How do you get pneumonia from internal bleeding?

I had a hysterectomy a few weeks back, and stayed one night in the hospital. That night
I woke up and my abdomen hurt terribly, and it was hard to breathe. The nurse said it was from all the gas they put in my belly. The next day my blood count was low and the dr. said I had some minor internal bleeding and sent me home. The next morning at 6AM the pain was so terrible we had to call an ambulance. I had to have 2 blood transfusions for internal bleeding, and they also discovered I had double pneumonia. Several docs listened to my lungs and heart prior to surgery, there was no problem then, and surgery went on as scheduled. Now my doc is saying I must have had it before, but I think he is covering his a$$. I still have a large and painful hematoma in my belly. I'm wondering if my doc was negligent? Is it customary to send home a patient who has internal bleeding? How do you get pneumonia from this? It's not like I had been convalescing for weeks. Should I seek legal recourse?

Thank you all for your genuine responses. I'm one of those 'trouble' patients who actually takes an active part in their diagnosis/recovery. This Dr. was my 3rd opinion (results were severe adenomyosis, debilitated me for 3 years before I finally decided to have the surgery). This was my 3rd lap procedure as well, so I knew what to expect. The bloating and pain was far worse than any of the others, which I tried to explain to the doc & nurses, no one would listen, 'its normal...blah blah'. I KNOW my body. Now there IS a huge trust issue, he offered no explanation why it took him 7 long hours to get to the ER, why he would not alleviate my pain. I lay begging to just die it was so bad. When my PMC dr. showed up he was an angel from God and put me on the pain pump, said 'i'm taking over your case'. now i have to find a new gyno who actually take me, with all this baggage.......i need to go in for post hyst follow up and am scared of my old dr.

Like it has been mentioned previously, this is not very uncommon. When a surgeon cuts through your muscles to operate on you, then sews you up again, it can be quite painful, obviously, to take deep breaths. In addition your body is just more vulnerable to pathogens, especially ones commonly found in a hospital.
When your belly is in pain the typical response is to breathe with much more shallow breaths. This shallow breathing isn't sufficient to properly inflate the entire lung. The regions of the lungs that remain under-inflated for a period of time tend to develop what is called atelectasis. In those areas, secretions that would normally be removed on a regular basis due to normal respirations and coughing, just sit there and that dark, moist area is perfect for developing infection. We call these hospital acquired infections, nosicomial.
Whatever you call it, its fairly common and is frequently just part of the package with any major surgery.
As far as the bleeding goes, there is no way to know if there is going to be excessive bleeding until it has happened. In any case, it has been an unfortunate set of circumstances, but certainly not unheard of and sound like fairly common issues post operative.
Good luck with your recovery.

This is actually very very common. I dont think your doc was being negligent. Many surgical patients acquire pnemonia after surgery. I don't think the pnemonia was caused by the internal bleeding. After surgery, because of pain, it is difficult to breathe deeply. But breathing and keeping your lungs clear after surgery is very important. You probably acquired the pnemonia from being in the hospital.

Internal bleeding does not cause pneumonia. Often, after a person has had a surgical procedure, such as yours, they dont do the deep breathing and coughing excercises well because it is painful. Shallow respirations and inadequate oxygen exchange is what results in the pneumonia.

From what you have said, you would not have a legal cause of action against your doctor.