2026 SOAP Annual Meeting

Background

Physiologic effect:

Morphine increases sphincter of Oddi (SO) basal pressure and contractility and raises common bile duct pressure (1).

Clinical Manifestation:

This effect can trigger dose-dependent biliary colic–like pain and nausea/vomiting, which may mimic acute abdominal emergencies (2-4).

Diagnostic Challenge in Pregnancy:

Severe abdominal pain during labor or late pregnancyinclude a wide differential, both obstetric and non-obstetric, complicating diagnosis.

Clinical Implications:

Evaluation and management must consider competing etiologies for effective analgesia while maintaining maternal-fetal safety

Case: 29-year-old G5P3013 at 34w3d with history of Roux-en-Y gastric bypass and cholecystectomy admitted after ground-level fall with preterm contractions

Initial Management: Monitoring for concealed placental abruption; patient received IM morphine 10mg for early labor pain.

Acute Symptom Onset: Developed sudden severe epigastric pain with nausea, vomiting, chills, flushing, and distress.

Diagnosis & Treatment: Morphine-induced sphincter of Oddi spasm considered; IV naloxone 0.4 mg ×3 resulted in rapid pain resolution with stable maternal and fetal status.

Epidural Attempt & Delivery: Standard epidural attempted. During procedure, urge to push andpatient delivered precipitously. No medications given. No postpartum opioids.

Vitals and Exam

Vitals stable; abdomen soft with epigastric tenderness; fetal heart tracing reassuring and cervix unchanged at 1.5 cm.

Workup:

Labs:

-Hgb 9.3-10.3 and fibrinogen 270s-340s

-Liver panel, lipase, lactate, INR, rest of CBC, VBG— within normal limits

EKG: normal sinus rhythm
OB US: Growth ~34 weeks. No obvious abnormality concerning for abruption.Normal amniotic fluid.

Differentials:

Obstetric: Placental abruption, uterine rupture, preeclampsia/HELLP

Surgical: Post-Roux-en-Y gastric bypass complications, appendicitis

Medical: Pancreatitis, gastritis, medication-induced sphincter of Oddi spasm

Morphine-induced sphincter of Oddi dysfunction (SOD): Teaching Points

Clinical Recognition

Rare complication of morphine administration
Presents with acute biliary-type pain, potentially mimicking obstetric or surgical emergencies

Diagnosis

Temporal relationship between morphine administration and symptom onset ~20 min post administration (2)
Exclusion of other causes (e.g. placental abruption, uterine rupture, surgical abdomen)

Risk Factors

Prior cholecystectomy reported as a risk factor in several studies and case report (5-7)

Management

Naloxone may relieve symptoms (2-3)

Use minimum effective dose to avoid opioid withdrawal and loss of labor analgesia

FDA reports possible risk with neuraxial morphine administration. No clinical cases reported. (8)

2026 SOAP Annual Meeting

When Pain Relief Causes Pain: Morphine-Induced Sphincter of Oddi Spasm During Preterm Labor

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