzono⁹ found no significant difference between overall patient satisfaction and improvement in haemoglobin level, Rubino, et al,¹⁰ showed significant improvement in uterine fibroid symptoms and health-related quality of life at 12 months when myomectomy was performed using HTRs.

Resection of endometrial polyps
Though malignancy is uncommon in polyps, it can occur in 0–12.9% of cases  depending on the population studied.¹¹ Increasing age during the reproductive period, obesity, tamoxifen  use, and polyp size may increase the prevalence and risk of malignancy and hyperplasia.¹² Given these factors, polyp removal for diagnosis and treatment of abnormal uterine bleeding are regularly performed.

Polypectomy can be done via several surgical methods: diagnostic hysteroscopy before and after blind dilatation and avulsion with polyp forceps, cold scissors and grasper under hysteroscopic vision, hysteroscopic resection with loop cautery, hysteroscopic morcellation, tissue vapourising technique using bipolar vapourisation (Versapoint) or laser (diode), and polyp snares (Cook’s Polyp Snare).

Blind endometrial polypectomy by polyp forceps, only yielded a complete extraction rate of 41%.¹² Malignant cells at the base of the polyp can be missed,¹³ while recurrence rate can be as high as 15%.¹⁴

Resection using cold scissors, diathermy resectoscopes, or HTRs are safe, simple, and superior to blind techniques. Despite the longer duration and probably higher cost of hysteroscopic resection, uterine perforation risk is lower as direct vision of polyp resection is allowed during procedure.¹⁵ Not a single recurrence of endometrial polyp was reported when resection was performed under direct vision compared with removal using grasping forceps.¹⁴ Tissue vapourising device such as Versapoint bipolar vapourisation or laser device (eg, diode) is also used under direct vision through a hysteroscope. However, as the device vapourises tissues upon contact, the entire specimen may not be available for pathological evaluation.

Hysteroscopy with a polyp snare utilizes a specially designed hook placed through the hysteroscopic operative channel and around the base of the polyp. A current is applied, and the endometrial polyp is cut at the base and removed under vision.¹⁵ The results are similar to hysteroscopic resection.

Endometrial ablation
Endometrial ablation is a minimally invasive surgical alternative to hysterectomy for the treatment of menorrhagia.

First-generation techniques using conventional hysteroscopy and diathermy rollerball or transcervical resection of endometrium (TCRE) were common during the 1990s and led to significant reduction in hysterectomies performed. In recent years, second-generation techniques have gained worldwide popularity. High-temperature fluids within a balloon (Thermachoice and Cavaterm), microwave (Microsulis), or bipolar radiofrequency electrical energy (NovaSure) are most frequently used (Figure 2).



A meta-analysis of RCTs¹⁶ suggested that second-generation techniques were at least as effective as first-generation techniques but had fewer surgical complications, shorter operative time, were easier to perform, and more likely to be performed under local anaesthesia and in an outpatient setting.

Among all the second-generation techniques, bipolar radiofrequency and microwave ablation showed superior results.¹⁷ Bipolar radiofrequency ablation resulted in a higher rate of amenorrhoea compared with thermal balloon ablation and reduced the rate of heavy bleeding compared with free-fluid ablation.¹⁶ In the same review, bipolar radiofrequency ablation appeared to be more favourable to patients than free-fluid thermal ablation at 12 months.¹⁶ Locally, overall satisfaction rate is >90%.¹⁸

However, limitations were observed for second-generation ablation techniques. Because of the design of individual devices, second-generation endometrial ablations are restricted to uterus of normal size or equivalent to 12 weeks gestation. Despite potential complications reported with previous caesarean scars and coexisting fibroids, previous transverse scars¹⁹ and fibroids less than 3 cm did not appear to affect the effectiveness of bipolar radiofrequency devices.²⁰ Pregnancy after endometrial ablation has an estimated risk of 0.24–5.2% and is associated with high risk of miscarriage, intrauterine death, intrauterine growth retardation, morbid adherent placentas, and post-partum hysterectomies.^21-22 The procedure should be avoided by women who have fertility wish, and long-term contraception is advised prior to the procedure.

Resection of endometrial adhesions/septum and management of fertility
The presence of polyps, fibroids, uterine septum, or intrauterine adhesions may prevent implantation and cause fertility problems.

Improving the chance of fertility by removing pathological lesion remains controversial. The Cochrane review²³ suggested that hysteroscopic removal of polyps before intrauterine insemination improved fertility rates from 28% to 50–76%. Fertility also improved from 21% to 39% after removal of submucosal fibroids. However, there are limited studies to deduce concrete evidence, and all studies included small samples.

Regarding uterine septum and uterine adhesions, there is insufficient evidence to conclude that a uterine septum is associated with infertility, but several observational studies indicated that hysteroscopic incision of uterine septum is associated with improved pregnancy rates.²⁴ Removal of intrauterine adhesions has also been shown to increase clinical pregnancy rates in those with recurrent implantation failure.

For fibroids and polyps, conventional resectoscope or HTRs can be used. However, electrosurgical devices, such as resectoscopes, are best suited for removal of uterine septum. Resection of uterine septum and adhesions was associated with the highest risk of uterine perforation at 4.5%.²³

Hysteroscopic sterilization
Currently, the Essure device is the only available FDA-approved method of hysteroscopic sterilization. The device consists of a micro-insert, and a delivery catheter, and is deployed using a continuous-flow hysteroscope with a 5-French operating channel. The micro-insert has a stainless steel inner coil, a nickel titanium elastic outer coil, and polyethylene fibres. When released, the outer coil expands to 1.5–2.0 mm to anchor the micro-insert into the fallopian tube. The polyethylene fibres then induce fibrosis over a period of 3 months, causing permanent tubal occlusion.²⁵ At 3 months post-procedure, a hysterosalpingogram (US) or pelvic ultrasound (UK and Europe) should be performed to confirm positioning of the device. Bilateral placement of the Essure device is possible in 81–99% of cases²⁵ with sterilization that showed a 99.83% success rate based on a 5-year study.²⁶ The total pregnancy rate was reported to be 1.09/1,000²⁵ or 0.36-1.2% in other studies conducted in France and the US.²⁶

Complications of hysteroscopic sterilization include pain, discomfort, and heavy menstrual bleeding in 20% of women, and spontaneous expulsion in 0.04–3%.²⁶ Uterine perforation risk was 1–2%, while device migrating risk was 0.04%, subsequently embedding in the intra-abdominal structures as reported in the MAUDE database.²⁷ About 14–18% of women²⁷ reported allergic reaction to the device, which resulted in urticaria and erythema and required device removal.

Hysteroscopic resection of placenta or retained products of conception
Prevalence of placental remnants after pregnancy (after miscarriage, vaginal delivery, caesarean section, or termination of pregnancy) can be as high as 19% of pregnancies. Blind dilatation curettage is most commonly performed but is an important risk factor for intrauterine adhesion formation particularly if repeatedly performed. Hysteroscopic resection, either by loop resection or HTRs, has been shown to be an alternative surgical approach to dilatation and curettage that enables selective removal of the remnant tissue under direct vision. The procedure is likely to achieve higher rates of complete removal and lower risk of postoperative adhesions. An RCT by Hamerlynck, et al, revealed a 94.5% complete resection rate with either the diathermy hysteroscopic resection or the HTR technique for placental remnants up to 3 cm. However, HTR showed a shorter surgical procedure time.²⁸

Infrequently, morbidly adherent placentas may be left in situ after delivery. If conservative management fails, hysteroscopic resection of retained placenta through single or multiple procedures are options to prevent major complications and preserve fertility.²⁹ Caesarean scar pregnancies can also be managed hysteroscopically. In cases of caesarean scar pregnancies or morbidly adherent placentas, resectoscope with electrocauterization may be preferred to avoid bleeding.^30-31

GENERAL COMPLICATIONS OF HYSTEROSCOPIC SURGERY
Minor complications such as infection and bleeding are potential risks of hysteroscopy. Severe complications including uterine perforation can occur in up to 0.76% of cases,³² with subsequent bowel and bladder damage in some cases. With over 70% of uterine perforation cases occurring during the cervical dilatation stage, advancement in hysteroscopic surgeries tends to involve reducing the diameter of the hysteroscopes.

Consequence of excessive systemic absorption
Excessive systemic fluid absorption is a major complication but is much more prevalent in operative hysteroscopy (0.1–0.2%).³³

Distension media for UK, when excessively absorbed, leads to systemic expansion, cardiac failure, and pulmonary oedema. Hypotonic and electrolyte-free solutions carry additional risks (ie, hypo-osmolality, hyponatraemia), which might consequently lead to complications such as systemic expansion and cerebral oedema. As excessive absorption occurs, osmotic imbalance is created between extracellular fluid and cells including those in brain. In healthy patients, the brain compensates itself and causes minimal harm. However, under conditions of hyponatraemia, water moves into the brain cells causing cerebral oedema which then leads to pressure necrosis, brain stem herniation and, in rare cases, death.³³ Those with underlying medical conditions, particularly cardiac or renal diseases, must be treated with caution. Premenopausal status was associated with a higher risk of neurological complication and suppressive effects of oestrogen on ATPase pump, which regulates electrolytes through the blood-brain barrier. It has been suggested that the use of gonadotrophin-releasing hormone (GnRH) analogue prior to the procedure may reduce such risks.³⁴

Fluid absorption into the systemic circulation can occur by several ways:
•    Retrograde passage of the fluid through the fallopian tubes
•    Through the endometrium
•    Operative disruption of venous sinus in the deep endometrium and myometrium. When these vessels or sinuses are transected, it provides access for the media to enter the systemic circulation.³³

Factors influencing fluid absorption:
•    Intrauterine pressure – the higher the pressure, the greater the degree of absorption into the body. Intrauterine pressure over 75 mm Hg increases the volume of media passing back along the fallopian tubes and into the peritoneal cavity.³⁴
•    Mean arterial pressure (MAP) – the lower the MAP, the lower the intrauterine pressure required to cause passage of fluid into the systemic circulation.³⁴
•    Depth of myometrial penetration – the deeper the damage to the myometrium, the more open the myometrial venous sinus, causing increased   absorption.
•    Duration of surgery – the longer the procedure, the more time for fluid to accumulate within the body.
•    Size of uterine cavity – a larger cavity increases the endometrial surface area, which may require a longer procedure time and higher intrauterine pressure, and could increase absorption risk.
•    Distension media – all types of fluid media are associated with rapid systemic absorption. However, it is more likely with hypotonic and electrolyte-free distension media as they create an osmotic imbalance between extracellular and intracellular   fluid via hyponatraemia and hypo-osmolality, while isotonic media does not cause hyponatraemia.³⁴

Distension media

Carbon dioxide
Carbon dioxide (CO₂) should be used as a distending medium for diagnostic hysteroscopy only. This is because bleeding obscures view, and CO₂ is unable to clear the bleeding debris.

CO₂ is highly soluble in blood and can enter the circulation system. A moderate amount is quickly absorbed and has no clinical impact. However, if large volume of CO₂ reaches the systemic circulation, cardiorespiratory collapse can occur.³³

High-viscosity distending media (eg, 32% dextran 70 in 10% glucose)
They are generally used in cases of bleeding, as they are immiscible with blood. However, it causes fluid expansion when excessively absorbed leading to heart failure and pulmonary oedema. The maximum recommended volume of infused fluid should be between 300 and 500 mL.³³

Low-viscosity distending media (eg, commonly used – 1.5% glycine, normal saline, 3% sorbitol, and 5% mannitol)
Hypotonic solution such as glycine is metabolized to ammonia and free water in the liver, which results in reduced serum osmolality. Excess absorption may cause electrolyte imbalance, particularly hyponatraemia. It has been established that a decrease in serum sodium of 10 mmol/L corresponds to an absorbed volume of 1,000 mL has traditionally been used and recommended by the British Society for Gynaecological Endoscopy (BSGE) as the threshold at which hysteroscopy should not be performed in women when using these media.³⁴

Normal saline and Ringer’s lactate are isotonic solutions and are generally safer to use as distension media. Despite the low likelihood of hyponatraemia, excessive absorption can lead to expansion of extracellular fluid, fluid overload, pulmonary oedema, hypertension, heart failure, and cerebral oedema. The BSGE/European Society for Gynaecological Endoscopy (ESGE) recommended a limit of 2,500 mL in fluid deficit when using an isotonic solution and that the procedure be abandoned on reaching this limit.³⁴

Strategies to reduce risk of excessive fluid absorption

Intrauterine pressure
Should be kept between 70 and 100 mm Hg – higher pressure may improve visualization but increase the amount of fluid absorbed.³⁴

Distension media
Isotonic electrolyte containing distension media such as normal saline should be used with mechanical instrumentation and bipolar electrosurgery. Hypotonic, electrolyte-free distension media such as glycine should only be used with monopolar electrosurgical instrument.³⁴

GnRH
Pre-operative administration of GnRH should be considered in premenopausal women before hysteroscopic resection of fibroids as it reduces electrolyte disturbance complications and the incidence of fluid overload.^35-36

Choice of operative technique
During resection of submucosal fibroids or polyps, bipolar devices should be considered instead of monopolar devices and isotonic medium can be used. Mechanical tissue-removing device should also be considered over loop resection as it has been shown to reduce operative time.

As for endometrial ablation, second-generation endometrial ablation should be considered over TCRE as it has been shown to reduce operative time.

Monitoring and when to stop procedure
Strict input and output of fluid, and fluid deficit monitoring during delivery of distension media should be performed. Operative staff should constantly keep the surgeon informed. Surgeons should abandon the procedure when fluid deficit of 1,000 mL for hypotonic solution or 2,500 mL for isotonic solution is reached. A two-step procedure should be considered if procedure cannot be completed in the first instance.

OUTPATIENT HYSTEROSCOPY
Traditionally, outpatient hysteroscopy was limited to diagnostic hysteroscopy. As technology advances and as most patients prefer to avoid general anaesthetics, diagnostic and operative hysteroscopies are now being performed in outpatient settings.

Hysteroscopes of less than 5 Fr in diameters are being produced to allow for the passage of hysteroscopic scissors and graspers during surgery. In addition, new techniques are being developed to reduce operative time, allowing for a more tolerable procedure under office settings.

Endometrial ablation
Bipolar radiofrequency and balloon ablation have been shown to be feasible in the outpatient settings with analgesia and paracervical block.^37-39 According to a study by Marsh, et al,³⁸ more than 70% of women prefer the procedure as an office procedure with local anaesthesia.

Hysteroscopic resection of polyps
Hysteroscopic devices with working channels allowing for the insertion of the cold scissors and excision of polyps are widely available. Their diameters can be as small as 1.9 mm, with a 3.5-mm expandable operating channel. Small hysteroscopic morcellators¹⁵ allow complete resection without dilatation in the outpatient setting. Despite the potential risk of failure due to technical difficulty (eg, cervical stenosis) or patient intolerance, outpatient hysteroscopy and polypectomy are acceptable to most women and considered to be less painful than their usual menstruation.¹⁵

CONCLUSION
Hysteroscopic surgery is a common procedure but carries some complications such as excessive fluid overload. Gynaecologists should be aware of advanced techniques that reduce operative time and patient risks and are potentially useful in post-pregnancy-associated conditions that were not commonly performed in the past.

About the author
Dr Man Hin Menelik Lee is an Associate Consultant in the Department of Obstetrics & Gynaecology, Queen Elizabeth Hospital, Hong Kong SAR. Conflict of interest: None.