Post-Partum Involution of the Canine Uterus – Gross Anatomical and Histological Features DC Orfanou 1 , HN Ververidis 2 , A Pourlis 1 , IA Fragkou 1 , AN Kokoli 2 , CM Boscos 2 , IA Taitzoglou 2 , A Tzora 3 , CM Nerou 1 , L Athanasiou 1 and GC Fthenakis 1 1 Veterinary Faculty, University of Thessaly, Karditsa; 2 School of Veterinary Medicine, Aristotle University of Thessaloniki, Thessaloniki; 3 TEI Epirus, Arta, Greece Contents We aimed to study the normal puerperium in the bitch. Ovariohysterectomy was performed in nine bitches, each at a different day after normal whelping; their genital tract was subject to gross anatomical examination, as well as to histological examination and electron microscopy scanning. Corpora albicans were evenly distributed in the left and right ovaries and placental sites were evenly distributed among left and right uterine horns. Placental sites were initially of dark green to grey colour, later becoming dark brown; their length and height progressively decreased. Height of the myometrium and diameter of the uterine glands progressively decreased. Trophoblast-like cells were consistently observed at the placental sites and on the surface of the interplacental areas, at all time points where hysterectomy had been performed. It is suggested that involution of the canine genital tract can last up to 3 months and is slow. Continuous (up to D84 post-partum) presence of prominent placental sites should be considered a normal feature of canine uterine post-partum involution. Introduction The puerperium is the period during which the genital system prepares to return to cyclicity. In contrast to other domestic mammalian species, literature on the normal puerperium of the bitch is very limited. The aim of this study was to describe the gross anatomical and histological features of the post-partum involution of the genital tract of the bitch, after normal whelping. It is a part of a wider study into the canine puerperium. The work was carried out under a licence for experimental procedures issued by the Greek Ministry of Agriculture, based on EU guidelines. Materials and Methods Nine primiparous Beagle bitches, aged 12–17 months, which had whelped normally, were monitored for up to 3 months after parturition. Regular clinical examina- tions of the animals were carried out during the study. Furthermore, samples were collected after inserting a sterile swab into the anterior part of the vagina, for bacteriological and cytological examination by using conventional techniques; details have been presented by Orfanou et al. (2008). Ovariohysterectomy was carried out on one experi- mental animal at each of the following days (D) after whelping: D7, D21, D28, D35, D42, D56, D70 and to two animals on D84, for a detailed anatomical exam- ination of the ovaries and the uterus. All animals recovered uneventfully from surgery. The genital tract was removed under sterile condi- tions. A small incision was performed on the lateral part of the uterine body and, by using an aseptic technique, a sterile swab was used to sample the content of the uterus. Subsequently, dimensions of the ovaries were measured. Number and diameter of corpora albicans were determined after performing one longitudinal section on each ovary. The appear- ance of the uterus was recorded. Length of uterine horns (from the apex to the bifurcation) was measured. Diameter of uterine horns was measured at placental sites and interplacental areas. The uterus was then dissected; the placental and interplacental sites were assessed and their dimensions (length and height) were measured. Uterine swab samples were plated onto Columbia 5% blood agar; the media were incubated aerobically at 37°C for up to 72 h. Throughout this study, all bacteria isolated were identified by using conventional tech- niques (Euzeby 1997) and the ‘API SYSTEM’ quick identification strips (BioMerieux S.A., Marcy-l’-Etoile, France). Swabs were also rolled on glass slides and stained by using the Giemsa technique. Finally, tissue samples were collected for processing with haematoxy- lin–eosin stain for histological examination and mor- phometric analysis. Tissue samples were also prepared for ultrastructural examination by using scanning electron microscope. The specimens were fixed in a sodium cacodylate (0.1 M) buffered solution of 2% glutaraldehyde and 2% para- formaldehyde. Consequently, they were washed in several changes of sodium cacodylate buffer, transferred for 1 h to 1% OsO 4 and dehydrated in graded acetone. Tissues were critically point dried in carbon dioxide, mounted onto stubs and sputter coated with palladium and gold in a Bal-Tec (Balzers, Liechtenstein) sputter coater. They were observed in a JEOL (Tokyo, Japan), JSM 840 scanning electron microscope. Differences in findings between the various time points, throughout the study were detected with the Wilcoxon signed-rank test, as appropriate. Statistical significance was set at p = 0.05. Results All animals whelped normally five to nine puppies (median value: 7; total number of puppies born: 66) and remained clinically healthy throughout the experimental period. Results of bacteriological and cytological Reprod Dom Anim 44 (Suppl. 2), 152–155 (2009); doi: 10.1111/j.1439-0531.2009.01388.x ISSN 0936-6768 Ó 2009 The Authors. Journal compilation Ó 2009 Blackwell Verlag GmbH