Hernia Prevention Using Biologic Mesh and/or Small Bites: A Multispecialty 2 × 2 Factorial Randomized Controlled Trial.

BACKGROUND: Ventral incisional hernias are the most common complication after abdominal operation. Randomized trials have shown efficacy of prophylactic synthetic mesh and small bites. Adoption of these practices has been limited due to concerns with placement of synthetic mesh in contaminated cases and small bites in an overweight population. We sought to assess the efficacy of prophylactic biologic mesh and small bites to prevent postoperative major complications: ventral incisional hernias, surgical site infection, reoperation, and death. STUDY DESIGN: High-risk patients (overweight/obese, current smoker) undergoing abdominal operation with a midline incision (5 cm or greater) were randomized (2 × 2 factorial trial) to receive either sublay biologic mesh or no mesh and either small bites (0.5 × 0. 5cm) or large bites (1 × 1 cm) fascial closure. The primary outcome measure was major complications at 1 year postoperative. CONSORT guidelines were followed, and this study was registered on clinicaltrials.gov (NCT03148496). Assuming α = 0.05, ß = 0.20, and Δ = 20%, it was estimated that 105 patients were needed. Primary outcome was assessed using Fisher's exact test. RESULTS: A total of 107 patients were randomized: 52 (49%) to mesh, 55 (51%) to no mesh, 55 (51%) to small bites, and 52 (49%) to large bites. Of the patients, 16% were smokers, 31% were overweight, and 55% were obese. At 1 year postoperative, there were no differences in major complications between groups (mesh vs no mesh 21% vs 16%, p = 0.62; small vs large bites 18% vs 19%, p = 1.00). CONCLUSIONS: In this trial, biologic mesh and small bites appear to have no benefit. Further randomized trials are needed among high-risk patients before widespread adoption of prophylactic biologic mesh or small bites.

Same day discharge following elective, minimally invasive, colorectal surgery : A review of enhanced recovery protocols and early outcomes by the SAGES Colorectal Surgical Committee with recommendations regarding patient selection, remote monitoring, and successful implementation.

BACKGROUND: As enhanced recovery programs (ERPs) have continued to evolve, the length of hospitalization (LOS) following elective minimally invasive colorectal surgery has continued to decline. Further refinements in multimodal perioperative pain management strategies have resulted in reduced opioid consumption. The interest in ambulatory colectomy has dramatically accelerated during the COVID-19 pandemic. Severe restrictions in hospital capacity and fear of COVID transmission forced surgical teams to rethink strategies to further reduce length of inpatient stay. METHODS: Members of the SAGES Colorectal Surgery Committee began reviewing the emergence of SDD protocols and early publications for SDD in 2019. The authors met at regular intervals during 2020-2022 period reviewing SDD protocols, safe patient selection criteria, surrogates for postoperative monitoring, and early outcomes. RESULTS: Early experience with SDD protocols for elective, minimally invasive colorectal surgery suggests that SDD is feasible and safe in well-selected patients and procedures. SDD protocols are associated with reduced opioid use and prescribing. Patient perception and experience with SDD is favourable. For early adopters, SDD has been the natural evolution of well-developed ERPs. Like all ERPs, SDD begins in the office setting, identifying the correct patient and procedure, aligning goals and objectives, and the perioperative education of the patient and their supporting significant others. A thorough discussion with the patient regarding expected activity levels, oral intake, and pain control post operatively lays the foundation for a successful application of SDD programs. These observations may not apply to all patient populations, institutions, practice types, or within the scope of an existing ERP. However, if the underlying principles of SDD can be incorporated into an existing institutional ERP, it may further reduce the incidence of post operative ileus, prolonged LOS, and improve the effectiveness of oral analgesia for postoperative pain management and reduced opioid use and prescribing. CONCLUSIONS: The SAGES Colorectal Surgery Committee has performed a comprehensive review of the early experience with SDD. This manuscript summarizes SDD early results and considerations for safe and stepwise implementation of SDD with a specific focus on ERP evolution, patient selection, remote monitoring, and other relevant considerations based on hospital settings and surgical practices.

Is robotic surgery feasible at a safety net hospital?

BACKGROUND: Robotic surgery offers potential advantages of improved ability to complete procedures using a minimally invasive approach, recovery, and clinical outcomes. It has been previously established that safety net hospitals are outliers for surgical complications. As such, the adoption of new technology may not achieve the same outcomes as other institutions. We hypothesized that, compared to laparoscopic and open surgeries, robotic surgeries have fewer post-operative Clavien-Dindo complications at our safety net hospital. METHODS: All robotic surgeries performed from 2017 to 2019 at a single, safety net hospital were reviewed. Cases were matched 1:3 to laparoscopic controls. Surgeries commonly performed open were additionally matched 1:3 to open counterparts. The primary outcome was Clavien-Dindo complications at 90 days post-operatively. Secondary outcomes included inadvertent enterotomy, conversion to open, operative duration, wound class, surgical site infection (SSI), surgical site occurrence (SSO), length of stay (LOS), reoperation, readmission, and recurrence. RESULTS: A total of 160 robotic surgeries were included and matched to 480 laparoscopic surgeries and 108 open surgeries. Open surgeries were associated with greater risk of Clavien-Dindo complication (OR = 2.7, p = 0.040, 95% confidence interval 1.0-6.9) than either robotic or laparoscopic surgeries. Robotic cases had increased operative duration when compared to laparoscopic (p < 0.001) but not open cases (p = 0.093). No difference was seen in enterotomy, conversion to open, SSI, SSO, LOS, reoperation, readmission, or recurrence between robotic and laparoscopic, and robotic and open cases. CONCLUSION: Robotic surgery is safe and feasible at a safety net hospital. Robotic and laparoscopic surgeries were associated with fewer Clavien-Dindo complications than open surgery, but no differences were seen between robotic and laparoscopic cases. Robotic surgery, compared to both laparoscopic and open surgery, had longer operative durations. Further studies are needed to assess the value of robotic as opposed to laparoscopic surgery in a safety net setting.

Is the American College of Surgeons Online Communities a safe and useful venue to ask for surgical advice?

BACKGROUND: Many surgeons rely on the American College of Surgeons (ACS) Community Forums for advice on managing complex patients. Our objective was to assess the safety and usefulness of advice provided on the most popular surgical forum. METHODS: Overall, 120 consecutive, deidentified clinical threads were extracted from the General Surgery community in reverse chronological order. Three groups of three surgeons (mixed academic and community perspectives) evaluated the 120 threads for unsafe or dangerous posts. Positive and negative controls for safe and unsafe answers were included in 20 threads, and reviewers were blinded to their presence. Reviewers were free to access all online and professional resources. RESULTS: There were 855 unique responses (median 7, 2-15 responses per thread) to the 120 clinical threads/scenarios. The review teams correctly identified all positive and negative controls for safety. While 58(43.3%) of threads contained unsafe advice, the majority (33, 56.9%) were corrected. Reviewers felt that a there was a standard of care response for 62/120 of the threads of which 50 (80.6%) were provided by the responses. Of the 855 responses, 107 (12.5%) were considered unsafe/dangerous. CONCLUSION: The ACS Community Forums are generally a safe and useful resource for surgeons seeking advice for challenging cases. While unsafe or dangerous advice is not uncommon, other surgeons typically correct it. When utilizing the forums, advice should be taken as a congregate, and any single recommendation should be approached with healthy skepticism. However, social media such as the ACS Forums is self-regulating and can be an appropriate method for surgeons to communicate challenging problems.

Ventral Hernia Management: Expert Consensus Guided by Systematic Review.

OBJECTIVE: To achieve consensus on the best practices in the management of ventral hernias (VH). BACKGROUND: Management patterns for VH are heterogeneous, often with little supporting evidence or correlation with existing evidence. METHODS: A systematic review identified the highest level of evidence available for each topic. A panel of expert hernia-surgeons was assembled. Email questionnaires, evidence review, panel discussion, and iterative voting was performed. Consensus was when all experts agreed on a management strategy. RESULTS: Experts agreed that complications with VH repair (VHR) increase in obese patients (grade A), current smokers (grade A), and patients with glycosylated hemoglobin (HbA1C) ≥ 6.5% (grade B). Elective VHR was not recommended for patients with BMI ≥ 50 kg/m (grade C), current smokers (grade A), or patients with HbA1C ≥ 8.0% (grade B). Patients with BMI= 30-50 kg/m or HbA1C = 6.5-8.0% require individualized interventions to reduce surgical risk (grade C, grade B). Nonoperative management was considered to have a low-risk of short-term morbidity (grade C). Mesh reinforcement was recommended for repair of hernias ≥ 2 cm (grade A). There were several areas where high-quality data were limited, and no consensus could be reached, including mesh type, component separation technique, and management of complex patients. CONCLUSIONS: Although there was consensus, supported by grade A-C evidence, on patient selection, the safety of short-term nonoperative management, and mesh reinforcement, among experts; there was limited evidence and broad variability in practice patterns in all other areas of practice. The lack of strong evidence and expert consensus on these topics has identified gaps in knowledge where there is need of further evidence.

Analysis of model development strategies: predicting ventral hernia recurrence.

BACKGROUND: There have been many attempts to identify variables associated with ventral hernia recurrence; however, it is unclear which statistical modeling approach results in models with greatest internal and external validity. We aim to assess the predictive accuracy of models developed using five common variable selection strategies to determine variables associated with hernia recurrence. METHODS: Two multicenter ventral hernia databases were used. Database 1 was randomly split into "development" and "internal validation" cohorts. Database 2 was designated "external validation". The dependent variable for model development was hernia recurrence. Five variable selection strategies were used: (1) "clinical"-variables considered clinically relevant, (2) "selective stepwise"-all variables with a P value <0.20 were assessed in a step-backward model, (3) "liberal stepwise"-all variables were included and step-backward regression was performed, (4) "restrictive internal resampling," and (5) "liberal internal resampling." Variables were included with P < 0.05 for the Restrictive model and P < 0.10 for the Liberal model. A time-to-event analysis using Cox regression was performed using these strategies. The predictive accuracy of the developed models was tested on the internal and external validation cohorts using Harrell's C-statistic where C > 0.70 was considered "reasonable". RESULTS: The recurrence rate was 32.9% (n = 173/526; median/range follow-up, 20/1-58 mo) for the development cohort, 36.0% (n = 95/264, median/range follow-up 20/1-61 mo) for the internal validation cohort, and 12.7% (n = 155/1224, median/range follow-up 9/1-50 mo) for the external validation cohort. Internal validation demonstrated reasonable predictive accuracy (C-statistics = 0.772, 0.760, 0.767, 0.757, 0.763), while on external validation, predictive accuracy dipped precipitously (C-statistic = 0.561, 0.557, 0.562, 0.553, 0.560). CONCLUSIONS: Predictive accuracy was equally adequate on internal validation among models; however, on external validation, all five models failed to demonstrate utility. Future studies should report multiple variable selection techniques and demonstrate predictive accuracy on external data sets for model validation.

Do risk calculators accurately predict surgical site occurrences?

INTRODUCTION: Current risk assessment models for surgical site occurrence (SSO) and surgical site infection (SSI) after open ventral hernia repair (VHR) have limited external validation. Our aim was to determine (1) whether existing models stratify patients into groups by risk and (2) which model best predicts the rate of SSO and SSI. METHODS: Patients who underwent open VHR and were followed for at least 1 mo were included. Using two data sets-a retrospective multicenter database (Ventral Hernia Outcomes Collaborative) and a single-center prospective database (Prospective)-each patient was assigned a predicted risk with each of the following models: Ventral Hernia Risk Score (VHRS), Ventral Hernia Working Group (VHWG), Centers for Disease Control and Prevention Wound Class, and Hernia Wound Risk Assessment Tool (HW-RAT). Patients in the Prospective database were also assigned a predicted risk from the American College of Surgeons National Surgical Quality Improvement Program (ACS-NSQIP). Areas under the receiver operating characteristic curve (area under the curve [AUC]) were compared to assess the predictive accuracy of the models for SSO and SSI. Pearson's chi-square was used to determine which models were able to risk-stratify patients into groups with significantly differing rates of actual SSO and SSI. RESULTS: The Ventral Hernia Outcomes Collaborative database (n = 795) had an overall SSO and SSI rate of 23% and 17%, respectively. The AUCs were low for SSO (0.56, 0.54, 0.52, and 0.60) and SSI (0.55, 0.53, 0.50, and 0.58). The VHRS (P = 0.01) and HW-RAT (P < 0.01) significantly stratified patients into tiers for SSO, whereas the VHWG (P < 0.05) and HW-RAT (P < 0.05) stratified for SSI. In the Prospective database (n = 88), 14% and 8% developed an SSO and SSI, respectively. The AUCs were low for SSO (0.63, 0.54, 0.50, 0.57, and 0.69) and modest for SSI (0.81, 0.64, 0.55, 0.62, and 0.73). The ACS-NSQIP (P < 0.01) stratified for SSO, whereas the VHRS (P < 0.01) and ACS-NSQIP (P < 0.05) stratified for SSI. In both databases, VHRS, VHWG, and Centers for Disease Control and Prevention overestimated risk of SSO and SSI, whereas HW-RAT and ACS-NSQIP underestimated risk for all groups. CONCLUSIONS: All five existing predictive models have limited ability to risk-stratify patients and accurately assess risk of SSO. However, both the VHRS and ACS-NSQIP demonstrate modest success in identifying patients at risk for SSI. Continued model refinement is needed to improve the two highest performing models (VHRS and ACS-NSQIP) along with investigation to determine whether modifications to perioperative management based on risk stratification can improve outcomes.

Sublay versus underlay in open ventral hernia repair.

BACKGROUND: The ideal location for mesh placement in open ventral hernia repair (OVHR) remains under debate. Current trends lean toward underlay or sublay repair. We hypothesize that in patients undergoing OVHR, sublay versus underlay placement of mesh results in fewer surgical site infections (SSIs) and recurrences. MATERIALS AND METHODS: A multi-institution database of all OVHRs performed from 2010 to 2011 was accessed. Patients with mesh placed in the sublay or underlay position and at least 1 mo of follow-up were included. Primary outcome was SSI. Secondary outcome was hernia recurrence. Multivariate analysis was performed using logistic regression for SSI and Cox regression for recurrence. Subgroup analysis of elective, midline ventral incisional hernias was also performed. RESULTS: Of 447 patients, 139 (31.1%) had a sublay repair. The unadjusted analysis showed no difference in SSI and lower recurrence using sublay compared with underlay. On multivariate analysis, there was no difference in SSI using sublay compared with underlay (odds ratio 1.5, 95% confidence interval [CI] 0.8-2.8). Recurrence was less common with sublay (hazard ratio 0.4, 95% CI 0.2-0.8). On subgroup analysis of elective, midline incisional hernias only (n = 247), there were more SSIs with sublay compared with underlay repair (28.0% versus 15.1%, P = 0.018); however, there was no difference in major SSI (sublay 9.3% versus underlay 5.8%, P = 0.315). There were fewer recurrences using sublay repair compared with underlay repair (10.7% versus 25.0%, P = 0.010). CONCLUSIONS: In this multi-center, risk-adjusted study, sublay repair was associated with fewer recurrences than underlay repair and no difference in SSI. Randomized controlled trials are warranted to validate these findings.

Suture, synthetic, or biologic in contaminated ventral hernia repair.

BACKGROUND: Data are lacking to support the choice between suture, synthetic mesh, or biologic matrix in contaminated ventral hernia repair (VHR). We hypothesize that in contaminated VHR, suture repair is associated with the lowest rate of surgical site infection (SSI). METHODS: A multicenter database of all open VHR performed at from 2010-2011 was reviewed. All patients with follow-up of 1 mo and longer were included. The primary outcome was SSI as defined by the Centers for Disease Control and Prevention. The secondary outcome was hernia recurrence (assessed clinically or radiographically). Multivariate analysis (stepwise regression for SSI and Cox proportional hazard model for recurrence) was performed. RESULTS: A total of 761 VHR were reviewed for a median (range) follow-up of 15 (1-50) mo: there were 291(38%) suture, 303 (40%) low-density and/or mid-density synthetic mesh, and 167(22%) biologic matrix repair. On univariate analysis, there were differences in the three groups including ethnicity, ASA, body mass index, institution, diabetes, primary versus incisional hernia, wound class, hernia size, prior VHR, fascial release, skin flaps, and acute repair. The unadjusted outcomes for SSI (15.1%; 17.8%; 21.0%; P = 0.280) and recurrence (17.8%; 13.5%; 21.5%; P = 0.074) were not statistically different between groups. On multivariate analysis, biologic matrix was associated with a nonsignificant reduction in both SSI and recurrences, whereas synthetic mesh associated with fewer recurrences compared to suture (hazard ratio = 0.60; P = 0.015) and nonsignificant increase in SSI. CONCLUSIONS: Interval estimates favored biologic matrix repair in contaminated VHR; however, these results were not statistically significant. In the absence of higher level evidence, surgeons should carefully balance risk, cost, and benefits in managing contaminated ventral hernia repair.

Laparoscopic ventral hernia repair with primary fascial closure versus bridged repair: a risk-adjusted comparative study.

BACKGROUND: Laparoscopy, specifically the bridged mesh technique, is a popular means used for ventral hernia repair. While laparoscopy has decreased the incidence of surgical site infection (SSI), hernia recurrence rates remain unchanged. Some surgeons advocate laparoscopic primary fascial closure (PFC) with placement of intraperitoneal mesh to decrease recurrence rates. We hypothesize that in patients undergoing laparoscopic ventral hernia repair (LVHR), PFC compared to a bridged mesh repair decreases hernia recurrence rates. METHODS: A multicenter, retrospective database of all ventral hernia repairs performed from 2010-2012 was accessed. Patients who underwent LVHR with mesh were reviewed. Patients who had PFC were compared to bridged repair. Primary outcome was hernia recurrence determined by clinical examination or CT scan. Secondary outcomes included SSI and seroma formation. RESULTS: A total of 1594 patients were identified. Following exclusion, a total of 196 patients were left who underwent LVHR with a mean follow-up period of 17.5 months. Ninety-seven patients underwent PFC, while 99 underwent bridged repairs. Initial comparisons between both groups was negative for any significant statistical difference in terms of recurrence, seroma formation, SSI, deep/organ space SSI, reoperation, and readmission. The same initial findings held true during subgroup analysis. Propensity score analysis was then performed for recurrence, seroma, and SSI controlling for age, gender, immune status, ASA class, BMI, smoking status, and acute repair. No statistically significant differences were identified in either group. CONCLUSION: Primary fascial closure during laparoscopic hernia repairs did not result in reduced recurrence, seroma, and SSI as compared to bridge repairs in a retrospective, multi-institutional study. However, additional research is needed to further evaluate benefits to the patient in terms of pain, function, cosmesis, and overall satisfaction. Randomized, blinded, control trials should focus on these parameters in future investigations.

Use of Computed Tomography in Diagnosing Ventral Hernia Recurrence: A Blinded, Prospective, Multispecialty Evaluation.

IMPORTANCE: Physical examination misses up to one-third of ventral hernia recurrences seen on radiologic imaging. However, tests such as computed tomographic (CT) imaging are subject to interpretation and require validation of interobserver reliability. OBJECTIVE: To determine the interobserver reliability of CT scans for detecting a ventral hernia recurrence among surgeons and radiologists. We hypothesized there would be significant disagreement in the diagnosis of a ventral hernia recurrence among different observers. Our secondary aim was to determine reasons for disagreement in the interpretation of CT scans. DESIGN, SETTING, AND PARTICIPANTS: One hundred patients who underwent ventral hernia repair from 2010-2011 at an academic health care center with a postoperative CT scan were randomly selected from a larger cohort. This study was conducted from July 2014 to March 2015. Prospective assessment of the presence or absence of a recurrent ventral hernia on CT scans was compared among 9 blinded reviewers and the radiology report. Five reviewers (consensus group) met to discuss all CT scans with disagreement. The discussion was assessed for keywords and key concepts. The remaining 4 reviewers (validation group) read the consensus group recommendations and reassessed the CT scans. Pre- and post-review κ were calculated; the post-review assessments were compared with clinical examination findings. MAIN OUTCOMES AND MEASURES: Interobserver reliability in determining hernia recurrence radiographically. RESULTS: Of 100 CT scans, there was disagreement among all 9 reviewers and the radiology report on the presence/absence of a ventral hernia in 73 cases (κ = 0.44; 95% CI, 0.35-0.54; P < .001). Following discussion among the consensus group, there remained disagreement in 10 cases (κ = 0.91; 95% CI, 0.83-0.95; P < .001). Among the validation group, the κ value had a slight improvement from 0.21 (95% CI, 0.12-0.33) to 0.34 (95% CI, 0.23-0.46) (P < .001) after reviewing the consensus group proposals. There was disagreement between clinical examination and the consensus group assessment of CT scans on the presence/absence of a ventral hernia in 25 cases. The concepts most frequently discussed were the absence of an accepted definition for a radiographic ventral hernia and differentiating pseudorecurrence from recurrence. CONCLUSIONS AND RELEVANCE: Owing to the high interobserver variability, CT scan was not associated with reliable diagnosing in ventral hernia recurrence. Consensus guidelines and improved communication between surgeon and radiologist may decrease interobserver variability.

Laparoscopic repair reduces incidence of surgical site infections for all ventral hernias.

BACKGROUND: The role of laparoscopic repair of ventral hernias remains incompletely defined. We hypothesize that laparoscopy, compared to open repair with mesh, decreases surgical site infection (SSI) for all ventral hernia types. METHODS: MEDLINE, EMBASE, and Cochrane databases were reviewed to identify studies evaluating outcomes of laparoscopic versus open repair with mesh of ventral hernias and divided into groups (primary or incisional). Studies with high risk of bias were excluded. Primary outcomes of interest were recurrence and SSI. Fixed effects model was used unless significant heterogeneity, assessed with the Higgins I square (I(2)), was encountered. RESULTS: There were 5 and 15 studies for primary and incisional cohorts. No difference was seen in recurrence between laparoscopic and open repair in the two hernia groups. SSI was more common with open repair in both hernia groups: primary (OR 4.17, 95%CI [2.03-8.55]) and incisional (OR 5.16, 95%CI [2.79-9.57]). CONCLUSIONS: Laparoscopic repair, compared to open repair with mesh, decreases rates of SSI in all types of ventral hernias with no difference in recurrence. These data suggest that laparoscopic approach may be the treatment of choice for all types of ventral hernias.

Primary fascial closure with laparoscopic ventral hernia repair: systematic review.

Laparoscopic ventral hernia repair (LVHR) has grown in popularity. Typically, this procedure is performed with a mesh bridge technique that results in high rates of seroma, eventration (bulging), and patient dissatisfaction. In an effort to avoid these complications, there is growing interest in the role of laparoscopic primary fascial closure with intraperitoneal mesh placement. This systematic review evaluated the outcomes of closure of the central defect during LVHR. A literature search of PubMed, Cochrane databases, and Embase was conducted using PRISMA guidelines. MINORS was used to assess the methodologic quality. Primary outcome was hernia recurrence. Secondary outcomes were surgical-site infection, seroma formation, bulging, and patient-centered items (satisfaction, chronic pain, functional status). Eleven studies were identified, eight of which were case series (level 4 data). Three comparative studies examined the difference between closure and nonclosure of the fascial defect during laparoscopic ventral incisional hernia repairs (level 3 and 4 data). These studies suggested that primary fascial closure (n = 138) compared to nonclosure (n = 255) resulted in lower recurrence rates (0-5.7 vs. 4.8-16.7 %) and seroma formation rates (5.6-11.4 vs. 4.3-27.8 %). Follow-up periods for both groups were similar (1-108 months). Only one study evaluated patient function and clinical bulging. It showed better outcomes with primary fascial closure. Closure of the central defect during LVHR resulted in less recurrence, bulging, and seroma than nonclosure. Patients with closure were more satisfied with the results and had better functional status. The quality of the data was poor, however. A randomized controlled trial to evaluate the role of closure of the central defect during LVHR is warranted.

Anemia and jejunal intussusception: An unusual presentation for a metastatic phyllodes breast tumor.

INTRODUCTION: Phyllodes tumor of the breast is a rare cause of breast cancer, accounting for less than 0.5% of breast cancers. These tumors are classified as benign, borderline, or malignant, with malignant tumors compromising nearly 25% of cases. Metastases occur in 20% of malignant tumors, lungs, bones, liver and brain being the frequent sites of metastases. PRESENTATION OF CASE: We present a case of a metastatic phyllodes tumor to the small bowel causing jejunal intussusception, symptomatic anemia, and small bowel obstruction. DISCUSSION: Patients with phyllodes tumor of the breast can develop disease recurrence even years after initial treatment. Phyllodes tumor metastasizing to the small bowel is extremely rare, with only three known previously described case reports in the literature. CONCLUSION: High risk patients, with a past medical history of phyllodes breast cancer, should be monitored closely. Even years after breast cancer treatment, these patients may present with gastrointestinal complaints such as obstruction or bleeding, and therefore metastatic disease to the small bowel should be considered on the differential with subsequent abdominal imaging obtained.

Methylphenidate (Ritalin): behavioral studies in the rat.

Attention Deficit Hyperactivity Disorder (ADHD) is a neuropsychiatric syndrome with an onset in childhood characterized by an inability to remain focused or to concentrate for prolonged periods of time. Children suffering from this disease are many times described as either inattentive or as hyperactive-impulsive depending on what form of the disease they manifest. Methylphenidate is the preferred treatment for this behavioral disorder and is used for long term disease management. Much still remains unknown concerning this stimulant and its effects on behavior and future abuse potential are pertinent questions. Since animal models are used to study the mechanism of drug action and rats are used often in drug studies, the objective of this review is to summarize the research reports that mainly have used rats as the model to investigate the action of methylphenidate. Topics discussed in this review include: (1) What effect does a single dose of methylphenidate have on locomotion activity; (2) Does repeated administration of methylphenidate result in tolerance or sensitization; and (3) Does methylphenidate have rewarding properties as measured by the self-administration and condition placed preference paradigms.