What diagnostic examination should a nurse anticipate for a patient presenting with black tarry stools?

When a patient presents with black tarry stools, commonly referred to as melena, it is indicative of upper gastrointestinal bleeding. The dark color of the stools results from the digestion of blood as it moves through the gastrointestinal tract, typically from sources such as a bleeding ulcer or varices.

The most appropriate diagnostic examination in this scenario is endoscopy. This procedure allows for direct visualization of the upper gastrointestinal tract, specifically the esophagus, stomach, and duodenum. By using an endoscope, healthcare providers can identify the source of the bleeding, obtain tissue samples if necessary, and sometimes even perform therapeutic interventions, such as cauterizing bleeding vessels.

In contrast, while an ultrasound might be useful for other conditions, it does not provide adequate visualization of the upper GI tract and is not effective for diagnosing the source of melena. A barium enema is primarily used for assessing the lower GI tract and would not provide insights into the upper digestive system that could cause the symptoms observed. Anorectal manometry is a test that evaluates the function of the rectum and anal sphincter; it does not address the source of upper gastrointestinal bleeding and is not relevant in this case.

Thus, endoscopy stands out as the most suitable investigation