Died of Wounds
"Includes died of wounds where wounding occurred in theater and death occurred elsewhere."As of April 8, it shows "Total Hostile Deaths" at 450, 512 of which are "Died of Wounds".
http://web1.whs.osd.mil/mmid/casualty/OIF-Total.pdfA few other PDFs:
http://web1.whs.osd.mil/mmid/casualty/castop.htmWhen you think about a soldier wearing a kevlar vest to protect internal organs, injuries are going to tend to result in immediate death (shot to head, whole body completely blown to bits) or not be life threatening (wounded extremity).