Ovariohysterectomy in Six Mares

Six mares had ovariohysterectomy performed for chronic pyometra associated with cervical abnormalities, uterine neoplasia, or removal of a macerated fetus. Ovariohysterectomy was performed through a ventral midline incision with access to the ovarian and uterine vessels aided by traction on the uterus and retraction of abdominal viscera. Abdominal pain, the most common complication after surgery, occurred in four mares but resolved within 36 hours. Peritonitis occurred in two mares; one mare was subsequently euthanatized. Other complications that resolved with treatment included infection of the uterine stump (two mares), abdominal hemorrhage (one mare), diarrhea (one mare), and incisional infection (one mare). Complications after surgery can be reduced by removing as much of the uterus as possible, minimizing peritoneal contamination with uterine contents, and providing a secure closure of the caudal reproductive tract.     

Clinical signs and treatment of chronic uterine torsion in two mares

Two mares were evaluated because of chronic uterine torsions of 2 and 4 weeks' duration; both were pyrectic, anemic, tachycardic, and anorectic, had signs of depression, and had an abnormal uterus and contents on transrectal examination. Both mares underwent cesarean section for lysis of adhesions from the uterus to the peritoneum, correction of the torsion, and ovariohysterectomy Both mares recovered with only minor complications and returned to be used as riding horses. Chronic uterine torsion should be considered in mares in late stages of gestation that have vague clinical signs and transrectal palpation findings that are unlike those described in typical cases of uterine torsion. Prognosis for life can be good after treatment by ventral midline celiotomy, cesarean section, correction of the torsion, and ovariohysterectomy.     

A two-step ovariohysterectomy with unilateral left flank laparoscopic assistance in a Quarter Horse mare

This case report describes the technique and outcome of a two-step laparoscopic-assisted ovariohysterectomy in a Quarter Horse mare performed through the left paralumbar fossa for the treatment of chronic pyometra. Ovariohysterectomy is a procedure uncommonly performed in the horse. It is surgically demanding, invasive and can be associated with significant complications when a ventral midline approach is performed. Laparoscopic-assisted techniques reduce the invasiveness and some of the complications associated with ovariohysterectomy through ventral midline alone. The described modification further reduces the invasiveness of laparoscopic-assisted ovariohysterectomy and has the potential to reduce the overall surgical time of the procedure. Further work is needed to determine if the technique could be extrapolated to large-sized mares.     

Omentalization of a nonresectable uterine stump abscess in a dog

One month after ovariohysterectomy, a 2-year-old spayed female Golden Retriever was evaluated because of an extensive uterine stump abscess. Clinical signs included intermittent vomiting, signs of depression, lethargy, and pollakiuria. The dog underwent abdominal surgery; the greatly enlarged uterine stump was tightly adhered to the dorsal surface of the bladder, encompassing the distal portions of the ureters and the bladder's neurovascular supply. En bloc resection of the uterine stump was not considered an acceptable treatment option because of the risk of surgical damage to and subsequent devitalization of the bladder or ureters, urinary incontinence, or urinary tract obstruction. Therefore, the diseased uterine tissue that extended cranial to the bladder was resected, and the remaining abscess cavity was lavaged and packed with omentum. The dog recovered fully from the procedure. The omentum is an effective physiologic drain; its extensive vascular and lymphatic networks absorb fluid and actively promote elimination of infection. Omentalization appears to be an option for surgical management of nonresectable uterine stump abscesses in dogs.     

A preliminary study of uterine derived polymorphonuclear cell function in mares with chronic uterine infections

From 6 mares with chronic uterine infection, polymorphonuclear neutrophils (PMNs) were obtained from the uterus. In order to recover an adequate number of viable PMNs, 0.1% oyster glycogen was infused into the uterus as a mild irritant 12 h prior to the uterine flushing. Phagocytosis and chemotaxis of the uterine derived PMNs were determined. The supernatant from the uterine flushing was compared with autologous serum for its capacity as an opsonin and chemoattractant. There was a significant increase of both phagocytosis and chemotaxis when autologous serum was used compared with the supernatant from the uterine flushing. This study indicates that autologous serum has a greater opsonizing capacity than uterine secretion from mares with chronic uterine infection. Since all mares conceived following this study, the use of oyster glycogen was not considered to have deleterious effect on the uterine mucosa.     

Hand-assisted laparoscopic ovariohysterectomy in the mare

OBJECTIVE: To develop a minimally invasive, hand-assisted laparoscopic ovariohysterectomy (HALS-OHE) technique in the mare and to evaluate safety and any associated complications. STUDY DESIGN: Experimental study. ANIMALS: Eight, 11-24-year-old mares with anatomically normal urogenital tracts. METHODS: The surgical technique was developed in 2 non-survival mares and subsequently evaluated in 6 survival procedures. Food was withheld for 48 hours, then mares were anesthetized and positioned in dorsal recumbency for laparoscopic surgery. A hand access device (Omniport) was placed followed by 4 laparoscopic portals. Transection of the ovarian pedicles and broad ligaments was achieved using a combination of a laparoscopic stapling instrument (Endo GIA II), an ultrasonically activated instrument (Harmonic Scalpel), and endoscopic clips (Endo Clip II ML). The genital tract was exteriorized through the laparotomy, and the uterus transected and sutured in a conventional pattern. Horses were evaluated through postoperative day 14 when a necropsy was performed. RESULTS: Four mares recuperated well after surgery, 1 mare was euthanatized because of bilateral femur fracture during anesthetic recovery, and another developed severe pleuropneumonia. At necropsy all but 1 abdominal incision was healing routinely. One mare had abscessed along the celiotomy incision and developed visceral adhesions. Uncomplicated healing of transected mesovarial, mesometrial, and uterine remnants was observed. CONCLUSIONS: Ovariohysterectomy in horses can be accomplished using HALS technique. CLINICAL RELEVANCE: HALS-OHE technique represents a minimally invasive and technically feasible alternative for conventional OHE. Careful patient selection and preparation may reduce the complications observed. The HALS technique may be useful in other laparoscopic surgical procedures.     

The effect of uterine torsion on mare and foal survival: a retrospective study, 1985--2005

REASONS FOR PERFORMING STUDY: Anecdotal speculation suggests that prognosis for survival of mares and foals following correction of uterine torsion has improved over the past 30 years. OBJECTIVES: To determine statistically the outcome of uterine torsion according to duration of clinical signs, stage of gestation, parity, physical examination findings, method of correction, prognosis for survival and reproductive health of the mare, and prospects for the foal within the neonatal period. METHODS: This retrospective study combined cases from 4 equine referral hospitals. RESULTS: The stage of gestation at which uterine torsion occurred was a risk factor for survival of mare and foal. Overall mare survival was 53/63 (84%); when uterine torsion occurred at < 320 days gestation, 36/37 (97%) of mares survived compared to 17/26 (65%) survival rate when uterine torsion occurred at > or = 320 days gestation. Overall foal survival was 54% (29/54). When uterine torsion occurred at < 320 days gestation, 21/29 (72%) foals survived compared to 8/25 (32%) when uterine torsion occurred at > or = 320 days gestation. Thirty mares were discharged from the hospital carrying a viable fetus following uterine torsion correction and 25/30 (83%) of these mares delivered live foals that survived beyond the neonatal period. CONCLUSIONS: Prognosis for survival for mares and foals following uterine torsion is good and improves if torsion occurs < 320 days compared to > or = 320 days gestation. CLINICAL RELEVANCE: Gestational timing of uterine torsion should be considered when advising clients about the prognosis for survival of the mare and foal. The prognosis for a mare delivering a live foal is good if the mare is discharged from the hospital following uterine torsion correction with a viable fetus.     

Bilateral ovariectomy as a treatment for chronic pyometra in four horses

The objective of this retrospective study was to describe the use of bilateral laparoscopic ovariectomy without hysterectomy for chronic pyometra in horses. Four client-owned horses were included, each having chronic pyometra that was unresponsive to treatment. Bilateral laparoscopic ovariectomy was performed on the horses under standing sedation. A final uterine lavage was performed either 24 hours before or after surgery, with no further treatment of the uterus. No complications were encountered during surgery or post-operatively, and each horse had resolution of the pyometra without recurrence of clinical signs over at least 3 years. All owners were satisfied with the procedure. Following histopathology, one horse was found to be a true hermaphrodite, with one vestigial testis and one ovotestis. Ovariectomy alone was an effective treatment for four horses with chronic pyometra, without complications. Ovarian steroids and abnormal uterine or cervical conformation are important influences in the pathogenesis of pyometra, and removal of the hormone source via ovariectomy should be considered to avoid a more invasive surgery and the potential complications associated with ovariohysterectomy in horses.     

Standing laparoscopic-assisted vaginal ovariohysterectomy in a mare

A 20-year-old Arabian mare presented to Washington State University Veterinary Teaching Hospital for evaluation of haemorrhagic vaginal discharge of 3 months' duration. The referring veterinarian had identified a mass within the uterine wall via transrectal ultrasonographic examination. On presentation, the mare had an unremarkable physical examination with the exception of a mild haemorrhagic vaginal discharge. Rectal palpation was performed and an approximately 9 cm diameter mass with a granular texture was identified associated within the uterine body and left uterine horn. Endoscopic examination of the reproductive tract revealed a linear defect in the ventral uterine wall near the cervix with direct communication into the abdomen. Standing laparoscopic-assisted vaginal ovariohysterectomy (OHE) was performed, which involved laparoscopic facilitated dissection and haemostasis of uterine and ovarian structures, and inversion of the uterus through the cervix. Removal of the uterus was performed vaginally. No post operative complications were noted. Standing laparoscopic-assisted vaginal OHE is an alternative to traditional OHE techniques. This technique allowed for excellent direct visual observation during dissection and ligation and did not require general anaesthesia.     

Surgical treatment of uterine torsion using a ventral midline laparotomy in 19 mares

OBJECTIVE: To report on the outcome of surgical treatment of uterine torsion in preterm mares. DESIGN: Retrospective case series of pregnant mares with uterine torsion presented to the Clinic for Obstetrics, Gynaecology and Andrology of Large and Small Animals. METHODS: Hospital records of all pregnant mares that underwent ventral midline laparotomy for uterine torsion between 1998 and 2004 were reviewed. The signalment, history, clinical signs, results of diagnostic procedures, direction and degree of the uterine twist, treatment and outcome were retrieved from each case record. RESULTS: This study comprised 19 mares between months 5 and 11 of pregnancy (8.7 +/- 1.9) and suffering from uterine torsion. In all cases ventromedian laparotomy was carried out under general anaesthesia. Gastrointestinal disorders were also present in 52.6% of horses. Postoperative complications included subcutaneous seromas (five mares), peritonitis (one mare) and abortion (two mares). In four mares (21%) the operation was unsuccessful (i.e. these mares had to be euthanased intra- or postoperatively). Of the surviving 15 mares, 13 (86.6%) gave birth to viable foals at full term. The foals developed normally. Only two mares aborted. CONCLUSIONS: Because of its versatility the ventral midline approach should be considered for correction of uterine torsion. The approach has many advantages, including rapid and clear access to the abdominal cavity, safety, visual assessment of uterine wall viability, correction of concomitant gastrointestinal tract problems, and performance of hysterotomy or hysterectomy, if indicated. In this study, managing uterine torsion in this way resulted in a high percentage of cases (86.6%) in which pregnancy was maintained, with the birth of a viable, mature foal.     

Uterine neoplasia in 13 cats.

Thirteen uterine tumors were diagnosed in 13 cats and accounted for 0.29% of all feline neoplasms received during a 9.6-year period. Age at diagnosis ranged from 3 to 16 years; median 9 years. Six were Domestic Shorthair cats, and 7 were purebred cats of 5 different breeds. Eight adenocarcinomas and 1 mixed Müllerian tumor (adenosarcoma) comprised the endometrial tumors. Myometrial tumors included 3 leiomyomas and 1 leiomyosarcoma. One of the adenocarcinomas developed in the uterine stump of an ovariohysterectomized cat; the other cats were sexually intact. Concurrent mammary adenocarcinoma was diagnosed in 1 cat with uterine adenocarcinoma and in another with uterine leiomyoma. Tumors were discovered during elective ovariohysterectomy in 2 cats, but at least 3 others had experienced reproductive problems (infertility or pyometra). Five cats presented for abdominal or pelvic masses. Endometrial adenocarcinomas were positive immunohistochemically for cytokeratins and negative for smooth muscle actin (SMA): 1 of 6 cats was positive for vimentin and 4 of 8 were positive for estrogen receptor-alpha (ER alpha). Adenosarcoma stromal cells were positive for vimentin and ER alpha but negative for cytokeratins and SMA. Smooth muscle tumors were positive for vimentin and SMA and negative for cytokeratins. Leiomyomas, but not the leiomyosarcomas, were positive for ER alpha. Adenocarcinomas in 4 cats had metastasized by the time of ovariohysterectomy. Two other cats were euthanized 5 months after ovariohysterectomy; at least one of these cats had developed an abdominal mass that was not examined histologically. Only 2 cats with endometrial adenocarcinoma had disease-free intervals longer than 5 months after surgery. Metastasis was not detected in any mesenchymal tumor; however, these cats were either euthanized on discovery of the tumor or the tumor was first detected at necropsy.     

An evaluation of the haemostatic suture in hysterotomy closure in the mare.

This study was designed to evaluate the haemostatic suture as a means of preventing haemorrhage from the hysterotomy in mares after caesarean section. At 2 university hospitals 1982-1994, 48 mares had caesarean section for dystocia, 10 as an elective, and 8 mares concurrently with colic surgery. The haemostatic suture was used in 31 of 66 mares (47%) and surgery period was significantly (P<0.05) shorter when it was not applied. Anaemia (PCV<30%) was recorded in 13 (22%) of 58 mares, excluding the colic group, and the haemostatic suture did not after this proportion of mares that had anaemia. Anaemia was 5 times more probable following caesarean section than vaginal delivery, evidence that bleeding from the hysterotomy is a serious and common complication of caesarean section in mares. Severe uterine haemorrhage was recorded in 3 mares that had an haemostatic suture (10%) and in 2 mares that did not (6%). The latter two mares died of haemorrhage. The suture, therefore did not eliminate post operative anaemia and severe uterine haemorrhage. If omitted, the hysterotomy should be closed with a full thickness pattern that is sufficiently tight to compress vessels in the uterine wall.     

Measurement of total volume and protein concentration of intrauterine secretion after intrauterine inoculation of bacteria in mares that were either resistant or susceptible to chronic uterine infection.

Undiluted uterine secretion was used to determine the concentration of total protein and the accumulated volume of uterine secretion after a bacterial inoculation in mares susceptible and resistant to chronic uterine infection (CUI). The uterus of 6 susceptible and 5 resistant mares was inoculated with 5 x 10(6) Streptococcus zooepidemicus on the third day of estrus. Using a tampon inserted in the uterus, secretions were sampled at 5, 12, 24, and 36 hours after inoculation, followed by intrauterine lavage with phosphate buffered saline solution. The concentration of protein was determined in the undiluted secretion as well as in the uterine washing and the total amount of accumulated uterine secretion was calculated. Protein concentrations in plasma were compared before and after absorption by the tampon. Protein concentration of plasma before and after absorption by the tampon did not differ. Mares susceptible to CUI accumulated significantly (P less than 0.001) more fluid in the uterus than mares resistant to CUI, and uterine washings from the resistant mares were significantly (P less than 0.05) more dilute than those from the susceptible mares. Significant differences in protein concentrations between susceptible and resistant mares were not found. It was concluded from this study that the described method to sample undiluted uterine secretion was practical and reliable for the analysis of protein concentration. Various concentrations of uterine secretions in washings from susceptible and resistant mares emphasizes the importance in using undiluted uterine secretions or dilution markers in washings when intrauterine products are analyzed.     

Effect of seminal plasma on uterine inflammation, contractility and pregnancy rates in mares

REASONS FOR PERFORMING STUDY: There is conflicting evidence over the role seminal plasma plays in sperm transport and inflammation within the uterus of mares. In in vitro studies, seminal plasma has been shown to reduce polymorphonuclear neutrophil (PMN) function, but the opposite effect on uterine inflammation has been reported in vivo. OBJECTIVES: To study the effect of seminal plasma on uterine contractility, inflammation and pregnancy rates by inseminating mares with low doses of sperm free from seminal plasma (Group 1) and containing seminal plasma (Group 2). METHODS: Synchronised mares were inseminated with 50 x 10(6) sperm in either skim milk extender or seminal plasma. Uterine lavage was performed 6 h after insemination to assess the inflammatory response. The contraction frequency of the uterus was measured over a 4 min period 10 mins and 6 h after insemination, using B-mode ultrasonography. Pregnancy rates were assessed 16 days after insemination. RESULTS: Uterine contractions were less frequent in Group 1 mares inseminated with seminal plasma and significantly more PMNs were found in the lavage fluid of those mares. Pregnancy rates were identical in both groups (62%). CONCLUSIONS: This study provides evidence that seminal plasma decreases uterine contractility and increases the inflammatory response of the uterus to semen. No effect of seminal plasma on pregnancy rates was demonstrated. POTENTIAL RELEVANCE: Mares that develop persistent mating-induced endometritis may have inherently poor uterine contractility and impaired uterine clearance. The presence of seminal plasma during breeding may not be desirable in these mares. The role of seminal plasma in problem mares warrants additional study.     

Uterine adenocarcinoma with abdominal metastases in an ovariohysterectomised cat

SURGICAL FINDINGS: an adenocarcinoma of the uterine stump with abdominal metastases is described in a 12.5-year-old incompletely ovariohysterectomised domestic shorthair cat. At the time of presentation, the adenocarcinoma had metastasised to the right perirenal lymph node, the abdominal aorta and the right ureter, resulting in the formation of a large cystic structure. This had compressed and displaced surrounding structures, including the abdominal vena cava and the right kidney, and formed multiple adhesions to the body wall and adjacent abdominal structures. Metastatic extension to the aorta had resulted in its regression into a 2 mm diameter non-pulsatile vessel. PRACTICAL RELEVANCE: only one case of uterine adenocarcinoma has previously been reported in an ovariohysterectomised cat. As such, this represents a very unusual and severe complication following an incomplete ovariohysterectomy. Invasion of the tumour tissue into surrounding structures created further complications.     

The effects of dexamethasone and prednisolone on pituitary and ovarian function in the mare

Reasons for performing study: Persistent mating induced endometritis is among the most common causes of infertility in the mare. Recently, improved pregnancy rates have been reported when corticosteroids were administered to ‘problem mares’ specifically, to modulate the post mating inflammatory response; however, the effect of treatment on pituitary and ovarian function requires further study. Objectives: To evaluate the effects of prolonged treatment with glucocorticoids on pituitary and ovarian function. Methods: Eighteen cycling Quarter Horse mares in early oestrus were assigned randomly to one of 3 treatment groups: dexamethasone 0.05 mg/kg bwt i.v. twice a day, prednisolone 0.5 mg/kg per os twice a day, or placebo for 5 days. Mares were examined by ultrasound daily to evaluate reproductive function. Blood samples were collected daily to measure luteinising hormone (LH), progesterone and cortisol levels. Results: Dexamethasone treatment caused greater (P<0.05) suppression of endogenous cortisol concentration (9.4 ± 1.1 ng/ml) compared to prednisolone‐ (41.9 ± 4.0 ng/ml) or placebo‐treated mares (32.4 ± 3.8 ng/ml). After 24 h, mares treated with dexamethasone exhibited lower uterine oedema scores than prednisolone‐ or placebo‐treated mares. An ovulation rate of 40% was observed in dexamethasone‐treated mares (2/5) compared to 83% for prednisolone (5/6) and 100% for placebo‐treated (6/6) mares. An absence of a LH surge was noted in 3 of 5 dexamethasone‐treated mares and one of 6 prednisolone‐treated mares. Conclusions: Repeated administration of dexamethasone to mares in oestrus is associated with decreased uterine oedema, suppression of LH and a high rate of ovulation failure. It is recommended that dexamethasone treatment is limited to only 1 or 2 days and that a lower dose is considered in the management of persistent mating induced endometritis to avoid potential adverse affects on reproductive function.     

Lectin binding patterns of uterine glands in mares with chronic endometrial degeneration

OBJECTIVE: To evaluate changes of glycoconjugate in uterine glands of endometrial tissues obtained from mares. ANIMALS: adult mares. PROCEDURE: Uterine biopsy samples were collected during the breeding season and analyzed histologically for signs of chronic endometrial degeneration. Stage of the estrous cycle was established, using clinical examination and determination of hormonal status. Uterine tissue samples were analyzed, using lectin histochemical and immunohistochemical techniques (estrogen and progesterone receptors). Connective tissues were stained to determine alterations of ground substance in periglandular fibrosis. RESULTS: Of 50 mares, 30 (60%) were classified as normal or having modest alterations, and 20 (40%) were classified as having moderate or severe endometrial degeneration. In normal equine endometrium, several lectins (Helix pomatia agglutinin, Lotus tetragonolobus agglutinin, Ricinus communis I agglutinin, Ulex europaeus agglutinin, and wheat germ agglutinin) bound to glycoconjugates of the luminal epithelium and openings of uterine glands. Lectin binding patterns of cystic dilated glands or fibrotic glands in endometrial samples were remarkably strong, whereas normal surrounding cells remained unstained. Lotus tetragonolobus lectin was not suitable for detecting endometrial alterations. Connective tissues stained with Alcian blue and results of Hale colloidal-iron binding revealed acidic ground substance in periglandular fibrosis. Estrogen and progesterone receptors were evenly distributed in healthy and affected endometrial samples. CONCLUSIONS AND CLINICAL RELEVANCE: Glycoconjugate patterns of uterine glands were altered in mares with chronic endometrial degeneration. Therefore, uterine secretions are likely to be altered. These changes are not induced by changes in content of estrogen and progesterone receptors in endometrial tissues.     

Elevating the uterus (uteropexy) of five mares by laparoscopically imbricating the mesometrium

Reasons for performing study: There is a need for study of a method for restoring a ventrally positioned uterus to a horizontal position involving fertility of mares with delayed uterine clearance. Hypothesis: A ventrally‐angled uterus can be elevated to a horizontal position using a laparoscopic technique. Objective: To develop a laparoscopic technique of imbricating the mesometria to elevate the uterus to a horizontal position. Methods: The right and left mesometria of 5 pluriparous mares, all barren for 1–8 years (mean 3.8 years), with a pendulous, ventrally‐angled uterus were shortened laparoscopically, by imbrication, with the mares standing, to raise the uterine body and horns to a horizontal position. Sutures were placed through the dorsal aspect of the uterine body and uterine horn and the adjacent region of the mesometrium using a simple continuous suture pattern. Results: The uterus of all 5 mares was elevated successfully to a horizontal position. Three of the mares became pregnant the same year, without other treatment, after the procedure. Conclusions: A pendulous, ventrally‐angled uterus can be returned to a normal, horizontal position by imbricating the mesometria, using a laparoscopic technique. Potential relevance: Elevating a ventrally‐angled uterus to a horizontal position may improve egress of uterine debris, thereby improving fertility.     

The effect of age and parity on the development of equine chronic endometrial disease

The results of a retrospective analysis of 3,804 endometrial biopsy specimens collected from non-pregnant mares during the course of routine equine stud farm practice demonstrates a significant and practically useful correlation between the severity of chronic degenerative endometrial disease (CDE) diagnosed and age of mare at the time of examination. There were significant correlations between the number of foals born and the mares' barren years prior to biopsy and the severity of CDE, but the differences were not sufficiently large to be useful. Correlations between the severity of chronic infiltrative endometritis (CIE) and age or pre-biopsy parity were minimal. The results suggest that using similar histopathological criteria to those used by Kenney and Doig (1986), mares up to nine years of age should have no signs of CDE, mares up to 13 years of age should have no more than mild signs, mares up to 15 years of age should have no more than moderate signs and mares aged 17 years or older are likely to have severe signs. We believe that these guidelines are a useful, objective aid for formulating a breeding prognosis.     

Effect of exogenous ovarian steroids on the uterine luminal prostaglandins in ovariectomised mares with experimental endometritis

Prostaglandins (PGs) F and E2 were measured in lavage fluid from the uterus of ovariectomised mares after experimental induction of uterine inflammation. Treatment with progesterone alone, or progesterone followed by oestradiol, significantly increased the concentrations of these PGs in the lavage compared with mares treated with oestradiol or control mares. Ovarian steroids, therefore, influenced uterine PG synthesis in response to an inflammatory stimulus. To determine whether the uterine lavage procedure might contribute to the concentrations of prostaglandins in the lavage, the procedure was also performed on six intact mares. With the exception of washings obtained at luteolysis, uterine concentrations of PGF (measured as the plasma metabolite 15-keto-13,14-dihydro PGF2 alpha) had returned to prewashing levels within 30 minutes of the start of uterine lavage. Lavage was therefore unlikely to have influenced the concentrations of prostaglandins in the lavage fluid.