Differential Diagnosis for Lower Abdominal Pain

Given the clinical presentation of lower abdominal pain for 1 day with negative CTAP (Computed Tomography Angiography of the Pelvis) and CT Angio AP (Abdomen and Pelvis), without leukocytosis, and a lactic acid level of 4.0, the following differential diagnoses are considered:

• Single Most Likely Diagnosis

  • Constipation or Musculoskeletal Pain: The absence of leukocytosis and negative imaging studies suggest that the cause of pain might not be related to an acute infectious or vascular process. The elevated lactic acid could be a non-specific finding or related to dehydration or another metabolic issue. Constipation or musculoskeletal pain could present with lower abdominal pain and might not be immediately identified on CT scans.

• Other Likely Diagnoses

  • Ovarian Cyst or Torsion: Although CTAP was negative, ovarian pathology, especially if it involves torsion, can sometimes be missed on initial imaging. The absence of leukocytosis does not rule out this condition.
  • Diverticulitis: Early diverticulitis might not show significant findings on CT, especially if the study was not specifically focused on the colon or if the disease process is in its initial stages. The lack of leukocytosis could indicate an early or mild process.
  • Urinary Tract Infection or Pyelonephritis: These conditions can cause lower abdominal pain and might not always present with leukocytosis, especially in early stages or in diabetic patients.

• Do Not Miss Diagnoses

  • Ectopic Pregnancy: This is a critical diagnosis to consider in any female patient of childbearing age presenting with lower abdominal pain, regardless of the imaging findings. A negative CT does not rule out ectopic pregnancy, and a pregnancy test should be performed.
  • Appendicitis: Although CT scans are sensitive for appendicitis, false negatives can occur, especially if the appendix is not well visualized or if the disease is in its early stages. Clinical suspicion should remain high if symptoms persist.
  • Mesenteric Ischemia: The elevated lactic acid level raises concern for bowel ischemia. While CT Angio was negative, this condition can sometimes be subtle on imaging, and clinical correlation is crucial.

• Rare Diagnoses

  • Inflammatory Bowel Disease (IBD) Flare: Although less common, an flare of IBD (Crohn's disease or ulcerative colitis) could present with lower abdominal pain and might not always show significant findings on CT, especially if the disease is limited to the mucosa.
  • Endometriosis: This condition can cause chronic or acute lower abdominal pain and might not be identified on CT scans unless there are associated findings like endometriomas.