Differential Diagnosis for Severe Vomiting and Upper Abdomal Pain

Given the presentation of a 50-year-old male with severe vomiting and upper abdominal pain for 36 hours, along with the provided lab results, we can approach the differential diagnosis as follows:

• Single Most Likely Diagnosis

  • Metabolic Alkalosis: The patient's lab results show a high pH (7.55), elevated bicarbonate (HCO3- = 40 mmol/L), and a high pCO2 (50 mmHg) which compensates for the metabolic component. The severe vomiting likely led to the loss of hydrogen ions, resulting in metabolic alkalosis. The elevated amylase (1222 U/L) suggests pancreatitis, which can be associated with vomiting and metabolic disturbances.

• Other Likely Diagnoses

  • Respiratory Alkalosis: Although the primary issue appears to be metabolic, respiratory alkalosis could initially present with a high pH. However, the pCO2 level is elevated, suggesting a compensatory mechanism rather than a primary respiratory cause.
  • Pancreatitis: Indicated by the significantly elevated amylase level, pancreatitis is a likely condition given the upper abdominal pain and vomiting. It can lead to or exacerbate metabolic disturbances.

• Do Not Miss Diagnoses

  • Peptic Ulcer Disease: Severe vomiting and upper abdominal pain could be indicative of a peptic ulcer, especially if the patient has a history of NSAID use or Helicobacter pylori infection. Although not directly related to the lab values, missing this diagnosis could lead to significant morbidity.
  • Gastrointestinal Obstruction: This condition can cause severe vomiting and abdominal pain. While the lab values do not directly point to obstruction, it's a critical diagnosis to consider due to its potential for severe complications if not promptly addressed.

• Rare Diagnoses

  • Zollinger-Ellison Syndrome: A rare condition characterized by excessive gastric acid production leading to peptic ulcers and diarrhea. It could potentially cause severe vomiting and abdominal pain, though it's less likely given the metabolic alkalosis.
  • Cystic Fibrosis: Although more commonly diagnosed in childhood, cystic fibrosis can present in adults with gastrointestinal symptoms, including pancreatitis and intestinal obstruction. However, it would be an unusual diagnosis in a 50-year-old without a previous diagnosis.