What is the most probable diagnosis for a patient presenting with vaginal bleeding and fever 15 days post cesarean section (C-section)?

Postpartum Endometritis

The most probable diagnosis is C. Endometritis. A patient presenting with vaginal bleeding and fever 15 days after cesarean section most likely has postpartum endometritis, which is the leading cause of postpartum fever and is significantly more common after cesarean delivery than vaginal delivery 1.

Why Endometritis is Most Likely

Endometritis is the primary infectious cause of postpartum fever, particularly after cesarean section, presenting as a multi-organism syndrome with high fever, abdominal pain, uterine tenderness, and foul-smelling lochia 1. The timing at 15 days post-cesarean falls within the typical presentation window, as 84% of endometritis cases occur within 7 days but can present later 2.

Key Supporting Evidence:

• Cesarean section increases the risk of endometritis 5-7 times compared to vaginal delivery, especially when performed after labor onset or membrane rupture 1, 3
• The combination of fever and vaginal bleeding in this timeframe strongly suggests endometritis rather than other complications 1
• Postpartum endometritis has a mean temperature of 102.2°F at diagnosis, with fever being the hallmark presenting sign 2

Why Other Options Are Less Likely

A. Wound Infection

• While wound infections do occur after cesarean section (6.8% incidence), they typically present with localized wound symptoms (erythema, drainage, tenderness at the incision site) rather than vaginal bleeding 4
• Wound infections would not explain the vaginal bleeding component of this presentation 1

B. Retained Products of Conception (RPOC)

• RPOC is the most common cause of late postpartum hemorrhage but is more likely after vaginal delivery than cesarean 5
• RPOC typically presents with persistent bleeding and cramping, and while fever can occur, it is not the primary presenting feature 6, 5
• The prominence of fever in this case makes endometritis more likely than RPOC 1

D. Mastitis

• Mastitis presents with breast-specific symptoms (breast pain, erythema, induration) and would not cause vaginal bleeding 1
• This diagnosis does not fit the clinical presentation at all

Clinical Reasoning Algorithm

When evaluating postpartum fever with vaginal bleeding after cesarean section:

1. Assess timing: 15 days post-cesarean is within the typical window for endometritis (most cases within 7 days, but can occur up to 6 weeks) 2, 1

2. Evaluate fever pattern: High fever (>100.4°F) is the hallmark of endometritis 7, 2

3. Assess bleeding characteristics:

   • Heavy bleeding with fever → likely endometritis
   • Heavy bleeding without fever → consider RPOC or vascular complications 5

4. Look for associated symptoms:

   • Uterine tenderness and foul-smelling lochia strongly support endometritis 1, 2
   • Localized wound symptoms would suggest wound infection 4

Important Clinical Pitfalls

• Do not delay antibiotic therapy while waiting for imaging or cultures in suspected endometritis, as 93.7% respond to initial antibiotics but delays can lead to serious complications including pelvic abscess or septic thrombophlebitis 2
• Failure to respond to initial antibiotics mandates imaging (ultrasound or CT) to evaluate for complications such as abscess, hematoma, or RPOC 1, 7
• The overall postpartum febrile morbidity rate after cesarean section is 20.5%, with endometritis accounting for 9.8% of cases 4

Initial Management Approach

• Start broad-spectrum antibiotics with anaerobic coverage immediately for temperatures >38.7°C (101.6°F) in the first 24 hours or >38.0°C (100.4°F) on any two of the first 10 days postpartum 7
• Obtain transvaginal ultrasound with Doppler if patient fails to respond to antibiotics within 48-72 hours to evaluate for complications 5, 7
• Monitor for bacteremia (occurs in 5% of cases) and severe complications like pelvic abscess (1.9% of cases) 2