What are the potential causes and management options for right upper abdominal pain during the third trimester of pregnancy?

Right Upper Abdominal Pain in Third Trimester

In pregnant women with right upper abdominal pain during the third trimester, immediately assess for life-threatening internal herniation (if prior bariatric surgery), HELLP syndrome/preeclampsia, acute cholecystitis, and appendicitis, using ultrasound as first-line imaging followed by MRI if non-diagnostic, while recognizing that delayed diagnosis beyond 48 hours significantly increases maternal and fetal mortality.

Critical Life-Threatening Conditions to Rule Out First

Internal Herniation After Bariatric Surgery

• If the patient has a history of Roux-en-Y gastric bypass (RYGB), internal herniation is a surgical emergency that must be excluded immediately 1
• Internal herniation occurs in 8% of pregnancies after RYGB, and 32.8% of women with upper abdominal pain after RYGB have internal herniation 1
• All maternal and perinatal deaths from internal herniation occurred when treatment was delayed beyond 48 hours after symptom onset 1
• Maternal mortality is 9% and fetal mortality is 13.6% in case series of internal herniation during pregnancy 1
• The most common location is Petersen's space (45.5% of cases) 1
• Patients typically present with abdominal pain, and 50% have nausea/vomiting 1
• Immediate surgical consultation is mandatory; do not delay for imaging if clinical suspicion is high 1

HELLP Syndrome and Severe Preeclampsia

• Right upper quadrant pain is a cardinal symptom of HELLP syndrome (hemolysis, elevated liver enzymes, low platelets) 1
• This represents a coagulopathy that is potentially life-threatening 1
• Check blood pressure, complete blood count, liver enzymes, and platelet count immediately 2

Acute Cholecystitis

• Gallstone disease is the second leading cause of non-obstetric acute abdominal pain during pregnancy 3
• Ultrasound is the imaging modality of choice, looking for gallbladder wall thickening >3mm, pericholecystic fluid, and sonographic Murphy sign 2, 3
• Laparoscopic cholecystectomy is superior to conservative management and is safe in all trimesters, though ideally performed in the second trimester 3
• Conservative management leads to recurrent symptoms in 60% of patients and higher rates of cesarean delivery 3
• For presentation late in the third trimester, postponing surgery until after delivery may be reasonable if no risk to maternal/fetal health 3

Diagnostic Imaging Algorithm

First-Line: Ultrasound

• Ultrasound is mandatory as the initial imaging study for all pregnant patients with right upper abdominal pain 2, 3, 4
• Ultrasound avoids ionizing radiation and has good sensitivity for cholecystitis, hydronephrosis, and ovarian pathology 2, 4
• Limitations include difficulty visualizing the appendix in third trimester (63% nonvisualization rate) 1

Second-Line: MRI Without IV Contrast

• If ultrasound is non-diagnostic, proceed immediately to MRI without IV contrast 2, 4
• MRI has 97% sensitivity and 95% specificity for appendicitis in pregnancy 2
• MRI is highly effective for depicting hydronephrosis, perinephric edema, and other pathology 4
• Gadolinium-based contrast should only be used when potential benefit significantly outweighs unknown fetal risk 1

Reserve CT for Life-Threatening Situations

• CT with IV contrast should be reserved only for hemodynamically unstable patients or when MRI is unavailable/inconclusive 2, 4
• The radiation risk must be weighed against the risk of missed diagnosis 1

Differential Diagnosis Beyond Life-Threatening Causes

Appendicitis

• Appendicitis is the most common cause of abdominal pain requiring emergency surgery in pregnancy 2
• Anatomical displacement of the appendix in third trimester makes diagnosis challenging 2, 5
• US abdomen or MRI abdomen/pelvis without IV contrast are appropriate initial imaging 1
• US performance varies by trimester with AUC 0.86 in third trimester 1

Urolithiasis and Pyelonephritis

• Right flank pain with fever, tachycardia, or signs of sepsis suggests pyelonephritis or complicated urolithiasis 4
• Ultrasound first, then MRI if non-diagnostic 4
• Do not delay intervention if sepsis or hemodynamic instability present 4

Ovarian Torsion

• Can occur in third trimester, though rare with cysts <5cm 2, 6
• Ultrasound shows enlarged ovary with decreased or absent Doppler flow 2
• Emergency laparoscopy/laparotomy should be performed if suspected to prevent ovarian damage 6

Gastric Band Complications (if applicable)

• Gastric band slippage occurs in 12% of pregnancies after adjustable gastric banding (AGB) compared to 3-5% in general AGB population 1
• Increased risk due to vomiting and increased intra-abdominal pressure 1

Critical Clinical Pitfalls to Avoid

• Never dismiss upper abdominal pain in post-bariatric surgery patients as "normal pregnancy discomfort" - the 48-hour window for intervention is critical 1
• Leukocytosis is physiologically elevated in pregnancy and may be misleading 3
• Murphy's sign is difficult to evaluate in late third trimester due to uterine size 3
• Physiologic hydronephrosis of pregnancy can confuse the picture with urologic pathology 4
• Do not delay imaging or surgical consultation in pregnant patients with severe or persistent pain - complications carry significant maternal and fetal morbidity and mortality 4, 5

Management Priorities

• Immediate surgical consultation for suspected internal herniation, appendicitis with peritonitis, or ovarian torsion 1, 2, 6
• Multidisciplinary team involvement (maternal-fetal medicine, surgery, anesthesiology) for any surgical intervention 3
• For acute cholecystitis, surgery is preferred first-line to avoid drug toxicity and complications 3
• Conservative management with IV hydration and symptom control only for uncomplicated biliary colic or conditions that can safely wait until postpartum 3