Delays in definitive endoscopic resection of previously manipulated colorectal polyps as a risk factor for inferior resection outcomes.

BACKGROUND AND AIMS: Manipulation of colorectal polyps by biopsy, incomplete resection, or tattoo placement under the lesion has been shown to cause submucosal fibrosis and associated inferior outcomes. The effect of delays between index manipulation and definitive resection on the incidence of fibrosis is unknown. METHODS: Patients undergoing EMR of previously manipulated colorectal polyps ≥10 mm from 2016 to 2021 at a tertiary referral center were included. Time from index manipulation to definitive resection and the presence of fibrosis were noted. The effects of fibrosis on EMR outcomes were assessed. RESULTS: Among 221 previously manipulated lesions (180 biopsy, 23 incomplete/failed resection, 1 tattoo under lesion, 17 multiple types of manipulation), 51 (23%) demonstrated fibrosis. Fibrotic lesions were found to have been resected significantly later than nonfibrotic lesions (76 vs 61 days; P = .014). In a multivariate analysis controlling for other predictors of fibrosis, each 2-week delay was associated with a 14% increase in the odds of fibrosis. Fibrotic lesions had inferior outcomes with a lower en-bloc resection rate (8% vs 24%; P = .014) and longer procedure time (71 vs 52 minutes; P < .001). Adverse event and recurrence rates were similar between groups. CONCLUSIONS: Delays in definitive resection of previously manipulated polyps are associated with an increased incidence of fibrosis with time and associated inferior outcomes. Manipulation should be discouraged, and if it occurs, prompt referral and scheduling for definitive resection should be prioritized.

Submucosal injection fluid and tattoo agents.

BACKGROUND AND AIMS: EMR and endoscopic submucosal dissection (ESD) are minimally invasive endoscopic techniques, developed for the removal of benign and early malignant lesions throughout the GI tract. Submucosal injection of a marking agent can help to identify lesions during surgery. Endoscopic resection frequently involves "lifting" of the lesions by injection of a substance within the submucosal space to create a cushion for safe resection. This review summarizes the current techniques and agents available for endoscopic marking and lifting of GI tract lesions. METHODS: The MEDLINE database was searched through April 2023 for relevant articles related to the lifting and marking aspect of EMR by using key words such as "endoscopy" or "endoscopic" combined with "marking," "tattoo," and "lifting." The report was drafted, reviewed, and edited by the American Society for Gastrointestinal Endoscopy Technology Committee and approved by the Governing Board of the American Society for Gastrointestinal Endoscopy. RESULTS: This technology review describes the techniques for endoscopic tattoo placement and submucosal lifting, along with currently available agents, safety, and costs. CONCLUSIONS: Endoscopists performing EMR and ESD have several choices in submucosal injection materials for lifting and marking agents for tattoos. These may be commercially prepared agents or off-the-shelf materials with or without additives to facilitate visualization. A thorough understanding of the indications, techniques, properties of various agents, costs, and adverse events is necessary in choosing the appropriate materials and technique to optimize lesion resection in EMR and ESD.

Lessons Learned From the Comprehensive Care for Joint Replacement Model at an Academic Tertiary Center: The Good, the Bad, and the Ugly.

BACKGROUND: Our institution participated in the Comprehensive Care for Joint Replacement (CJR) model from 2016 to 2020. Here we review lessons learned from a total joint arthroplasty (TJA) care redesign at a tertiary academic center amid changing: (1) CJR rules; (2) inpatient only rules; and (3) outpatient trends. METHODS: Quality, financial, and patient demographic data from the years prior to and during participation in CJR were obtained from institutional and Medicare reconciled CJR performance data. RESULTS: Despite an increase in true outpatients and new challenges that arose from changing inpatient-only rules, there was significant improvement in quality metrics: decreased length of stay (3.48-1.52 days, P < .001), increased home discharge rate (70.2-85.5%, P < .001), decreased readmission rate (17.7%-5.1%, P < .001), decreased complication rate (6.5%-2.0%, P < .001), and the Centers for Medicare and Medicaid Services (CMS) Composite Quality Score increased from 4.4 to 17.6. Over the five year period, CMS saved an estimated $8.3 million on 1,486 CJR cases, $7.5 million on 1,351 non-CJR cases, and $600,000 from the voluntary classification of 371 short-stay inpatients as outpatient-a total savings of $16.4 million. Despite major physician time and effort leading to marked improvements in efficiency, quality, and large cost savings for CMS, CJR participation resulted in a net penalty of $304,456 to our institution, leading to zero physician gainsharing opportunities. CONCLUSION: The benefits of CJR were tempered by malalignment of incentives among payer, hospital, and physician as well as a lack of transparency. Future payment models should be refined based on the successes and challenges of CJR.

Hemostatic efficacy of pathogen-reduced platelets in children undergoing cardiopulmonary bypass.

BACKGROUND: Pediatric patients undergoing cardiopulmonary bypass (CPB) often require blood component transfusions. Pathogen-reduction (PR) of platelets reduces the risk of microbial contamination; however, its effect on hemostatic efficacy in this population is unclear. This study sought to characterize the hemostatic efficacy of PR platelets in children undergoing CPB. STUDY DESIGN AND METHODS: We performed a retrospective chart review of patients admitted to a pediatric intensive care unit following CPB surgery from 2015 to 2019. Demographic data, validated scoring of repair complexity, products received, and outcomes were compared. The primary outcome was postoperative chest tube bleeding. RESULTS: A total of 140 patients were enrolled. The majority of surgeries (124/140) were Risk Adjustment for Congenital Heart Surgery (RACHS) 1-3 repairs. Seventy-four percent of patients (104/140) received only standard platelets whereas 26% (36/140) received PR platelets. There were no differences between the groups in the age (p = .90), sex (p = .20) or RACHS score (p = .06). Postoperatively, there was no difference in the median chest tube output for 1 h (p = .27), 2 h (p = .26), 4 h (p = .09), 8 h (p = .16), or for the first 24 h following surgery (p = .23) in patients who received standard versus PR platelets. There was also no difference in receipt of platelets (p = .18), cell saver (p = .79), or cryoprecipitate (p = .28). CONCLUSION: Patients receiving PR platelets did not have more blood loss or require more transfusions than those who received standard platelets. This suggests that PR platelets may provide acceptable hemostasis with the additional benefits of reduced risk of microbial contamination in pediatric patients undergoing CPB.

The 2021 Association Research Circulation Osseous Classification for Early-Stage Osteonecrosis of the Femoral Head to Computed Tomography-Based Study.

BACKGROUND: The Association Research Circulation Osseous developed a novel classification for early-stage (precollapse) osteonecrosis of the femoral head (ONFH). We hypothesized that the novel classification is more reliable and valid when compared to previous 3 classifications: Steinberg, modified Kerboul, and Japanese Investigation Committee classifications. METHODS: In the novel classification, necrotic lesions were classified into 3 types: type 1 is a small lesion, where the lateral necrotic margin is medial to the femoral head apex; type 2 is a medium-sized lesion, with the lateral necrotic margin being between the femoral head apex and the lateral acetabular edge; and type 3 is a large lesion, which extends outside the lateral acetabular edge. In a derivation cohort of 40 early-stage osteonecrotic hips based on computed tomography imaging, reliabilities were evaluated using kappa coefficients, and validities to predict future femoral head collapse by chi-squared tests and receiver operating characteristic curve analyses. The predictability for future collapse was also evaluated in a validation cohort of 104 early-stage ONFH. RESULTS: In the derivation cohort, interobserver reliability (k = 0.545) and intraobserver agreement (63%-100%) of the novel method were higher than the other 3 classifications. The novel classification system was best able to predict future collapse (P < .05) and had the best discrimination between non-progressors and progressors in both the derivation cohort (area under the curve = 0.692 [0.522-0.863], P < .05) and the validation cohort (area under the curve = 0.742 [0.644-0.841], P = 2.46 × 10-5). CONCLUSION: This novel classification is a highly reliable and valid method of those examined. Association Research Circulation Osseous recommends using this method as a unified classification for early-stage ONFH. LEVEL OF EVIDENCE: Level III, diagnostic study.

Trends in Hospital and Surgeon Charges and Reimbursements for Revision Total Knee Arthroplasty.

BACKGROUND: The relationship between surgeon and hospital charges and reimbursements for revision total knee arthroplasty (TKA) has not been well examined. The objective of this study is to report trends and variations in hospital charges and payments compared to surgeons for stage 1 (S1) vs stage 2 (S2) septic revision TKA and aseptic revision (AR) TKA. METHODS: The 5% Medicare sample was used to capture hospital and surgeon data for revision TKA from 2005 to 2014. The charge multiplier (CM) and ratio of hospital to surgeon charges, and the payment multiplier (PM) and ratio of hospital to surgeon payments were calculated. Year-to-year variation and regional trends in-patient demographics, Charlson Comorbidity Index, length of stay (LOS), CM, and PM were evaluated. RESULTS: In total, 4570 AR, 1323 S1, and 863 S2 TKA patients were included. CM increased for all cohorts: 8.1-13.8 for AR (P < .001), 21.0-22.5 (P = .07) for S1, and 11.8-22.0 (P < .001) for S2. PM followed a similar trend, increasing 8.1-13.8 (P < .001) for AR, 19.8-27.3 (P = .005) for S1, and 14.7-30.7 (P < .001) for S2. Surgeon reimbursement decreased for all cohorts. LOS decreased for AR (3.8-2.8 days), S1 (12.8-6.9 days), and S2 (4.5-3.9 days). Charlson Comorbidity Index remained stable for AR patients but increased significantly for S1 and S2 cohorts. CONCLUSION: Hospital charges and payments relative to the surgeons have significantly increased for revision TKA in the setting of stable or increasing patient complexity and decreasing LOS.

Reimbursements for Revision Total Hip Arthroplasty Have Increased for Hospitals but Not for Surgeons.

BACKGROUND: With increases in total hip arthroplasty procedures the need for revision total hip arthroplasty (rTHA) has increased as well. This study aims to analyze the trends in hospital charges and payments relative to corresponding surgeon charges and payments in a Medicare population for rTHA for aseptic revisions, stage 1 and stage 2 revisions. METHODS: The 5% Medicare sample database was used to capture hospital and surgeon charges and payments related to 4449 patients undergoing aseptic revision, 517 for stage 1 revision, and 300 for stage 2 revision in between the years 2004 and 2014. Two values were calculated: (1) the ratio of hospital to surgeon charges (CM) and (2) the ratio of hospital to surgeon payments (PM). Year-to-year variation and trends in patient demographics, Charlson Comorbidity Index (CCI), length of stay (LOS), CM, and PM were evaluated. RESULTS: The mean CCI for aseptic revisions and stage 1 revisions did not significantly change (P < .088 and P < .063). The CCI slightly increased for stage 2 revisions (P < .04). The mean LOS decreased significantly over time in all 3 procedure types. The CM increased by 39% (P < .02) in aseptic revisions, 109% in stage 1 revisions (P < .001) but did not significantly change in stage 2 revisions (P < .877). PM for aseptic revisions increased around 103% (P < .001), 107% for stage 1 revisions (P < .001), and 9.7% for stage 2 revisions (P < .176). CONCLUSION: Hospital charges and payments relative to surgeon charges and payments have increased substantially for THA aseptic revisions, stage 1 revisions, and stage 2 revisions despite stable patient complexity and decreasing LOS.

Obesity and Postoperative Complications Following Ankle Arthrodesis: A Propensity Score Matched Analysis.

Obese patients undergoing orthopedic procedure have been reported to have higher rates of postoperative complications, but the published associations have numerous confounders. This study aims to evaluate the independent effect of obesity on postoperative complications and hospital utilization following ankle arthrodesis. A database review of a Medicare database was performed on patients less than 85 years old who underwent ankle arthrodesis between 2005 and 2014. Patient cohorts were defined using International Classification of Diseases-9 coding for body mass index (BMI)-obese (30-40 kg/m2), and morbidly obese (>40 kg/m2). Normal BMI patients were defined as those without the respect codes for obesity (30-40 kg/m2), morbidly obese (>40 kg/m2), or underweight (<19 kg/m2). All groups were propensity score matched by demographics and comorbidities. Outcomes of interest included 90-day major and minor medical complications, and hospital burden. Morbid obesity was associated with an increased risk of acute kidney injury (4.4% vs 2.4%, OR 1.94, 95% CI 1.37-2.74, p < .001), urinary tract infection (5.2% vs 3.2%, OR 1.66, 95% CI 1.21-2.25, p = .001), readmission (13.6% vs 10.8%, OR 1.33, 95% CI 1.10-1.61, p = .003), and overall minor complications (16.0% vs 11.8%, OR 1.44, 95% CI 1.19-1.74, p < .001) compared to normal BMI patients, and an increased risk for acute kidney injury (4.4% vs 1.9%, OR 2.25, 95% CI 1.32-3.97, p = .003) compared to obese patients. Obesity was not associated with increased medical complications (p > .05). While morbid obesity was associated with an increase in the postoperative complications, obesity was not associated with any increase in postoperative complications following ankle arthrodesis.

Is Needle Knife Fistulotomy a Shortcut to Preventing Postendoscopic Retrograde Pancreatitis?

Post-endoscopic retrograde cholangiopancreatography pancreatitis (PEP) remains a common and potentially severe adverse event, with continued research efforts to reduce PEP incidence. Robust evidence exists supporting the selective use of pancreatic duct stent placement, administration of rectal indomethacin, wire-guided cannulation technique, and aggressive fluid hydration using lactated Ringer solution. Jang et al. presented a randomized control trial describing primary needle-knife fistulotomy and its benefit for biliary access and reduced PEP incidence. Although these data are compelling, we discuss the key study limitations and the need for further studying the role of primary needle-knife fistulotomy.

Surgeon Reimbursement Unchanged as Hospital Charges and Reimbursements Increase for Total Joint Arthroplasty.

BACKGROUND: Despite increasing demands on physicians and hospitals to increase value and reduce unnecessary costs, reimbursement for healthcare services has been under downward pressure for several years. This study aimed to analyze the trend in hospital charges and payments relative to corresponding surgeon charges and payments in a Medicare population for total hip (THA) and knee arthroplasty (TKA). METHODS: The 5% Medicare sample database was used to capture hospital and surgeon charges and payments related to 56,228 patients who underwent primary THA and 117,698 patients who underwent primary TKA between 2005 and 2014. Two values were calculated: (1) the charge multiplier (CM), the ratio of hospital to surgeon charges and (2) the payment multiplier (PM), the ratio of hospital to surgeon payments. Year-to-year variation and regional trends in patient demographics, Charlson Comorbidity Index, length of stay (LOS), CM, and PM were evaluated. RESULTS: Hospital charges were significantly higher than surgeon charges and increased substantially for both THA (CM increased from 8.7 to 11.5, P < .0001) and TKA (CM increased from 7.9 to 11.4, P < .0001). PM followed a similar trend, increasing for both THA and TKA (P < .0001). LOS decreased significantly for both THA and TKA (P < .0001), while Charlson Comorbidity Index remained stable. Both CM (r2 = 0.84 THA, 0.90 TKA) and PM (r2 = 0.75 THA, 0.84 TKA) were strongly negatively associated with LOS. CONCLUSION: Hospital charges and payments relative to surgeon charges and payments have increased substantially for THA and TKA despite stable patient complexity and decreasing LOS.

Urinary Self-Catheterization is Not Associated with Increased Risk of Major Complications Following Total Hip and Knee Arthroplasty.

BACKGROUND: The objective of this study is to evaluate urinary self-catheterization as a potential risk factor for postoperative complications following total hip (THA) and knee (TKA) arthroplasty procedures. METHODS: Self-catheterization patients who underwent total joint arthroplasty from 2005 to 2014 were identified in a national insurance database. Rates of death, hospital readmission, emergency room visit, infection, revision, and dislocation for THA or arthrofibrosis for TKA were calculated, as well as cost and length of stay. Self-catheterizing patients were then compared to a 4:1 matched control cohort using a logistic regression analysis to control for confounding factors. RESULTS: Sixty-nine patients underwent THA, and 128 patients who underwent TKA and who actively self-catheterized at the time of surgery were identified. Self-catheterization was not associated with infection, emergency room visits, readmissions, revision surgery, arthrofibrosis, or cost compared to the 4:1 matched control cohort. However, self-catheterization was associated with significantly longer length of stay (difference for THA = 1.91 days, confidence interval = 0.97-2.86, P < .001; difference for TKA = 0.61, odds ratio = 0.16-1.06, P = .01). CONCLUSION: Self-catheterization does not appear to be associated with increased risk of major complications following total joint arthroplasty with the numbers available in this study. Reassurance can be given regarding concerns for infection and other complications following surgery in this patient population.

Hospital and Surgeon Reimbursement Trends for Femoral Neck Fractures Treated With Hip Hemiarthroplasty and Total Hip Arthroplasty.

BACKGROUND: The economic impact of hip fractures on the health care system continues to rise with continued pressure to reduce unnecessary costs while maintaining quality patient care. This study aimed to analyze the trend in hospital charges and payments relative to surgeon charges and payments in a Medicare population for hip hemiarthroplasty and total hip arthroplasty (THA) for femoral neck fracture. METHODS: The 5% Medicare sample database was used to capture hospital and surgeon charges and payments related to 32,340 patients who underwent hemiarthroplasty and 4323 patients who underwent THA for femoral neck fractures between 2005 and 2014. Two values were calculated: (1) charge multiplier (CM, ratio of hospital to surgeon charges), and (2) payment multiplier (PM, ratio of hospital to surgeon payments). Year-to-year variation and regional trends in patient demographics, Charlson Comorbidity Index (CCI), length of stay (LOS), 90-day and 1-year mortality, CM, and PM were evaluated. RESULTS: Hospital charges were significantly higher than surgeon charges and increased substantially for hemiarthroplasty (CM of 13.6 to 19.3, P < .0001) and THA (CM of 9.8 to 14.9, P = .0006). PM followed a similar trend for both hemiarthroplasty (14.9 to 20.2; P = .001) and THA (11.9 to 17.4; P < .0001). LOS decreased significantly for hemiarthroplasty (3.78 to 3.37d; P < .0001) despite increasing CCI (6.36 to 8.39; P = .018), whereas both LOS (3.71 to 3.79 days; P = .421) and CCI (5.34 to 7.08; P = .055) remained unchanged for THA. CONCLUSION: Hospital charges and payments relative to surgeon charges and payments have increased substantially for hemiarthroplasty and THA performed for femoral neck fractures.

Hypogonadism Is Associated With Increased Risks of Postoperative Complications Following Total Hip Arthroplasty.

BACKGROUND: Despite being a relatively common problem among aging men, hypogonadism has not been previously studied as a potential risk factor for postoperative complications following total hip arthroplasty (THA). METHODS: In total, 3903 male patients with a diagnosis of hypogonadism who underwent primary THA from 2006 to 2012 were identified using a national insurance database and compared to 20:1 matched male controls using a logistic regression analysis. RESULTS: Hypogonadism was associated with an increased risk of major medical complications (odds ratio [OR] 1.24, P = .022), urinary tract infection (OR 1.43, P < .001), wound complications (OR 1.33, P = .011), deep vein thrombosis (OR 1.64, P < .001), emergency room visit (OR 1.24, P < .001), readmission (OR 1.14, P = .015), periprosthetic joint infection (OR 1.37 and 1.43, P < .05), dislocation (OR 1.51 and 1.48, P < .001), and revision (OR 1.54 and 1.56, P < .001) following THA. A preoperative diagnosis of hypogonadism was associated with increased total reimbursement and charges by $390 (P < .001) and $4514 (P < .001), respectively. CONCLUSION: The diagnosis of hypogonadism is associated with an elevated risk of postoperative complications and increased cost of care following primary THA. Data from this study should influence the discussion between the patient and the provider prior to undergoing joint replacement and serve as the basis for further research.

Preoperative Pain Management: Is Tramadol a Safe Alternative to Traditional Opioids Before Total Hip Arthroplasty?

BACKGROUND: Preoperative opioid use has been associated with worse clinical outcomes and higher rates of prolonged opioid use following lower extremity arthroplasty. Tramadol has been recommended for management of osteoarthritis-related pain; however, outcomes following total hip arthroplasty (THA) in patients taking tramadol in the preoperative period have not been well described. The aim of this study is to examine the effect of preoperative tramadol use on postoperative outcomes in patients undergoing elective THA. METHODS: A total of 5304 patients who underwent primary THA for degenerative hip pathology from 2008 to 2014 were identified using the Humana Claims Database. Patients were grouped by preoperative pain management modality into 3 mutually exclusive populations including tramadol, traditional opioid, or nonopioid only. A multivariate logistic regression was used to evaluate all postsurgical outcomes of interest. RESULTS: Tramadol users had an increased risk of developing prolonged narcotic use (odds ratio [OR], 2.17; confidence interval [CI], 1.89-2.49; P < .001) following surgery compared to nonopioid-only users. When compared to traditional opioid use, tramadol use was associated with decreased risk of subsequent 90-day minor medical complications (OR, 0.75; CI, 0.62-0.90; P = .002), emergency department visits (OR, 0.70; CI, 0.57-0.85; P < .001), and prolonged narcotic use (OR, 0.43; CI, 0.37-0.49; P < .001). Traditional opioid use significantly increased length of stay by 0.20 days (P = .001) when compared to tramadol use. CONCLUSION: Preoperative tramadol use is associated with prolonged opioid use following THA but is not associated with other postoperative complications. Patients taking tramadol preoperatively appear to have a lower risk of postoperative complications compared to patients taking traditional opioids preoperatively.

Normal Pressure Hydrocephalus Is Associated With Increased Risks of Postoperative Complications Following Total Knee and Total Hip Arthroplasty.

BACKGROUND: Normal pressure hydrocephalus (NPH) has not been studied as a potential risk factor for postoperative complications after primary total knee (TKA) and total hip arthroplasty (THA). METHODS: Nearly 2000 patients with a diagnosis of NPH who underwent TKA or THA from 2005 to 2014 were identified in a national insurance database and compared to 10:1 matched controls using a logistic regression analysis. RESULTS: NPH was associated with an increased risk of hospital readmission, emergency room visit, and infection following TKA (odds ratio 1.48-2.70, all P < .01). NPH was associated with an increased risk of hospital readmission, emergency room visit, and dislocation following THA (odds ratio 2.40-2.50, all P < .01). NPH was also associated with significantly higher costs and hospital length of stay following both procedures. CONCLUSION: The diagnosis of NPH is associated with an elevated risk of postoperative complications and increased resource utilization following TKA and THA.

Patients With Multiple Sclerosis are at Increased Risk for Postoperative Complications Following Total Hip and Knee Arthroplasty.

BACKGROUND: Multiple sclerosis (MS) is a chronic inflammatory demyelinating disease affecting the central nervous system. Patients with MS are living longer due to improved medical therapy and thus the demand for arthroplasty in this population will increase. The objective of this study is to evaluate MS as a potential risk factor for postoperative complications following total hip arthroplasty (THA) and total knee arthroplasty (TKA). METHODS: Patients with a diagnosis of MS who underwent THA or TKA from 2005 to 2014 were identified in a national insurance database. Rates of death, hospital readmission, emergency room visits, infection, revision, and dislocation (for THA) or stiffness (for TKA) were calculated, in addition to cost and length of stay. MS patients were then compared to a matched control population. RESULTS: In total, 3360 patients who underwent THA and 6436 patients who underwent TKA with a history of MS were identified and compared with 10:1 matched control cohorts without MS. The MS group for both TKA and THA had significantly higher incidences of hospital readmission (THA odds ratio [OR] 2.05, P < .001; TKA OR 1.99, P < .001), emergency room visits (THA OR 1.41, P < .001; TKA OR 1.66, P < .001), and infection (THA OR 1.35, P = .001; TKA OR 1.32, P < .001). MS patients who underwent THA had significantly higher rates of revision (OR 1.35, P = .001) and dislocation (OR 1.52, P < .001). Diagnosis of MS was also associated with significantly higher costs and hospital length of stay for patients undergoing both TKA and THA. CONCLUSION: A diagnosis of MS is associated with increased risk of postoperative complications and higher costs following both THA and TKA.

MRI proton density fat fraction is robust across the biologically plausible range of triglyceride spectra in adults with nonalcoholic steatohepatitis.

BACKGROUND: Proton density fat fraction (PDFF) estimation requires spectral modeling of the hepatic triglyceride (TG) signal. Deviations in the TG spectrum may occur, leading to bias in PDFF quantification. PURPOSE: To investigate the effects of varying six-peak TG spectral models on PDFF estimation bias. STUDY TYPE: Retrospective secondary analysis of prospectively acquired clinical research data. POPULATION: Forty-four adults with biopsy-confirmed nonalcoholic steatohepatitis. FIELD STRENGTH/SEQUENCE: Confounder-corrected chemical-shift-encoded 3T MRI (using a 2D multiecho gradient-recalled echo technique with magnitude reconstruction) and MR spectroscopy. ASSESSMENT: In each patient, 61 pairs of colocalized MRI-PDFF and MRS-PDFF values were estimated: one pair used the standard six-peak spectral model, the other 60 were six-peak variants calculated by adjusting spectral model parameters over their biologically plausible ranges. MRI-PDFF values calculated using each variant model and the standard model were compared, and the agreement between MRI-PDFF and MRS-PDFF was assessed. STATISTICAL TESTS: MRS-PDFF and MRI-PDFF were summarized descriptively. Bland-Altman (BA) analyses were performed between PDFF values calculated using each variant model and the standard model. Linear regressions were performed between BA biases and mean PDFF values for each variant model, and between MRI-PDFF and MRS-PDFF. RESULTS: Using the standard model, mean MRS-PDFF of the study population was 17.9 ± 8.0% (range: 4.1-34.3%). The difference between the highest and lowest mean variant MRI-PDFF values was 1.5%. Relative to the standard model, the model with the greatest absolute BA bias overestimated PDFF by 1.2%. Bias increased with increasing PDFF (P < 0.0001 for 59 of the 60 variant models). MRI-PDFF and MRS-PDFF agreed closely for all variant models (R2 = 0.980, P < 0.0001). DATA CONCLUSION: Over a wide range of hepatic fat content, PDFF estimation is robust across the biologically plausible range of TG spectra. Although absolute estimation bias increased with higher PDFF, its magnitude was small and unlikely to be clinically meaningful. LEVEL OF EVIDENCE: 3 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2018;47:995-1002.