Does liver appearance predict histopathologic findings: prospective analysis of routine liver biopsies during bariatric surgery

Compare the Combined Diagnostic Accuracy of Transient Elastography and Visual Liver Score in Assessing Non-Alcoholic Fatty Liver Disease (NAFLD) and Compare it with Liver Biopsy in Morbidly Obese Patients Undergoing Bariatric Surgery: An Observational Study

INTRODUCTION

A liver biopsy is the gold standard for the diagnosis of non-alcoholic fatty liver disease (NAFLD) and non-alcoholic steatohepatitis (NASH). Here, we combine preoperative transient elastography (TE) and intraoperative standardized visual liver score (VLS) which is compared with intraoperative liver biopsy for prediction of NAFLD and NASH in patients undergoing bariatric surgery.

AIM

Evaluate the combined diagnostic accuracy of TE and VLS in assessing NAFLD or NASH and compare it with liver biopsy in patients undergoing bariatric surgery.

METHODS

In a prospective cohort of 70 morbidly obese undergoing bariatric surgery, preoperative TE and intraoperative VLS were calculated. Findings of TE and VLS were compared with histology from intraoperative liver biopsy.

RESULTS

Histologically, 44 (62.85%) had NAFLD (≥ S1). Significant steatosis was seen in 20 (28.57%) while significant fibrosis was visible in 18 (25.71%). Area Under the Receiver Operating Characteristics (AUROC) TE for diagnosis of NAFLD was excellent (0.844, p = 0.001). At the optimal cutoff of 8.1, the positive predictive value (PPV) was 92.9%, and diagnostic accuracy was 90.6%. VLS had a sensitivity of 90.9% for NAFLD. The combined sensitivity of TE + VLS was 95.5% for ruling out NAFLD. Fourteen (20%) had NASH. VLS had a diagnostic accuracy of 97% in identifying NASH in comparison to TE. AUROC-VLS was 0.987, p ≤ 0.001, and a sensitivity of 100%. The overall sensitivity of combined TE and VLS was 100% with a negative predictive value (NPV) of 100%.

CONCLUSION

TE when combined with intraoperative VLS is comparable to liver biopsy and can be used for the diagnosis of NAFLD and NASH in patients undergoing bariatric surgery.

Can Surgeons Reliably Identify Non-cirrhotic Liver Disease During Laparoscopic Bariatric Surgery?

INTRODUCTION

Identification of liver disease during bariatric operations is an important task given the patients risk for occult fatty liver disease. Surgeon's accuracy of assessing for liver disease during an operation is poorly understood. The objective was to measure surgeons' performance on intra-operative visual assessment of the liver in a simulated environment.

METHODS

Liver images from 100 patients who underwent laparoscopic bariatric surgery and pre-operative ultrasound elastography between July 2020 and July 2021 were retrospectively evaluated. The perception of 15 surgeons regarding the degree of hepatic steatosis and fibrosis was collected in a simulated clinical environment by survey and compared to results determined by ultrasonographic exam.

RESULTS

The surgeons' ability to correctly identify the class of steatosis and fibrosis was poor (accuracy 61% and 59%, respectively) with a very weak correlation between the surgeon's predicted class and its true class (r = 0.17 and r = 0.12, respectively). When liver disease was present, surgeons completely missed its presence in 26% and 51% of steatosis and fibrosis, respectively. Digital image processing demonstrated that surgeons subjectively classified steatosis based on the "yellowness" of the liver and fibrosis based on texture of the liver, despite neither correlating with the true degree of liver disease.

CONCLUSION

Laparoscopic visual assessment of the liver surface for identification of non-cirrhotic liver disease was found to be an inaccurate method during laparoscopic bariatric surgery. While validation studies are needed, the results suggest the clinical need for alternative approaches.

Prospective Study to Analyze the Concordance Between a Standardized Visual Method With Pathology to stratify Nonalcoholic Fatty Liver Disease in Cadaveric Liver Grafts Evaluated for Transplantation

Background

The main challenge of liver transplantation is the discrepancy in demand and availability. Marginal grafts or full organs from donors with expansion criteria have been considered to reduce the shortage and assist a greater number of patients. Nonalcoholic fatty liver disease (NAFLD) is one of the most important defining criteria for expanded criteria organs. The present study proposes that an organized visual analysis method could correctly identify and classify NAFLD and organ viability without the need for liver biopsy and its logistical concerns.

Methods

Pictures from the grafts were taken at a standardized method (same distance, light conditions, and register device) before and after the perfusion. The visual liver score (VLS) was applied by transplant surgeons; biopsies of the grafts were analyzed by a pathologist in a double-blind design. Score performance and interobserver agreement for NAFLD detection and grading, as graft viability evaluation, were calculated.

Results

Fifty-seven grafts were analyzed. At least 1 previous expansion criterion was presented by 59.64% of donors. The prevalence of NAFLD was 94.73%, with 31.57% borderline nonalcoholic steatohepatitis and 5.26% nonalcoholic steatohepatitis. Steatosis was identified with 48.68% (preperfusion) and 64.03% (postperfusion) accuracy. NAFLD stratification was performed with 49.53% (preperfusion) and 46.29% (postperfusion) accuracy. Viability related to NAFLD was identified with 51.96% (preperfusion) and 48.52% (postperfusion) accuracy. Interobserver agreement was moderate for total VLS and poor for individual components of VLS.

Conclusions

Although a standardized method was not reliable enough for visual evaluation of NALFD compared with pathology, efforts should be made to expand access to biopsy. Further studies are needed to understand whether the VLS needs to be adapted or even excluded in the liver transplant scenario, to assess the importance of ectoscopy related to posttransplant clinical outcomes, and to determine its role in graft selection.

A Novel Digital Algorithm for Identifying Liver Steatosis Using Smartphone-Captured Images

Access to lifesaving liver transplantation is limited by a severe organ shortage. One factor contributing to the shortage is the high rate of discard in livers with histologic steatosis. Livers with <30% macrosteatosis are generally considered safe for transplant. However, histologic assessment of steatosis by a pathologist remains subjective and is often limited by image quality. Here, we address this bottleneck by creating an automated digital algorithm for calculating histologic steatosis using only images of liver biopsy histology obtained with a smartphone.

Routine Versus Selective Liver Biopsy During Bariatric Surgery: Postoperative Outcomes and Preoperative Predictors of NASH

BACKGROUND

Nonalcoholic steatohepatitis (NASH) is common in patients with obesity. Liver biopsy (LB) can be routinely or selectively performed during bariatric surgery to identify patients with NASH.

METHODS

Patients undergoing bariatric surgery between 2016 and 2020 at our institution were identified. Chart review identified patients undergoing concurrent LB. LB results were compared between patients undergoing routine LB and selective LB. Patient demographics and postoperative outcomes were compared between those who received LB and those who did not (non-LB). In the LB cohort, preoperative characteristics of patients with NASH were compared to those without NASH, and multivariable regression was used to identify predictors of NASH.

RESULTS

Two thousand three hundred ninety-three patients were identified, of which 400 (16.7%) had liver biopsies (LB) and 1,993 (83.3%) did not (non-LB). Three hundred thirty LB were performed routinely, and 70 were selective. Compared to selective LB, routine LB identified significantly higher rates of steatosis (83.6% vs. 4.5%, p < 0.01), periportal inflammation (67.0% vs. 3.2%, p < 0.01), fibrosis (65.8% vs. 2.1%, p < 0.01), and NASH (10.9% vs. 1.5%, p < 0.01). There were no differences in postoperative complications, blood transfusions, readmissions, or reoperations between LB and non-LB. On multivariable regression, highest BMI > 40 (OR 2.85, 95% CI 1.43-5.67) and insulin-dependent diabetes (OR 4.83, 95% CI 1.70-13.69) were associated with a higher odds of NASH, while Black race was associated with lower odds (OR 0.25, 95% CI 0.09-0.65).

CONCLUSIONS

Routine liver biopsies during bariatric surgery identify higher rates of advanced NAFLD compared to selective biopsies, and can be safely performed without an increased risk of postoperative complications.

Decision Tree for the Performance of Intraoperative Liver Biopsy During Bariatric Surgery

BACKGROUND AND AIMS

Bariatric surgery provides a useful opportunity to perform intraoperative liver biopsy to screen for non-alcoholic steatohepatitis (NASH). There is currently no consensus on whether intraoperative liver biopsy should be systematically performed. The aim of this study was to develop and validate a decision tree to guide that choice.

APPROACH AND RESULTS

This prospective study included 102 consecutive patients from the severe obesity outcome network (SOON) cohort in whom liver biopsy was systematically performed during bariatric surgery. A classification and regression tree (CART) was created to identify the nodes that best classified patients with and without NASH. External validation was performed. Seventy-one biopsies were of sufficient quality for analysis (median body mass index 43.3 [40.7; 48.0] kg/m²). NASH was diagnosed in 32.4% of cases. None of the patients with no steatosis on ultrasound had NASH. The only CART node that differentiated between a "high-risk" and a "low-risk" of NASH was alanine aminotransferase (ALT). ALT>53IU/L predicted NASH with a positive predictive value (PPV) of 68% and a negative predictive value (NPP) of 89%, a sensitivity of 77%, and a specificity of 84%. In the external cohort (n=258), PPV was 68%, NPV was 62%, sensitivity was 27%, and specificity was 90%.

CONCLUSIONS

The present work supports intraoperative liver biopsy to screen for NASH in patients with ALT>53IU/L; however, patients with no steatosis on ultrasound should not undergo biopsy. The CART failed to identify an algorithm with a good sensitivity to screen for NASH in patients with ultrasonography-proven steatosis and ALT≤53IU/L.

Safety of liver biopsy at the time of bariatric surgery: an analysis of the MBSAQIP database

BACKGROUND

The majority of patients undergoing bariatric surgery have hepatic steatosis. Liver biopsy is not technically difficult to perform at the time of metabolic and bariatric surgery (MBS), but there may be concerns for bleeding complications. The safety of liver biopsy (LBx) at the time of MBS has been studied in single institutional studies but has not been studied on a national level.

METHODS

The MBSAQIP database for 2015-2018 was examined. The codes for Roux-en-Y gastric bypass (RYGB) of 43644 and sleeve gastrectomy (SG) 43775 were used along with 47000 (percutaneous liver biopsy), 47001 (percutaneous liver biopsy at time of other procedure), and 47379 (unlisted laparoscopic procedure, liver). Outcomes such as operative time, complications, and length of stay were examined. Propensity-matched analysis was performed to evaluate for adjusted associations.

RESULTS

There were 546,532 patients that met our inclusion criteria. Of those, 21,367 (3.9%) underwent LBx. Only 5.5% (8012) of patients undergoing RYGB had a LBx and 3.3% (13,355) of SG patients. Patients who underwent a LBx had a longer operative time before (103 min vs 84 min, p < 0.001) and after propensity matching [regression coefficient (RC): 10.7 (8.87, 12.5)]. There was no increase in length of stay. There was an increased risk in mortality in the unadjusted analysis (prevalence ratio = 1.61, p = 0.02), but when propensity-matched analysis was done, there was no statistically significant difference between the two groups. Concerning bleeding or transfusion, there was no difference in bleeding or rates of transfusion (p= 0.22, p = 0.21).

CONCLUSION

Liver biopsy at the time of MBS is safe. It adds operative time, but there is no increase in length of stay, bleeding complications, morbidity, or death.

Safety and Utility of Liver Biopsy During Bariatric Surgery in the New Zealand Setting

BACKGROUND

Asymptomatic liver disease is common in bariatric patients and can be diagnosed with intraoperative biopsy. This study aimed to establish the risk-benefit profile of routine liver biopsy, prevalence of clinically significant liver disease, relationship between liver pathology and body mass index, and compare outcomes between ethnic groups.

METHODS

This retrospective cohort study included all patients who had index bariatric surgery at Auckland City Hospital between 2009 and 2016. Diagnosis of liver disease was based on intraoperative biopsy histology. Outcomes included safety (biopsy-related complication) and utility (liver pathology meeting criteria for referral). Liver pathology and referral rates were compared between ethnic groups.

RESULTS

Of 335 bariatric surgery patients, 234 (70%) underwent intraoperative liver biopsy. There were no biopsy-related complications. Histological findings were as follows: normal 25/234 (11%), non-alcoholic fatty liver disease (NAFLD) 207/234 (88%), and other pathological findings in 35/234 (15%). Histological finding meeting referral criteria was present in 22/234 (9%). Of these, 12/22 (55%) were referred. Number needed to biopsy to identify histology meeting referral criteria: n = 11. Māori had a similar NAFLD rate to non-Māori [51/56 versus 156/178, p = 0.48]. Pasifika patients had a higher rate than non-Pasifika [39/40 versus 168/194, p = 0.049]. Māori and Pasifika patients had similar referral rates to non-Māori and non-Pasifika [2/3 versus 5/9, p = 0.73; 2/2 versus 5/10, p = 0.19].

CONCLUSIONS

Intraoperative liver biopsy during bariatric surgery is safe and identified liver disease in 89%, with 9% meeting referral criteria. Pasifika patients have a higher rate of NAFLD than non-Pasifika.

Clinical relevance of liver histopathology and different histological classifications of NASH in adults

Nonalcoholic fatty liver disease (NAFLD) encompasses simple steatosis and steatohepatitis (NASH) with or without fibrosis/cirrhosis and hepatocellular carcinoma. NAFLD occurs epidemically in most areas of the world, contributes to cardiovascular events and liver-related mortality and therefore exacts a major economic toll. Areas covered: Here we summarize what clinicians should know about NAFLD histopathology in adults. We report on the individual histological features and scoring systems of NAFLD: the NAFLD activity score (NAS) introduced by the NASH-Clinical Research Network, the 'Fatty Liver Inhibition of Progression' algorithm and Steatosis, Activity, and Fibrosis (SAF) score. Pros and cons of histological classifications in NASH are discussed. Special emphasis is given to liver histopathology in some high-risk patient groups, such as those with severe obesity and type 2 diabetes. Moreover, we also examine the relationship between liver histopathology and clinical features, and the impact of liver histopathology on the long-term prognosis of NAFLD. Finally, we propose an integrated diagnostic approach which utilizes both non-invasive tools and liver biopsy in those individual patients with suspected NAFLD. Expert commentary: Based on expert opinions, we conclude with a research agenda on NAFLD which focuses on the most burning topics to be addressed over the next five years.

Influence of Liver Disease on Perioperative Outcome After Bariatric Surgery in a Northern German Cohort

OBJECTIVES

The aim of this study was to assess the prevalence of non-alcoholic fatty liver disease (NAFLD) in morbidly obese patients and evaluate the influence on perioperative complications.

BACKGROUND

Patients undergoing bariatric surgery have a high incidence of non-alcoholic steatohepatitis (NASH). Upcoming data indicates that liver disease has a significant effect on perioperative complications. However, the influence of NAFLD/NASH on perioperative outcome in bariatric patients is still controversial.

METHODS

We identified a total of 302 patients with concomitant liver biopsies, while performing either laparoscopic Roux-Y gastric bypass or sleeve gastrectomy. Liver biopsy was performed in case of abnormal liver appearance at time of bariatric surgery. Histological results were compared to perioperative complication rate.

RESULTS

NAFLD is common in our patient cohort. Abnormal findings in liver histology were found in 82.3 % of our patients. Liver cirrhosis was newly diagnosed in 12 patients (4 %). There were no complications due to liver biopsy. The mortality rate was 0.3 %, leakage rate was 1 %, and postoperative bleeding occurred in 3.3 %. Pulmonary complications were observed in 1.7 % and cardiovascular complications in 1.3 %. One patient developed portal vein thrombosis and one patient acute pancreatitis; both were treated conservatively. No patient had postoperative liver failure. We found no association between histological findings and perioperative outcomes.

CONCLUSIONS

The prevalence of NAFLD among morbidly obese surgical patients was high, although this condition was not associated with increased risk for postoperative complications. Because of unexpected findings in intraoperative liver biopsies, the routine indication of liver biopsies in patients at high risk for liver disease should be discussed.

Pathology of non-alcoholic fatty liver disease

Non-alcoholic fatty liver disease (NAFLD) covers a spectrum of lesions ranging from steatosis (Non-alcoholic Fatty Liver or NAFL) to a complex pattern with hepatocellular injury and inflammation (non-alcoholic steatohepatitis; NASH) in the absence of alcohol intake. However, it is increasingly clear that intermediate patterns may exist. The histopathological evaluation of liver biopsy samples is central in the diagnosis of NAFLD and NASH in the absence of sufficiently accurate non-invasive tests because a precise definition of each group is a key issue. When at least 5% of hepatocytes display steatosis, patients can be defined as having NAFLD in an appropriate clinical context. When, in addition, lobular inflammation and liver cell clarification/ballooning are present, then the lesion is usually defined as NASH. Evaluation of the stage of fibrosis is even more fundamental than necroinflammation since it is the main prognostic factor of this disease. Semi-quantitative histological scoring systems have been proposed for NAFLD, but they are not useful in clinical practice and each has certain limitations. For comprehensive purposes, we suggest describing histopathological lesions in NAFLD using the SAF (Steatosis, Activity, Fibrosis) score which assesses separately the grade of steatosis (S, from S0 to S3), the grade of activity (A from A0 to A4 by adding grades of ballooning and lobular inflammation, both from 0 to 2) and the stage of fibrosis (F from F0 to F4).

Utility of Ultrasound, Transaminases, and Visual Inspection to Assess Nonalcoholic Fatty Liver Disease in Bariatric Surgery Patients

BACKGROUND

Nonalcoholic fatty liver disease (NAFLD) is common in adults with extreme obesity and can impact long-term health and survival. Liver biopsy is the only accurate test for diagnosis and staging, but is invasive and costly. Non-invasive testing offers an attractive alternate, but the overall accuracy remains a significant issue. This study was conducted to determine the accuracy and clinical utility of pre-operative ultrasound and liver transaminase levels, as well as intra-operative hepatic visual inspection, for assessing presence of NAFLD as confirmed by hepatic histology.

METHODS

Data was collected prospectively from 580 morbidly obese adult patients who underwent Roux-en-Y gastric bypass surgery with intraoperative wedge biopsy between January 2004 and February 2009. Complete data for ultrasound, ALT and AST levels, and documented visual inspection was available for 513 patients.

RESULTS

The prevalence of NAFLD was 69 % and that of NASH was 32 %. The individual non-invasive clinical assessments demonstrated low sensitivity, specificity, and accuracy for detecting the presence of steatosis, steatohepatitis, or fibrosis. The combination of normal or abnormal results for all tests improved predictive utility. Abnormal tests with all three assessments had a sensitivity of 95-98 % and a specificity of 28-48 % for major histologic findings in NAFLD/NASH. Normal tests with all three assessments had a sensitivity of 12-22 % and a specificity of 89-97 % for major histologic findings in NAFLD/NASH.

CONCLUSIONS

Although individual clinical tests for NAFLD have limited accuracy, the use of combined clinical tests may prove useful.

Prevalence and Predictors of Non-Alcoholic Fatty Liver Disease in Morbidly Obese South Indian Patients Undergoing Bariatric Surgery

BACKGROUND

Numerous studies worldwide have identified a high prevalence of non-alcoholic fatty liver disease (NAFLD) among morbidly obese subjects. Several predictors have been found to be associated with NAFLD and its histological high-risk components. Similar data from India is lacking. We aimed to determine the prevalence and the predictors of NAFLD and its histological high-risk components in a cohort of Indians with morbid obesity undergoing bariatric surgery. Safety of a routine intraoperative liver biopsy was also assessed.

METHODS

There were 134 morbidly obese patients who underwent bariatric surgery with concomitant liver biopsy. These were assessed for NAFLD and its histological high-risk components. Clinical, biochemical, and histological features were evaluated, and predictors of NAFLD, non-alcoholic steatohepatitis (NASH), fibrosis, and advanced fibrosis were identified.

RESULTS

Mean BMI was 44.66 ± 9.81. Eighty-eight (65.7 %) showed NAFLD. Forty-five (33.6 %) showed NASH and 42 (31.3 %) showed fibrosis both not mutually exclusive. Nineteen (14.1 %) showed advanced fibrosis. Higher alanine aminotransferase (ALT) independently predicted NAFLD and was significantly associated with NASH and fibrosis. Type 2 diabetes mellitus (T2DM) and the metabolic syndrome were significantly associated with fibrosis. Systemic hypertension (HT) independently predicted NASH and fibrosis. There were no intraoperative or postoperative complications related to the liver biopsy.

CONCLUSIONS

NAFLD has a high prevalence among morbidly obese patients. Elevated ALT, HT, T2DM, and the metabolic syndrome are predictors for NAFLD and its high-risk histological components. Routine intraoperative liver biopsy is safe in morbidly obese undergoing bariatric surgery for diagnosing NAFLD.

Liver disease in the morbidly obese: a review of 1000 consecutive patients undergoing weight loss surgery

BACKGROUND

Liver disease among the morbidly obese is increasingly prevalent, contributing to significant morbidity. Obesity-related liver pathologies including nonalcoholic steatohepatitis (NASH) have become a leading cause for liver transplant. However, risk factors for developing severe liver disease in the morbidly obese remain unknown. The objective of this study was to determine the frequency of abnormal liver pathology and any relationship to patient-related factors.

METHODS

One thousand consecutive patients undergoing weight loss surgery were reviewed. All patients had a liver biopsy at the time of surgery. Frequency of benign pathology, steatosis, NASH, and fibrosis on pathologic examination of liver biopsy specimens were recorded. Pathologic findings were compared and analyzed to age and body mass index (BMI) of all patients.

RESULTS

All patients in the study population had a BMI>35 kg/m2. Of these patients, 80.2% had liver disease related to obesity on pathology, including 65.9% with steatosis (grade 1-3), and 14.3% with NASH and/or fibrosis. Mean BMI of patients with liver disease was 48.1 compared to a BMI of 47.7 with benign pathology (P=.523). Mean age of patients with and without abnormal pathology was 48.3 and 47.3, respectively (P=.294).

CONCLUSION

Liver disease is highly prevalent in the obese, but is not associated with increased age or BMI. Although all morbidly obese patients appear at significant risk for developing severe liver pathology, further risk factors are unknown.

Hepatic pathology among patients without known liver disease undergoing bariatric surgery: observations and a perspective from the longitudinal assessment of bariatric surgery (LABS) study

Liver biopsy is not routine during bariatric surgery. Alanine aminotransferase (ALT) is widely used to screen for liver disease. We assessed the relationship between ALT and pathology in biopsies from Longitudinal Assessment of Bariatric Surgery (LABS) patients with normal preoperative ALTs. Biopsies from the LABS-1 and LABS-2 studies were scored using the NASH CRN and Ishak systems. Diagnosis and histology were examined in relation to alanine aminotransferase (ALT) values. Six-hundred ninety-three suitable biopsies were evaluated. Biopsied patients had a median age of 45 years; 78.6% were female and 35.1% diabetic; median body mass index was 46 kg/m(2). Six-hundred thirty-five biopsied patients had preoperative ALTs. Median ALT was 25 IU/L (interquartile range [IQR] 19-36 IU/L); 26.6% had an ALT > 35 IU/L and 29.9% exceeded the more restrictive Prati criteria for normal. Using the Prati criteria, 7.9% of participants with normal ALT had steatohepatitis and 5.3% had ≥ stage 2 fibrosis. Logistic regression models were used to predict the probabilities of having bridging fibrosis/cirrhosis or a diagnosis of borderline/definite steatohepatitis in the unbiopsied LABS-2 sample. The proportion of biopsied participants with these findings was very similar to the modeled results from the unbiopsied cohorts. We estimated that 86.0% of participants with advanced fibrosis and 88.1% of participants with borderline/definite steatohepatitis were not biopsied and went undiagnosed. As ALT did not reliably exclude significant obesity-related liver disease in bariatric surgery patients, consideration should be given to routine liver biopsy during bariatric surgery and medical follow-up of significant hepatic pathology.

Nonalcoholic fatty liver disease and bariatric surgery in adolescents

Obesity is a multi-organ system disease with underlying insulin resistance and systemic chronic inflammation. Nonalcoholic fatty liver disease (NAFLD) is a hepatic manifestation of the underlying metabolic dysfunction. This review provides a highlight of the current understanding of NAFLD pathogenesis and disease characteristics, with updates on the challenges of NAFLD management in obese and severely obese (SO) patients and recommendations for the pediatric surgeons' role in the care of SO adolescents.

Chemoprevention of nonalcoholic fatty liver disease by dietary natural compounds

Nonalcoholic fatty liver disease (NAFLD) refers to a wide spectrum of liver disease that is not from excess alcohol consumption, but is often associated with obesity, type 2 diabetes, and metabolic syndrome. NAFLD pathogenesis is complicated and involves oxidative stress, lipotoxicity, mitochondrial damage, insulin resistance, inflammation, and excessive dietary fat intake, which increase hepatic lipid influx and de novo lipogenesis and impair insulin signaling, thus promoting hepatic triglyceride accumulation and ultimately NAFLD. Overproduction of proinflammatory adipokines from adipose tissue also affects hepatic metabolic function. Current NAFLD therapies are limited; thus, much attention has been focused on identification of potential dietary substances from fruits, vegetables, and edible plants to provide a new strategy for NAFLD treatment. Dietary natural compounds, such as carotenoids, omega-3-PUFAs, flavonoids, isothiocyanates, terpenoids, curcumin, and resveratrol, act through a variety of mechanisms to prevent and improve NAFLD. Here, we summarize and briefly discuss the currently known targets and signaling pathways as well as the role of dietary natural compounds that interfere with NAFLD pathogenesis.

Current histological classification of NAFLD: strength and limitations

Nonalcoholic fatty liver disease (NAFLD) covers a spectrum of lesions ranging from pure steatosis without significant necroinflammatory injury (NAFL) to a complex pattern with lesions of hepatocyte injury and inflammation (nonalcoholic steatohepatitis, NASH) in the absence of significant alcohol intake. Because histopathological evaluation of liver biopsy samples remains central in NAFLD in the absence of a non-invasive test with enough accuracy, precise definition of each group is a key issue. When at least 5 % of hepatocytes display steatosis, patients can be qualified for NAFLD in an appropriate clinical context. When, in addition, lobular inflammation and liver cell clarification/ballooning are present, then the lesion can be qualified for NASH. Like for other chronic liver diseases, semiquantitative histological scoring has been proposed for NAFLD. These scoring systems are not useful in clinical practice, and each has some limitation. For comprehensive purposes, we suggest describing histopathological lesions in NAFLD using the SAF score, which assesses together and separately (1) the grade of steatosis (S, from S0 to S3) and (2) the grade of activity (A from A0 to A4 by adding the grades of ballooning and lobular inflammation, both from 0 to 2) and the stage of fibrosis (F from F0 to F4). Such a semiquantitative score could be used for assessing changes in paired biopsies spontaneously or during clinical trials. Finally, the SAF score could help to correctly describe borderline cases of fatty liver diseases that do not fulfill all of the diagnostic criteria of simple steatosis or steatohepatitis, but as for any scoring system, a comprehensive description of the different lesions in their appropriate context is still necessary.

Epidemiology and Natural History of Non-alcoholic Fatty Liver Disease

Non-alcoholic fatty liver disease (NAFLD) is an important cause of liver disease burden across the world. By definition, although the histopathologic features of NAFLD are identical to that of alcoholic liver disease, its diagnosis requires absence of significant alcohol use and absence of other causes of chronic liver disease. We now know that NAFLD is not simply a disease of the Western world. It is manifested across the world, in varying rates, across gender, across varying ethnicities, and in its association with other host factors. In this review article, the definition of NAFLD, its spectrum, ranging from mild steatosis to hepatocellular injury and inflammation defined as non-alcoholic steatohepatitis (NASH) is discussed. Mild steatosis is generally a stable disease whereas NASH can be progressive. Based on current published literature, current incidence and prevalence of NAFLD and NASH are discussed. It is also accepted that these processes will continue to increase in prevalence with the rise of obesity, type II diabetes, and associated metabolic syndrome. Some of the risk factors have been well-established and are discussed. In addition, this review also presents emerging associations with other risk factors for NAFLD. Natural history of NAFLD is variable depending upon the histologic subtypes and other underlying comorbidities and is discussed in this review as well.

Systematic review: the epidemiology and natural history of non-alcoholic fatty liver disease and non-alcoholic steatohepatitis in adults

BACKGROUND

Non-alcoholic fatty liver disease (NAFLD) is a common cause of chronic liver disease, and its worldwide prevalence continues to increase with the growing obesity epidemic. This study assesses the epidemiology of NAFLD in adults based on clinical literature published over the past 30 years.

AIM

To review epidemiology and natural history of non-alcoholic fatty liver disease and non-alcoholic steatohepatitis in adults based on clinical literature published over the past 30 years.

METHODS

An in-depth search of PubMed (1980-2010) was based on five search terms: 'non-alcoholic fatty liver disease' OR 'non-alcoholic steatohepatitis' OR 'fatty liver' OR 'steatosis' AND 'incidence' [MeSH Terms] OR 'prevalence' [MeSH Terms] OR 'natural history'. Studies of paediatric cohorts were excluded. Articles were categorised by topic and summarised, noting generalisations concerning their content.

RESULTS

Four study categories included NAFLD incidence, prevalence, risk factors and natural history. Studies related to NAFLD prevalence and incidence indicate that the diagnosis is heterogeneous and relies on a variety of assessment tools, including liver biopsy, radiological tests such as ultrasonography, and blood testing such as liver enzymes. The prevalence of NAFLD is highest in populations with pre-existing metabolic conditions such as obesity and type II diabetes. Many studies investigating the natural history of NAFLD verify the progression from NASH to advanced fibrosis and hepatocellular carcinoma.

CONCLUSIONS

Non-alcoholic fatty liver disease is the most common cause of elevated liver enzymes. Within the NAFLD spectrum, only NASH progresses to cirrhosis and hepatocellular carcinoma. With the growing epidemic of obesity, the prevalence and impact of NAFLD continues to increase, making NASH potentially the most common cause of advanced liver disease in coming decades.

Drug metabolism alterations in nonalcoholic fatty liver disease

Drug-metabolizing enzymes play a vital role in the elimination of the majority of therapeutic drugs. The major organ involved in drug metabolism is the liver. Chronic liver diseases have been identified as a potential source of significant interindividual variation in metabolism. Nonalcoholic fatty liver disease (NAFLD) is the most common chronic liver disease in the United States, affecting between 60 and 90 million Americans, yet the vast majority of NAFLD patients are undiagnosed. NAFLD encompasses a spectrum of pathologies, ranging from steatosis to nonalcoholic steatohepatitis and fibrosis. Numerous animal studies have investigated the effects of NAFLD on hepatic gene expression, observing significant alterations in mRNA, protein, and activity levels. Information on the effects of NAFLD in human patients is limited, though several significant investigations have recently been published. Significant alterations in the activity of drug-metabolizing enzymes may affect the clearance of therapeutic drugs, with the potential to result in adverse drug reactions. With the enormous prevalence of NAFLD, it is conceivable that every drug currently on the market is being given to patients with NAFLD. The current review is intended to present the results from both animal models and human patients, summarizing the observed alterations in the expression and activity of the phase I and II drug-metabolizing enzymes.

Histopathology of nonalcoholic fatty liver disease

Histological analysis of liver biopsies remains a standard against which other methods of assessment for the presence and amount of hepatic injury due to nonalcoholic fatty liver disease (NAFLD) are measured. Histological evaluation remains the sole method of distinguishing steatosis from advanced forms of NAFLD, i.e. nonalcoholic steatohepatitis (NASH) and fibrosis. Included in the lesions of NAFLD are steatosis, lobular and portal inflammation, hepatocyte injury in the forms of ballooning and apoptosis, and fibrosis. However, patterns of these lesions are as distinguishing as the lesions themselves. Liver injury in adults and children due to NAFLD may have different histological patterns. In this review, the rationale for liver biopsy, as well as the histopathological lesions, the microscopically observable patterns of injury, and the differential diagnoses of NAFLD and NASH are discussed.

Pathology of nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) is a significant complication of obesity and is recognized as the hepatic manifestation of the metabolic syndrome. The process occurs in adults and children and is characterized by the presence of increased amounts of fat in the liver (steatosis). With inflammation, cell death and scarring (fibrosis), the process may result in end-stage liver disease, or be a precursor for hepatocellular carcinoma. Excess hepatic fat is now recognized as an independent marker for increased cardiovascular risk. Even though imaging studies and laboratory-based tests are accurate at detecting significant steatosis and/or advanced fibrosis, respectively, the diagnosis and characterization of NAFLD ultimately depend on histopathologic evaluation, as the parenchymal alterations that comprise the spectrum of injury in NAFLD include patterns as well as specific lesions. Histologic findings in children may differ from those in adults. In this Review, the histologic features that are diagnostic and discriminatory between steatosis and steatohepatitis, the significance of the distinction between steatosis and steatohepatitis, the types and locations of fibrosis, and the histologic variances between adult and pediatric NAFLD are discussed. Clinical advantages as well as potential drawbacks of liver biopsy are presented. Current pathophysiologic concepts relevant to histologic findings are discussed.

The incapacity of the surgeon to identify NASH in bariatric surgery makes biopsy mandatory

BACKGROUND

Nonalcoholic steatohepatitis (NASH) is a morbid condition highly related to obesity. It is unclear if the macroscopic liver appearance correlates with the histopathologic findings. The goal of this prospective study was to determine the relationship between the intraoperative liver appearance and the histopathologic diagnosis of NASH in morbidly obese subjects undergoing bariatric surgery. We also aimed to determine variables that could predict NASH preoperatively.

METHODS

Consecutive 51 subjects undergoing bariatric surgery without evidence of other liver disease underwent intraoperative liver biopsy. An intraoperative liver visual (macroscopic and tactile examination) was recorded. The liver aspect was compared with the liver histologic findings. Histological assessment was categorized into two groups: NASH and non-NASH (including normal histology and simple steatosis). Clinical and biochemical parameters were obtained from the patient databases and were compared between groups to identify preoperatively predictive factors of NASH.

RESULTS

From 51 patients, only one presented totally normal histology. Forty-three (86.2%) presented simple steatosis, and seven (13.7%) were classified as NASH. Clinical parameters were not different between groups. At biochemical analysis, only VLDL cholesterol level was significantly higher in the NASH group (p=0.037) but yet within the normal range. Association between macroscopic liver appearance and the presence of histological NASH is poor (sensitivity of 14%, specificity of 56%, positive predictive value of 5%, and negative predictive value of 80%).

CONCLUSIONS

No predictor of NASH was found. Surgeons' evaluation could not identify NASH individuals. Routine liver biopsy during bariatric operations is mandatory to differentiate NASH and nonalcoholic fatty liver disease.