Sisa Plasenta

01Pathophysiology

After delivery of the fetus, the third stage of labor involves separation and expulsion of the placenta. Normal placental separation occurs through cleavage at the decidua basalis (the spongy layer), driven by uterine contractions that reduce the surface area of the placental bed. When the placenta or fragments of it fail to separate completely, the retained tissue prevents the myometrium from contracting fully around the spiral arteries at the placental site. This is the fundamental mechanism: an occupied uterus cannot contract properly, and without contraction, the open sinusoidal vessels at the former placental bed continue to bleed.

The pathophysiology directly explains the clinical picture. The uterus feels boggy and enlarged because it cannot involute with tissue still inside. The bleeding is persistent or recurrent because the exposed vessels at the implantation site lack the mechanical hemostasis that comes from myometrial contraction (the so-called "living ligature" or "physiologic suture" of the uterus). If fragments remain for days to weeks, the necrotic tissue becomes a nidus for infection, leading to endometritis, which further impairs uterine contractility and worsens bleeding.

In cases of placenta accreta spectrum (accreta, increta, percreta), the pathology is different at the tissue level: the chorionic villi are abnormally adherent to or invading through the myometrium due to a deficient or absent decidua basalis (often at a prior cesarean scar). In these cases, forceful removal can cause catastrophic hemorrhage, and the retained tissue is not simply "left behind" but rather cannot be separated safely.

A secondary mechanism involves retained membranes or succenturiate (accessory) lobes. A succenturiate lobe is an accessory placental lobe connected to the main disc by vessels running through the membranes. If unrecognized at delivery, this lobe stays in utero and causes delayed postpartum hemorrhage. On exam, the hallmark is a torn vessel running to the edge of the membranes with no corresponding placental tissue, a finding the delivering provider should identify on routine placental inspection.

02Classification and Clinical Manifestation

By Timing of Presentation

By Type of Retained Tissue

By Severity

03Diagnostic Workup

The very first "test" is not a lab or an image: it is systematic inspection of the placenta and membranes immediately after delivery. The delivering provider should lay the placenta maternal-side-up and check that the cotyledonary surface is complete with no missing segments. The membranes should be examined for torn vessels that trail off the edge, which would suggest a retained succenturiate lobe. This step is zero-cost and catches the problem before the patient even starts bleeding.

When a patient presents with postpartum bleeding and retained tissue is suspected, the best initial imaging study is pelvic ultrasound. A thickened, heterogeneous endometrial echo with echogenic foci within the cavity is suggestive of retained products. However, ultrasound has moderate sensitivity and can be confounded by postpartum blood clots, decidual tissue, or a normal postpartum endometrium. Color Doppler helps distinguish vascularized retained tissue (which has internal blood flow) from avascular clot.

The gold standard for diagnosis is histopathological examination of evacuated tissue. Finding chorionic villi under the microscope confirms the diagnosis definitively. This means the diagnosis is often confirmed retrospectively, after the tissue has already been removed.

Serum beta-hCG is a useful adjunct. After a normal delivery, beta-hCG should decline steadily and become undetectable within approximately 3 to 4 weeks. A persistent or plateau pattern raises suspicion for retained placental tissue (or, less commonly, gestational trophoblastic disease, which must be considered in the differential).

A CBC establishes the degree of anemia and guides transfusion decisions. If the bleeding is heavy or prolonged, a coagulation panel (including fibrinogen) is essential to rule out disseminated intravascular coagulation (DIC), which is both a consequence of and a contributor to ongoing hemorrhage.

04Management and Treatment

Step 1: Secure IV access and initiate uterotonics. Begin with two large-bore IV lines and start crystalloid resuscitation. Simultaneously, administer oxytocin: 20 to 40 units mixed in 1000 mL of normal saline or Ringer Lactate, infused at 60 drops per minute. Give an additional 10 units of oxytocin intramuscularly. The oxytocin promotes uterine contraction, which compresses the bleeding vessels and helps define the retained tissue for removal. Once initial stabilization occurs, reduce the infusion to a maintenance rate of 20 units in 1000 mL at 40 drops per minute, and continue until bleeding stops.

Step 2: Evacuate the retained tissue. The approach depends on the cervical status:

• If the cervix is open and admits fingers, perform digital (manual) exploration of the uterine cavity. Sweep the cavity systematically to identify and remove adherent tissue, blood clots, and membrane fragments. This is done under analgesia or light sedation.

• If the cervix only admits instruments (not wide enough for a hand), proceed with manual vacuum aspiration (MVA) or dilation and curettage (D&C). MVA is generally preferred in resource-limited settings because it can be performed under local anesthesia and carries a lower perforation risk than sharp curettage. D&C is an alternative, performed under regional or general anesthesia. In either case, use ultrasound guidance when available to reduce the risk of perforation and ensure completeness of evacuation.

Step 3: Administer prophylactic antibiotics. After any intrauterine procedure, give a single prophylactic dose of ampicillin 2 g intravenously combined with metronidazole 500 mg. The ampicillin covers common gram-positive and some gram-negative organisms, while metronidazole provides anaerobic coverage. This combination targets the polymicrobial flora most likely to cause postprocedural endometritis.

Step 4: If bleeding persists despite evacuation, treat the patient as having concurrent uterine atony. Escalate with additional uterotonics:

• Ergometrine (methylergonovine) 0.2 mg IM (contraindicated in hypertension and preeclampsia)

• Misoprostol 600 to 800 mcg sublingual or rectal

• Carboprost (15-methyl prostaglandin $F_{2\alpha }F\_\{2\backslash alpha\}$) 250 mcg IM, repeated every 15 minutes up to 8 doses (contraindicated in asthma)

If pharmacologic measures fail, proceed to mechanical and surgical interventions: intrauterine balloon tamponade (e.g., Bakri balloon), uterine compression sutures (B-Lynch), uterine artery ligation, or ultimately hysterectomy as a life-saving measure.

Step 5: Supportive care. Monitor vital signs and urine output closely. Transfuse packed red blood cells for hemodynamic instability or hemoglobin below 7 g/dL (or per clinical judgment). Correct coagulopathy with fresh frozen plasma, cryoprecipitate, or platelets as indicated by labs.

Contraindications and Cautions

• Ergometrine is contraindicated in patients with hypertension, preeclampsia, or heart disease due to its vasoconstrictive effects.

• Carboprost is contraindicated in patients with asthma because it causes bronchospasm.

• If placenta accreta spectrum is suspected (placenta does not separate at all, prior cesarean scar, ultrasound showing myometrial invasion), do not attempt forceful manual removal. This requires surgical management, often hysterectomy, with multidisciplinary preparation.

05Differential Diagnosis and Distractors

06Traps and High-Yield Pearls

The most common way students lose points on this topic is by confusing retained placenta with uterine atony and selecting uterotonics alone as the definitive treatment. Both conditions cause a boggy uterus and postpartum bleeding, and uterotonics are used in both. However, the critical difference is that in retained placenta, uterotonics are adjunctive (they reduce bleeding and promote contraction around the remaining tissue), while the definitive treatment is removal of the retained tissue. If a vignette describes a boggy uterus, continued bleeding despite oxytocin, and an incomplete placenta on inspection, the next best step is evacuation, not more oxytocin.

Another common trap is the succenturiate lobe. The vignette may describe a seemingly complete placenta with normal cotyledons, but the student must notice the mention of "torn vessels at the membrane edge" or "a vessel trailing to the edge of the membranes without corresponding tissue." This is the classic description of a missing accessory lobe, and the answer is to explore the uterus and retrieve it.

Students also sometimes confuse the approach based on cervical status. If the cervix is open, digital (manual) exploration is the appropriate first move. If the cervix is closed or only admits instruments, the answer shifts to MVA or D&C. The vignette will usually tell you the cervical status, and the correct intervention depends on it.

Finally, be aware of the accreta trap: if a vignette describes a placenta that "does not separate" despite prolonged manual efforts, especially in a patient with prior cesarean deliveries, the answer is not to pull harder. The answer is to suspect placenta accreta and prepare for operative management. Forceful removal in accreta causes life-threatening hemorrhage.

The core competency being tested is the ability to systematically evaluate postpartum hemorrhage using the "4 T's" framework (Tone, Tissue, Trauma, Thrombin), correctly identify "Tissue" as the cause, and select the appropriate intervention based on the clinical scenario.