Why is the uterus typically palpable above the level of the umbilicus in uterine atony?

Why the Uterus is Palpable Above the Umbilicus in Uterine Atony

In uterine atony, the uterus is palpable above the umbilicus because the relaxed, non-contracted uterine muscle fails to compress blood vessels at the placental site, leading to significant blood accumulation within the uterine cavity that causes enlargement and upward displacement of the uterus. 1

Pathophysiology of Uterine Atony

Uterine atony is characterized by the failure of the uterus to contract effectively after delivery, which is the most common cause of postpartum hemorrhage (PPH), accounting for >75% of early PPH cases 1. The normal physiological process after delivery involves:

1. Normal uterine involution: Strong myometrial contractions that compress blood vessels at the placental implantation site
2. In atony: Lack of these contractions allows continued bleeding

When atony occurs:

• Blood accumulates within the uterine cavity
• The uterus becomes enlarged and boggy
• The fundus rises above the umbilicus due to this enlargement
• The uterus feels soft and non-contracted on palpation

Clinical Presentation and Diagnosis

Uterine atony is primarily a clinical diagnosis 1 characterized by:

• Palpable uterine fundus above the umbilical level
• Soft, boggy uterus on palpation
• Excessive vaginal bleeding
• Vital sign changes consistent with blood loss (tachycardia, hypotension)

Management Considerations

Early recognition and management are critical to prevent significant morbidity and mortality:

1. First-line treatment: Uterine massage and uterotonic drugs such as oxytocin 1, 2
2. Second-line agents: Methylergonovine is indicated for routine management of uterine atony and hemorrhage following delivery of the placenta 3, 2
3. Additional options: Prostaglandins (carboprost, misoprostol) when first-line treatment fails 2, 4, 5

Imaging Findings

Although uterine atony is primarily a clinical diagnosis, imaging may be helpful when initial treatments fail:

• CT findings: Enlarged uterus with focal or diffuse arterial or venous oozing and/or hematoma within the uterine cavity 1
• Ultrasound: May show an enlarged uterine cavity with accumulated blood 1

Pitfalls and Caveats

• Delayed recognition: Failure to recognize the enlarged, supra-umbilical uterus as a sign of atony can lead to significant blood loss
• Misdiagnosis: An enlarged uterus above the umbilicus might be confused with normal postpartum status, but the soft, boggy consistency distinguishes atony
• Treatment delays: Early intervention with uterotonic agents is crucial; delays may lead to need for surgical management 5
• Incomplete assessment: Always evaluate for other causes of PPH when atony is suspected, including retained placental fragments, lacerations, and coagulopathies 1

Advanced Management Options

If medical management fails to control hemorrhage from uterine atony:

• Uterine tamponade techniques (balloon catheters) 2, 4
• Novel approaches like uterine wrapping with elastic bandages 6
• Interventional radiology procedures (arterial embolization) 2
• Surgical interventions (compression sutures, ligation of vessels, hysterectomy) 2

Understanding that the supra-umbilical location of the uterus in atony is due to blood accumulation within the uterine cavity helps clinicians recognize this emergency promptly and initiate appropriate management to prevent severe morbidity and mortality.