Differential Diagnosis for 18-Week Pregnant Female with Generalized Abdominal Pain and Nausea/Vomiting

• Single Most Likely Diagnosis
  • Gastroenteritis: This is a common condition that can cause generalized abdominal pain, nausea, and vomiting in pregnant women, similar to the non-pregnant population. The symptoms presented are consistent with a viral or bacterial infection of the gastrointestinal tract.
• Other Likely Diagnoses
  • Urinary Tract Infection (UTI): UTIs are common during pregnancy due to physiological changes that can predispose women to infection. Symptoms can include abdominal pain, nausea, vomiting, and specific urinary symptoms like dysuria or frequency.
  • Constipation: Constipation is a frequent complaint in pregnancy, caused by hormonal changes, pressure from the expanding uterus, or changes in bowel habits. It can lead to abdominal pain and discomfort.
  • Preterm Labor: Although less common at 18 weeks, preterm labor can occur and presents with abdominal pain, back pain, and a change in vaginal discharge. Nausea and vomiting can also be associated due to the stress response.
• Do Not Miss Diagnoses
  • Ectopic Pregnancy: Although the patient is at 18 weeks of gestation, which is beyond the typical timeframe for ectopic pregnancy diagnosis (usually presenting before 10 weeks), it's crucial not to miss this potentially life-threatening condition if there's any suspicion based on the patient's history or if the dating of the pregnancy is uncertain.
  • Appendicitis: Appendicitis can occur at any gestational age and is a surgical emergency. The presentation may be atypical in pregnancy, with pain sometimes localized to the upper abdomen due to the appendix being pushed upwards by the uterus.
  • Placental Abruption: This condition involves the premature separation of the placenta from the uterus and can cause severe abdominal pain, vaginal bleeding, and nausea/vomiting. It's a medical emergency that requires immediate attention.
  • Preeclampsia: While typically associated with hypertension and proteinuria, preeclampsia can also cause abdominal pain and nausea. In severe cases, it can lead to more dangerous conditions like eclampsia or HELLP syndrome.
• Rare Diagnoses
  • Pancreatitis: Although rare in pregnancy, pancreatitis can cause severe abdominal pain, nausea, and vomiting. It's more commonly associated with gallstones or hypertriglyceridemia.
  • Adrenal Crisis: In a pregnant woman with a history of adrenal insufficiency, an adrenal crisis can occur, presenting with abdominal pain, nausea, vomiting, and potentially life-threatening hypotension.
  • Ovarian Torsion: This is a rare condition that can cause severe, sudden-onset abdominal pain. It's more common in women with ovarian cysts or other adnexal masses.