Stefan, this is a difficult problem for 2 reasons: uncertainty with diagnosis of NEC, and limited evidence on what constitutes adequate treatment for NEC of various degrees of severity.
The diagnosis of pneumatosis intestinalis versus gas bubbles in stool is difficult; there is commonly lack of agreement on the presence of pneumatosis, and the interpretation is easily biased by other clinical findings. Sometimes, babies with questionable pneumatosis are labeled as having non-specific colitis, or (protein)-allergic colitis, and they may be treated with only bowel rest, or additionally a couple of days of antibiotics, and feedings resumed in 3-5 days if radiological and clinical exams are reassuring. Some neonatologists will have a lower threshold for diagnosing NEC (could be Bell stage 2 in the scenario you gave) and treating for at least 7 days.
Even when there is consensus on the presence of pneumatosis, the extent and location of pneumatosis may be important; for example, isolated colonic pneumatosis tends to be seen in older babies and it has a milder clinical presentation. We usually treat for at least 7 days, though some babies' abnormal findings may resolve in 2 or 3 days.
I have not seen evidence on gastric decompression. It makes physical sense that intestinal distension and increased intra-abdominal pressure would tend to decrease intestinal blood flow, and they might also cause discomfort to the patient, so we start gastric suction early, until distension and other signs such as bilious aspirates resolve; then, we leave the orogastric tube to gravity drainage.
I hope this helps.
Joaquim Pinheiro, MD, MPH
Professor of Pediatrics
Albany, NY, USA