Final answer:
The Nurse Practitioner should suspect C) Perforation if an upright abdominal x-ray shows free air, as this indicates a possible hole in the gastrointestinal tract.
Step-by-step explanation:
If an upright abdominal x-ray shows free air, the Nurse Practitioner (NP) should suspect C) Perforation. Free air in the abdominal cavity, often referred to as pneumoperitoneum, indicates that there is a hole in the gastrointestinal tract allowing air to escape into the abdominal cavity. This condition is usually a surgical emergency and can be a result of a perforated ulcer, perforated diverticulum, or trauma.
An abdominal ultrasound is utilized primarily to detect gallstones that might block the outflow of fluid from the pancreas, and may show an abscess or a pancreatic pseudocyst, but it is not typically used to diagnose free air in the abdomen. To investigate gallbladder disease further, a HIDA scan or a CT scan might be conducted.