What Causes Pain In Lower Ribs And Difficulty In Breathing After C-section?

my sister in law had a baby boy 2 weeks ago via c-section. she started with severe pain on this past monday and went to the hospital on Wednesday the pain in her lower ribs was so unbearable and she was having difficultiy breathing. She has now been admitted as she continues to get 102 fevers and her white blood counts are elevated. they have done xrays, and ultrasounds and labs and can not find the source of infection. any ideas