The yield of diagnostic laparoscopy with peritoneal lavage in gastric adenocarcinoma: A retrospective cohort study.

INTRODUCTION: Diagnostic laparoscopy (DL) with peritoneal lavage has been adopted as a standard staging procedure for patients with gastric cancer (GC). Evaluation of the value of DL is important given ongoing improvements in diagnostic imaging and treatment. As contemporary data from European centres are sparse, this retrospective cohort study aimed to assess the yield of DL in patients with potentially curable gastric cancer, and to identify predictive factors for peritoneal metastases. METHODS: Patients with adenocarcinoma of the stomach, treated between January 2016 and December 2018, were identified from institutional databases of two high volume European Upper-GI centres. Patients who underwent a DL with peritoneal lavage for potentially curable disease after clinical staging with imaging (cT1-4N0-3M0) were included. The primary outcome was the proportion of patients with a positive DL, defined as macroscopic metastatic disease, positive peritoneal cytology washings (PC+) or locally irresectable disease. RESULTS: Some 80 of 327 included patients (24.5%) had a positive DL, excluding these patients from neoadjuvant treatment (66 of 327; 20.2%) and/or surgical resection (76 of 327; 23.2%). In 34 of 327 patients (10.3%), macroscopic metastatic disease was seen, with peritoneal deposits in 30 of these patients. Only 16 of 30 patients with peritoneal disease had positive cytology. Some 41 of 327 patients (12.5%) that underwent DL had PC+ in the absence of macroscopic metastases and five patients (1.5%) had an irresectable primary tumour. Diffuse type carcinoma had the highest risk of peritoneal dissemination, irrespective of cT and cN categories. CONCLUSION: The diagnostic yield of staging laparoscopy is high, changing the management in approximately one quarter of patients. DL should be considered in patients with diffuse type carcinoma irrespective of cT and cN categories.

Tumor-positive peritoneal cytology in patients with gastric cancer is associated with poor outcome: A nationwide study.

BACKGROUND: The clinical significance of tumor-positive peritoneal cytology (CYT+) in gastric cancer (GC) patients is unclear. This nationwide cohort study aimed to i) assess the frequency of cytological analysis at staging laparoscopy; ii) determine the prevalence of CYT+GC; and iii) compare overall survival (OS) in CYT+ patients versus those with (PM+) and those without (PM-) macroscopic peritoneal disease. METHODS: All patients diagnosed with cT1-4, cN0-2 and M0 or synchronous PM GC between 2016-2021 were identified in the Netherlands Cancer Registry database and linked to the nationwide pathology database. RESULTS: A total of 4397 patients was included, of which 40 % underwent cytological assessment following staging laparoscopy (863/1745). The prevalence of CYT+ was 8 %. A total of 69 patients had CYT+(1.6 %), 789 (17.9 %) had PM+ and 3539 (80.5 %) had PM- disease. Hazard ratio for OS in CYT+ versus PM+ was 0.86 (95 %CI 0.64-1.17, p-value=0.338), and in PM- versus PM+0.43 (95 %CI 0.38-0.49, p-value<0.001). No survival difference was found between systemic chemotherapy versus surgical resection in CYT+ patients. DISCUSSION: In this nationwide study, OS for gastric cancer patients with CYT+ was equally unfavorable as for those with PM+ and significantly worse as compared to those with PM-. The optimal treatment strategy has yet to be established.

Revisiting the Use of Normal Saline for Peritoneal Washing in Ovarian Cancer.

The omentum is the predominant site of ovarian cancer metastasis, but it is difficult to remove the omentum in its entirety. There is a critical need for effective approaches that minimize the risk of colonization of preserved omental tissues by occult cancer cells. Normal saline (0.9% sodium chloride) is commonly used to wash the peritoneal cavity during ovarian cancer surgery. The omentum has a prodigious ability to absorb fluid in the peritoneal cavity, but the impact of normal saline on the omentum is poorly understood. In this review article, we discuss why normal saline is not a biocompatible solution, drawing insights from clinical investigations of normal saline in fluid resuscitation and from the cytopathologic evaluation of peritoneal washings. We integrate these insights with the unique biology of the omentum and omental metastasis, highlighting the importance of considering the absorptive ability of the omentum when administering agents into the peritoneal cavity. Furthermore, we describe insights from preclinical studies regarding the mechanisms by which normal saline might render the omentum conducive for colonization by cancer cells. Importantly, we discuss the possibility that the risk of colonization of preserved omental tissues might be minimized by using balanced crystalloid solutions for peritoneal washing.

Predictive impacts of peritoneal washing cytology for surgical resection-intended pancreatic cancer cases: Establishment of planned staging laparoscopy criteria.

BACKGROUND: Staging laparoscopy (SL) has been advocated for pancreatic cancer, mainly to evaluate the peritoneal washing cytology (CY) status, which seems to impact the prognosis of pancreatic cancer. To establish an optimal treatment strategy for CY positive (CY+) pancreatic cancer cases, real-world clinical data about CY status-depending surgical outcomes should be accumulated. METHODS: Peritoneal washing samples were collected from 183 consecutive patients who could be classified as either resectable or borderline resectable (BR) pancreatic cancer between January 2012 and December 2020. Correlations between the CY status and other clinicopathological parameters with the recurrence patterns and survival outcomes were examined. In addition, we analyzed several risk factors for the CY+ status and attempted to identify the patient population that may benefit most from SL. RESULTS: A total of 24 of the 183 patients were CY+. Peritoneal recurrence occurred more frequently in CY+ cases than in CY- cases (29% vs. 6%, p < .001) and median survival time after surgery was significantly shorter in CY+ cases than in CY- cases (28.5 months vs. 67.5 months; p < .001). In detail, almost all CY+ patients among curative resection-intended cases had either elevated preoperative serum CA19-9 levels (≥250 U/mL) or DUPAN-2 levels (≥150 U/mL). Significant predictive factors of CY positivity were BR status (p = .028) and serum CA19-9 level exceeding 250 U/mL (p = .008). CONCLUSION: CY status was identified as an independent prognostic factor, and SL examination should be recommended, especially for patients with risk factors for CY positivity, such as BR cancer and elevated serum CA19-9 levels.

Efficacy of staging laparoscopy for resectable pancreatic cancer on imaging and the therapeutic effect of systemic chemotherapy for positive peritoneal cytology.

BACKGROUND: The frequency and prognosis of positive peritoneal washing cytology (CY1) in resectable pancreatic ductal adenocarcinoma (R-PDAC) remains unclear. The objective of this study was to identify the clinical implications of CY1 in R-PDAC and staging laparoscopy (SL). METHODS: We retrospectively analyzed 115 consecutive patients with R-PDAC who underwent SL between 2018 and 2022. Patients with negative cytology (CY0) received radical surgery after neoadjuvant chemotherapy, while CY1 patients received systemic chemotherapy and were continuously evaluated for cytology. RESULTS: Of the 115 patients, 84 had no distant metastatic factors, 22 had only CY1, and nine had distant metastasis. Multivariate logistic regression revealed that larger tumor size was an independent predictor of the presence of any distant metastatic factor (OR: 6.30, p = .002). Patients with CY1 showed a significantly better prognosis than patients with distant metastasis (MST: 24.6 vs. 18.9 months, p = .040). A total of 11 CY1 patients were successfully converted to CY-negative, and seven underwent conversion surgery. There was no significant difference in overall survival between patients with CY0 and those converted to CY-negative. CONCLUSION: SL is effective even for R-PDAC. The prognosis of CY1 patients converted to CY-negative is expected to be similar to that of CY0 patients.

Failure of peritoneal lavage to prevent operative site infection and peritoneal tumor recurrence in pancreatic surgery.

BACKGROUND: Although intraoperative peritoneal lavage often is performed routinely with the aim of reducing peritoneal contamination, evidence of lavage benefit in elective pancreatic surgery is limited. METHODS: We retrospectively classified patients who had undergone pancreatic surgery to groups given or not given peritoneal lavage, then comparing clinical results. This saline lavage was performed at the end of the operation. The primary endpoint was rate of surgical site infection. Frequency of peritoneal recurrence also was evaluated. RESULTS: Among all 104 patients in the study, incidence of infectious complications in the lavage group (n = 65) was significantly higher than in the non-lavage group (n = 39; 35% vs. 15%, P = 0.041), while incidences of postoperative complications overall and surgical site infection did not differ between lavage (80% and 26%) and non-lavage groups (67% and 10%, P = 0.162 and 0.076, respectively). Among 63 patients undergoing pancratoduodenectomy, frequencies of positive bacterial cultures of drainage fluids on postoperative days 1 and 3 were greater in the non-lavage group (P < 0.001 and P = 0.012), but surgical site infection was significantly more frequent in the lavage group (P = 0.043). Among patients with pancreatic and biliary cancers, lavage did not affect frequency of peritoneal recurrence. CONCLUSION: Intraoperative lavage did not prevent surgical site infection or peritoneal recurrence of pancreatobiliary cancer.

Techniques of staging laparoscopy and peritoneal fluid assessment in gastric cancer: a systematic review.

BACKGROUND: Staging laparoscopy for gastric cancer is recommended to assess the tumor's locoregional extension and exclude peritoneal disease. As there is no consensus on optimizing the procedure's diagnostic accuracy, we aimed to systematically review the literature on operative techniques, followed by peritoneal lavage fluid assessment in gastric cancer patients. Specifically, we sought to indicate the most common characteristics of the procedure and cytological evaluation. METHODS: This study was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA). The protocol for this systematic review was registered on PROSPERO database (CRD: 42022306746). On September 2022, a search was carried out using Embase, Medline ALL, Cochrane Central Register of Controlled Trials, and Web of Science Core Collection. RESULTS: The search identified 1632 studies on staging laparoscopy and 2190 studies on peritoneal fluid assessment. Some 212 studies were included. Open Hasson was the method of choice in accessing the peritoneal cavity in 65% of the studies, followed by establishing a pneumoperitoneum at 10-12 mmHg in 52% of reports. Most frequently, the patient was positioned supine (70%), while a 30° scope and three ports were used to assess the peritoneal cavity clockwise (72%, 77%, and 85%, respectively). Right and left upper abdomen quadrants were the predominant area of laparoscopic exploration (both 65%), followed by the primary tumor region (54%), liver and pelvis (both 30%), and small bowel and spleen (19% and 17%, respectively). Regions of peritoneal lavage and aspiration were limited to the pelvis (50%), followed by right and left upper abdomen quadrants (37.5% and 50%, respectively). No studies compared different methods of operative techniques or analysis of ascites/fluid. CONCLUSIONS: This study indicates a high heterogeneity in the technique of staging laparoscopy and peritoneal fluid assessment in gastric cancer patients. Further research and initiatives to reach a consensus on the standardization of the procedure are warranted.

LC-1000 flow cytometry system complements intraoperative peritoneal cytology for pancreatic and biliary tract cancer.

BACKGROUND: The exfoliative cell analyzer, LC-1000, is medical device that utilizes the principles of flow cytometry, and might provide digital diagnostic information for cytology using a different approach from conventional cytomorphology. In this study, wae examined the usefulness of the LC-1000 as a diagnostic support system for intraoperative peritoneal lavage cytology and its prognostic impact for pancreatic (PC) and biliary tract cancer (BTC). METHODS: Patients with PC and BTC who underwent surgical treatment were included. First, we identified useful indicators of LC-1000 and established cutoff values to discriminate positive cytology. Next, we verified the validity of these cutoff values. RESULTS: In the test set (n = 48), of the LC-1000 indicators examined, only MR-CPIx was significantly different between the negative and positive cytology groups, yielding a cutoff value of 0.86. In the validation set (n = 52), the sensitivity, specificity, positive and negative predictive value of the LC-1000 for cytology results was 1.0, 0.49, 0.11 and 1.0, respectively. In patients who had undergone radical resection, recurrence-free survival rate was significantly higher in the LC-1000 negative group than in the positive group in PC, but not in BTC. CONCLUSION: The LC-1000 was useful as digital support system for peritoneal cytology, and it might have potential as a prognostic factor for PC.

The role of peritoneal lavage in benign gynecologic laparoscopic surgery.

OBJECTIVE: Laparoscopic surgery offers many advantages compared to invasive surgery but one of the main problems is postoperative pain, partially resulting from the peritoneal inflammatory process mediated by inflammatory cytokines. The rationale of this study is that intraperitoneal washing could remove inflammatory mediators that are the cause of postoperative pain and could help in the removal of CO2 from the abdominal cavity. This article aims to analyze the effects of peritoneal lavage in the reduction of postoperative shoulder pain. PATIENTS AND METHODS: 277 patients enrolled to undergo laparoscopic gynecologic surgery were included in the study. Women are randomized into two groups, according to the use or non-use of peritoneal lavage with saline solution at the end of laparoscopic gynecological major procedures. RESULTS: Data show that the peritoneal lavage can significantly reduce postoperative pain in the first 36 hours after surgery, as well as patients' requests for analgesics: during the first 3 postoperative days, requests for paracetamol were lower in the YW (Yes Washing) group than the NW (No Washing) group (77 vs. 101; p<0.05); similar results are obtained considering ketorolac administration (62 vs. 71; p<0.05). CONCLUSIONS: Peritoneal lavage after gynecological laparoscopic procedures may be effective in the reduction of postoperative pain and use of analgesics.

Evaluation of peritoneal Carcinoembryonic Antigen as a survival prognostic factor in gastric cancer patients: a single western center experience.

The aim of this study is to define the importance of peritoneal CEA (pCEA) as a prognostic factor of overall survival (OS) and disease-free survival (DFS) in gastric cancer (GC) patients surgically treated with a curative intent In our department. A total of 64 patients affected by gastric cancer with intraoperatively measurement of CEA on peritoneal lavage were enrolled in the study. Patients were divided into two groups: (A) the peritoneal lavage CEA ( -) with CEA < 0.5 ng/ml and (B) the peritoneal lavage CEA ( +) with CEA ≥ 0.5 ng/ml. Then we analyzed OS and DFS of the two groups correlating them to others clinico-pathological features. Furthermore, we investigated the correlation between pCEA and peritoneal cytology. We demonstrated a strong significant difference in OS and in DFS in CEA ( +) patients. We emphasized that pCEA had a strong survival impact, in both OS and DFS, in selected patients affected by diffuse histotype GC (p = 0.0048 and p = 0.0030 respectively), stage III (p = 0.015 and p = 0.021, respectively) and distal gastric cancer (p = 0.0036 and p = 0.0017, respectively). There is a strong need to recognize prognostic factors that can help clinicians to stratify patients at high risk to develop post-surgical recurrences and moreover to recognize who could benefit from an aggressive surgical treatment of cytoreductive surgery and intra-peritoneal chemotherapy.pCEA is a good predictor of survival in advanced gastric cancer and could discriminate which patients need a more accurate follow-up program and an intensive therapeutic strategy.

Diagnostic Peritoneal Aspiration or Lavage in Stratified Groups of Hypotensive Blunt Trauma Patients.

BACKGROUND: Some reports suggest Diagnostic peritoneal aspiration (DPA) or lavage (DPL) may better select which hypotensive blunt trauma patients (BTPs) require operation, compared to ultrasonography. However, whether both moderately hypotensive (systolic blood pressure [SBP] < 90 mmHg) and severely hypotensive (SBP < 70 mmHg) patients benefit from DPA/DPL is unclear. We hypothesized DPA/DPL used within the first hour increases risk of death for severely vs moderately hypotensive BTPs. METHODS: The 2017-2019 Trauma Quality Improvement Program database was queried for BTPs ≥ 18 years old with hypotension upon arrival. We compared moderately and severely hypotensive groups. A multivariable logistic regression analysis was performed controlling for age, comorbidities, emergent operation, blood transfusions, and injury profile. RESULTS: From 134 hypotensive patients undergoing DPA/DPL, 66 (49.3%) had severe hypotension. Patients in both groups underwent an emergent operation (43.9% vs 58.8%, P = .09) in a similar amount of time (median, 42-min vs 54-min, P = .11). Compared to the moderately hypotensive group, severely hypotensive patients had a higher rate and associated risk of death (84.8% vs 50.0%, P < .001) (OR 5.40, CI 2.07-14.11, P < .001). The strongest independent risk factor for death was age ≥ 65 (OR 24.81, CI 4.06-151.62, P < .001). DISCUSSION: Among all BTPs undergoing DPA/DPL within the first hour of arrival, an over 5-fold increased risk of death for patients with severe hypotension was demonstrated. As such, DPA/DPL within this group should be used with caution, particularly for older patients, as they may be better served by immediate surgeries. Future prospective research is needed to confirm these findings and elucidate the ideal DPA/DPL population in the modern era of ultrasonography.

Laparoscopic lavage for Hinchey III perforated diverticulitis: factors for treatment failure in two randomized clinical trials.

BACKGROUND: The Scandinavian Diverticulitis (SCANDIV) trial and the LOLA arm of the LADIES trial randomized patients with Hinchey III perforated diverticulitis to laparoscopic peritoneal lavage or sigmoid resection. The aim of this analysis was to identify risk factors for treatment failure in patients with Hinchey III perforated diverticulitis. METHODS: This was a post hoc analysis of the SCANDIV trial and LOLA arm. Treatment failure was defined as morbidity requiring general anaesthesia (Clavien-Dindo grade IIIb or higher) within 90 days. Age, sex, BMI, ASA fitness grade, smoking status, previous episodes of diverticulitis, previous abdominal surgery, time to surgery, and surgical competence were all tested in univariable and multivariable logistic regression analyses using an interaction variable. RESULTS: The pooled analysis included 222 patients randomized to laparoscopic lavage and primary resection (116 and 106 patients respectively). Univariable analysis found ASA grade to be associated with advanced morbidity in both groups, and the following factors in the laparoscopic lavage group: smoking, corticosteroid use, and BMI. Significant factors for laparoscopic lavage morbidity in multivariable analysis were smoking (OR 7.05, 95 per cent c.i. 2.07 to 23.98; P = 0.002) and corticosteroid use (OR 6.02, 1.54 to 23.51; P = 0.010). CONCLUSION: Active smoking status and corticosteroid use were risk factors for laparoscopic lavage treatment failure (advanced morbidity) in patients with perforated diverticulitis.

Clinical Evaluation of Continuous Renal Replacement Therapy Combined with Peritoneal Lavage for Severe Acute Pancreatitis: A Retrospective Cohort Study.

BACKGROUND We aimed to investigate the clinical efficacy of continuous renal replacement therapy (CRRT) in combination with peritoneal lavage for the treatment of severe acute pancreatitis. MATERIAL AND METHODS We retrospectively reviewed data from 52 patients with severe acute pancreatitis between January 2014 and December 2021 at Jiangyin People's Hospital. The patients were divided into 2 groups: CRRT (n=26) and CRRT in combination with peritoneal lavage (n=26). The following results and outcomes were retrospectively compared: procalcitonin, interleukin-6, and C-reactive protein levels, duration of systemic inflammatory response, Acute Physiology and Chronic Health Evaluation II (APACHE II) scores, abdominal distention relief time, abdominal pain relief time, length of intensive care unit stay, length of hospital stay, inpatient hospital costs, incidence of complications, and mortality. RESULTS There were significant differences in interleukin-6 and procalcitonin levels and APACHE-II scores after 3 and 7 days of treatment. The duration of systemic inflammatory response, abdominal distention relief time, abdominal pain relief time, length of intensive care unit stay, and length of hospital stay were considerably shorter in the combination group than in the CRRT group (P<0.01). Inpatient hospital costs were significantly lower in the combination group than in the CRRT group (P<0.01). However, incidence of complications and mortality showed no significant differences between the 2 groups. CONCLUSIONS CRRT combined with peritoneal lavage is an important adjuvant therapy in the early stages of acute severe acute pancreatitis and has better clinical efficacy than CRRT alone.

Accurate and Rapid Detection of Peritoneal Metastasis from Gastric Cancer by AI-Assisted Stimulated Raman Molecular Cytology.

Peritoneal metastasis (PM) is the mostcommon form of distant metastasis and one of the leading causes of death in gastriccancer (GC). For locally advanced GC, clinical guidelines recommend peritoneal lavage cytology for intraoperative PM detection. Unfortunately, current peritoneal lavage cytology is limited by low sensitivity (<60%). Here the authors established the stimulated Raman molecular cytology (SRMC), a chemical microscopy-based intelligent cytology. The authors firstly imaged 53 951 exfoliated cells in ascites obtained from 80 GC patients (27 PM positive, 53 PM negative). Then, the authors revealed 12 single cell features of morphology and composition that are significantly different between PM positive and negative specimens, including cellular area, lipid protein ratio, etc. Importantly, the authors developed a single cell phenotyping algorithm to further transform the above raw features to feature matrix. Such matrix is crucial to identify the significant marker cell cluster, the divergence of which is finally used to differentiate the PM positive and negative. Compared with histopathology, the gold standard of PM detection, their SRMC method could reach 81.5% sensitivity, 84.9% specificity, and the AUC of 0.85, within 20 minutes for each patient. Together, their SRMC method shows great potential for accurate and rapid detection of PM from GC.

Long-term adjuvant chemotherapy after resection for pancreatic cancer patients with positive peritoneal lavage cytology.

PURPOSE: The significance of resection for pancreatic cancer with positive peritoneal lavage cytology (CY +) remains controversial, and the lack of evidence concerning adjuvant chemotherapy (AC) in these patients remains an issue. The aim of the present study was to investigate the prognostic impacts of AC and its duration on the survival outcome in patients with CY + pancreatic cancer. METHODS: A total of 482 patients with pancreatic cancer who underwent pancreatectomy between 2006 and 2017 were retrospectively analyzed. The overall survival (OS) was compared among the patients with CY + tumors according to the duration of AC. RESULTS: Among the resected patients, 37 (7.7%) had CY + tumors: 13 received AC for > 6 months, 15 received AC for ≤ 6 months and 9 did not receive AC. The OS of 13 patients with resected CY + tumors who received AC for > 6 months was comparable to that of 445 patients with resected CY- tumors (median survival time 43.0 vs. 33.6 months, P = 0.791), and was significantly better than that of 15 patients with resected CY + tumors who received AC for ≤ 6 months (vs. 16.6 months, P = 0.017). The duration of AC (> 6 months) was an independent prognostic factor in patients with resected CY + tumors (hazard ratio 3.29, P = 0.005). CONCLUSION: Long-term AC (> 6 months) may improve postoperative survival in pancreatic cancer patients with CY + tumors.

Tumor DNA in Peritoneal Lavage as a Novel Biomarker for Predicting Peritoneal Recurrence in Patients With Gastric Cancer.

BACKGROUND: Peritoneal lavage cytology positivity (CY1) has been identified as a prognostic factor for distant metastases that is equivalent to peritoneal dissemination in Japan. Peritoneal lavage cytology is usually diagnosed by microscopic findings; a diagnostic procedure using a liquid biopsy (LB) technique has not yet been established. PATIENTS AND METHODS: We evaluated the feasibility of a LB approach using peritoneal lavage samples from 15 patients with gastric cancer. Samples were collected from both the Douglas pouch and the left subdiaphragmatic area, and cell-free DNA was extracted for analysis of TP53 mutations using droplet digital polymerase chain reaction. RESULTS: All 10 patients with CY1 had positive cytology for the left subdiaphragmatic specimen. However, only six out of the 10 patients had positive cytology for their Douglas pouch specimens, and these six patients had peritoneal tumor DNA (ptDNA) in these specimens. In all five patients with CY0, ptDNA was not detected. The overall survival was significantly shorter in the ptDNA-positive group than in the ptDNA-negative group. The survival of the group with a high amount of DNA from free intraperitoneal cells (ficDNA) was significantly worse than that of those with a low amount. In contrast, the group with a high amount of DNA from peritoneal cell-free DNA (pcfDNA) had significantly better survival than the group with a low amount. CONCLUSION: LB cytology showed equivalent utility to that of conventional microscopic examinations regarding its diagnostic ability. Therefore ptDNA, pcfDNA and ifcDNA are expected to be useful as prognostic factors.

Separation and single-cell analysis for free gastric cancer cells in ascites and peritoneal lavages based on microfluidic chips.

BACKGROUNDS: Detecting free cancer cells from ascites and peritoneal lavages is crucial for diagnosing gastric cancer (GC). However, traditional methods are limited for early-stage diagnosis due to their low sensitivity. METHODS: A label-free, rapid, and high-throughput technique was developed for separating cancer cells from ascites and peritoneal lavages using an integrated microfluidic device, taking advantage of dean flow fractionation and deterministic lateral displacement. Afterward, separated cells were analyzed using a microfluidic single-cell trapping array chip (SCTA-chip). In situ immunofluorescence for EpCAM, YAP-1, HER-2, CD45 molecular expressions, and Wright-Giemsa staining were performed for cells in SCTA-chips. At last, YAP1 and HER-2 expression in tissues was analyzed by immunohistochemistry. FINDINGS: Through integrated microfluidic device, cancer cells were successfully separated from simulated peritoneal lavages containing 1/10,000 cancer cells with recovery rate of 84.8% and purity of 72.4%. Afterward, cancer cells were isolated from 12 patients' ascites samples. Cytological examinations showed cancer cells were efficiently enriched with background cells excluded. Afterwards, separated cells from ascites were analyzed by SCTA-chips, and recognized as cancer cells through EpCAM+/CD45- expression and Wright-Giemsa staining. Interestingly, 8 out of 12 ascites samples showed HER-2+ cancer cells. At last, the results through a serial expression analysis showed that YAP1 and HER-2 have discordant expression during metastasis. INTERPRETATION: Microfluidic Chips developed in our study could not only rapidly detect label-free free GC cells in ascites and peritoneal lavages with high-throughput, they could also analyze ascites cancer cells at the single-cell level, improving peritoneal metastasis diagnosis and investigation of therapeutic targets. FUNDING: This research was supported by National Natural Science Foundation of China (22134004, U1908207, 91859111); Natural Science Foundation of Shandong Province of China (ZR2019JQ06); Taishan Scholars Program of Shandong Province tsqn (201909077); Local Science and Technology Development Fund Guided by the Central Government (YDZX20203700002568); Applied Basic Research Program of Liaoning Province (2022020284-JH2/1013).