- SUBINVOLUTION OF PLACENTAL SITES
- Armed Forces Institute of Pathology
- COAGULATIVE NECROSIS/EDEMA
- SIPS is a failure of trophoblasts that have penetrated the uterine wall to regress postpartum, resulting in delayed re-epithelialization of the endometrium and prolonged uterine bleeding, After whelping, uterine bleeding typically ceases within 7-10 days and uterine placental sites usually involute within 12 weeks. SIPS results in prolonged uterine hemorrhage that manifests as bloody vaginal discharge lasting more than six weeks and may lead to ascending infection, endometritis, and open pyometra. In this particular image, the area of white on the surface of the hemorrhagic uterus is fibrin. The key to diagnosis is the presence of viable trophoblasts weeks after whelping. Interstingly, collagen plaques, normally considered a finding in chronic inflammation, arise in these lesions within about 4 weeks, and disappear several weeks later.