Differential Diagnosis

The patient presents with nausea, cyclic vomiting, epigastric and right upper quadrant tenderness, elevated white count, and abnormal chemistry results including a high anion gap and lactate level. The following differential diagnoses are considered:

• Single Most Likely Diagnosis

  • Mesenteric Ischemia: Given the patient's symptoms of nausea, vomiting, and abdominal tenderness, along with the elevated lactate level (9.5) and high anion gap (21), mesenteric ischemia is a strong consideration. The presence of atherosclerotic vascular disease on the CT scan supports this diagnosis, as it increases the risk of mesenteric ischemia. The absence of evidence for acute pancreatitis and the singular cholelithiasis without signs of cholecystitis also points towards mesenteric ischemia as a primary concern.

• Other Likely Diagnoses

  • Cholecystitis: Although the CT scan shows only a singular cholelithiasis without direct evidence of cholecystitis, the patient's symptoms of right upper quadrant tenderness and elevated white count could still suggest cholecystitis, especially if the stone is obstructing the cystic duct.
  • Sepsis of Abdominal Origin: The high white count (28.7) with a predominance of neutrophils (91%) could indicate a septic process. While the source is not clearly identified, any abdominal process (including cholecystitis or even a perforated viscus not seen on CT) could lead to sepsis.

• Do Not Miss Diagnoses

  • Bowel Obstruction: Although not directly suggested by the CT findings, bowel obstruction can lead to elevated lactate levels due to bowel ischemia and can present with nausea, vomiting, and abdominal tenderness. It's crucial to consider and rule out this diagnosis due to its potential for severe consequences if missed.
  • Perforated Viscus: Similar to bowel obstruction, a perforated viscus is a surgical emergency that can present with abdominal pain and tenderness. The elevated white count and lactate could be indicative of peritonitis and ischemia, respectively.

• Rare Diagnoses

  • Diabetic Ketoacidosis (DKA): Although the patient's glucose level is not provided, DKA can cause a high anion gap metabolic acidosis. However, the clinical context (absence of mention of diabetes, presence of abdominal symptoms) makes this less likely.
  • Lactic Acidosis due to Medication or Toxin: Certain medications and toxins can cause lactic acidosis. Without more information on the patient's medication use or exposure history, this remains a rare but possible consideration.