窥知

4.pdf Best Practice & Research Clinical Obstetrics and Gynaecology Vol. xx, No. xx, pp. 1–16, 2008 doi:10.1016/j.bpobgyn.2008.08.003 ARTICLE IN PRESSavailable online at http://www.sciencedirect.com10Diagnosis and management of placenta accretaJosé Miguel Palacios-Jaraquemada* MD, PhD Professor CEMIC University Hospital, Department of Gynaecology and Obstetrics; J. J. Naón Morphological Institute, School of Medicine, University of Buenos Aires; and Fundación Cientı́fica del Sur, Lomas de Zamora, Buenos Aires, ArgentinaThe diagnosis of placenta accreta begins with clinical suspicion in patients at risk. Ultrasound and Doppler are first-choice diagnostic methods because of their accessibility and high sensitivity. Placental MRI is an accurate method of topographic stratification that makes it possible to define anatomy, to plan the surgical approach and to consider other therapeutic possibilities. Manage- ment of placenta percreta involves great technical dexterity and significant clinical support. The main challenges include controlling the haemorrhage and dissection of the invaded tissues. Now- adays, there are two treatment options: caesarean hysterectomy or a conservative approach. With the latter, there is a choice between leaving the placenta in situ and waiting for its later resolution, and a one-step surgery that addresses the problems of invasion, vascular control and myometrial damage in a single surgical act. Key words: conservative treatment; diagnosis; one-step surgery; placenta accreta; therapeutic approach. INTRODUCTION Placenta accreta is a disorder characterized by abnormal placental penetration into the uterine wall. It is currently one of the main causes of maternal morbidity and mortality. This entity has been historically classified according to the degree of pathological pen- etration and includes superficial invasions (placenta accreta), middle-layer invasions (placenta increta), and deep invasions (placenta percreta). This chapter refers to all these varieties as placenta accreta. As a result of its close relation to caesarean section1,2, the incidence of placenta accreta has grown in the last few decades. Myometrial damage secondary to repeated* Av. Corrientes 5087 4 a C14141 AJD Ciudad Autónoma de Buenos Aires, Argentina. Tel./fax: þ54 11 4857 1331. E-mail address: jpalacios@fmed.uba.ar 1521-6934/$ - see front matter ª 2008 Elsevier Ltd. All rights reserved. Please cite this article in press as: José Miguel Palacios-Jaraquemada, Diagnosis and management of pla- centa accreta, Best Practice & Research Clinical Obstetrics and Gynaecology (2008), doi:10.1016/ j.bpobgyn.2008.08.003 2 J. M. Palacios-Jaraquemada ARTICLE IN PRESScaesarean sections, and other myometrial injuries associated with dilatation and curet- tage (D&C) and corrective surgeries, among others, are the main predisposing factors. Ultrasound (US) and Doppler3,4 are two first-line methods for the diagnosis of pla- centa accreta; both have a high degree of diagnostic sensitivity and both methods have made it possible to establish diagnostic signs that allow the suspicion of an abnor- mally implanted placenta in a high percentage of cases. In addition, placental nuclear magnetic resonance imaging (pMRI) has proved to be a noteworthy auxiliary when it comes to plan the surgery of placenta accreta.5 Placen- tal MRI (pMRI) makes it possible to have total acquisition of images; its multiplane char- acteristic allows a correct three-dimensional (3D) reconstruction, necessary for surgical planning. Placenta accreta causes morbidity and mortality due to haemorrhage, coagulopathy and its inherent surgical difficulty; these facts make this disorder the first cause of obstetric hysterectomy.6 Traditionally, the treatment of placenta accreta has consisted of puerperal hysterec- tomy. This is a high-risk procedure, especially when haemorrhage and coagulation dis- orders coexist. To minimize damage and conserve the reproductive potential in women, a series of procedures that aim to preserve the uterus affected by placenta accreta have been incorporated.7,8 These conservative tactics have proved to be effec- tive and safe under controlled conditions. Below, we provide a synthesis of the current knowledge about placenta accreta, in- cluding practical data for obstetricians and surgeons. We emphasize early detection of risk factors, diagnostic guidelines and treatment alternatives in accordance with the human and technical resources available. TERMINOLOGY From a histopathological perspective, there are marked differences among placenta ac- creta, increta and percreta. However, from a clinical–surgical point of view, sectors that show a different degree of invasion can coexist in the same patient. This phenom- enon leads to discrepancies between what is observed during surgery and the final pathological diagnosis. This difference is not only semantic; it makes comparisons of surgical techniques and clinical results from different authors virtually impossible. Unlike other illnesses, the histopathological study of invasive placenta does not al- ways constitute a diagnostic ‘‘gold standard’’. This phenomenon occurs when biopsy is obtained in an area without invasion or with a degree of minor penetration. In these cases, there is a mismatch between histology and the surgical finding. We prefer to define placenta accreta according to its clinical–surgical characteristics.9,10 RISK FACTORS Patients with myometrial damage secondary to repeated caesarean sections in associ- ation with placenta praevia constitute the main risk factor for placenta accreta.11,12 Multiple uterine D&C, particularly those performed in patients who have had previous caesarean section(s)13, are closely associated with adherent placentation. Myometrial tissue damage, whether surgical, instrumental or physical14, followed by a secondary collagen repair, is closely related to the appearance of placenta accreta. The challenge of confirming or discarding the diagnosis of invasive placenta is greatest when the topography of the uterine lesion coincides with the placentation zone.Please cite this article in press as: José Miguel Palacios-Jaraquemada, Diagnosis and management of pla- centa accreta, Best Practice & Research Clinical Obstetrics and Gynaecology (2008), doi:10.1016/ j.bpobgyn.2008.08.003 Diagnosis and management of placenta accreta 3 ARTICLE IN PRESSDIAGNOSTIC METHODS Ultrasound Transabdominal ultrasound (US) is the simplest, most widespread and cost-effective method for the initial diagnosis of placenta accreta. However, US does not allow ad- equate visualization of a low-segment cervix or common areas of placental invasions after multiple caesareans. Transvaginal ultrasound (TVUS) enables a more accurate examination of the distal uterine sector (Figure 1). However, the posterior wall cannot be assessed correctly by this method. It is worth highlighting that this is a safe imaging method for patients with placenta praevia. Detailed visualization of the cervix and low segment with TVUS increases diagnostic accuracy in low-insertion placentas.15,16Figure 1. Transvaginal ultrasound: anterior placenta percreta in patient with twin pregnancy. LMVL, loss of myometrial-vesical layer; NFV, newly-formed vessels. Please cite this article in press as: José Miguel Palacios-Jaraquemada, Diagnosis and management of pla- centa accreta, Best Practice & Research Clinical Obstetrics and Gynaecology (2008), doi:10.1016/ j.bpobgyn.2008.08.003 4 J. M. Palacios-Jaraquemada ARTICLE IN PRESSUltrasound signs Certain patterns have been associated with placenta accreta. One such sign is the presence of placental lagoons, which, unlike those seen in the second trimester, are large, irregular and multiple. The aetiology of these placental lagoons is unknown. Their presence, characteristics and number are not directly related to the gravity of placenta accreta. The sensitivity of this ultrasound sign is 79%, with a positive predic- tive value of 92%, when identified between weeks 15 and 40.16 The loss of the retroplacental hypoecogenic zone, represented by the absence of the retroplacental vascular bed, basal decidua and placental advancement over the my- ometrium is another ultrasound sign associated with the presence of placenta accreta. This sign does not have great significance when found in isolation. Certain authors question its importance due to its low diagnostic and predictive sensitivity and a false-positive rate of nearly 50%. Progressive thinning of the retroplacental myometrium indicates the extreme prox- imity of the placental tissue to the peritoneal serosa or to the neighbouring organs, another sign of placenta accreta. Segmental myometrial thinning of less than 1 mm is suggestive of abnormal placental adherence, with sensitivity of 93%, specificity of 79% and predictive value of 73%.17 Thinning or disruption of the uterine–vesical serosa occurs due to the lack of my- ometrial tissue, leaving the visceral serosa exposed. It is not easy to make a differential diagnosis between placenta accreta and the irregularities of the vesical wall. Disruption of the serosa indicates a higher degree of compromise; the presence of extrauterine placental parenchyma confirms placenta percreta. US grey-scale general capacity is enough to diagnose placenta accreta with sensitiv- ity 87%, specificity 98%, a positive predictive value 93% and a negative predictive value 98%.18 The presence of vessels perpendicular to the uterine axis indicates the presence of pla- cental vessels from and towards the myometrium or other neighbouring tissues17–19; this pattern is associated with the presence of different degrees of placenta accreta. Magnetic resonance imaging of the placenta Initially, the aim was to determine whether placental magnetic resonance imaging (pMRI) can improve the diagnostic sensitivity of ultrasound in the detection of placenta ac- creta.20–22 The first prospective study was performed in 1997. The report included 18 patients and did not find any diagnostic differences between the techniques, although it did identify a higherdiagnostic sensitivity in pMRI in the case of posterior placenta accreta. In 2005, a prospective series comprising 300 cases showed that pMRI adequately outlined the topographic anatomy of the invasion, relating it to the regional anasto- motic vascular distribution. The characteristics of the invasion confirmed the possibil- ity of bleeding, the occurrence of complications, and the inherent technical difficulty in certain cases. It is the only published study to date that has been able to confirm the presence of parametrial invasion (axial slices)5; an important factor associated with the possibility of urethral damage during surgery. Diagnostic practice points Clinical risk factors for placenta accreta: repeated caesarean sectionsþ placenta praevia, multiple D&C, caesarean and D&C, placenta inserted in the site of previous uterine surgeries, pelvic radiation, endometrial thermoablation.Please cite this article in press as: José Miguel Palacios-Jaraquemada, Diagnosis and management of pla- centa accreta, Best Practice & Research Clinical Obstetrics and Gynaecology (2008), doi:10.1016/ j.bpobgyn.2008.08.003 Diagnosis and management of placenta accreta 5 ARTICLE IN PRESS US signs of morbidly adherent placentae: loss or thinning of the retroplacental hypoecogenic zone, multiple intraplacental lagoons, thinning or disruption of the uterine–vesical serosa, extrauterine placental tissue mass.  Signs of morbidly adherent placentae: absence of Doppler signal in the hypoecogenic zone, diffuse lacunar colour flow pattern, turbulent flow with pericervical vascular di- lation, arterial vessels emanating from the placenta towards neighbouring organs or tissuesTechnical aspects Like other diagnostic methods, pMRI has certain technical details that can enhance or emphasize its diagnostic accuracy. The main aim of the imaging study is to obtain the best definition of the uterine–placental interphase and its relation to the bladder (Figure 2).Figure 2. pMRI (sagital slice): isodense placental tissue is present inside the bladder, a characteristic sign of placenta percreta. Please cite this article in press as: José Miguel Palacios-Jaraquemada, Diagnosis and management of pla- centa accreta, Best Practice & Research Clinical Obstetrics and Gynaecology (2008), doi:10.1016/ j.bpobgyn.2008.08.003 ...