**2. Definition**

NAFLD definition [1] requires that there is evidence of hepatic steatosis, either by imaging or by histology and there are no causes for secondary hepatic fat accumulation (Table 1).

NAFLD is usually associated with metabolic risk factors such as metabolic syndrome, obesi‐ ty, diabetes mellitus, and dyslipidaemia.

90s and finally to 60% nowadays [4]. Even in non-obese patients, the prevalence of steatosis

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In children/adolescents, over the last 20 years, obesity has increased from 11% to 21%, sus‐ pected NAFLD from 4% to 10, and the prevalence of altered aminotransferases among obese

Liver biopsy remains the gold standard for characterizing liver histology in patients with NAFLD. However, it is expensive and carries some morbidity and very rare mortality risk. Thus, it should be performed in those who would benefit the most from diagnostic, thera‐

The last guideline for NAFLD management recommends liver biopsy [1]: in patients who are at risk to have steatohepatitis and advance fibrosis; theses patients could be identified by the presence of metabolic syndrome and NAFLD fibrosis score; and a liver biopsy should be considered in patients in whom other etiologies are suspected and cannot be excluded with‐

Liver biopsy allows confirming the diagnosis, evaluation and semiquantitation of necroin‐

On the other hand, liver biopsy suffers from challenges. An adequate biopsy represents only 1/50000-1/65000 of the organ. Sampled area should be carefully chosen and sample length must be enough, a least 15mm. This size can reduce sample error. Finally, experienced path‐

NAFLD represents a histopathologic spectrum ranging from steatosis alone, to necroinflam‐

The histologic characterization of NAFLD and NASH may include description of steatosis and cell injury in addition to inflammation and fibrosis. Kleiner and Brunt [7] propose cate‐

The main histological characteristic of NAFLD is the accumulation of fat in the form of tri‐ glyicerides within hepatocytes, lesion termed steatosis (Figure 1 and 2); this term is defined by the guideline [1] as NAFL – non-alcoholic fatty liver, where the risk of progression to cir‐ rhosis and liver failure is minimal. The presence of >5% steatoic hepatocytes in a liver biopsy

mation, summarized as NASH; and progression to advanced fibrosis and cirrhosis.

gorizing the histologic changes when studying NAFLD as follows in table 2.

is accepted as the minimum criterion for thehistological diagnosis of NAFLD [8].

increased from 12%, to 27% and 36%, respectively [5].

adolescents has increased from 17% to 37% [6].

peutic guidance, and prognostic perspectives.

ologist is important to haver a greater yield of findings.

**4. NAFLD and liver biopsy**

out a liver biopsy.

flammatory lesions and fibrosis.

**5. Histology of NAFLD**

#### **COMMON CAUSES OF SECONDARY HEPATIC STEATOSIS**

#### **Macrovesicularsteatosis**

Excessive alcohol consumption. Hepatitis C (genotype 3) Wilson's disease. Lipodistrophy Starvation Parenteral nutrition. Abetalipoproteinemia. Medication (amiodarone, methotrexate, tamoxifen, corticosteroids)

#### **Microvesicularstatosis**

Reye's syndrome. Medications (valproate, anti-retroviral medicines) Acutte fatty liver of pregnancy HELLP syndrome Inborn errors of metabolism (LCAT deficiency, cholesterol ester storage disease, Wolman disease)

**Table 1.** Causes of secondary fat accumulation.

NAFLD includes a constellation of histological findings that goes from steatosis, to necroin‐ flammation, called NASH and progression to advanced fibrosis and cirrhosis.
