Placenta Increta: MRI

29 yr old multiparous lady with history of LSCS  suggests low lying placenta on USG at 20 weeks gestation. MRI clearly delineates  irregular large placenta with villi invading  myometrium with subtle bleed on T1 and FFE with  villi  not reaching to serosa and beyond suggesting   invasive placenta of increta variety

Teaching points by Dr MGK Murthy and Mr Samuel MRI technician

1.Low lying placenta is placental edge that comes within 2 cm of cervix on USG (better measured on TVS). Invasive placenta are (a) Accreta , abnormally adherent  placental villi attached directly in to myometrium, but not invade it   (b) Increta is  villi invade myometrium when they reach serosal surface , percreta is suggested

2. Placenta previa (normally 1 in 300 patients )  is higher with advancing age , history of Caesarean, with maternal  mortality (3 per 1000 cases)and abruption placenta possible

3. Invasive placental aetiologies  include  impairment of  the  apparent  relative  cranial migration  (with differential growth rates of uterus)/ scarred lower uterine  segment not growing adequately in 3rd trimester, smoking (hypoxic mechanism),  thin, incompletely developed   or absent decidua basalis (including protective nitabuchs layer), multiparous lady (because of thicker palcenate), any circumstance leading to damaged uterus or myometrium or decidua etc

4. Overdistended bladder may produce false  previa on USG(routine use of post void scan in high risk useful). TVS is specific to  low lying placenta  in view of proximity. Transperineal USG may help

5. USG shows  absence of normal retroplacental clear space, placental tissue contiguous with myometrium, prominent venous lakes, vascularity (abnormal basal plate) , absent hypoechoic zone suggesting decidua defect. Doppler shows continuum of lacunar flow from placenta through myometrium

6.Treatment of  invasive variety is  obviously  challenging   including bleeding, thrombolysis, thromboprophylaxis after delivery etc  and is usually individualized

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