Ultrasonography and CT examination of ovarian follicular development in 'Testudo graeca' during 1 year in captivity.

BACKGROUND: The Greek or Mediterranean tortoise (Testudo graeca), commonly known as the spur-thighed tortoise, is a species of tortoise in the family Testudinidae that is found in North Africa, Western Asia and Europe. Several species of this genus are under threat in the wild, mainly from habitat destruction therefore, accurate information about the sexual cycle and the exact time of follicular development can be effective in successful reproduction planning and preventing species extinction. OBJECTIVE: The experimental part of this study is focused on the evaluation of the reproductive apparatus of tortoises and development of follicles in ovaries during 1 year by ultrasonography and computed tomography. METHODS: Ultrasonography and CT scanning was carried out on 10 female 'T. Graeca' tortoises which were maintained at Tehran Eram Zoo from November 2021 to November 2022 (1 year). Ultrasonography and CT exams were performed on all animals. RESULTS: In the first study, on 28 November 2021, the ovarian cycle was characterized by the presence of previtellogenic follicles and atretic follicles. The numbers of follicles were best demonstrated on CT examination. Ultrasonography and CT scan in the second study showed no change in type of follicles from previous study. In the third study, atretic follicles were more than previtellogenic follicles, whereas in the fourth one, the numbers of previtellogenic follicles were more than atretic follicles. In following, at 6 and 29 June 2022, the absence of atretic follicles and just presence of previtellogenic follicles were observed. On 20 July 2022, the presence of a few number of atretic follicles and more previtellogenic follicles were noticed. On 30 July 2022, the absence of atretic follicles and presence of previtellogenic follicles and, for the first time, preovulatory follicles were obvious. In four following studies the absence of atretic follicles and the presence of previtellogenic follicles were diagnosed. In the last study, the absence of atretic follicles and the presence of preovulatory and previtellogenic follicles were observed. CONCLUSION: In current study, the reproductive cycle of female T. Graeca is evaluated during 1 year in captivity with ultrasonography and CT scan. It can be concluded that in captivity, the reproductive cycle does not result in the formation of eggs or calcareous shells and atretic follicles in the study year continued as before; so this should be highly considered in captivity breeding programmes. This study also revealed that among imaging modalities, CT scan is the best modality for detecting the shape, size, type and numbers of the follicles for further evaluation of location and shape of the follicles.

Doppler ultrasonography can be used to evaluate the arterial blood supply of hip joints in skeletally immature cats.

OBJECTIVE: To investigate hemodynamics and morphology of hip joint vasculature in cats with the use of color and pulsed-wave Doppler ultrasonography. ANIMALS: 30 client-owned healthy skeletally immature cats presented for routine examinations between September 7, 2022, and March 25, 2023. METHODS: Cats between 3.5 to 18 months old with healthy hip joints and Hct within reference ranges (26% to 44.2%) were eligible for inclusion. Color and pulsed-wave Doppler ultrasonography was performed without sedation. Peak systolic velocity (PSV), mean diastolic velocity (MDV), resistance index (RI), and pulsatility index (PI) were measured for major arteries of the hip joints. RESULTS: Intermediate pulsatility, resistance to flow, and pandiastolic anterograde flow were evident for all arteries evaluated for each joint except for the ligamentum capitis ossis femoris artery (LCOFA). Spectral waveforms for the LCOFA showed a low-resistance pattern with continuous forward diastolic flow. No significant differences were found in the mean PI or MDV between the left and right sides for the ascending branch of the lateral circumflex femoral artery or in the mean PI of the ascending branch of the medial circumflex femoral artery. Mean PSV of the LCOFA was lower (but nonsignificantly) for left hip joints vs right hip joints, whereas other values were often higher on cats' left side vs their right. CLINICAL RELEVANCE: This study provided insight into the morphology and hemodynamics of the femoral head vasculature in skeletally immature cats and showed Doppler ultrasound values to study the clinically normal blood supply to hip joints in cats.

Computed Tomographic Features of Thymus in Dogs: Correlation with Age, Gender, Breed and Body Fat Content.

BACKGROUND: The thymus is the first lymphoid organ formed to regulate a newborn's immunity. It reaches its maximum size during puberty, after which it undergoes an atrophic procedure called involution, but its ability to grow again in response to some stresses, such as infections, neoplasia, surgeries, chemotherapy, and radiotherapy is maintained. There is no comprehensive study on computed tomographic features of thymus in dogs. So, the goal of the present study is to gain better insight into the thymus using computed tomography as a non-invasive method. METHODS: One hundred and fifty dogs classified in five age groups and five breed groups were recruited to this study and the thymus was evaluated using a 2-slice computed tomography machine. The inclusion criteria for the present study were having a normal complete blood count, plain and post-contrast CT scan examination of the thoracic region and no history of neoplasia, chemotherapy or radiotherapy. The visibility, density, enhancement, grade, size, volume, shape, borders and lateralization of the thymus were evaluated and statistical analysis was performed. The effect of obesity on thymic grade and volume was also investigated. RESULTS: The visibility, density, dorsal length, volume and grade decreased with increasing age. The thymic shape and lateralization were mostly wedge shaped and left sided, respectively. The borders became concave with aging and increasing body fat content caused an increase in the fatty degeneration of the thymus. CONCLUSIONS: Declining thymic density, grade, size and volume with aging are related to thymic involution and fatty degeneration was accelerated by increasing body fat content. Females and males were different only in thymic shape and small and large breeds were different only in thymic volume. The thymus was visible in some geriatric dogs with no underlying disease. We expect that the present work can be used by radiologists in reading thoracic computed tomography but investigation of thymic characteristics in dogs with neoplasia and history of chemotherapy, radiotherapy and thoracic surgeries can complete this study.

CT anatomy and normal radiography of the skull of the Rhesus monkey (Macaca mulatta).

BACKGROUND: Considering the relationship between human morphology and physiology with the Rhesus monkey, this animal is the most prominent species of laboratory primate for human and animal health research. Moreover, sending Macaca mulatta monkey into space and simulating a living environment for humans shows the similarity of this animal's physiology with humans. OBJECTIVE: So far, no comprehensive study has been done on computed tomography (CT) scan and radiography of skulls in Rhesus monkeys. Therefore, providing accurate documents from the CT anatomy of the skull in these animals can help us to better understand normal conditions and diseases, and we can use a functional atlas of diagnostic imaging from the skull of this animal. METHODS: Ten mature monkeys weighing 6.5 kg were used for this project (five males and five females). A radiographic examination with standard views was performed during general anaesthesia. Then the monkeys were placed in a spherical CT scan during general anaesthesia with standard sternal recumbency. RESULTS: The frontal bone was seen as two parallel radiopaque lines coming forward and downward. The frontal sinus in the Rhesus monkey was not visible in both lateral and dorsoventral radiographs, which could indicate the degeneration of this sinus in this species. The number of teeth in an adult monkey was 32. Molar teeth had a bilophodont arrangement. CONCLUSIONS: The comparison between the size of the eye ball in human and Rhesus monkey, unlike other measured parameters, did not differ much, and this indicates that the volume ratio of the eye ball to the whole skull in Rhesus monkey is higher than that of humans.

Radiologic features of radiolucent foreign bodies ingestion in common mynah (Acridotheres tristis).

BACKGROUND: In mynahs with foreign body ingestion, delayed diagnosis increases the risk of poor outcomes. OBJECTIVE: The aim of this study was to evaluate various radiologic features on plain and contrast radiographs in mynahs for assessing the presence of ingested foreign bodies. METHODS: In our cross-sectional study, a total of 41 mynahs were included. The diagnosis was made by history, surgery, excision by forceps or excretion in the faeces. Overall, 21 mynahs were considered not to have a foreign body in their gastrointestinal tract. Plain and post-contrast [oral administration of barium sulphate colloidal suspension of 25% weight/volume (20 mg/kg)] lateral and ventrodorsal radiographs from the cervical and coelomic cavity were taken. Different parameters including oesophageal, proventricular, and small intestinal diameters and opacities were assessed. Image evaluation was performed by two national board-certified radiologists blinded to the final diagnoses. RESULTS: The inter- and intra-observer reliabilities of the diagnostic features were significant (p < 0.001). The diagnosis of the foreign body was highly accurate [90.2% (95% CI: 76.9%, 92.3%)] with the sensitivity, specificity, and area under the representative characteristic curve of 90.0%, 90.5%, and 0.93%, respectively for plain radiographs. The size and opacity of the oesophagus, proventriculus, and intestinal loops as well as serosal details were significantly different between mynahs with and without foreign body intake (p < 0.05). CONCLUSIONS: Lateral and ventrodorsal plain radiographs are highly reliable for diagnosing the presence of non-opaque obstructing objects in the gastrointestinal tract of mynahs. Attention should be paid to the size and opacity of the oesophagus, extension, and opacity of the proventriculus, segmental opacity of intestinal loops, and decrease in serosal details.

Evaluation of aglepristone and oxytocin on induction of parturition in guinea pig.

BACKGROUND: Induction of parturition in guinea pigs appears to be essential because these animals have a higher rate of reproductive problems than rabbits and small rodents. OBJECTIVES: Since aglepristone (AGL) is a competitive progesterone antagonist acting through binding to progesterone receptors while oxytocin (OT) is a powerful constituent of uterine smooth muscle, the aim of this study was to evaluate the clinical and ultrasonographic impacts of AGL and OT on guinea pig parturition induction. METHODS: In this study, guinea pigs were allocated into five groups; each included five animals on the 61st day of pregnancy. In the aglepristone group (Agle), AGL was administrated subcutaneously (SC) once daily on 2 consecutive days (Days 61 and 62 post mating). Oxytocin (OT) was administered subcutaneously once and twice at 4-h intervals on Day 62 post mating in oxytocin 1 (Oxy1) and oxytocin 2 (Oxy2) groups, respectively. The animals in the aglepristone-oxytocin group (Agle-Oxy) received AGL subcutaneously once daily on 2 consecutive days (Days 61 and 62 post mating) and OT on Day 62 post mating. The remaining sows received saline solution (0.9% NaCl) in the control group. RESULTS: According to the results, fetal heart rate, temperature, neonatal and maternal survival rates were not significantly different between the treatment and control groups (p > 0.05). Biparietal diameter of head and body weight of neonates in the Agle, Oxy2 and Agle-Oxy groups showed a significant decline, compared to the control group (p < 0.05). The time interval between injection and delivery and the duration of pregnancy was significantly reduced in Agle, Oxy2, Agl-Oxy groups, compared to the control and Oxy1 groups. CONCLUSIONS: In conclusion, it seems that treatment Oxy2 can induce parturition in guinea pigs without side effects and lower pain during induction of parturition.

Introducing a noninvasive, non-surgical, and reversible animal model for fecal incontinence using abobotulinumtoxinA in dogs.

The aim of this study was to introduce a new animal model of fecal incontinence (FI) by injecting abobotulinumtoxinA in the external anal sphincter (EAS) muscle of dogs which replaces models based on anal sphincter destructions that are invasive, mostly require surgical procedures, expensive, permanent, and painful to the animals. 4 healthy mongrel dogs were used in this study. First, they were received NaCl 0.09% (as control) injections in EAS muscle and effects were assessed by means of Electromyography (EMG) and clinically evaluated by sphincter pinch test and presence of leakage of feces for 2 weeks. Then, they received abobotulinumtoxinA in EAS muscle and reevaluated for 6 weeks to see short-term and medium-term effects of abobotulinumtoxinA injection. Saline had no significant changes in results obtained from EMG, however, there were significant decreases in amplitudes of action potentials after receiving abobotulinumtoxinA in comparison with no injection or saline injection in EAS muscle. Pinch tests were normal after saline injection assessment period, however, then started to be negative, ranging from two days after abobotulinumtoxinA injection to seven days after receiving abobotulinumtoxinA. Animals also had significant presentations of fecal incontinence (leakage of feces and cage contamination with feces) from the 1st week after receiving abobotulinumtoxinA until the 6th week after receiving abobotulinumtoxinA. AbobotulinumtoxinA caused paralysis in the EAS and producd FI conditions in dogs. This animal model was an appropriate substitute to the various invasive, expensive and also complicated procedures with an easy, feasible, noninvasive and non-painful single-stage abobotulinumtoxinA injection.

Evaluation of thoracic vertebrae in healthy White New Zealand rabbit (Oryctolagus Cuniculus): Computed tomographic and morphometric study.

BACKGROUND: Computed tomography currently has a prominent role in diagnosis and evaluation of vertebral column. On the other hand, a thorough knowledge about vertebral column property in normal state is prerequisite an accurate diagnosis of different abnormalities in this region. OBJECTIVE: The purpose of this study was to present a complete and exact descriptive and morphometric evaluation of thoracic vertebrae in rabbits with computed tomography. In images which were constructed by CT, several structures and different parts of the thoracic vertebrae have been named. METHODS: Ten healthy, mature, White New Zealand rabbits were evaluated. The morphologic and morphometric parameters of the thoracic vertebrae were studied. In this study, several parameters of thoracic vertebrae, such as vertebral body height, spinous process height, transverse process length, transverse process width, etc., were measured by computed tomography. RESULTS: Some parameters, such as spinal canal height, spinal canal width, pedicle length, pedicle width, end plate width, and endplate height, had no significant difference through thoracic vertebrae but other parameters, such as vertebral body height, transverse process length, transverse process width, spinous process angle, transverse process angle, and vertebral body length, had a significant difference. CONCLUSIONS: In this study, a comprehensive anatomic atlas of CT anatomy of the thoracic vertebrae was produced for use by veterinary radiologists, clinicians, and surgeons. Finally, we must mention these two important points: (1) Many of the differences observed between rabbits and humans are based on the way the trunks of these two creatures are located on the ground and the differences in the way their bodies move. (2) In studies that are done by modelling humans on animals, it should be noted that the terms used in animal anatomy are different and the names are used using the principles of veterinary anatomy.

Basal cell carcinoma in an albino pindani (Chindongo socolofi) and a cobalt-zebra (Maylandia callainos): Diagnostic imaging, clinical and histopathological study.

A female albino pindani (Chindongo socolofi) and female cobalt-zebra (Maylandia callainos) were referred to the Ornamental Fish Clinic with a soft tissue mass on their upper jaw. Also, during clinical examination, an unencapsulated intraoral soft tissue mass was observed in the cobalt-zebra cichlid. Digital radiography showed soft tissue masses and osteolytic lesions. Computed tomography (CT) imaging confirmed that osteolytic lesions occurred in skull bones of cobalt-zebra. Also, soft tissue mass invaded to the intraoral space. Histopathologically, a non-encapsulated, multilobulated and densely cellular neoplastic mass was identified. Extensive infiltration of neoplastic cells to the dermis and subcutaneous tissue was observed in both cases. The masses were composed of multiple coalescing nests, sheets, lobules and trabeculae of neoplastic cells within a fibrovascular stroma. The palisading basaloid neoplastic cells were markedly extended from the basal cells of the epidermis into the dermis and subcutis. The majority of the neoplastic cells had scant amounts of eosinophilic cytoplasm with indistinct margins, round to ovoid nuclei and typically a single small basophilic nucleolus. There was invasion of basaloid neoplastic cells into the bone tissue that caused osteolytic lesions. Mitotic figures were three to seven per high-power field. Epidermal basement membrane was periodic acid-Schiff (PAS) positive and neoplastic cell extension into the dermis was identified by the PAS staining. Fibrovascular stroma of the mass was also stained blue with Masson's trichrome. Based on histopathological and histochemical findings, the masses were diagnosed as infiltrative type of basal cell carcinoma (BCC).

The diagnostic value of intravenous contrast computed tomography in addition to plain computed tomography in dogs with head trauma.

BACKGROUND: The aim of this study is to evaluate additional findings which can be detected by post-contrast computed tomography (CCT) in relation to plain CT (PCT) findings in patients presented with head trauma. Medical records of canine patients with the history of head trauma from three institutions were reviewed. PCT- and CCT-anonymized images were evaluated by a veterinary radiologist separately. From the categorized findings the following conclusions were drawn as: abnormalities were identified on (A) PCT but missed on CCT, (B) CCT but missed on PCT, (C) both PCT and CCT. RESULTS: Thirty-two patients were included. The results showed that findings identified on CCT or PCT (category A and B) but missed on the other series were limited to mild soft tissue and sinus changes. Overall, 61 different fracture areas, 6 injuries of the temporomandibular joint (TMJ), 4 orbital injuries, 14 nasal cavities with soft tissue density filling, 13 areas of emphysema, 4 symphysis separations, 12 intracranial hemorrhages, 6 cerebral edema, 5 cerebral midline shifts, 3 intracranial aeroceles, 3 brain herniations and 6 intraparenchymal foreign bodies (defined as an abnormal structure located within the brain: e.g. bony fragments, bullet, teeth,..) were identified on both PCT and CCT separately (category C). Severity grading was different in 50% (3/6) of the reported cerebral edema using PCT and CCT images. CONCLUSION: The results showed that PCT is valuable to identify the presence of intracranial traumatic injuries and CCT is not always essential to evaluate vital traumatic changes.

Ultrasound-guided induced fetal death, an alternative method for induction of abortion in the bitch.

This study was performed to achieve abortion in a short time and with minimum side effects in a bitch, as an alternative method for termination of unwanted pregnancy. The experimentation was performed on 10 privately owned crossbred pregnant bitches, in their late second trimester of pregnancy, having a variable number of fetuses (3 to 9). Fetal death was induced by transabdominal intracardiac injection of potassium chloride (KCl) into the fetal heart under ultrasonographic guidance. Pregnancy was terminated within 36 to 72 hr (51.60 ± 16.04 hr) and none of the patients experienced any side effects or clinical complications. Data presented in this report provided evidence for the possible use of this technique to selectively reduce the number of canine fetuses without terminating the whole pregnancy. Ultrasound-guided induced fetal death is a safe procedure and a viable method for the induction of abortion in a short time and with no apparent side effects.

Comparison of computed tomographic and cytological results in evaluation of normal prostate, prostatitis and benign prostatic hyperplasia in dogs.

Prostate gland can be structurally evaluated by computed tomography (CT) with taking advantages of tomographic feature and post-contrast parenchymal changes. The current examination initiated to determine association between computed tomographic and cytological results in evaluation of canine prostate. Thirty mature male dogs were included and under gone by both CT and fine needle sampling of prostate. The cytology and CT examination results showed 18/30 (60.00%) and 15/30 (50.00%) normal prostate, 5/30 (16.66%) and 4/30 (13.33%) prostatitis and 7/30 (23.33%) and 11/30 (36.66%) benign prostatic hyperplasia, respectively. Moderate agreement has been found between cytology and final diagnosis based on pre-contrast CT images, however fair agreement was existed between cytological diagnosis and final CT interpretation according to post-contrast and both pre- and post- contrast CT series. Additionally, the internal iliac lymph node length showed statistically significant difference in prostatitis compared to normal and benign hyperplastic prostates in this study. In conclusion, the fair and moderate associations between cytology and final diagnosis based on CT images should be considered and they can be used in further investigations and clinical examinations. Also, using internal iliac lymph node length to differentiate prostatitis with normal and benign hyperplastic prostates can be used efficiently in diagnosis to choose the best method of management and have a proper follow up and prognosis.

Ratio of the Bronchial Lumen to Pulmonary Artery Diameter in Rhesus Macaques (Macaca mulatta) without Clinical Pulmonary Disease.

In human medicine, CT is widely used to detect changes in bronchial luminal diameter. The diameter of the artery that runs adjacent to the bronchus does not change dramatically along the airway path, such that this artery can be used as a reference to detect changes in the bronchial luminal diameter. The bronchoarterial ratio is increasingly used in veterinary medicine for the detection of lower airway diseases in animals. The purpose of this study was to establish the bronchoarterial ratio in rhesus macaques. We used CT to evaluate 12 rhesus macaques (Macaca mulatta) without clinical signs of pulmonary diseases and measured the bronchoarterial ratio in the right and left superior, middle, inferior and cardiac lung lobes. The overall bronchoarterial ratio (mean ± 1 SD) at all 7 locations in the 12 macaques was 0.59 ± 0.05. Moreover, there was no correlation between the BA ratio and age or sex in the study population. However, the BA ratio and weight of animals showed positive linear correlation. In this study, we established the reference range for the bronchoarterial ratio in clinically healthy rhesus macaques. This ratio is consistent among lung lobes and between animals.

Transplantation of Autologous Bone Marrow Mesenchymal Stem Cells with Platelet-Rich Plasma Accelerate Distraction Osteogenesis in A Canine Model.

OBJECTIVE: Distraction osteogenesis (DO) is a surgical procedure used to generate large volumes of new bone for limb lengthening. MATERIALS AND METHODS: In this animal experimental study, a 30% lengthening of the left tibia (mean distraction distance: 60.8 mm) was performed in ten adult male dogs by callus distraction after osteotomy and application of an Ilizarov fixator. Distraction was started on postoperative day seven with a distraction rate of 0.5 mm twice per day and carried out at a rate of 1.5 mm per day until the end of the study. Autologous bone marrow mesenchymal stem cells (BM-MSCs) and platelet-rich plasma (PRP) as the treatment group (n=5) or PRP alone (control group, n=5) were injected into the distracted callus at the middle and end of the distraction period. At the end of the consolidation period, the dogs were sacrificed after which computerized tomography (CT) and histomorphometric evaluations were performed. RESULTS: Radiographic evaluationsrevealed that the amount and quality of callus formations were significantly higher in the treatment group (P<0.05). As measured by CT scan, the healing parametersin dogs of the treatment group were significantly greater (P<0.05). New bone formation in the treatment group was significantly higher (P<0.05). CONCLUSION: The present study showed that the transplantation of BM-MSCs positively affects early bony consolidation in DO. The use of MSCs might allow a shortened period of consolidation and therefore permit earlier device removal.

Effect of dietary calcium deficiency on the cardiac function of broiler chickens based on electro- and echocardiography.

To determine the effects of dietary calcium deficiency on the heart function of broiler chickens based on electro- and echocardiography, chicks were reared for 42 days and fed rations with different amounts of calcium. At 28 and 42 days of age, electrocardiographic and echocardiographic parameters were assessed. There were significant reductions of R wave amplitude (leads II and aVR) in the Ca-deficient group II at 42 day of age as compared to the control. S wave amplitudes were decreased in most leads but the decrease was significant (P < 0.05) only at 28 days (lead aVL, Ca-deficient group I) and 42 days (leads III, aVR, aVF, Ca-deficient groups I and II). T wave amplitudes were significantly (P < 0.05) decreased at 42 days (leads II, aVR and aVF) in the Ca-deficient group II compared to the control group. Variations in QT, ST and RR intervals were insignificant in the Ca-deficient groups compared with the control. There was a significant (P < 0.05) increase in left ventricular diameter at end-systole and a reduction of left ventricular fractional shortening in the Ca-deficient group II at 28 and 42 days as compared to the controls. Right ventricular fractional shortening was significantly (P < 0.05) decreased only in the Ca-deficient group II at 42 days of age. These results suggest that dose-dependent dietary calcium deficiency alters variations in electro- and echocardiographic parameters which could reflect decreased cardiac function in growing broiler chickens.

Assessment of the acetaminophen absorption test as a diagnostic tool for the evaluation of the reticular groove reflex in lambs.

OBJECTIVE: To assess the acetaminophen absorption test (APAT) for use in determining function of the reticular groove reflex in lambs. ANIMALS: 12 Baluchi lambs. PROCEDURES: 2 consecutive APATs were performed at each of 3 developmental stages (stage 1, before weaning; stage 2, at weaning; and stage 3, after weaning). Lambs suckled a test solution consisting of acetaminophen and barium sulfate and 1 week later were tube fed the same test solution. Abdominal radiographs were obtained immediately after administration of the test solution. Plasma acetaminophen concentrations were determined before and 30, 60, 90, 120, 150, and 180 minutes after intake of the test solution. RESULTS: Closure of the reticular groove after suckling the test solution was confirmed in all 12 lambs at stage 1, in 8 lambs at stage 2, and in 0 lambs at stage 3. Maximum plasma acetaminophen concentrations and area under the plasma acetaminophen concentration-time curves from 0 to 180 minutes were significantly higher in lambs suckling the test solution, compared with values for tube-fed lambs. Receiver operating characteristics analysis revealed that the plasma acetaminophen concentration at 60 minutes after administration was best suited to determine closure of the reticular groove in lambs. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggested that the APAT can be a useful diagnostic instrument to assess function of the reticular groove reflex in lambs. We propose a cutoff value for the plasma acetaminophen concentration of 25 microg/mL at 60 minutes after administration to determine function of the reticular groove mechanism in lambs.

The effects of amniotic fluid on the histopathologic changes of exposed spinal cord in fetal sheep.

BACKGROUND: Experimental studies have shown that in myelomeningocele, the primary malformation is neural tissue damage resulting from exposure of neural tissue to amniotic fluid. In this study, the effects of amniotic fluid on histopathologic changes of exposed spinal cord in fetal sheep were evaluated. METHODS: In an experimental trial, 10 fetal sheep in two groups containing five subjects (group A) and five shams (group B) were studied. In the sheep at 90 - 100 days of gestation (term: 145 - 150 days) the lumbar skin was incised, paraspinal soft tissues were excised, laminectomy was performed at L2 - L4, and dura matter was opened. In group A, the dura matter was not dorsally closed and thus the spinal cord was left exposed to amniotic fluid, and in group B the skin was immediately closed. The lambs were delivered near term by cesarean section and were assessed clinically and morphologically. RESULTS: In group A, all lambs (n=5) had a complete or incomplete flaccid sensorimotor paraplegia and suffered from urine incontinence. Four lambs in this group were stool incontinent. In group B (n=4), only one lamb had paraparesis (P=0.048) and all lambs were urine and stool continent. In group A, all lambs had hypoplastic longitudinal muscles of the rectum but well- developed circular muscles. The anal sphincter muscles did not develop normally. In group B, all lambs had well-developed longitudinal and circular muscles and anal sphincter muscles developed normally (P=0.048). Histopathologic examination of the spinal cords showed edema, focal calcification, fibrosis, and capillary cell proliferation in group A, but in group B such changes were not seen. The number of ganglion cells was significantly higher in group B compared with group A (P<0.0005). CONCLUSION: Exposure of spinal cord to amniotic fluid causes structural neural tissue damage that can be prevented by fetal surgery through repairs of myelomeningocele.