How should a patient at 26 weeks gestation presenting with lower abdominal pain but no vaginal bleeding be evaluated and managed?

Evaluation and Management of Lower Abdominal Pain at 26 Weeks Gestation Without Bleeding

Initial Approach

Begin with transabdominal ultrasound immediately to evaluate for placental abruption, preterm labor, uterine rupture (especially if prior cesarean), appendicitis, urolithiasis, ovarian torsion, and other acute abdominal pathology. 1, 2

The absence of bleeding does not exclude serious obstetric complications—placental abruption can present with pain alone, and ultrasound identification of abruption is associated with worse perinatal outcomes even when bleeding is absent. 1

Critical History Elements

Query these specific features to narrow the differential:

• Pain character and location: Constant versus intermittent pain; note that appendicitis presents atypically in pregnancy because the appendix migrates superiorly and laterally as the uterus enlarges, so classic right-lower-quadrant tenderness may be absent. 2
• Contractions or uterine tightening: Regular painful contractions suggest preterm labor. 1
• Prior cesarean delivery: Raises concern for uterine rupture or dehiscence. 1
• Fever, dysuria, or costovertebral angle tenderness: Points toward pyelonephritis or urolithiasis. 2
• Nausea, vomiting, or changes in bowel habits: Suggests appendicitis or other gastrointestinal pathology. 2

Physical Examination Priorities

• Palpate for uterine tenderness and contractions: Focal tenderness over the uterus may indicate abruption; regular contractions suggest labor. 1
• Assess for peritoneal signs: Rebound tenderness or guarding raises concern for appendicitis, uterine rupture, or other surgical emergency. 2
• Check costovertebral angle tenderness: Indicates possible pyelonephritis or urolithiasis. 2
• Perform speculum examination if safe: Visualize the cervix to assess for dilation or membrane status, but avoid digital examination if placenta previa has not been excluded. 1

Laboratory Evaluation

• Complete blood count: Recognize that pregnancy normally elevates white blood cell count to 6,000–16,000/µL, reducing the specificity of leukocytosis for infection or inflammation. 2
• Urinalysis and urine culture: Essential to detect urinary tract infection or hematuria suggesting stones. 2

Imaging Algorithm

Step 1: Transabdominal Ultrasound (First-Line)

Transabdominal ultrasound is the preferred initial procedure and provides the majority of necessary diagnostic information. 1, 2

Evaluate systematically for:

• Placental assessment: Identify location, any retroplacental clot suggesting abruption (appears as an area contiguous with the placenta), and placental separation. 1 Use color or power Doppler to identify areas without blood flow that suggest acute clot, though ultrasound is not highly sensitive for abruption. 1
• Myometrial continuity: Look for any disruption suggesting uterine rupture, particularly in the lower uterine segment; a thickness <2.5 mm predicts uterine dehiscence. 1
• Cervical evaluation: Measure cervical length from external to internal os; a short cervix with associated pain significantly increases preterm delivery risk. 1
• Appendix: Diameter >6 mm, lack of compressibility, or peri-appendiceal fluid indicate appendicitis. 2
• Kidneys and ureters: Detect hydronephrosis, echogenic stones, or perinephric fluid. 2
• Adnexa: Identify ovarian masses or absent Doppler flow suggesting torsion. 2
• Gallbladder: Check for cholelithiasis, wall thickening, or pericholecystic fluid. 2

Step 2: Transvaginal Ultrasound (When Transabdominal Is Inconclusive)

Transvaginal ultrasound is frequently necessary when transabdominal imaging is inadequate, providing superior visualization of the cervix, lower uterine segment, and adnexa. 1, 2

• Cervical assessment: Measure length precisely and evaluate for funneling or membrane prolapse into the cervical canal. 1
• Lower uterine segment: Assess the uterine isthmus for integrity and thickness. 1
• Placental margin: Measure distance from the leading placental edge to the internal os if low-lying placenta is suspected. 1
• Adnexal structures: Detect ovarian torsion or complex masses with higher resolution than transabdominal imaging. 2

Caution: If premature rupture of membranes is suspected, use transvaginal ultrasound judiciously, though one randomized trial of 92 patients found no increased chorioamnionitis risk. 1

Step 3: Non-Contrast MRI (If Ultrasound Remains Equivocal)

MRI without gadolinium demonstrates 99% accuracy for acute abdominal pathology when ultrasound is nondiagnostic, avoiding ionizing radiation. 2

• Appendicitis confirmation: MRI reliably identifies appendiceal inflammation when ultrasound is inconclusive. 2
• Urolithiasis: Visualizes stones as filling defects and delineates the level of obstruction. 2
• Adnexal masses: Provides superior tissue characterization. 2
• Bowel pathology: Identifies obstruction or inflammatory bowel disease. 2

Critical Pitfalls to Avoid

• Do not delay imaging: Postponed diagnosis of appendicitis increases the risk of perforation and fetal loss. 2
• Do not dismiss pain without bleeding: Placental abruption can present with pain alone, and ultrasound-confirmed abruption predicts worse outcomes. 1
• Do not rely on typical appendix location: Migration during pregnancy masks classic findings. 2
• Do not interpret leukocytosis in isolation: Pregnancy-related elevation reduces diagnostic specificity. 2
• Do not use CT as the initial study: Reserve for trauma or when ultrasound and MRI are unavailable. 2

Management Based on Imaging Findings

Immediate Obstetric Consultation Required:

• Placental abruption identified on ultrasound: Even without bleeding, abruption is associated with worse perinatal outcomes. 1
• Short cervix (<25 mm) with pain: Significantly increases preterm delivery risk. 1
• Uterine rupture or dehiscence: Any myometrial disruption or lower uterine segment <2.5 mm. 1
• Regular contractions with cervical change: Indicates preterm labor. 1

Immediate Surgical Consultation Required:

• Confirmed appendicitis: Diameter >6 mm with lack of compressibility or peri-appendiceal fluid. 2
• Ovarian torsion: Absent Doppler flow in adnexal structures. 2
• Acute cholecystitis with complications: Gallbladder wall thickening with pericholecystic fluid. 2
• Bowel obstruction: Identified on imaging. 2

Urologic Consultation Required:

• Obstructing urolithiasis with hydronephrosis: Ultrasound remains first-line; ureteroscopic stone removal is safe and effective during pregnancy and superior to temporizing stenting, which requires frequent exchanges due to rapid encrustation. 2
• Pyelonephritis unresponsive to antibiotics: Persistent fever or flank pain despite treatment. 2

Conservative Management with Close Follow-Up:

• Simple urinary tract infection: Treat with antibiotics and monitor response. 2
• Non-obstructing kidney stones ≤5 mm: Expectant management with hydration and analgesia. 2
• Functional pain with completely normal imaging: Reassurance and symptom management, but maintain low threshold for repeat evaluation if symptoms worsen. 2