Guide › Abdominal Ultrasound in the Assessment of Fatty Liver (Hepatic Steatosis)

Abdominal Ultrasound in the Assessment of Fatty Liver (Hepatic Steatosis)

1. Introduction

Hepatic steatosis, defined histologically as the accumulation of triglycerides in more than 5% of hepatocytes, represents the most common chronic liver disease worldwide (Younossi et al., 2016). With the global prevalence of metabolic dysfunction-associated steatotic liver disease (MASLD), previously termed nonalcoholic fatty liver disease (NAFLD), estimated at approximately 30–38% of the general population, accurate and accessible diagnostic tools have become essential for clinical practice (Rinella et al., 2023). Ultrasound remains the most commonly used initial imaging modality for detecting hepatic steatosis due to its non-invasive nature, lack of ionizing radiation, wide availability, and relatively low cost (EASL-EASD-EASO, 2024).

Think of your liver like a sponge. Normally, it has a certain texture and appearance on an ultrasound scan. When fat builds up in the liver, what doctors call “fatty liver” or hepatic steatosis, the liver looks different on the scan. It appears brighter and “whiter” than it should, almost like a bright light reflecting off the screen. This happens because the fat droplets inside liver cells bounce the ultrasound waves back differently than healthy liver tissue. Ultrasound is often the first test doctors use to check for fatty liver because it’s safe (no radiation), painless, relatively quick, and available in most hospitals and clinics. It’s like taking a photograph of your liver using sound waves instead of light.

2. Sonographic Findings Suggestive of Hepatic Steatosis

2.1 Increased Echogenicity (Bright Liver)

The hallmark sonographic feature of hepatic steatosis is increased parenchymal echogenicity, commonly referred to as a “bright liver” appearance (Ferraioli et al., 2019). Fat accumulation within hepatocytes creates additional acoustic interfaces that increase the reflection of ultrasound waves, resulting in a hyperechoic liver parenchyma. The degree of brightness generally correlates with the severity of fat infiltration, though this relationship is not perfectly linear and is subject to considerable observer variability (Palmentieri et al., 2006).

The grading of hepatic steatosis by B-mode ultrasound is typically classified as follows (Saverymuttu et al., 1986; Tan et al., 2024):

  • Grade 0 (Normal): The liver echotexture appears normal and isoechoic compared to the renal cortex, with adequate visualization of hepatic vessels and the diaphragm.
  • Grade 1 (Mild): A slight and diffuse increase in fine hepatic echoes with normal visualization of the diaphragm and intrahepatic vessel borders.
  • Grade 2 (Moderate): A moderate increase in liver echogenicity with slightly impaired visualization of the portal vein walls and diaphragm.
  • Grade 3 (Severe): Marked increase in liver echogenicity with poor or absent visualization of the portal vein walls, diaphragm, and posterior portions of the right liver lobe.

2.2 Hepatorenal Contrast (Liver Brighter Than Kidney)

Hepatorenal contrast refers to the comparison of echogenicity between the liver parenchyma and the cortex of the right kidney. Under normal circumstances, the liver and renal cortex demonstrate similar echogenicity. In hepatic steatosis, the liver appears distinctly brighter than the adjacent kidney, creating increased hepatorenal contrast (Dasarathy et al., 2009).

When a sonographer examines your liver, they often compare how bright it looks compared to your right kidney, which sits just next to the liver. In a healthy person, the liver and kidney look about the same brightness on the screen. But when fat accumulates in the liver, it becomes noticeably brighter—like how a white shirt stands out next to a gray one. This comparison between the liver and kidney is one of the most reliable ways to spot fatty liver on an ultrasound because it gives doctors a built-in reference point right there in the same image.

The hepatorenal index (HRI) represents a semiquantitative method for assessing this contrast by calculating the ratio between the mean echogenicity of the liver and the renal cortex (Webb et al., 2009). In a landmark study by Webb et al. (2009), a hepatorenal sonographic index cutoff of 1.49 demonstrated 100% sensitivity and 91% specificity for detecting steatosis greater than 5% of hepatocytes. Subsequent meta-analyses have confirmed the high diagnostic accuracy of HRI, with pooled sensitivity of 87% and specificity of 89% for detecting hepatic steatosis (Wang et al., 2025).

2.3 Vascular Blunting

As hepatic fat content increases, the intrahepatic vessels become progressively less visible due to increased attenuation and scatter of the ultrasound beam. This phenomenon, termed vascular blunting, manifests as decreased conspicuity of the portal vein walls and hepatic vein walls (Chauhan et al., 2016). Portal vein blurring typically becomes apparent in moderate steatosis and is more pronounced in severe steatosis. Dasarathy et al. (2009) demonstrated that vascular blunting criteria (portal vein blurring and hepatic vein blurring) had moderate sensitivity and specificity for detecting hepatic steatosis involving 20% or more of the liver area.

2.4 Deep Attenuation

Deep beam attenuation refers to the progressive decrease in ultrasound signal intensity as the beam penetrates deeper into fatty liver tissue. Fat within hepatocytes causes significant attenuation of the ultrasound beam, resulting in poor visualization of deep hepatic structures and the posterior aspect of the right liver lobe (Ballestri et al., 2019). In severe steatosis, the diaphragm may become poorly visualized or invisible altogether. This attenuation is caused by absorption and scattering of sound energy by the lipid-laden hepatocytes.

2.5 Advanced Findings: Surface Changes and Morphological Alterations

In advanced liver disease progressing toward cirrhosis, additional sonographic findings may be observed (Liver Imaging StatPearls, 2023):

  • Surface nodularity: An irregular or nodular hepatic surface suggests underlying fibrosis or cirrhosis and indicates advanced disease progression beyond simple steatosis.
  • Lobe size alterations: Changes in relative lobe proportions, particularly caudate lobe hypertrophy with right lobe atrophy, may indicate progression to cirrhosis.
  • Coarsened echotexture: A heterogeneous, coarsened parenchymal pattern may develop as steatosis progresses to steatohepatitis and fibrosis.

2.6 Splenomegaly

Splenomegaly, defined as a longitudinal spleen length greater than 13 cm, has traditionally been associated with portal hypertension in advanced cirrhosis (Mendes et al., 2012). However, its significance in MASLD is complex. While splenomegaly is classically associated with advanced fibrosis and portal hypertension, recent evidence suggests it may occur independent of fibrosis stage in MASLD. Srivastava et al. (2022) found no correlation between spleen size and degree of underlying liver disease in patients with biopsy-proven NAFLD, with splenomegaly present in 27.4% of subjects across all fibrosis stages, including those with no fibrosis. Interestingly, spleen size correlated more strongly with body weight, suggesting visceral adiposity rather than liver disease severity may drive splenic enlargement in this population.

The spleen is an organ near your stomach that can become enlarged when there’s increased pressure in the blood vessels of the liver—a condition called portal hypertension. Doctors sometimes look at the spleen during a liver ultrasound because an enlarged spleen can be a warning sign of serious liver problems.

However, recent research has shown that in people with fatty liver disease, an enlarged spleen doesn’t necessarily mean the liver disease is severe. In many cases, people who are overweight or obese have larger spleens simply because of their body size, not because of advanced liver disease. So while doctors still check the spleen, they interpret this finding carefully in patients with fatty liver.

3. Ultrasound Subtypes and Advanced Techniques

3.1 Controlled Attenuation Parameter (CAP)

Controlled attenuation parameter is a novel ultrasound-based technology integrated with vibration-controlled transient elastography (FibroScan®, Echosens, Paris, France) that measures ultrasound attenuation as a surrogate marker of hepatic steatosis (Sasso et al., 2010). CAP exploits the principle that fat attenuates ultrasound waves, with the degree of attenuation correlating with liver fat content. Values are expressed in decibels per meter (dB/m), ranging from 100 to 400 dB/m.

According to the AASLD Practice Guidance (Rinella et al., 2023), CAP provides a point-of-care semiquantitative assessment of hepatic steatosis, though it does not accurately quantify or monitor changes in liver fat. A meta-analysis evaluating CAP performance reported area under the receiver operating characteristic curve (AUROC) values of 0.95 for detecting any steatosis (≥S1) and 0.84 for moderate steatosis (≥S2) (Karlas et al., 2017). CAP score can only be measured on special machines (called Fibroscan) which we will talk in separate article.

3.2 Ultrasound Attenuation Coefficient (AC)

The ultrasound attenuation coefficient represents an emerging quantitative technique that measures sound wave attenuation through liver tissue using standard ultrasound systems with specialized software (Jang et al., 2022). Different manufacturers have developed proprietary attenuation imaging technologies, including Attenuation Imaging (ATI; Canon Medical Systems), Attenuation Measurement Function (ATT; Samsung), and Ultrasound-Guided Attenuation Parameter (UGAP; GE Healthcare).

A systematic review and meta-analysis by Jang et al. (2022) reported pooled sensitivity and specificity of 76% and 84% for detecting any steatosis (S≥1), and 87% and 79% for detecting advanced steatosis (S≥2). Importantly, AC showed higher sensitivity than CAP in head-to-head comparisons, possibly due to the image-guided approach allowing accurate placement of regions of interest.

3.3 Ultrasound-Derived Fat Fraction (UDFF)

Ultrasound-derived fat fraction represents a newer quantitative approach combining attenuation coefficient with backscatter coefficient measurements to estimate liver fat content, expressed as a percentage directly comparable to MRI proton density fat fraction (PDFF) (Ferraioli et al., 2019). A recent systematic review demonstrated excellent correlation with MRI-PDFF (average r = 0.848) and high reproducibility, with proposed cutoffs ranging from 5% to 23% for different steatosis grades (MDPI Diagnostics, 2025).

4. Portal Venous Doppler Assessment

Portal venous Doppler ultrasound provides hemodynamic information that complements B-mode assessment in patients with hepatic steatosis. Several studies have documented significant alterations in portal and hepatic hemodynamics associated with fatty liver disease (Solhjoo et al., 2011; Balasubramanian et al., 2016).

4.1 Portal Vein Hemodynamic Changes

Patients with NAFLD demonstrate reduced portal venous velocity compared to healthy controls. Balci et al. (2011) reported significantly lower portal venous velocity (17.50 ± 3.55 cm/s vs. 19.58 ± 2.17 cm/s) and mean time-averaged velocity in NAFLD patients compared to healthy controls. The portal vein pulsatility index (VPI), calculated as (Vmax – Vmin) / Vmax, is also reduced in NAFLD, correlating with the presence of steatosis (Monteiro et al., 2016).

Beyond just looking at the liver’s appearance, doctors can use a special type of ultrasound called Doppler to measure how blood flows through the liver. In fatty liver disease, the blood flow pattern often changes. The portal vein—the main blood vessel bringing blood from the intestines to the liver—typically shows slower blood flow in people with fatty liver. Additionally, the flow pattern in the hepatic veins (vessels carrying blood out of the liver) can become abnormal, changing from a normal three-wave pattern to a flatter pattern. These blood flow changes can provide additional clues about liver health beyond what’s visible on a regular ultrasound image.

4.2 Hepatic Vein Waveform Patterns

The hepatic vein normally demonstrates a triphasic waveform pattern reflecting cardiac pulsations transmitted through the inferior vena cava. In hepatic steatosis and steatohepatitis, this pattern may become biphasic or monophasic due to decreased hepatic compliance (Solhjoo et al., 2011). Solhjoo et al. (2011) found that abnormal hepatic vein Doppler waveform patterns were significantly more common in NAFLD patients (55.2%) compared to controls (3.2%).

4.3 Clinical Utility and Limitations

While Doppler parameters can detect hemodynamic changes associated with steatosis, they have limitations in clinical practice. Monteiro et al. (2016) demonstrated that portal and hepatic vein indices allow non-invasive steatosis diagnosis (with portal venous pulsatility index cutoff of 0.26 yielding 91% sensitivity and 79.6% specificity) but are limited in quantifying steatosis severity. Doppler findings are also influenced by numerous technical factors including patient positioning, respiratory phase, fasting state, and operator technique, contributing to variable reproducibility (Berzigotti et al., 2023).

5. Ultrasound Diagnostic Accuracy: Advantages and Limitations

5.1 Advantages of Ultrasound

B-mode ultrasound offers numerous advantages as a first-line imaging modality for hepatic steatosis assessment (Hernaez et al., 2011; EASL-EASD-EASO, 2024):

  1. Non-invasive: No ionizing radiation or need for contrast agents
  2. Widely available: Present in virtually all healthcare settings worldwide
  3. Cost-effective: Significantly less expensive than MRI or CT
  4. Real-time imaging: Allows dynamic assessment and immediate interpretation
  5. Portable: Bedside examinations possible in critically ill patients
  6. Well-tolerated: No contraindications for claustrophobic patients
  7. Comprehensive evaluation: Can simultaneously assess for other pathology including gallstones, masses, ascites, and biliary abnormalities

5.2 Diagnostic Performance

The landmark meta-analysis by Hernaez et al. (2011), analyzing 49 studies with 4,720 participants, established the diagnostic accuracy of conventional ultrasound for hepatic steatosis. For detecting moderate-severe fatty liver (≥20–30% steatosis), ultrasound demonstrated:

  • Pooled sensitivity: 84.8% (95% CI: 79.5–88.9%)
  • Pooled specificity: 93.6% (95% CI: 87.2–97.0%)
  • Positive likelihood ratio: 13.3 (95% CI: 6.4–27.6)
  • AUROC: 0.93 (95% CI: 0.91–0.95)

An updated meta-analysis by Ballestri et al. (2021), evaluating studies published from 2011–2021, confirmed these findings and additionally assessed detection of mild steatosis (≥5% fat):

  • For ≥5% steatosis: sensitivity 82%, specificity 80%
  • For ≥30% steatosis: sensitivity 85%, specificity 85%

How good is ultrasound at finding fatty liver? Large research studies pooling data from thousands of patients have shown that ultrasound is very good at detecting moderate to severe fatty liver—it correctly identifies about 85% of people who have it and correctly rules it out in about 94% of people who don’t. However, it’s not as reliable for detecting very mild fatty liver (less than 20–30% fat). Think of it like trying to see rain on the windshield: a heavy downpour is obvious, but a light mist might be harder to spot. This is why doctors might recommend additional tests if they strongly suspect fatty liver but the ultrasound looks normal.

5.3 Conventional Ultrasound Limitations

Despite its widespread use, conventional B-mode ultrasound has important limitations (Rinella et al., 2023; Petzold, 2022):

  1. Operator dependence: Image quality and interpretation vary with operator experience and technique
  2. Qualitative assessment: Provides semiquantitative grading rather than precise fat quantification
  3. Limited sensitivity for mild steatosis: Reduced accuracy for detecting steatosis involving less than 20–30% of hepatocytes (sensitivity 60–65% for mild steatosis)
  4. Obesity limitations: Technical difficulty and reduced image quality in patients with high body mass index due to increased subcutaneous fat thickness
  5. Inability to distinguish steatosis from steatohepatitis: Cannot differentiate simple steatosis from NASH, as inflammation is not visible on ultrasound
  6. Poor sensitivity for fibrosis: Limited ability to detect or stage hepatic fibrosis
  7. Confounding factors: Similar echogenic appearance can be caused by fibrosis, glycogen storage, or other infiltrative processes
  8. Absence of standardization: No universally accepted standardized protocol or reporting system

The 2023 AASLD Practice Guidance explicitly states that “although standard ultrasound can detect hepatic steatosis, it is not recommended as a tool to identify hepatic steatosis due to low sensitivity across the NAFLD spectrum” (Rinella et al., 2023). The absence of detectable steatosis on ultrasound does not exclude the presence of NASH or fibrosis.

6. Clinical Significance and Practical Application

Ultrasound is appropriate for initial detection of hepatic steatosis in clinical practice but should be interpreted within the context of clinical assessment and combined with additional diagnostic tools (EASL-EASD-EASO, 2024). The clinical utility of ultrasound in MASLD evaluation includes:

6.1 Screening and Initial Detection

In patients with metabolic risk factors (obesity, type 2 diabetes, dyslipidemia, hypertension), abnormal liver function tests, or clinical suspicion of fatty liver disease, B-mode ultrasound serves as an appropriate first-line imaging study. The 2024 EASL-EASD-EASO Clinical Practice Guidelines recommend that individuals with radiological signs of hepatic steatosis undergo further assessment for underlying etiology and fibrosis risk (EASL-EASD-EASO, 2024).

6.2 Comprehensive Evaluation

The comprehensive ultrasound examination should include:

  • Assessment of liver echogenicity and comparison with renal cortex
  • Evaluation of intrahepatic vascular conspicuity
  • Documentation of liver size and surface contour
  • Assessment for features of portal hypertension (splenomegaly, ascites, collateral vessels)
  • Evaluation for other hepatic abnormalities (masses, focal lesions, biliary abnormalities)
  • Documentation of any focal fat sparing or focal fat deposition patterns

6.3 Integration with Clinical Assessment

Ultrasound findings should be integrated with:

  • Clinical history and metabolic risk factors
  • Laboratory findings (liver enzymes, lipid profile, fasting glucose/HbA1c)
  • Non-invasive fibrosis markers (FIB-4 index, NAFLD Fibrosis Score)
  • Assessment of alcohol intake and exclusion of other causes of liver disease

7. Next Steps in the Diagnostic Pathway

When ultrasound detects hepatic steatosis or when liver function tests are abnormal, the subsequent diagnostic pathway typically involves additional assessments to characterize disease severity and exclude advanced fibrosis (Rinella et al., 2023; EASL-EASD-EASO, 2024).

7.1 Liver Elastography

Vibration-controlled transient elastography (VCTE/FibroScan) and its alternative elastography methods has become an essential tool in MASLD evaluation, providing simultaneous assessment of liver stiffness (a surrogate for fibrosis) and controlled attenuation parameter (for steatosis). The 2023 AASLD Guidance recommends that if FIB-4 is ≥1.3, VCTE, MRE, or ELF may be used to exclude advanced fibrosis (Rinella et al., 2023).

VCTE has demonstrated good accuracy for identifying advanced fibrosis in NAFLD populations:

  • AUROC 0.83 (95% CI: 0.79–0.87) for advanced fibrosis (≥F3)
  • AUROC 0.93 for cirrhosis (F4)
  • A liver stiffness measurement cutoff of 6.5 kPa excludes advanced fibrosis with negative predictive value of 0.91

(Eddowes et al., 2019)

7.2 MRI-Based Assessment

MRI proton density fat fraction (MRI-PDFF) represents the most accurate non-invasive tool for hepatic steatosis quantification (Reeder & Sirlin, 2010; AASLD, 2024). MRI-PDFF demonstrates:

  • Strong correlation with histological fat fraction (r = 0.75–0.87)
  • High sensitivity (approaching 100%) for detecting any steatosis
  • Ability to precisely quantify liver fat content
  • Excellent reproducibility across different MRI platforms

However, MRI-PDFF use is limited by cost, availability, and the need for patient cooperation. The 2023 AASLD Guidance states that “MRI-PDFF can additionally quantify steatosis” but notes its primary role is in clinical trials and specialized centers (Rinella et al., 2023).

MR elastography provides highly accurate assessment of liver fibrosis with AUROC exceeding 0.90 for advanced fibrosis, though its availability remains limited (Park et al., 2017).

7.3 CT Assessment

Computed tomography can detect hepatic steatosis based on decreased hepatic attenuation values but has several limitations:

  • Lower sensitivity than ultrasound for mild steatosis (72% sensitivity for >5% fat vs. 82% sensitivity for ≥20–33% fat)
  • Exposure to ionizing radiation
  • Confounding by iron deposition
  • Primarily useful for incidental detection rather than screening

A threshold of 48 Hounsfield units on unenhanced CT has 100% specificity for moderate-to-severe steatosis (≥30%), though with only 54% sensitivity (Haghshomar et al., 2024).

If ultrasound suggests fatty liver, doctors often recommend additional tests to better understand how severe the problem is and whether there’s any scarring (fibrosis) of the liver. The most common next step is FibroScan, a painless test that measures liver stiffness—stiffer liver means more scarring. Some patients may need an MRI scan, which can measure the exact amount of fat in the liver very precisely. CT scans can also show fatty liver but are less commonly used specifically for this purpose because they involve radiation exposure. The key point is that ultrasound is just the first step. If it shows fatty liver, your doctor will work with you to determine if additional testing is needed and what lifestyle changes or treatments might help.

8. Conclusion

Abdominal ultrasound remains a valuable first-line imaging tool for the detection of hepatic steatosis. Its accessibility, safety, and cost-effectiveness make it ideal for initial screening in clinical practice. However, clinicians must recognize its limitations, particularly reduced sensitivity for mild steatosis and inability to assess inflammation or fibrosis. A comprehensive evaluation of suspected MASLD requires integration of ultrasound findings with clinical assessment, laboratory testing, and non-invasive fibrosis markers, with advanced imaging (MRI-PDFF) or liver biopsy reserved for cases requiring precise quantification or histological characterization.

9. References

  1. Balci A, Karazincir S, Sumbas H, et al. (2011). Evaluation of portal venous velocity with Doppler ultrasound in patients with nonalcoholic fatty liver disease. Korean Journal of Radiology, 12(4):450-455. https://doi.org/10.3348/kjr.2011.12.4.450

    • This prospective study demonstrated that patients with NAFLD have significantly lower portal venous velocities compared to healthy controls.

  2. Balasubramanian P, Boopathy V, Govindasamy E, Venkatesh BP. (2016). Assessment of portal venous and hepatic artery haemodynamic variation in non-alcoholic fatty liver disease (NAFLD) patients. Journal of Clinical and Diagnostic Research, 10(8):TC07-10. https://doi.org/10.7860/JCDR/2016/19315.8268

    • Documents hemodynamic variations in hepatic vessels associated with NAFLD.

  3. Ballestri S, Mantovani A, Nascimbeni F, et al. (2021). Diagnostic accuracy of ultrasonography for the detection of hepatic steatosis: an updated meta-analysis of observational studies. Metabolism and Target Organ Damage, 1:5. https://doi.org/10.20517/mtod.2021.05

    • Updated meta-analysis confirming ultrasound diagnostic accuracy for any steatosis (≥5%) and moderate-severe steatosis.

  4. Ballestri S, Nascimbeni F, Lugari S, et al. (2019). A critical appraisal of the use of ultrasound in hepatic steatosis. Expert Review of Gastroenterology & Hepatology, 13(7):667-681. https://doi.org/10.1080/17474124.2019.1621164

    • Comprehensive review of ultrasound techniques, advantages, and limitations in hepatic steatosis assessment.

  5. Chauhan A, Sultan LR, Furth EE, et al. (2016). Diagnostic accuracy of hepatorenal index in the detection and grading of hepatic steatosis. Journal of Clinical Ultrasound, 44(9):580-586. https://doi.org/10.1002/jcu.22382

    • Demonstrates the utility of hepatorenal index for steatosis detection and grading.

  6. Dasarathy S, Dasarathy J, Khiyami A, et al. (2009). Validity of real time ultrasound in the diagnosis of hepatic steatosis: a prospective study. Journal of Hepatology, 51(6):1061-1067. https://doi.org/10.1016/j.jhep.2009.09.001

    • Prospective study establishing sensitivity and specificity of specific ultrasound criteria for hepatic steatosis.

  7. EASL-EASD-EASO. (2024). EASL–EASD–EASO Clinical Practice Guidelines on the management of metabolic dysfunction-associated steatotic liver disease (MASLD). Journal of Hepatology, 81(3):492-542. https://doi.org/10.1016/j.jhep.2024.04.031

    • Joint European guideline providing comprehensive recommendations for MASLD diagnosis and management.

  8. Eddowes PJ, Sasso M, Allison M, et al. (2019). Vibration-controlled transient elastography to assess fibrosis and steatosis in patients with nonalcoholic fatty liver disease. Clinical Gastroenterology and Hepatology, 17(1):156-163.e2. https://doi.org/10.1016/j.cgh.2018.04.043

    • Multicenter study establishing VCTE diagnostic accuracy for fibrosis and steatosis in NAFLD.

  9. Ferraioli G, Berzigotti A, Barr RG, et al. (2019). Quantification of liver fat content with ultrasound: a WFUMB position paper. Ultrasound in Medicine & Biology, 45(7):1560-1582. https://doi.org/10.1016/j.ultrasmedbio.2019.03.015

    • World Federation for Ultrasound in Medicine and Biology position paper on quantitative ultrasound techniques.

  10. Haghshomar M, Antonacci D, Smith AD, et al. (2024). Diagnostic accuracy of CT for the detection of hepatic steatosis: a systematic review and meta-analysis. Radiology, 313(2):e241171. https://doi.org/10.1148/radiol.241171

    • Comprehensive meta-analysis of CT performance for hepatic steatosis detection.

  11. Hernaez R, Lazo M, Bonekamp S, et al. (2011). Diagnostic accuracy and reliability of ultrasonography for the detection of fatty liver: a meta-analysis. Hepatology, 54(3):1082-1090. https://doi.org/10.1002/hep.24452

    • Landmark meta-analysis establishing ultrasound diagnostic accuracy (sensitivity 84.8%, specificity 93.6%) for moderate-severe fatty liver.

  12. Jang JK, Lee SS, Lee JM, et al. (2022). Accuracy of the ultrasound attenuation coefficient for the evaluation of hepatic steatosis: a systematic review and meta-analysis of prospective studies. Ultrasonography, 41(1):83-92. https://doi.org/10.14366/usg.20193

    • Meta-analysis demonstrating good diagnostic performance of ultrasound attenuation coefficient for steatosis assessment.

  13. Karlas T, Petroff D, Sasso M, et al. (2017). Individual patient data meta-analysis of controlled attenuation parameter (CAP) technology for assessing steatosis. Journal of Hepatology, 66(5):1022-1030. https://doi.org/10.1016/j.jhep.2016.12.022

    • Large meta-analysis establishing CAP diagnostic accuracy and optimal cutoffs for steatosis grades.

  14. Mendes FD, Suzuki A, Sanderson SO, et al. (2012). Prevalence and indicators of portal hypertension in patients with nonalcoholic fatty liver disease. Clinical Gastroenterology and Hepatology, 10(9):1028-1033.e2. https://doi.org/10.1016/j.cgh.2012.05.008

    • Study documenting prevalence of portal hypertension signs in NAFLD and their correlation with fibrosis stage.

  15. Monteiro MLG, Ferreira De Almeida E, Borges V, et al. (2016). Liver hemodynamic patterns in nonalcoholic steatosis: Doppler ultrasonography and histological evaluation. Minerva Gastroenterologica e Dietologica, 62(1):19-29. PMID: 26887796

    • Study correlating Doppler hemodynamic parameters with histological steatosis.

  16. Palmentieri B, de Sio I, La Mura V, et al. (2006). The role of bright liver echo pattern on ultrasound B-mode examination in the diagnosis of liver steatosis. Digestive and Liver Disease, 38(7):485-489. https://doi.org/10.1016/j.dld.2006.03.021

    • Study establishing the significance of bright liver echogenicity for steatosis diagnosis.

  17. Park CC, Nguyen P, Hernandez C, et al. (2017). Magnetic resonance elastography vs transient elastography in detection of fibrosis and noninvasive measurement of steatosis in patients with biopsy-proven nonalcoholic fatty liver disease. Gastroenterology, 152(3):598-607.e2. https://doi.org/10.1053/j.gastro.2016.10.026

    • Comparative study of MRE and VCTE performance in NAFLD assessment.

  18. Petzold G. (2022). Role of ultrasound methods for the assessment of NAFLD. Journal of Clinical Medicine, 11(15):4581. https://doi.org/10.3390/jcm11154581

    • Comprehensive review of ultrasound methods including B-mode, Doppler, and quantitative techniques for NAFLD assessment.

  19. Petzold G, Lasser L, Rühl J, et al. (2020). Diagnostic accuracy of B-Mode ultrasound and hepatorenal index for graduation of hepatic steatosis in patients with chronic liver disease. PLoS ONE, 15(5):e0231044. https://doi.org/10.1371/journal.pone.0231044

    • Study evaluating B-mode ultrasound and HRI diagnostic accuracy using modern high-end devices.

  20. Reeder SB, Sirlin CB. (2010). Quantification of liver fat with magnetic resonance imaging. Magnetic Resonance Imaging Clinics of North America, 18(3):337-357. https://doi.org/10.1016/j.mric.2010.08.013

    • Comprehensive review establishing MRI-PDFF as the reference standard for liver fat quantification.

  21. Rinella ME, Neuschwander-Tetri BA, Siddiqui MS, et al. (2023). AASLD Practice Guidance on the clinical assessment and management of nonalcoholic fatty liver disease. Hepatology, 77(5):1797-1835. https://doi.org/10.1097/HEP.0000000000000323

    • American Association for the Study of Liver Diseases guidance document providing comprehensive recommendations for NAFLD clinical assessment.

  22. Sasso M, Beaugrand M, de Ledinghen V, et al. (2010). Controlled attenuation parameter (CAP): a novel VCTE guided ultrasonic attenuation measurement for the evaluation of hepatic steatosis. Ultrasound in Medicine & Biology, 36(11):1825-1835. https://doi.org/10.1016/j.ultrasmedbio.2010.07.005

    • Original description of controlled attenuation parameter technology.

  23. Saverymuttu SH, Joseph AE, Maxwell JD. (1986). Ultrasound scanning in the detection of hepatic fibrosis and steatosis. British Medical Journal, 292(6512):13-15. https://doi.org/10.1136/bmj.292.6512.13

    • Early study establishing ultrasound grading criteria for hepatic steatosis.

  24. Solhjoo E, Mansour-Ghanaei F, Moulaei-Langorudi R, Joukar F. (2011). Comparison of portal vein Doppler indices and hepatic vein Doppler waveform in patients with nonalcoholic fatty liver disease with healthy control. Hepatitis Monthly, 11(9):740-744. PMID: 22224084

    • Study demonstrating altered portal vein and hepatic vein Doppler patterns in NAFLD.

  25. Srivastava A, Sheridan MJ, Engstrand J, et al. (2022). Spleen size does not correlate with histological stage of liver disease in people with nonalcoholic fatty liver disease. Clinical Gastroenterology and Hepatology, 20(5):1175-1177. https://doi.org/10.1016/j.cgh.2022.01.020

    • Study demonstrating lack of correlation between splenomegaly and liver fibrosis stage in NAFLD.

  26. Tan ZY, Welman CJ, Saunders J, et al. (2024). Hepatic steatosis: qualitative and quantitative sonographic assessment in comparison to histology. Australasian Journal of Ultrasound in Medicine, 27(3):179-188. https://doi.org/10.1002/ajum.12381

    • Recent study comparing qualitative B-mode parameters and attenuation imaging with histopathology.

  27. Wang J, Chen Y, Zhao Q, et al. (2025). Reliability of ultrasonic hepatorenal indices in assessing hepatic steatosis: a systematic review and meta-analysis. Journal of Clinical Ultrasound, doi:10.1002/jcu.70006.

    • Updated meta-analysis confirming high diagnostic accuracy of hepatorenal index.

  28. Webb M, Yeshua H, Zelber-Sagi S, et al. (2009). Diagnostic value of a computerized hepatorenal index for sonographic quantification of liver steatosis. American Journal of Roentgenology, 192(4):909-914. https://doi.org/10.2214/AJR.07.4016

    • Landmark study establishing hepatorenal index methodology with 100% sensitivity and 91% specificity.

  29. Wong VW, Chan WK, Chitturi S, et al. (2018). Asia-Pacific Working Party on Non-alcoholic Fatty Liver Disease guidelines 2017—Part 1: Definition, risk factors and assessment. Journal of Gastroenterology and Hepatology, 33(1):70-85. https://doi.org/10.1111/jgh.13857

    • Asia-Pacific guidelines providing regional recommendations for NAFLD assessment.

  30. Younossi ZM, Koenig AB, Abdelatif D, et al. (2016). Global epidemiology of nonalcoholic fatty liver disease—meta-analytic assessment of prevalence, incidence, and outcomes. Hepatology, 64(1):73-84. https://doi.org/10.1002/hep.28431

    • Comprehensive meta-analysis establishing global NAFLD prevalence at approximately 25%.

Note: This chapter reflects current evidence and guidelines as of 2024–2025. Clinical practice should always incorporate the most recent guidelines and local protocols.