Prediction model for 30-day morbidity after gynecological malignancy surgery

OBJECTIVE

The potential risk of postoperative morbidity is important for gynecologic cancer patients because it leads to delays in adjunctive therapy and additional costs. We aimed to develop a preoperative nomogram to predict 30-day morbidity after gynecological cancer surgery.

METHODS

Between 2005 and 2015, 533 consecutive patients with elective gynecological cancer surgery in our center were reviewed. Of those patients, 373 and 160 patients were assigned to the model development or validation cohort, respectively. To investigate independent predictors of 30-day morbidity, a multivariate Cox regression model with backward stepwise elimination was utilized. A nomogram based on this Cox model was developed and externally validated. Its performance was assessed using the concordance index and a calibration curve.

RESULTS

Ninety-seven (18.2%) patients had at least one postoperative complication within 30 days after surgery. After bootstrap resampling, the final model indicated age, operating time, and serum albumin level as statistically significant predictors of postoperative morbidity. The bootstrap-corrected concordance index of the nomogram incorporating these three predictors was 0.656 (95% CI, 0.608-0.723). In the validation cohort, the nomogram showed fair discrimination [concordance index: 0.674 (95% CI = 0.619-0.732] and good calibration (P = 0.614; Hosmer-Lemeshow test).

CONCLUSION

The 30-day morbidity after gynecologic cancer surgery could be predicted according to age, operation time, and serum albumin level. After further validation using an independent dataset, the constructed nomogram could be valuable for predicting operative risk in individual patients.

Stratification of risk groups according to survival after recurrence in endometrial cancer patients

To identify prognostic factors for overall survival after recurrence (OSr) in endometrioid endometrial cancer (EC) patients and categorize patient subgroups that predict outcomes using these variables.Consecutive patients with recurrent endometrioid EC seen in our institution from 1989 to 2013 were retrospectively reviewed. Cox regression models were used to identify the clinicopathological factors associated with OSr. By summing scores proportionate to the hazard ratio (HR) for each significant variable, we stratified patients into 3 risk groups.Enrolled patients (n = 108) had a median time to recurrence of 15 (range, 3-163) months after initial treatment and a median OSr of 22 (range, 1-207) months. Twenty patients (18.5%) had locoregional recurrence, and 88 (81.5%) distant. One hundred three patients underwent salvage therapy; 51 (47.2%) received chemotherapy only, 22 (20.3%) received radiotherapy either alone or combined with chemotherapy, and 29 (26.9%) underwent salvage cytoreductive surgery. Multivariate regression analysis revealed that time to relapse after initial treatment, cancer antigen-125 level at recurrence, and the number of recurrent lesions were independent predictors of OSr. Incorporating these factors, we stratified patients into low-risk (n = 19), intermediate-risk (n = 43), and high-risk (n = 46) groups. The likelihood of cancer-specific death was higher in both the high-risk (HR = 8.948, 95% confidence interval [CI] = 3.498-22.893, P < .001) and the intermediate-risk (HR = 2.619, 95% CI = 1.002-6.850, P = .05) groups compared with the low-risk group.Incorporating 3 variables, recurrent endometrioid EC patients with a broad spectrum of outcome could be stratified according to OSr. This model may help predict outcomes in recurrent EC patients.

Comparison of Loop Electrosurgical Excision Procedure Using a Ring-Shaped Loop Versus a Right-Angled Triangular Loop

OBJECTIVE: To compare the resection margin (RM) status and postoperative severe hemorrhage using different loop electrosurgical excision procedure (LEEP) techniques for cervical intraepithelial neoplasia (CIN) 2/3 treatment. STUDY DESIGN: We retrospectively reviewed 278 patients who underwent LEEPs for CIN 2/3 treatment at our institute between 2005–2014. In type A surgery (N=148), a ring-shaped loop was used. If the first pass failed to remove the entire lesion, separate loop excisions for the intracervical portion were performed. In type B surgery (N=130), a right-angled triangular loop in a single pass was used. Surgical outcomes and postoperative severe hemorrhage were compared between the two groups. Logistic regression analysis was performed to identify the independent predictors of RM status. RESULTS: The mean LEEP depth was larger after type A surgery (2.2 vs. 2.0 cm, respectively; p=0.04). Type B surgery showed lower rate of 30-day postoperative hemorrhage (13.8% vs. 26.4%, p<0.05) and higher rate of negative RM (68.9% vs. 82.3%, p<0.05). Multivariate analysis identified the surgery type (p=0.01, OR=0.45 [0.24–0.83]) and a postoperative pathological diagnosis of CIN3 (p=0.01, OR=2.53 [1.22–5.26]) as independent risk factors for positive RM. CONCLUSION: LEEPs using a right-angled triangular loop could reduce positive RMs.

Bilateral salpingectomy can reduce the risk of ovarian cancer in the general population: A meta-analysis

BACKGROUND

The results of recent studies have suggested that high-grade serous ovarian cancer predominantly arises within the fallopian tubes. The reduction of ovarian cancer (OC) risk in women with a history of bilateral salpingectomy (BS) has been reported. We performed a meta-analysis to determine the impact of BS in preventing OC in the general population.

METHODS

We searched the PubMed, MEDLINE, and EMBASE databases and CENTRAL in the Cochrane Library for all English-language articles published up to January 2015, using the key words 'ovarian cancer' and 'bilateral salpingectomy.' Odds ratios (ORs) and their 95% confidence intervals (95% CIs) were calculated by standard meta-analysis techniques.

RESULTS

Of the 77 studies retrieved, three were included in this meta-analysis, including one cohort study and two population-based case-control studies with 3509 patients who underwent BS and 5,655,702 controls who did not undergo salpingectomy. Over the combined study period, 29 of the 3509 BS patients developed OC compared with 44,006 of the 5,655,702 without salpingectomy. The meta-analysis results based on the fixed effects model revealed a significant decrease in the risk of OC occurrence in the patients who underwent BS relative to the controls (OR=0.51, 95% CI 0.35-0.75, I(2)=0%). This pattern was also observed in subgroup analysis for the study type.

CONCLUSIONS

Our results suggest that removal of the fallopian tubes is an effective measure to reduce OC risk in the general population. Therefore, prophylactic bilateral salpingectomy should be considered for women who require hysterectomy with benign indications or sterilisation procedures.

Transvaginal Versus Conventional Laparoscopy for Ovarian Dermoid Cysts: A Matched Cohort Study

OBJECTIVE

To compare transvaginal versus conventional laparoscopy for dermoid cysts.

STUDY DESIGN

We retrospectively analyzed all con-secutive patients with dermoid cysts who underwent transvaginal (n = 219) or conventional (n = 245) laparoscopy from 2007-2013 at our institution. Each group of patients was matched (1:1 ratio) for age, body mass index, previous surgical history, cyst diameter, bilaterality, and cystectomy/oophorectomy. Surgical outcomes were compared between the 2 groups.

RESULTS

Overall, 165 pairs were matched. Operating times (expressed as median [interquartile range]) (64 [49-88] vs. 70 [54-93] minutes, p = 0.011), estimated blood loss (100 [70-200] vs. 90 [70-130] mL, p = 0.245), and postoperative hospital stay (1 [1-1] vs. 1 [1-2] days, p = 0.029) were similar between groups. Postsurgical pain scores after 3 (expressed as mean [standard deviation]) (3.52 [1.27] vs. 3.94 [1.05], p < 0.001), 8 (2.88 [0.92] vs. 3.60 [1.01], p < 0.001), and 16 (2.81 [0.97] vs. 3.38 [0.93], p = 0.005) hours were similar but statistically significant between groups. Perioperative complications occurred in 2 and 4 patients in the transvaginal and conventional groups, respectively.

CONCLUSION

Transvaginal laparoscopy shows feasibility and efficacy similar to those of conventional laparoscopy for management of dermoid cysts.

The impact of positive peritoneal cytology on prognosis in patients with cervical cancer: a meta-analysis

BACKGROUND

The impact of positive peritoneal cytology on the prognosis of cervical cancer is controversial. Thus, we performed a meta-analysis to determine its impact on recurrence, and to investigate correlations between abnormal cytology and/or lymph node metastasis in cervical cancer.

METHODS

A systematic literature review was conducted through July 2014. Odds ratios (ORs) and their 95% confidence intervals (95% CIs) were calculated by standard meta-analysis techniques with the fixed-effects models, if there was no significant statistical heterogeneity across studies by using I(2).

RESULTS

Of 303 studies retrieved, 6 were included in the meta-analysis. These six case-control observational studies included 1360 cervical cancer patients who showed negative peritoneal cytology and 64 who showed positive peritoneal cytology. Over the combined study period, 20 of 45 in the positive peritoneal cytology group experienced recurrence, whereas 88 of 539 controls did. The meta-analysis based on the fixed-effects model indicated a significant increase in the risk of recurrence in the positive peritoneal cytology group relative to the control group (OR: 4.47; 95% CI: 2.33-8.58, P<0.001, I(2)=0.0%). Moreover, the results of our meta-analysis suggested that the positive peritoneal cytology group displayed more lymph node metastasis than the negative peritoneal cytology group (OR: 3.73; 95% CI: 2.13-6.53, P<0.001, I(2)=0.0%).

CONCLUSIONS

Although based mainly on retrospective observational studies, our meta-analysis indicates that abnormal peritoneal cytology may be strongly associated with poor prognosis in patients with cervical cancer. Future research should verify this relationship through prospective observational studies over a longer term.

Nomogram for predicting incomplete cytoreduction in advanced ovarian cancer patients

OBJECTIVE

Accurately predicting cytoreducibility in advanced-ovarian cancer is needed to establish preoperative plans, consider neoadjuvant chemotherapy, and improve clinical trial protocols. We aimed to develop a positron-emission tomography/computed tomography-based nomogram for predicting incomplete cytoreduction in advanced-ovarian cancer patients.

METHODS

Between 2006 and 2012, 343 consecutive advanced-ovarian cancer patients underwent positron-emission tomography/computed tomography before primary cytoreduction: 240 and 103 patients were assigned to the model development or validation cohort, respectively. After reviewing the detailed surgical documentation, incomplete cytoreduction was defined as a remaining gross residual tumor. We evaluated each individual surgeon's surgical aggressiveness index (number of high-complex surgeries/total number of surgeries). Possible predictors, including surgical aggressiveness index and positron-emission tomography/computed tomography features, were analyzed using logistic regression modeling. A nomogram based on this model was developed and externally validated.

RESULTS

Complete cytoreduction was achieved in 120 patients (35%). Surgical aggressiveness index and five positron-emission tomography/computed tomography features were independent predictors of incomplete cytoreduction. Our nomogram predicted incomplete cytoreduction by incorporating these variables and demonstrated good predictive accuracy (concordance index = 0.881; 95% CI = 0.838-0.923). The predictive accuracy of our validation cohort was also good (concordance index = 0.881; 95% CI = 0.790-0.932) and the predicted probability was close to the actual observed outcome. Our model demonstrated good performance across surgeons with varying degrees of surgical aggressiveness.

CONCLUSION

We have developed and validated a nomogram for predicting incomplete cytoreduction in advanced-ovarian cancer patients which may help stratify patients for clinical trials, establish meticulous preoperative plans, and determine if neoadjuvant chemotherapy is warranted.

A Long-term follow-up study of 91 cases with ovarian granulosa cell tumors

AIM

To evaluate the prognostic factors of ovarian granulosa cell tumors (GCTs) and treatment outcomes in recurrent GCT cases.

PATIENTS AND METHODS

We retrospectively reviewed 91 patients with GCT who were treated in two tertiary Centers between 1989 and 2011.

RESULTS

Eighty patients had stage I tumors, five had stage II, and six had stage III. There were 15 cases of recurrence with a median follow-up time of 58 (3-254) months. Multivariate analysis identified greater tumor size and postoperative residual tumor as independent risk factors for recurrence. Twelve patients underwent secondary surgery at first recurrence. At a median follow-up of 50 (4-185) months from first recurrence, the 5-year survival was 60% for patients with and 100% for those without residual tumor after secondary surgery, respectively (p=0.018, log-rank test).

CONCLUSION

Complete cytoreduction is an important prognostic factor for recurrent cases as well as initial treatment of GCT.

Preoperative risk assessment model for identification of lymph node metastasis in early cervical cancer

5600

Background: The aim of this study was to develop a preoperative risk prediction model for lymph node metastasis in patients with early cervical cancer. Methods: The medical records of 504 patients with early cervical cancer who underwent hysterectomy and pelvic/paraaortic lymphadenectomy between 2007and 2012 in our center were retrospectively reviewed. According to the order of surgery performed, data between 2007 and 2010 were allocated to a model development cohort (n=314), and data between 2011 and 2012 were allocated to an external validation cohort (n=190). By using preoperative clinicopathologic data, magnetic resonance imaging (MRI) data, and positron emission/computed tomography (PET/CT) data, a multivariate logistic model was created. Based on this model, predictive nomogram was developed and externally validated. Results: Age, tumor size measured by MRI, and lymph node metastasis on PET/CT were found to be independent risk factors for nodal metastasis. Developed nomogram incorporating these three predictors showed good discrimination and calibration, with a bootstrap-adjusted concordance index of 0.772. Also, the validation set showed good discrimination with a bootstrap-adjusted concordance index of 0.783. Conclusions: We have developed a robust model to predict lymph node metastasis in patients with early cervical cancer. This new tool may be useful to clinicians and patients when deciding lymphadenectomy and maybe useful in designing clinical trials. [Table: see text]

Human amnion-derived mesenchymal stem cells are a potential source for uterine stem cell therapy

OBJECTIVES

Human amnion is an easy-to-obtain novel source of human mesenchymal stem cells, which poses little or no ethical dilemmas. We have previously shown that human amnion-derived mesenchymal (HAM) cells exhibit certain mesenchymal stem cell-like characteristics with respect to expression of stem cell markers and differentiation potentials.

MATERIALS AND METHODS

In this study, we further characterized HAM cells' potential for in vivo therapeutic application.

RESULTS

Flow cytometric analyses of HAM cells show that they express several stem cell-related cell surface markers, including CD90, CD105, CD59, CD49d, CD44 and HLA-ABC, but not CD45, CD34, CD31, CD106 or HLA-DR. HAM cells at the 10th passage showed normal karyotype. More interestingly, the AbdB-like HOXA genes HOXA9, HOXA10 and HOXA11 that are expressed in the mesenchyme of the developing female reproductive tract and pregnant uteri are also expressed in HAM cells, suggesting similarities between these two mesenchymal cell types. Progesterone receptor is also highly expressed in HAM cells and expression of genes or proteins in HAM cells could be manipulated with the aid of lentivirus technology or cell-permeable peptides. To test potentials of HAM cells for in vivo application, we introduced enhanced green fluorescence protein (EGFP)-expressing HAM cells to mice by intrauterine infusion (into uteri) or by intravenous injection (into the circulation). Presence of EGFP-expressing cells within the uterine mesenchyme after intrauterine infusion or in lungs after intravenous injection was noted within 1-4 weeks.

CONCLUSIONS

Collectively, these results suggest that HAM cells are a potential source of mesenchymal stem cells with therapeutic potential.

A new diterpenoid alkaloid from Aconitum jaluense

A new diterpenoid alkaloid, jaluenine (1), has been isolated from the roots of Aconitum jaluense. The structure of jaluenine was determined by spectroscopic methods including two dimensional NMR (1H-1H COSY, HMQC, HMBC, NOESY).

Antiobese and hypolipidemic effects of platycodin saponins in diet-induced obese rats: evidences for lipase inhibition and calorie intake restriction

OBJECTIVE

To investigate how and to what extent platycodin saponin (PS) from Platycodi Radix exerts a favorable influence on obesity and hyperlipidemia.

DESIGN

Sprague-Dawley rats were fed with a high fat (HF) diet for 4 weeks and then the animals were treated with 35 or 70 mg / kg of PS for another 4 weeks. Changes in body weight and daily calorie intake were measured regularly during the experimental period and the degree of linear correlation for the above two variables was further analyzed. The in vitro lipase inhibition of each PS compound and the in vivo fecal lipid excretion were examined in hope of revealing their relationship. The concentrations of hepatic triglyceride and cholesterol in serum.

RESULTS

The body weight reduction (13+/-4% vs HF control, P<0.05) by PS administration was highly correlated to the food intake restriction (Pearson's linear coefficient r=0.752, P<0.005). The in vitro inhibition of lipase by each isolated compound and mixture of PS were virtually identical. Consequently, the fecal TG excretion was increased by 2.1-3.2 folds depending on the dose of PS. The serum TG and LDL-cholesterol concentrations were decreased without noticeable changes in HDL-cholesterol levels. Concomitantly, the contents of the hepatic TG, cholesterol, and the liver surface fat pads were decreased in ubiquity, but no noticeable biochemical abnormalities or histological tissue damages were observed.

CONCLUSIONS

The administration of PS produced profound effects on the control of obesity and lipid metabolism, which resulted in LDL-cholesterol reduction. PS also caused a remarkable reduction in calorie intake, which was highly correlated to the body weight loss. These results suggest that PS has a greater role in anti-obesity, hypolipidemia, and liver protection than previously thought. Hence, PS could be a potential therapeutic alternative in the treatment of obesity and hyperlipidemia.

The prenatal diagnosis of cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) by mutation analysis

Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is an important cause of hereditary stroke. Mutations in the Notch3 gene are clearly causally linked to this progressive vascular disorder. Cerebral ischemic attacks, cognitive decline, strokes, and vascular dementia constitute the major manifestations of this disorder. This report details the prenatal detection of a Notch3 mutation in the fetus of a couple where the father had a known mutation in this gene. This is the first report of a prenatal diagnosis of CADASIL, and another example of a serious, highly penetrant, and relentlessly progressive degenerative genetic disorder presenting decades after birth and for which prenatal diagnosis is an option.

Molecular cytogenetic characterization of multiple intrachromosomal rearrangements of chromosome 2q in a patient with Waardenburg's syndrome and other congenital defects

At 6 years of age, a boy with bilateral sensorineural deafness, lateral displacement of inner canthi, a bulbous nasal tip, synophrys, and cryptorchidism was clinically diagnosed as having Waardenburg's syndrome type I (WS-1). In addition, he had a lumbar spina bifida with hydrocephalus shunted on the second day of life and severe mental retardation with a head circumference at the fifth percentile. Neither parent showed signs of WS-1, and the family history was negative. Because of the WS-1 features, attention was focused on the PAX3 location in 2q, at which time a de novo paracentric inversion of 2q23-q37.1 was noted. Subsequent high-resolution chromosome analysis 8 years later indicated a complex rearrangement involving regions 2q31-q35 and 2q13-q21. Whole chromosome painting and high-resolution comparative genomic hybridization yielded negative results for any translocation, duplication, or deletion of any chromosome segments. Sequencing of the PAX3 gene yielded no detectable mutation. Fluorescent in situ hybridization (FISH) studies with human BAC clones revealed five breakpoints in chromosome 2q resulting in two paracentric inversions and one insertion, the karyotype being interpreted as 46,XY,der(2)inv(2)(q13q21)inv(2)(q21q24.2)ins(2)(q24.2q33q35). In this extremely rare chromosomal rearrangement, the FISH result showed a breakpoint at 2q35 being proximal to and without involvement of the PAX3 gene. While further studies continue, possible interpretations include involvement of a regulatory gene(s) for PAX 3 and other genes at the other breakpoints related causally to the spina bifida and mental retardation.

Crystallographic orientation of ZrB2-ZrC composites manufactured by the spark plasma sintering method

The crystallographic grain orientation of ZrB2-ZrC composites manufactured using a spark plasma sintering (SPS) method, a new sintering technique in development for poorly sinterable ceramic materials, was analysed by the scanning electron microscopy-electron backscattered diffraction (SEM-EBSD) method. Their crystallographic features have been compared with those of a conventionally sintered specimen using a pressureless sintering (PLS) method. In the composite sintered by PLS, (0001) planes of ZrB2 were orientated in the direction parallel to the specimen surface (RD) but (1010) and (2110) planes randomly orientated. In the case of SPS, (0001) planes of ZrB2 were orientated normal to the specimen surface (ND) and weakly to the RD. In both cases of PLS and SPS, ZrC grains had a randomly orientated grain structure. The distribution of grain boundary misorientation of PLS and SPS-processed composites showed the same tendency that high-angle boundaries were more prevalent than low-angle boundaries. But in the case of ZrC grains in the SPS sample, the proportion of CSL boundaries with low sigma value (3, 5, 7, 9, 11) was relatively larger.

Two inv dup(15) chromosomes in a woman with repeated abortions

A 40-year-old, phenotypically normal woman, with a history of two repeated abortions and no child, had two additional, small, bisatellited, and apparently metacentric chromosomes. Various banding and microsatellite analyses indicated that the additional chromosomes were inv dup(15)(q11q11) without the Prader-Willi/Angelman syndromes critical region, and therefore without phenotypic effects. Her father had a single, identical additional inv dup(15) chromosome. Her husband was chromosomally normal, but sperm analysis indicated a reduced motility and a reduced frequency of morphologically normal sperm. In view of these findings, it was deduced that the inv dup(15) chromosome in the father was transmitted in duplicate to the woman. Individuals with two additional inv dup(15) chromosomes in the literature were reviewed, and possible correlation of the two additional inv dup(15) chromosomes in the woman and her repeated abortions was discussed.

Immunohistochemical detection of tyrosine hydroxylase and concentrations of monoamines in the substantia nigra and hypothalamus of hereditary microphthalmic rats

We compared tyrosine hydroxylase immunoreactivity in the substantia nigra and hypothalamus of hereditary microphthalmic rats with that of normal rats. A considerable number of neuronal cell bodies expressing tyrosine hydroxylase were present in the substantia nigra of the microphthalmic mutant as well as normal rats. Neuronal cells positive for tyrosine hydroxylase in the hypothalamus were fewer than in the substantia nigra in both rats. The concentrations of monoamines (dopamine, noradrenaline, adrenaline, and serotonin) in the substantia nigra and hypothalamus in the microphthalmic mutant were approximately the same as those of normal rats, although the diurnal fluctuation of a few monoamines was observed in normal rats. These results suggest that the metabolic aspects of catecholamine in the substantia nigra and hypothalamus of the microphthalmic mutant rat do not markedly differ from those of normal rats.

Stability and structure of MgSiO3 perovskite to 2300-kilometer depth in Earth's mantle

Unexplained features have been observed seismically near the middle (approximately 1700-kilometer depth) and bottom of the Earth's lower mantle, and these could have important implications for the dynamics and evolution of the planet. (Mg,Fe)SiO3 perovskite is expected to be the dominant mineral in the deep mantle, but experimental results are discrepant regarding its stability and structure. Here we report in situ x-ray diffraction observations of (Mg,Fe)SiO3 perovskite at conditions (50 to 106 gigapascals, 1600 to 2400 kelvin) close to a mantle geotherm from three different starting materials, (Mg0.9Fe0.1)SiO enstatite, MgSiO3 glass, and an MgO+SiO2 mixture. Our results confirm the stability of (Mg,Fe)SiO3 perovskite to at least 2300-kilometer depth in the mantle. However, diffraction patterns above 83 gigapascals and 1700 kelvin (1900-kilometer depth) cannot presently rule out a possible transformation from Pbnm perovskite to one of three other possible perovskite structures with space group P2(1)/m, Pmmn, or P4(2)/nmc.

The post-spinel transformation in Mg2SiO4 and its relation to the 660-km seismic discontinuity

The 660-km seismic discontinuity in the Earth's mantle has long been identified with the transformation of (Mg,Fe)2SiO4 from gamma-spinel (ringwoodite) to (Mg,Fe)SiO3-perovskite and (Mg,Fe)O-magnesiowüstite. This has been based on experimental studies of materials quenched from high pressure and temperature, which have shown that the transformation is consistent with the seismically observed sharpness and the depth of the discontinuity at expected mantle temperatures. But the first in situ examination of this phase transformation in Mg2SiO4 using a multi-anvil press indicated that the transformation occurs at a pressure about 2 GPa lower than previously thought (equivalent to approximately 600 km depth) and hence that it may not be associated with the 660-km discontinuity. Here we report the results of an in situ study of Mg2SiO4 at pressures of 20-36 GPa using a combination of double-sided laser-heating and synchrotron X-ray diffraction in a diamond-anvil cell. The phase transformation from gamma-Mg2SiO4 to MgSiO3-perovskite and MgO (periclase) is readily observed in both the forward and reverse directions. In contrast to the in situ multi-anvil-press study, we find that the pressure and temperature of the post-spinel transformation in Mg2SiO4 is consistent with seismic observations for the 660-km discontinuity.

Determination of omeprazole in rat plasma by HPLC with column switching

A new high-performance liquid chromatographic method with column switching has been developed for the determination of omeprazole in plasma. The plasma samples were injected onto a Bondapak phenyl/corasil (37-50 microns) precolumn and polar plasma components were washed with 0.06 M borate buffer. After valve switching, the concentrated drug were eluted in the back-flush mode and separated on a mu-Bondapak C18 column with acetonitrile-phosphate buffer as the mobile phase. The method showed excellent precision, accuracy and speed with detection limit of 0.01 microgram/ml-1. Total analysis time per sample was less than 20 min and the coefficients of variation for intra and inter-assay were less than 5.63%. This method has been successfully applied to plasma samples from rats after oral administration of omeprazole.