|Classification and external resources|
Micrograph showing a chronic endometritis with the characteristic plasma cells. Scattered neutrophils are also present. H&E stain.
Endometritis refers to inflammation of the endometrium, the inner lining of the uterus. Pathologists have traditionally classified endometritis as either acute or chronic: acute endometritis is characterized by the presence of microabscesses or neutrophils within the endometrial glands, while chronic endometritis is distinguished by variable numbers of plasma cells within the endometrial stroma. The most common cause of endometritis is infection. Symptoms include lower abdominal pain, fever and abnormal vaginal bleeding or discharge. Caesarean section, prolonged rupture of membranes and long labor with multiple vaginal examinations are important risk factors. Treatment is usually with broad-spectrum antibiotics.
Acute Endometritis 
Acute Endometritis is characterized by infection. The organisms isolated are most often infection are believed to be because of compromised abortions, delivery, medical instrumentation, and retention of placental fragments. Histologically, neutrophilic infiltration of the endometrial tissue is present during acute endometritis. The clinical presentation is typically high fever and purulent vaginal discharge. Menstruation after acute endometritis is excessive and in uncomplicated cases can resolve after 2 weeks of clindamycin and gentamicin IV antibiotic treatment.
Chronic Endometritis 
Chronic Endometritis is characterized by the presence of plasma cells in the stroma. Lymphocytes, eosinophils, and even lymphoid follicles may be seen, but in the absence of plasma cells, are not enough to warrant a histologic diagnosis. It may be seen in up to 10% of all endometrial biopsies performed for irregular bleeding. The most common organisms are Chlamydia trachomatis (chlamydia), Neisseria gonorrhoeae (gonorrhea), Streptococcus agalactiae (Group B Streptococcus), Mycoplasma hominis, tuberculosis, and various viruses. Most of these agents are capable of causing chronic pelvic inflammatory disease (PID). Patients suffering from chronic endometritis may have an underlying cancer of the cervix or endometrium (although infectious etiology is more common). Antibiotic therapy is curative in most cases (depending on underlying etiology), with fairly rapid alleviation of symptoms after only 2 to 3 days.
Chronic granulomatous endometritis is most often tuberculous in etiology. The granulomas are small, sparse, and without caseation. The granulomas take up to 2 weeks to develop and since the endometrium is shed every 4 weeks, the granulomas are poorly formed.
In human medicine pyometra (also a veterinary condition of significance) is regarded as a form of chronic endometritis seen in elderly women causing stenosis of the cervical os and accumulation of discharges and infection. Symptom in chronic endometritis is blood stained discharge but in pyometra the patient complaints of lower abdominal pain.
Pyometra, in medicine, is an accumulation of pus in the uterine cavity. This condition is very well known in veterinary medicine. Please see Pyometra in dogs. Two conditions must co-exist to develop pyometra:the first of which is presence of infection the second is blockage of cervix. It is manifested by lower abdominal suprapubic pain, rigors, fever, discharge of pus on introduction of a sound into the uterus. Treatment is by antibiotics according to culture and sensitivity.
See also 
- "endometritis" at Dorland's Medical Dictionary
- Hubert Guedj; Baggish, Michael S.; Valle, Rafael Heliodoro (2007). Hysteroscopy: visual perspectives of uterine anatomy, physiology, and pathology. Hagerstwon, MD: Lippincott Williams & Wilkins. p. 488. ISBN 0-7817-5532-8.
- Cohen CR, Manhart LE, Bukusi EA, et al. (March 2002). "Association between Mycoplasma genitalium and acute endometritis". Lancet 359 (9308): 765–6. doi:10.1016/S0140-6736(02)07848-0. PMID 11888591.