Retained placenta (also called retained afterbirth or retained fetal membranes) occurs when the placenta is not expelled from the uterus within the expected timeframe following parturition.
Overview and Clinical Importance
Retained placenta (also called retained afterbirth or retained fetal membranes) occurs when the placenta is not expelled from the uterus within the expected timeframe following parturition. In dogs, the placenta should be expelled within 15 minutes of each puppy's delivery. Retained placental tissue can rapidly become a nidus for bacterial infection, potentially leading to metritis, sepsis, and death if not promptly recognized and treated.
This condition is relatively uncommon in dogs compared to large animal species but carries significant morbidity when it occurs. Retained placenta is particularly important on the NAVLE because it tests your understanding of canine reproductive physiology, postpartum complications, and emergency medicine principles.
High-YieldOn the NAVLE, retained placenta questions often present as a postpartum bitch with dark green or foul-smelling vaginal discharge persisting beyond 24 hours. The green color is due to uteroverdin (a dehydrogenated form of bilirubin) from the marginal hematomas of the canine zonary placenta.
| Zone |
Description and Function |
| Labyrinth Zone |
Primary exchange region; composed of trophoblastic lamellae (cytotrophoblasts and syncytiotrophoblasts) covering maternal vessels; fetal vessels deeply indent the trophoblasts |
| Junctional Zone |
Transition area between labyrinth and glandular zones; contains tall columnar trophoblasts that invade into endometrial gland cavities; the deep portion is called the sponge zone |
| Glandular Zone |
Region of endometrial glands; provides histotrophic nutrition during early gestation and continues supporting placental function |
| Marginal Hematomas |
Located at each longitudinal edge of the zonary placenta; pools of maternal blood where specialized trophoblast cells (hematophagous) absorb iron and nutrients; source of green uteroverdin pigment |
Canine Placental Anatomy and Physiology
Placental Classification
The canine placenta is classified as zonary (by gross morphology), lamellar (by internal architecture), and endotheliochorial (by histological barrier). The zonary placenta forms a circumferential band around the equator of the chorionic sac, creating an intimate attachment to the endometrium at this region.
Histological Zones of the Canine Placenta
Normal Placental Expulsion (Stage III Labor)
During normal parturition, the placenta should be expelled within 15 minutes of each puppy's delivery. The labyrinth tears away through a plane running along the junctional zone. Key physiological mechanisms include:
- Oxytocin release: Promotes uterine contractions; triggered by nursing reflex and cervical/vaginal stimulation
- Prostaglandin F2alpha (PGF2alpha): Produced by placenta; causes luteolysis and myometrial contractions
- Decreased blood supply: Placental vessels constrict, reducing attachment strength
- Chorionic villus shrinkage: Allows separation from maternal crypts
NAVLE TipRemember that bitches often EAT the placentas immediately after delivery. This makes counting placentas difficult and can delay recognition of retained placenta. Always instruct owners to monitor whelping carefully and count expelled placentas when possible.
| Cause |
Mechanism |
| Uterine Inertia |
Primary or secondary; inadequate myometrial contractions fail to expel placental tissue; often associated with prolonged labor, large litters, or maternal exhaustion |
| Dystocia |
Prolonged labor leads to maternal exhaustion and secondary uterine inertia; fetal oversize or malpresentation may contribute |
| Large Litter Size |
Prolonged parturition leads to uterine fatigue and inadequate contractions for complete placental expulsion |
| Hypocalcemia |
Calcium is essential for myometrial contractility; low serum calcium impairs uterine contraction strength |
| Hormonal Imbalances |
Inadequate oxytocin release or prostaglandin production; abnormal oxytocin receptor expression |
| Abnormal Placentation |
Rare; includes placenta accreta/percreta (abnormal trophoblast invasion into myometrium preventing normal separation) |
Etiology and Risk Factors
Primary Causes
Breed and Patient Risk Factors
- Toy breeds: Higher incidence due to smaller pelvic size, higher rates of dystocia, and single-puppy pregnancies with oversized fetuses
- Brachycephalic breeds: Bulldogs, Boston Terriers, and similar breeds have higher dystocia rates, often requiring cesarean section
- Primiparous bitches: First-time mothers may have less efficient uterine contractions
- Poor body condition: Malnutrition or obesity can impair uterine function
| Clinical Sign |
Characteristics |
Timing |
| Vaginal Discharge |
Dark green, black, or sanguinopurulent; foul-smelling (fetid); copious volume |
Persistent beyond 24 hours postpartum; abnormal if dark green discharge continues |
| Fever |
Temperature greater than 103.5 degrees F (39.7 degrees C); may indicate developing metritis |
Typically develops 24-72 hours after infection begins |
| Systemic Signs |
Lethargy, anorexia, depression, vomiting; decreased milk production |
Indicates progression to metritis or sepsis; requires immediate intervention |
| Poor Maternal Behavior |
Disinterest in nursing puppies; failure to clean or care for neonates |
May be early indicator before overt systemic illness |
| Abdominal Discomfort |
Pain on abdominal palpation; tense abdomen; possible uterine enlargement |
Present in advanced cases; suggests uterine distension or peritonitis |
Clinical Signs and Presentation
Key Clinical Signs
Normal Postpartum Discharge (Lochia) vs Abnormal Discharge
Exam Focus: The hallmark distinguishing feature is that GREEN vaginal discharge persisting beyond 24 hours postpartum is ABNORMAL and suggests retained placenta or developing metritis. Normal lochia should transition from greenish (immediately postpartum from uteroverdin) to reddish-brown within 24 hours.
| Normal Lochia |
Abnormal (Retained Placenta/Metritis) |
| Reddish-brown color |
Dark green, black, or frankly purulent |
| Mild odor or no odor |
Foul, fetid odor |
| Decreasing volume over 2-6 weeks |
Copious, may be increasing or persistent |
| Dam is bright, alert, nursing well |
Fever, lethargy, anorexia, poor mothering |
| Resolves within 4-6 weeks (complete involution by 12-15 weeks) |
Persists beyond 24 hours with green/black coloration |
Diagnostic Approach
History and Physical Examination
A thorough history should include:
- Date and duration of parturition; any complications during whelping
- Number of puppies delivered and whether placentas were counted
- Character and timing of vaginal discharge
- Dam's appetite, attitude, and maternal behavior
- Puppy health and nursing activity
Physical examination findings:
- Vulvar discharge: color, consistency, odor
- Temperature (fever greater than 103.5 degrees F)
- Abdominal palpation: uterine enlargement, pain, masses
- Hydration status and mucous membrane color
- Mammary gland examination: milk production, mastitis signs
Diagnostic Testing
High-YieldDiagnosis of retained placenta can be challenging because bitches often eat the placentas. A presumptive diagnosis is made based on: (1) recent whelping history, (2) persistent green vaginal discharge beyond 24 hours, and (3) clinical signs of illness. Ultrasound is the preferred imaging modality but may not always visualize placental tissue. Treatment is often initiated empirically based on clinical suspicion.
| Test |
Findings |
Clinical Significance |
| CBC |
Leukocytosis with left shift; neutrophilia or neutropenia (severe sepsis); possible anemia |
Indicates inflammatory response; degenerative left shift suggests overwhelming infection |
| Serum Chemistry |
Hypoglycemia, azotemia, hypocalcemia, elevated liver enzymes possible; electrolyte abnormalities |
May reflect sepsis, endotoxemia, or concurrent periparturient hypocalcemia |
| Vaginal Cytology |
Numerous degenerate neutrophils, intracellular bacteria; may see trophoblast cells |
Confirms bacterial infection; helps distinguish from SIPS (non-septic); culture recommended |
| Abdominal Radiography |
Uterine enlargement; cannot visualize soft tissue placenta; may rule out retained fetus (fetal skeleton) |
Limited sensitivity for retained placenta alone; useful to rule out retained pup |
| Abdominal Ultrasound |
Enlarged, fluid-filled uterus; heterogeneous luminal content; may visualize echogenic mass |
Preferred imaging modality; can distinguish retained tissue from fluid; rules out retained pups |
Treatment
Medical Management
Medical therapy is the first-line treatment for uncomplicated retained placenta and includes uterotonic drugs, antibiotics, and supportive care.
Ecbolic (Uterotonic) Drugs
NAVLE TipOXYTOCIN is effective only within the first 24 hours postpartum because uterine oxytocin receptors are downregulated after this period. After 24 hours, PROSTAGLANDIN F2alpha becomes the preferred ecbolic drug. Always give CALCIUM before oxytocin to enhance contractility. Remember: Calcium + Oxytocin within 24 hours; PGF2alpha after 24 hours.
Antibiotic Therapy
Broad-spectrum antibiotics are essential to treat or prevent bacterial infection. Choice depends on severity, culture results, and nursing status of the dam.
Common bacterial pathogens: Escherichia coli (most common), Staphylococcus spp., Streptococcus spp., Proteus spp., and other gram-negative vaginal commensals. Culture and sensitivity testing is recommended to guide antibiotic selection.
Surgical Management
Indications for surgery:
- Failure of medical management (ecbolics and antibiotics)
- Severe systemic illness, sepsis, or endotoxemia
- Concurrent retained fetus
- Uterine rupture or peritonitis
- Owner does not desire future breeding (elective OVH)
Ovariohysterectomy (OVH) is curative and is the treatment of choice for severe cases or when future breeding is not desired. For valuable breeding animals, hysterotomy to remove retained tissue with uterine preservation may be attempted, though this carries higher risk of complications and should be combined with aggressive medical therapy.
Supportive Care
- IV fluid therapy: Correct dehydration and electrolyte imbalances; essential for septic patients
- Nutritional support: Ensure adequate caloric intake; nursing dams have high energy demands
- Antiemetics: Maropitant (Cerenia) 1 mg/kg SC/PO SID if vomiting present
- Temperature monitoring: Track fever resolution as indicator of treatment response
- Puppy care: May need supplemental feeding if dam is unable to nurse; temporary orphan care during acute illness
| Drug |
Dose |
When to Use |
Notes |
| Oxytocin |
0.5-2 U/bitch IM or SC; may repeat every 30 min x 3 doses |
Within 24 hours postpartum; first-line ecbolic |
Oxytocin receptors downregulate after 24 hours; high doses cause tetanic contractions |
| Prostaglandin F2alpha (Dinoprost) |
0.1-0.25 mg/kg SC every 12-24 hours for 5 days |
Greater than 24 hours postpartum; preferred after oxytocin window closes |
Side effects: panting, salivation, vomiting, diarrhea (transient); effective for uterine evacuation |
| Cloprostenol |
1-3 mcg/kg SC every 12-24 hours to effect |
Alternative to PGF2alpha; synthetic prostaglandin |
Fewer side effects than dinoprost; effective for uterine evacuation |
| Calcium Gluconate 10% |
1 mL/22 kg SC (uterotonic); 50-150 mg/kg IV slow (hypocalcemia) |
Given prior to oxytocin to enhance myometrial contractility |
Monitor ECG during IV administration; SC is safer for uterotonic use |
Differential Diagnosis
Key Differentials for Postpartum Vaginal Discharge
Subinvolution of Placental Sites (SIPS)
SIPS is a unique condition in dogs characterized by failure of normal uterine involution at placental attachment sites. It is important to distinguish from retained placenta because treatment differs significantly.
- Signalment: Young bitches (less than 3 years); usually after first litter
- Presentation: Serosanguineous to hemorrhagic discharge persisting beyond 6-8 weeks postpartum
- Key distinguishing feature: Dam is OTHERWISE HEALTHY - no fever, no systemic signs, normal appetite, nursing well
- Pathophysiology: Trophoblast cells fail to regress; continue to invade myometrium; prevents normal thrombus formation and re-epithelialization
- Diagnosis: Clinical history; vaginal cytology showing trophoblast-like cells; diagnosis of exclusion
- Treatment: Often self-limiting; low-dose megestrol acetate (0.1 mg/kg PO SID x 1 week, then 0.05 mg/kg PO SID x 1 week) stops bleeding; OVH rarely needed
- Prognosis: Excellent for life and future fertility
| Antibiotic |
Dose |
Notes |
| Amoxicillin-Clavulanate |
12.5-25 mg/kg PO BID for 14 days |
Good first-line choice; safe for nursing dams; covers most common pathogens |
| Cephalexin |
22-30 mg/kg PO BID-TID for 14 days |
Safe for nursing; good concentration in reproductive tissue |
| Ampicillin |
20 mg/kg IV/PO TID for 14 days |
Used while awaiting culture results; good gram-positive and some gram-negative coverage |
| Enrofloxacin (avoid) |
Do NOT use in nursing dams |
Fluoroquinolones cause cartilage damage in nursing puppies; contraindicated |
Prognosis and Complications
Prognosis
- Early intervention: Excellent prognosis with prompt medical treatment; most bitches recover fully
- Delayed treatment: Guarded if metritis or sepsis has developed; mortality possible
- Future fertility: Generally good if uterus is preserved and infection is controlled; may have increased risk of recurrence
- Post-OVH: Excellent prognosis once recovered from surgery; curative
Potential Complications
- Metritis: Bacterial infection of uterine wall; can progress to sepsis
- Sepsis/endotoxemia: Life-threatening systemic infection; requires aggressive ICU care
- Peritonitis: If uterine rupture occurs; carries poor prognosis
- Impaired lactation: Systemic illness decreases milk production; puppies may require supplemental feeding
- Infertility: Chronic endometritis may develop if infection is incompletely resolved
| Condition |
Distinguishing Features |
Treatment |
| Normal Lochia |
Reddish-brown discharge; decreasing volume; dam is healthy and nursing well; resolves within 4-6 weeks |
None required; normal process |
| Metritis |
Foul-smelling sanguinopurulent discharge; fever; systemic illness; may occur with or without retained placenta |
Antibiotics, ecbolics, supportive care; OVH if severe |
| SIPS |
Serosanguineous to hemorrhagic discharge beyond 6-8 weeks; dam is OTHERWISE HEALTHY with no systemic signs; young primiparous bitches |
Often self-limiting; low-dose progestogen if needed; rarely requires OVH |
| Retained Fetus |
Fetal skeleton visible on radiograph; may present similarly to retained placenta; rapid progression to sepsis |
Surgical removal usually required; ecbolics may help if recent |
| Pyometra |
Occurs during diestrus (not immediate postpartum); cystic endometrial hyperplasia complex; older intact bitches |
OVH is treatment of choice; medical management in select cases |