This study aims to evaluate the efficacy and safety of a novel blood sensing capsule (PillSense), to help emergency doctors better evaluate if patients have active upper digestive tract bleeding, to determine if they can be discharged safely. The PillSense System consists of the PillSense Capsule, a small single use capsule that is safe for human consumption and PillSense Receiver, an external real-time monitor for data display to detect the presence of bleeding in the upper digestive tract within 10 minutes.

The use of the PillSense System enables the clinician to make a more informed choice on the treatment plan for the patient. If the system revealed "No Blood Detected", this is suggestive there is absence of blood in the stomach. Together with the presenting symptoms, physical examination and laboratory tests, it gives the emergency physician a more accurate method to detect if patient is actively bleeding. If patient remained stable during the monitoring, the patient can be discharged home for early outpatient review, instead of waiting in Emergency Department (ED) for prolonged duration to be admitted and wait in the ward for investigations like gastroscopy to be performed. This reduces unnecessary strain on the hospital's limited resources and may improve overall patient's experience. Patients with 'Blood Detected' result will be admitted with early gastroscopy planned within 72 hours. Patients with 'No Blood Detected' result, will be monitored closely in ED and, if deemed to be stable, to be discharged with an outpatient gastroscopy within 96 hours. A product such as the PillSense System which employs a minimally invasive method to help clinicians detect whether or not a patient has blood in upper gastrointestinal tract within 10 minutes. This will be a quick and objective tool to determine if the patient is having active upper gastrointestinal bleeding (UGIB), to assist in triaging patients for more emergent definitive care. This system can also be easily administered by non-clinician and do not require special training to read the results, minimising the need for highly specialised staff to provide this service. The information provided by the PillSense System which taken together with other clinical parameters may lead to more efficient, safer and higher quality patient care.

Inclusion Criteria:

• Males or females aged 21 years and above and are able to give consent.
• Patients who are willing and able to comply with the study protocol (including undergoing endoscopy)
• Presented to Emergency Department with symptoms of acute overt upper gastrointestinal bleeding such as coffee ground vomiting and melena (but without melaena on physical examination)

Exclusion Criteria:

• Patients who had hemodynamic shock (systolic blood pressure below 90 mm Hg and pulse rate over 120/min)
• Patients who presented with fresh hematemesis, hematochezia and/or melaena
• Patients requiring urgent endoscopy / surgery at time of review or already planned for admission by ED physician for non UGIB related indications
• Patients who had conditions that might contraindicate the use of an ingestible capsule, such as capsule endoscopy (eg. Dysphagia, odynophagia, swallowing disorder, and/or Zenker's diverticulum, issues with the motility of the gastrointestinal tract, Crohn's disease, previous GI surgery, suspected ileus, bowel obstruction and/or perforation)
• Patients with a known history of oesophageal or gastric varices
• Patients with known UGI pathology (such as oesophageal/gastric cancer), or recent (within 3 months) upper GI ulcer bleeding, upper GI surgeries or procedures
• Patients who are on anticoagulation
• Patients with cardiac implantable electrical device (CIED)
• Patients who had altered mental status
• Pregnant and/or lactating women (Female patients below age 60, without history of hysterectomy or are not documented to be post-menopausal, will be given a urine pregnancy test to confirm they are not pregnant)
• Patients who have an MRI investigation planned within 2 weeks