this case describes a young non - pregnant cat that presented with uterine prolapse in association with an unusual diffuse , polypoid , fibrosing perimetritis and parametritis .
no intra - abdominal complications were seen on ultrasound examination 3 months postsurgery . at the time of writing ,
uterine prolapse in the cat is relatively rare and usually associated with the periparturient period .
inflammatory polypoid perimetritis and parametritis have not previously been documented in cats , and in dogs have only been reported in association with the administration of oestrogenic compounds .
the polypoid inflammation affecting the uterus and parametrium may have contributed to increased laxity of the uterine ligaments and predisposed to the development of uterine prolapse .
uterine prolapse is rare in the queen , usually occurring after delivery of kittens or abortion .
we report uterine prolapse in a non - pregnant queen and in association with an unusual diffuse , polypoid , fibrosis of the perimetrium and parametrium .
the perimetrium ( syn uterine tunica serosa ) is equivalent to the visceral peritoneal lining .
it is composed of loose connective tissue containing nerves and smooth muscle cells covered by mesothelium .
it blends in with the broad ligaments of the uterus , which is also covered by mesothelium and contains a core of connective tissue , the parametrium .
while peritonitis in cats is frequently associated with feline infectious peritonitis , specific lesions unique to the perimetrium have not been documented .
a stray 6- to 7-month - old domestic shorthair queen , weighing 2.15 kg , was presented to the university veterinary clinic with uterine prolapse after being observed for several days prior to capture . on examination
, both uterine horns were prolapsed , everted and swollen , with regions of hyperaemia , particularly towards the tips of the uterine horns .
no evidence of placental zoning or tissue necrosis , in particular gangrene , was noted ( figure 1 ) .
prolapsed and everted uterus following lavage which revealed swollen , hyperaemic and viable tissue clinical assessment revealed normal appetite and demeanour .
the vital parameters were within normal limits ( temperature 37.8c , respiratory rate 40 breaths / min , heart rate 140 beats / min ) .
the cat received hydromorphone hydrochloride injection ( hydromorphone ; west - ward pharmaceutical ) at 0.1 mg / kg iv q4h for pain management and to facilitate further examination .
initial haematological and blood biochemical evaluations revealed a markedly regenerative anaemia ( packed cell volume 24% [ reference interval ( ri ) 2545% ; erythrocytes 4.64  10/l [ ri 510  10/l ] , reticulocytes 375.84  10 /l [ ri 040  10/l ] ) and a neutrophilic leukocytosis with mild toxic changes ( leukocytes 37.72  10/l [ ri 5.519.5  10/l ] ; neutrophils 25.3  10/l [ ri 2.512.5  10/l ] ) .
blood biochemistry showed a mild hyperkalaemia ( 6.0 mmol / l [ ri 3.75.8 mmol / l ] ) and mild hypoglycaemia ( 66 mg / dl [ ri 70150 mg / dl ] ) .
oestrogen plasma concentrations were retrospectively evaluated at 25.7 pg / ml ( ri 1540 pg / ml ) .
intravenous crystalloid fluid solution ( plasmalyte ; travenol laboratories ) was administered to correct an estimated 8% dehydration deficit and maintenance requirement over 12 h. antibiotic therapy consisting of intravenous cefazolin sodium ( cefazolin for injection ; west - ward pharmaceutical ) at a dose rate of 22 mg / kg iv q8h was also administered .
attempts at reducing the uterus were again unsuccessful so an internal ovariectomy and external hysterectomy were performed .
the ovarian pedicles were transfixed and ligated prior to transection and before manipulating the uterine body further .
the everted uterus was circumferentially ligated distal to the cervix ( approximately 5 cm away from the vulva ) and transected .
the remaining uterus was returned to the abdominal cavity . from within the abdominal cavity ,
the serosa of uterine body was noted to be diffusely thickened by multiple - to - coalescing white villous projections ( figure 2 ) .
formalin - fixed perimetrial surface of uterine body revealing diffuse - to - coalescing polypoid lesions there was a small amount of mildly flocculent abdominal fluid present .
the cat recovered uneventfully and follow - up examinations in a 6 month period , including ultrasound at 3 months postsurgery , detected no abdominal abnormalities .
microscopic examination of the uterine body confirmed the presence of multiple nodular perimetrial proliferations of moderately loose connective tissue forming irregular polyps or plaques blending into the myometrium ( figures 3 and 4 ) .
most polyps contained multifocal randomly distributed lymphocyte and plasma cell infiltrations , and regions of neovascularisation .
polyps were covered by a combination of normal , attenuated and moderately swollen mesothelial cells . at sites of mesothelial cell loss ,
the stratum vascularis was moderately oedematous containing both congested medium - to - large size blood vessels and dilated lymphatics .
endometrium and uterine epithelium appeared unremarkable with a low glandular content , intact mucosal epithelium and minimal - to - no inflammatory cell infiltrations .
the lesion was characterised as a diffuse , chronic , polypoid , fibrotic perimetritis and parametritis .
cross - section of uterine body ( u ) revealing multiple polypoid perimetrial projections ( p ) ( haematoxylin and eosin ) polypoid structures blending with myometrium and containing ( a ) foci of angiogenesis and ( b ) regions of active fibroplasia ( haematoxylin and eosin )
uterine prolapse has rarely been documented in cats , with individual case reports citing complete or unilateral uterine prolapse with or without uterine mucosal eversion .
the majority have occurred in association with the periparturient period , one of which was proposed to be associated with oestrus .
furthermore , a novel lesion inducing extensive perimetrial fibrosis , not previously reported in cats , was noted and could potentially be implicated as the cause .
however , other factors have been suggested including uterine atony or excessive abdominal contractions , including tenesmus . for the uterus to prolapse
there is a requirement for laxity , stretching or rupture of uterine ligaments , and for patency of the cervix .
laxity of the uterine ligaments can occur due to repeated pregnancy , and changes in progesterone , oestrogen and relaxin concentrations near parturition .
cervical patency occurs at two time points , oestrus ( with or without ovulation ) and at parturition . based on the absence of any newborn animals ,
no mammary development and no histopathological features to suggest recent pregnancy , such as placental zoning , recent uterine haemorrhage , inflammation and endometrial regeneration , it is unlikely this animal was in advanced pregnancy or had aborted .
it was not possible , however , to establish if this animal had recently been in oestrus as oestrogen levels , which were within normal limits , can vary significantly over short periods of time within the oestrus cycle . while the uterus was large ,
this latter feature could potentially have contributed to uterine prolapse in at least two ways , namely by inducing ligament laxity and/or acting as a caudal abdominal irritant inducing abdominal contractions or tenesmus . while an active lesion
, the extent of mature fibrous tissue would suggest the presence of this lesion in advance of the uterine prolapse .
perimetrial inflammation can co - exist as part of peritonitis , and in cats peritonitis is frequently associated with feline infectious peritonitis or primary bacterial septic peritonitis where bacteroides species and fusobacterium species are mainly isolated . however , such lesions do not manifest as polypoid fibrous proliferations .
similar proliferative fibrotic lesions focused on the perimetrium have been described in dogs associated with experimental stilboestrol ( synthetic oestrogen ) administration .
perimetrial papillae consisting of proliferations of mesothelial cells and subjacent connective tissue were documented in ovariectomised dogs administered stilboestrol over 150350 days .
similar to the present case , such lesions were confined to genital organ serosal surfaces , including the broad ligament .
such perimetrial lesions were also noted in entire female dogs when administered synthetic oestrogens in association with other lesions , including oestrogen - induced renal fibrosis .
proposed mechanisms of regional fibrous proliferations suggested involvement of stromal oestrogen receptors . while the cat develops oestrogen - associated pathology , similar perimetrial pathology has not been documented in association with oestrogen .
the ovaries were not submitted for histopathological evaluation to eliminate ovarian pathology definitively ( cystic follicular disease , ovarian neoplasia ) as a potential source of hyperoestrogenism .
cats in the tropics are likely to cycle continuously and it is recognised that some unmated cats may appear to be in persistent oestrous , owing to a relatively short interoestrous period and thus remain in a physiological hyperoestrogenic state . it was also unlikely this cat had access to exogenous oestrogenic compounds . in humans , more generalised intra - abdominal ,
fibrosing lesions of peritoneal surfaces ( intra - abdominal fibromatosis ) are described in mesenteric , retroperitoneal and pelvic locations .
sclerosing peritonitis has been noted after surgery , following long - term continuous peritoneal dialysis and also as a side effect of utilising beta - blockers .
the pathogenesis of these lesions is thought to be the result of a delayed healing response due to loss of mesothelial cells or continued serosal irritation .
however , the appearance is not described as polypoid and ranges through a spectrum of gross changes in the appearance of the visceral peritoneum , from opacification of the serosa ( disorganised collagen fibres and stromal expansion ) through to  tanned peritoneum ( hyalinised collagen , fibrin and vessel sclerosis ) , which can progress to a stage where the viscera are palpably stiffened ( mural fibrosis ) .
the unique perimetritis and parametritis observed in this case highlights an additional potential cause of uterine prolapse and warrants that , in cases of uterine prolapse in non - pregnant animals , perimetrial and parametrial tissue should be evaluated for varying degrees of inflammation .
 case summarythis case describes a young non - pregnant cat that presented with uterine prolapse in association with an unusual diffuse , polypoid , fibrosing perimetritis and parametritis . 
 following ovariohysterectomy the cat recovered fully . 
 no intra - abdominal complications were seen on ultrasound examination 3 months postsurgery . at the time of writing , 
 the cat remains healthy.relevance and novel informationuterine prolapse in the cat is relatively rare and usually associated with the periparturient period . 
 inflammatory polypoid perimetritis and parametritis have not previously been documented in cats , and in dogs have only been reported in association with the administration of oestrogenic compounds . 
 the polypoid inflammation affecting the uterus and parametrium may have contributed to increased laxity of the uterine ligaments and predisposed to the development of uterine prolapse . 
Case summary
Relevance and novel information
Introduction
Case description
Discussion
Conclusions