What is the typical cause of postpartum rectal bleeding?

Postpartum Rectal Bleeding: Typical Causes

The typical cause of postpartum rectal bleeding is hemorrhoids (particularly thrombosed external hemorrhoids) or anal fissures, which occur in approximately one-third of postpartum women, with hemorrhoids being far more common than fissures. 1

Primary Etiologies

Hemorrhoidal Disease (Most Common)

• Thrombosed external hemorrhoids account for the majority of postpartum rectal bleeding, affecting 35.2% of women in the postpartum period compared to only 9.1% during pregnancy. 1
• 91% of thrombosed external hemorrhoids appear within the first day after delivery, making this the predominant early postpartum rectal pathology. 1
• These lesions are strongly associated with traumatic vaginal delivery, superficial perineal tears, and heavier babies. 1

Anal Fissures (Second Most Common)

• Anal fissures occur in approximately 15% of postpartum women (25 of 58 women with anal lesions in prospective studies). 1
• Unlike hemorrhoids, anal fissures show no temporal peak and are distributed throughout the first two months postpartum rather than clustering immediately after delivery. 1

Key Risk Factors

Primary Risk Factor

• Dyschezia (difficult or painful defecation) is the most important risk factor, with an odds ratio of 5.7 (95% CI: 2.7-12) for developing postpartum anal lesions. 1

Secondary Risk Factors

• Late delivery (post-dates pregnancy) carries an odds ratio of 1.4 (95% CI: 1.05-1.9). 1
• Traumatic vaginal delivery with perineal tears significantly increases hemorrhoid risk. 1
• Larger infant birth weight correlates with higher hemorrhoid incidence. 1

Critical Differential Diagnosis

When to Consider Alternative Diagnoses

While hemorrhoids and fissures are typical, you must exclude life-threatening intra-abdominal hemorrhage if the patient presents with:

• Acute abdominal pain with rectal bleeding 2
• Hypovolemic shock 2
• Signs of peritoneal irritation 2

Rare but reported: Bleeding from superficial rectal vessels into the peritoneal cavity can occur after normal vaginal delivery, presenting as hemoperitoneum with rectal involvement. 2 This carries high maternal mortality and requires immediate laparotomy. 2

Distinguishing from Postpartum Hemorrhage

• If the uterus is firm and well-contracted, genital tract lacerations (not uterine atony) become the leading cause of bleeding. 3
• Uterine atony accounts for 70-80% of postpartum hemorrhage overall but presents with a soft, boggy uterus. 3, 4
• Assess uterine tone first—if firm, thoroughly inspect the genital tract and perirectal area for lacerations or hemorrhoids. 3

Clinical Approach Algorithm

1. Immediate assessment: Verify hemodynamic stability and uterine tone 3
2. Direct visualization: Perform careful perianal and rectal examination to identify hemorrhoids or fissures 1
3. Exclude trauma: Inspect for vaginal/perineal lacerations that may extend to rectal area 3
4. Red flags: If abdominal pain, shock, or peritoneal signs present, obtain urgent imaging (ultrasound or CT) to exclude intra-abdominal hemorrhage 2

Common Pitfalls to Avoid

• Do not assume all postpartum bleeding is uterine in origin—one-third of women develop anorectal pathology that may be the primary source. 1
• Do not dismiss constipation history—dyschezia is the strongest predictor of postpartum anal lesions with nearly 6-fold increased risk. 1
• Do not delay imaging if systemic symptoms present—rare cases of rectal vessel bleeding into the peritoneum can be fatal if diagnosis is delayed. 2