Features of Undiagnosed Abdominal Pain and Diagnostic Status of Acute Hepatic Porphyria in Japan: A Retrospective Study.

The prevalence of acute hepatic porphyria (AHP) in Japan is unknown. To diagnose AHP, identifying populations with a high prevalence of AHP is essential. We focused on non-specific abdominal pain (NSAP); however, the criteria for NSAP vary across studies. Therefore, this study aimed to investigate the diagnostic process of undiagnosed abdominal pain in general medicine clinical practice before proposing a definition of NSAP. In addition, we aimed to examine the potential AHP-related symptoms and implementation of AHP testing in these patients. AHP is a rare but fatal and treatable disease; hence, its early diagnosis is essential. This retrospective observational study was conducted in the general medicine departments of six medical institutions in Japan over a 3-year period beginning on April 1, 2019. Patients with abdominal pain who underwent abdominal imaging examinations were included. The primary outcome was to characterize patients with undiagnosed abdominal pain. In addition, this study aimed to identify situations where physicians attempt to diagnose AHP in patients with abdominal pain. Of the 1915 eligible participants, 317 (16.6%) had undiagnosed abdominal pain, and none of them were diagnosed with AHP in diagnosed abdominal pain. The median patient age was 55 years, and 134 patients were male. Multivariate logistic analysis revealed that hospitalization, dull pain, and the absence of depressive symptoms were associated with abdominal pain. All patients with undiagnosed abdominal pain demonstrated two to four indicative symptoms of AHP. However, none underwent urinalysis for a definitive diagnosis of AHP. Depressive symptoms and the absence of dull pain were associated with undiagnosed abdominal pain. Hospitalization for examination contributed to improving the diagnosis of abdominal pain. Despite the presence of indicative symptoms, urinary markers for AHP diagnosis were not measured. Establishing a diagnostic strategy for undiagnosed abdominal pain would provide better opportunities for patients with NSAP and could help shorten the diagnostic journey for those with rare diseases such as AHP.