True about neonatal necrotizing enterocolitis –
Neonatal necrotizing enterocolitis 

Neonatal necrotizing enterocolitis is the most common life-threatening emergency of the gastrointestinal tract in the newborn period.
The disease is characterized by a various degree of mucosa/ or transmural necrosis of the intestine.
It occurs in premature or small for gestational age (LBW) infants.

Clinical manifestations of necrotizing enterocolitis can be devided into 3 stages :

Stage I : Suspected Unstable temperature, apnea, bradycardia, lethargy. Mild abdominal distension, vomiting blood in stool.

 Above signs + Bowel sounds are diminished, with or without abdominal tenderness

Stage II : Definite In more severe cases : Metabolic acidosis and mild thrombocytopenia

 X-Ray : Pneumatosis intestinalis and dilation of interesting.

Stage III : Advanced Above signs + infant has low BP, bradycardia, apnea, acidosis, DIC, anuria
Frank signs of peritonitis with abdominal tenderness, distension and erythema of abdominal wall.
X-Ray : shows Pneumoperitoneum.
Abdominal distension
Pneumoperitoneum
Decreased bowel sounds
All of the above