A 4 month old girl presents with 2 day history of colicky abdominal pain, vomiting, abdominal distention, bloody stools, and increasing lethargy.

General appearance: Alert infant in moderate distress
HR: 125, RR: 42, BP: 72/49, Temp: 37C
HEENT: Normal, mucous membranes dry
Neck: No cervical lymphadenopathy.
CVS: Normal S1 and S2. II/VI systolic flow murmur
Pulm: Chest clear to auscultation. Good air entry bilaterally.
Abdo: Distended. Tender. Difficult to examine.
Derm: No rashes or skin markings.

Given the above history, what is your differential diagnosis (name at least 5)?