Differential Diagnosis for 37-year-old Female with Six Days of Right Iliac Fossa (RIF) Pain and Nausea
Single Most Likely Diagnosis
- Ovarian Cyst: Given the location of the pain (RIF) and the presence of a trace amount of free pelvic fluid on ultrasound, a ruptured ovarian cyst is a plausible diagnosis. The normal WCC and CRP suggest that there may not be a significant infectious or inflammatory process, which aligns with this diagnosis.
Other Likely Diagnoses
- Appendicitis: Although the WCC and CRP are normal, early appendicitis can present with normal inflammatory markers. The RIF pain and nausea are consistent with appendicitis, making it a consideration despite the lack of elevated inflammatory markers.
- Pelvic Inflammatory Disease (PID): PID can cause lower abdominal pain, nausea, and can sometimes have a normal urinalysis and WCC. However, the absence of elevated CRP and the trace amount of free fluid might make this less likely.
- Gastrointestinal Issues (e.g., Gastroenteritis, Constipation): These conditions can cause abdominal pain and nausea. The normal lab tests do not rule out these diagnoses, but the specific location of the pain and the ultrasound findings make them less likely.
Do Not Miss Diagnoses
- Ectopic Pregnancy: Although the patient's presentation does not strongly suggest pregnancy, ectopic pregnancy is a life-threatening condition that must be considered in any female of childbearing age with abdominal pain, especially with the presence of free pelvic fluid. A pregnancy test should be performed.
- Ruptured Aneurysm or Vascular Emergency: While less common, a ruptured aneurysm or other vascular emergencies can present with abdominal pain and should be considered, especially if there are any signs of hemodynamic instability.
- Diverticulitis: If the patient has a history of diverticulosis, diverticulitis could be a consideration, especially if the pain is more left-sided but can sometimes present on the right. However, the normal WCC and CRP make this less likely.
Rare Diagnoses
- Endometriosis: While endometriosis can cause chronic pelvic pain, it is less likely to cause acute presentations like the one described. However, it could be considered if other diagnoses are ruled out.
- Mesenteric Lymphadenitis: This condition can mimic appendicitis but is less common. It might be considered if appendicitis is ruled out and the patient's symptoms persist.