Retained products of conception (RPOC) is the persistence of placental/decidual/trophoblastic tissue remnants in the uterine cavity after delivery or miscarriage. It is an important cause of postpartum hemorrhage (~1-6% of deliveries) and the most common cause of delayed postpartum hemorrhage. On US, endometrial thickening (>10 mm), heterogeneous endometrial mass, and increased vascularity on color Doppler are seen. Vascularity presence/absence is critically important for diagnosis and treatment planning — hypervascular RPOC contains viable trophoblastic tissue carrying massive hemorrhage risk during curettage, and embolization should be considered first. Avascular RPOC represents necrotic tissue or blood clot treatable with conservative management or safe curettage. Clinical presentation includes ongoing vaginal bleeding, fever, foul-smelling discharge, and failure of β-hCG to decline as expected.
Age Range
18-45
Peak Age
30
Gender
Female predominant
Prevalence
Uncommon
RPOC forms when trophoblastic tissue or placental cotyledons remain in the cavity after delivery or miscarriage — in normal delivery, placenta completely separates and is expelled, but abnormal placental adhesions, incomplete curettage, or rapid/traumatic delivery may cause retention. Retained tissue prevents uterine involution (return to normal size through postpartum contraction), keeping myometrial vessels open → active bleeding from spiral arteries continues. When trophoblastic tissue remains viable, pregnancy-induced vascular remodeling in spiral arteries is preserved — vessels with eliminated smooth muscle layer remain as low-resistance, high-capacity channels → increased vascularity and low-resistance arterial flow (RI <0.5) on Doppler. This vascularity is an indirect indicator of viable trophoblast and determines massive hemorrhage risk during curettage. In necrotic/devascularized RPOC, trophoblastic tissue has died → vascular structures undergo thrombotic occlusion → no vascularity on Doppler → low hemorrhage risk. Prolonged retention can lead to endometritis (bacterial colonization), pyometra (purulent collection in cavity), and sepsis. Echogenicity of retained tissue varies with composition: viable trophoblast → echogenic mass (high cellular density), necrotic tissue → heterogeneous/hypoechoic (coagulation necrosis + lysis), blood clot → variable echogenicity (depending on hematoma evolution). Rare but serious complication of uterine artery pseudoaneurysm may develop from trophoblastic invasion weakening arterial wall → pulsatile, round vascular structure with turbulent flow.
Echogenic mass in endometrial cavity of postpartum/post-abortion uterus + increased vascularity and low RI (<0.5) on Doppler — pathognomonic for vascularized RPOC. Uterine artery embolization should be evaluated before curettage.
Endometrial thickness >10 mm (anteroposterior diameter) or heterogeneous echogenic mass within the cavity is seen on TVUS in the postpartum/post-abortion uterus. Normal postpartum endometrium is <10 mm and homogeneous — thickening above this threshold raises RPOC suspicion. The echogenic mass in RPOC usually represents decidual-trophoblastic remnants showing broad contact surface with the cavity wall. Mass may be hypoechoic, echogenic, or mixed — depending on cellular content and necrosis degree. Intrauterine gas bubbles (dirty shadowing) suggest infection complication.
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A heterogeneous echogenic mass measuring __ mm in the endometrial cavity of the postpartum uterus is consistent with RPOC.
Increased vascularity within and around the endometrial mass is seen on color Doppler — low-resistance arterial flow (RI <0.5) indicates viable trophoblastic tissue maintaining pregnancy-induced vascular remodeling. Vascularity degree ranges from mild to intense (ring-of-fire-like pattern). Vascularity presence determines massive hemorrhage risk during curettage and necessitates prior uterine artery embolization consideration. Absence of vascularity suggests blood clot or necrotic tissue — this distinction is the foundation of treatment planning.
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Increased vascularity and low-resistance arterial flow (RI: __) within the endometrial mass on color Doppler is consistent with vascularized RPOC — embolization should be evaluated before curettage.
An enhancing mass in the endometrial cavity may be seen on contrast CT in arterial phase — usually used in emergency hemorrhage assessment or interventional planning. Intense arterial phase enhancement indicates viable trophoblastic tissue. Continued delayed phase enhancement is evidence of vascular remodeling. Uterine artery pseudoaneurysm complication is detected on CT as a focal, round, intensely enhancing vascular structure. Hemoperitoneum and pelvic free fluid are evaluated.
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An enhancing mass in the endometrial cavity on contrast CT is consistent with vascularized RPOC; evaluated for pseudoaneurysm and active bleeding.
On T2-weighted MRI, a mass with heterogeneous signal intensity is seen in the endometrial cavity. Viable trophoblast shows high T2 signal due to high cellular water content and vascular spaces; necrotic tissue gives low-intermediate signal from protein denaturation and coagulation necrosis. Blood products are assessed on T1 — subacute bleeding is T1 hyperintense from methemoglobin. On contrast MRI (gadolinium), vascularized RPOC enhances intensely while necrotic RPOC does not — this distinction correlates with US Doppler. Viable trophoblast may show diffusion restriction on DWI — high cellular density. MRI is superior to US in evaluating myometrial invasion, cavity-myometrium interface, and complications.
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A mass with heterogeneous signal intensity in the endometrial cavity on MRI with ___ (enhancement present/absent) on contrast MRI — consistent with RPOC.
Fluid (endometrial fluid/blood) and rarely gas may be seen in the cavity. Gas presence strongly suggests infection complication (endometritis/pyometra) — appears as 'dirty shadowing' on US. Fluid creates an anechoic background highlighting retained material contours and facilitating solid-fluid differentiation. Hemorrhagic fluid may show internal echoes and sedimentation.
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Fluid is seen in the cavity with gas ___ (present/absent) — evaluated for RPOC and infection complication.
Rare but serious uterine artery pseudoaneurysm complication is recognized on color Doppler by characteristic 'yin-yang' pattern (bidirectional turbulent intraluminal flow — red and blue mosaic). Pseudoaneurysm forms from trophoblastic invasion weakening the arterial wall and carries catastrophic hemorrhage risk during curettage. 'To-and-fro' flow pattern is seen on pulse-wave Doppler.
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A focal vascular structure at the myometrium/cavity level showing yin-yang pattern and to-and-fro flow on color Doppler is consistent with pseudoaneurysm.
Criteria
Increased vascularity on Doppler, RI <0.5, contains viable trophoblastic tissue
Distinct Features
High massive hemorrhage risk during curettage, uterine artery embolization should be considered first, hysteroscopic resection alternative, β-hCG usually persistently elevated
Criteria
No vascularity on Doppler, necrotic trophoblast or organized blood clot
Distinct Features
Conservative management possible (spontaneous expulsion may be awaited), safe curettage can be performed (low hemorrhage risk), medical treatment with misoprostol may be tried
Criteria
Fever, foul-smelling discharge, gas in cavity (dirty shadowing), leukocytosis
Distinct Features
Urgent antibiotic treatment + controlled curettage (sepsis risk), close vital sign monitoring, multidisciplinary management
Distinguishing Feature
PAS is diagnosed prenatally showing myometrial invasion (disrupted junctional zone, lacunae); RPOC is retained tissue in the cavity postpartum typically without myometrial invasion — timing and invasion degree difference
Distinguishing Feature
Molar pregnancy shows snowstorm pattern + very high β-hCG (>100,000); RPOC shows postpartum focal endometrial mass + β-hCG in declining trend or not declining — pattern and β-hCG level difference
Distinguishing Feature
Endometrial carcinoma is seen in postmenopausal period with different vascularity pattern; RPOC is seen in obstetric context (postpartum/post-abortion) differentiated by clinical history (pregnancy/delivery)
Urgency
urgentManagement
surgicalBiopsy
Not NeededFollow-up
specialist-referralRPOC treatment is planned based on vascularity status — Doppler evaluation determines treatment strategy. Avascular RPOC: conservative management (await spontaneous expulsion — in mild bleeding and stable clinical condition), medical treatment with misoprostol (uterine contraction induction), or safe curettage (low hemorrhage risk). Vascularized RPOC (RI <0.5): uterine artery embolization → safe curettage (after hemorrhage control), hysteroscopic resection (selective removal under direct visualization — fertility-sparing, least invasive approach), or high-risk curettage (if embolization unavailable — blood products ready, under anesthesia). When pseudoaneurysm is detected, curettage is ABSOLUTELY contraindicated — embolization must close the pseudoaneurysm first. Infected RPOC: broad-spectrum antibiotics + controlled curettage (sepsis risk), close vital sign monitoring. Oxytocic drugs (oxytocin, methylergonovine) may help control bleeding through uterine contraction. β-hCG monitoring is mandatory in all modalities — weekly measurements until negative. Persistent β-hCG elevation (not declining or rising) suggests retained viable trophoblast or gestational trophoblastic disease — requires additional evaluation.
RPOC is an important cause of postpartum and post-abortion bleeding. In vascularized RPOC, uterine artery embolization before curettage may reduce bleeding. Diagnosis: US + Doppler + β-hCG combination. Treatment: curettage for severe or persistent bleeding (US-guided recommended), conservative management may be tried in stable cases. Complications: endometritis, sepsis, DIC, Asherman syndrome (in repeated curettage).