Discussion:
Acute abdomen is a critical condition caused by various underlying causes such as infection, inflammation, or vascular problems [1]. The condition requires an urgent investigation, including a thorough examination and treatment based on the physical examination and clinical findings [1]. A variety of diseases, including perforated peptic ulcer (PPU) and acute pancreatitis (AP), can contribute to this condition[2].
Peptic ulcer disease (PUD), which is usually defined as insulation to the mucosa of the upper digestive tract, most commonly happens in the stomach and the duodenum [3,8]. H.Pylori infection and NSAID consumption are two significant factors leading to PUD [3]. Perforation is the second most common complication of the PUD, which happens in 4 to 14 cases per 100,000 individuals, and the risk increases with age [3]. The patient usually presents with the complaint of a sudden severe epigastric pain [3]. PPU is divided into four groups based on its location:  1. in the antrum, near the lesser curvature, 2. combined gastric and duodenal ulcer, 3. prepyloric ulcer, 4. ulcer in the proximal stomach or cardia [9]. The evaluation consists of a thorough blood test and imaging studies, including an abdominal and chest x-ray [3]. Although free air under the diaphragm is the most common finding in PPU, some studies have shown that it may be absent in some patients based on the condition of the ulcer [10]. The main treatment for PUD is surgical operation [3].
Moreover, AP is an inflammation of the pancreas frequently caused by bile stones or massive consumption of alcohol, which happens in 13 to 45 per 100,000 population years [5,6]. It is divided into three groups based on the severity of the disease: 1. Mild: no organ failure, 2. Moderate: transient organ failure which resolves in less than 48 hours, and 3. Severe: persistent organ failure that remains more than 48 hours [11]. The most common clinical symptom is epigastric pain which radiates to the back [12]. A rigorous blood test (including blood count, lipase, C-reactive protein, glucose, calcium, and liver and cholestasis enzymes) is mandatory for the diagnosis [12]. Imaging tools like CT scans are not usually recommended in patients with typical clinical manifestations and abnormal laboratory tests [13]. The primary treatment strategy is fluid resuscitation between 150 and 250 mL/h in the first 24–48 h, with Ringer lactate as the best choice [12]. It is also recommended that oral feeding be encouraged in the first days of admission if possible [14].
In this case report, a 71-year-old patient presented to the hospital with the chief complaint of sudden epigastric pain from last night. Although the patient did not have free air under the diaphragm, he underwent surgery due to the positive acute abdomen on physical examination. As the PPU was small and sealed off, the absence of free air on the Xray can be justified. All the debris was washed out with normal saline, and the perforation was fixed with the gastrorrahphy and the omental patch. The patient was hospitalized for ten days and treated for simultaneous pancreatitis with intravenous fluid.
Due to the similar clinical presentation of PPU and AP and the absence of free air in the X-ray of some patients, which is strongly in favor of PPU, it is crucial to take both diseases into account for differential diagnosis of the underlying cause the acute abdomen. Physical examination and thorough laboratory tests play an essential role in the diagnosis.