Table I.

Summary of selected studies for the diagnosis of RPOC.

Study	Year	Study Size	Characteristics	Conclusion
Sokol et al	2004	40	Normal trans-abdominal ultrasonographic findings of the uterus within 48h after un- complicated vaginal delivery	A thickened endometrial stripe and echogenic material in the endometrial cavity within 48h postpartum can be normal findings.
Edwards & Ellwood	2000	40	Normal trans-abdominal ultrasonographic findings of the uterus in the postpartum period on day 7, 14 and 21 after uncompli- cated vaginal delivery	No significant association found between bleeding duration and an echogenic mass in the uterine cavity on the postpartum ultrasound
Mulic- Lutvica et al	2001	42	Normal ultrasonographic findings of the uterus in the postpartum period, trans-ab- dominal on day 1,3, 7 and 14 and trans-vag- inal on day 28 and 56, after uncomplicated vaginal delivery	A standardized protocol on how the postpartum uterus should look like is difficult to generate on ultrasound.
Sellmyer et al	2013		Physiologic, Histologic and Imaging fea- tures of retained products of conception	A thickened EEC (range 8-13mm) on gray-scale US is the most sensitive finding of RPOC (80%). This or an endometrial mass with vascularity on Doppler US allows confident diagnosis of RPOC.
Pather et al	2005	2000	A retrospective chart review of patients who underwent a postpartum curettage. They want to assess which features are best to predict the presence of RPOC.	Thickened EEC (range 10-40 mm) is the most accu- rate individual predictor of RPOC with a PPV of 67% and a PPV of 80% in combination with a echogenic focus. The specificity is low.
Kamaya et al	2009	269	Postpartum ultrasonographic images ob- tained with gray-scale US and color Dop- pler, with attention for masses, vascularity and EEC	RPOC can best be diagnosed with images obtained from gray-scale US and color Doppler. The proposed threshold for thickened EEC is 10 mm.
Matijevic et al	2009	93	Examination of the accuracy of sonographic and clinical parameters in the prediction of RPOC after histopathological examination on women who were suspected for RPOC.	When no endometrial mass can be found and the EEC is less than 10 mm, RPOC is extremely rare.
Mulic- Lutvica & Axelsson	2006	79	Ultrasonographic findings on women with secondary PPH on the day they presented with PPH and on day 1, 3, 7, 14, 28 and 56 postpartum.	An echogenic mass is strongly associated with RPOC
Shen et al	2003	39	Ultrasonographic findings on women sus- pected with RPOC after examination of the placenta showed incomplete placentas	Ultrasound for predicting PROC: sensitivity 93,8% and specificity 73,9%
Neill et al	2002	53	Comparison of the diagnostic accuracy of clinical assessment with transabdominal ultrasound in the management of secondary PPH expected to be caused by RPOC	Combining ultrasound and clinical assessement im- proves the diagnostic accuracy when they are both the same
Hoveyda & MacKenzie	2001	75	Comparison of histological outcomes in women with secondary PPH with or without an ultrasound scan	Ultrasound does not provide a significant advantage over clinical assessment of RPOC
Hertzberg & Bowie	1991	53	Classification of postpartum ultrasound scans in five categories	Strong correlation between echogenic mass with stippled appearance due to hyperechogenic foci on US and RPOC
Carlan et al	1997	127	Postpartum ultrasounds performed within 5 minutes after placental delivery, followed by a manual exploration and sponge curet- tage.	Normal uterine strip does not exclude RPOC. Correla- tion between echogenic mass and RPOC.