Isolated Right Subphrenic Abscess as an Atypical Presentation of Perforated Duodenal Ulcer: A Case Report

Peptic ulcer perforation is a life‐threatening gastrointestinal emergency that typically presents with generalized peritonitis; however, atypical manifestations such as an apparently isolated subphrenic abscess on initial imaging, without overt peritoneal signs, are rare and may significantly delay diagnosis. We report the case of a 74‐year‐old male with multiple comorbidities who was initially admitted with clinical features suggestive of acute cholecystitis. Initial cross‐sectional imaging demonstrated a well‐encapsulated right subphrenic abscess in the absence of radiological evidence of diffuse peritonitis. Surgical exploration and subsequent re‐exploration identified a perforated duodenal ulcer as the source of the abscess. The patient required a staged surgical approach due to clinical deterioration and progression of intra‐abdominal sepsis, resulting in clinical improvement and a favorable outcome. This case emphasizes the importance of maintaining a high index of suspicion for atypical presentations of perforated peptic ulcer disease (PUD) and highlights the critical role of imaging in detecting unusual intra‐abdominal collections that may be the only initial indicator of an underlying visceral perforation.