The main objective of this study is to evaluate whether the use of ultrasound as a method of checking the normal positioning of the NGT is reliable, without requiring other diagnostic tests. Clinical trial that will include patients who had the NGT placed intraoperatively. 114 patients (57 with NGT and 57 without NGT) will be examined by ultrasound in the immediate postoperative period to diagnose the normal positioning of the NGT or its absence.

Can ultrasound quickly and effectively diagnose the normal positioning of the NGT? Can chest X-ray be avoided by introducing ultrasound in the verification of the normal positioning of the NGT in the immediate postoperative period?

The nasogastric tube (NGT) is an essential element of our daily clinical practice, commonly used for the administration of enteral nutrition and medication or for gastric decompression and diagnostic procedures. Despite its common use, it is still an invasive procedure with potential complications. Ultrasound is a noninvasive, inexpensive, widely available and rapid method that can speed up the proper verification of these devices. The main objective of this study is to evaluate whether the use of ultrasound as a method of checking the normal positioning of the NGT is reliable, without requiring other diagnostic tests. Clinical trial that will include patients who had the NGT placed intraoperatively. 114 patients (57 with NGT and 57 without NGT) will be examined by ultrasound in the immediate postoperative period to diagnose the normal positioning of the NGT or its absence. Patients who have had the NGT placed will have had their NGT placed correctly by chest X-ray. The upper part of the patient will be covered for the examiner, who will only have access to the patient's abdomen and will not know which patients have NGT or not.

Inclusion Criteria:

• Patients classified as ASA I-IV according to the American Society of Anesthesiologists
• Patients over 18 years old.
• Informed consent signed by the patient or their family representatives

Exclusion Criteria:

• Patients classified as ASA V.
• Patients under 18 years old.
• Refusal to participate in the study.
• Contraindication for nasogastric tube placement: ingestion of caustics, nasal or skull fractures, and cervical surgery.
• Patients with anatomical abnormalities at the cervical or pharyngoesophageal level.

The upper part of the patients will be covered for the investigator, who will only have access to the patient's abdomen and will not know which patients have NGT or not.