In a large skillet, cook sausage and onion until sausage is no longer pink; drain.
Transfer to a 4-qt. slow cooker. Add the broth, pumpkin, syrup, pie spice, garlic powder and nutmeg. Cover and cook on low until flavours are blended, 3-4 hours. Stir in milk; heat through. If desired, serve with croutons or crackers.