57.2 Chronic Liver Disease: MASLD/NAFLD, Cirrhosis & Portal Hypertension

Metabolic Dysfunction-Associated Steatotic Liver Disease (MASLD & MASH)

Chronic liver disease is a leading cause of premature morbidity and mortality in primary care. Driven by the global syndemic of obesity and type 2 diabetes, steatotic liver disease has emerged as the most prevalent chronic liver disease worldwide, affecting approximately 30% of adults.

Multi-Society Nomenclature Update

In 2023, an international consensus panel representing AASLD, EASL, and ALEH updated the nomenclature from non-alcoholic fatty liver disease (NAFLD) to Metabolic Dysfunction-Associated Steatotic Liver Disease (MASLD), and from non-alcoholic steatohepatitis (NASH) to Metabolic Dysfunction-Associated Steatohepatitis (MASH). This affirmative diagnostic framework removes exclusionary and stigmatizing terminology, anchoring the disease directly to underlying cardiometabolic pathophysiology:

• MASLD Definition: Presence of hepatic steatosis (demonstrated by imaging, blood biomarkers, or histology) in the presence of at least one of five cardiometabolic risk factors, in the absence of other secondary causes of hepatic fat accumulation and without excessive alcohol intake:
  1. Overweight / Obesity: BMI >=25 kg/m² (>=23 kg/m² in Asian individuals) OR waist circumference >94 cm (men) / >80 cm (women).
  2. Dysglycemia: Fasting plasma glucose >=100 mg/dL (5.6 mmol/L), 2-hour post-oral glucose load >=140 mg/dL, HbA1c >=5.7%, or diagnosed Type 2 diabetes mellitus or specific antidiabetic pharmacotherapy.
  3. Hypertension: Blood pressure >=130/85 mmHg or documented antihypertensive medication use.
  4. Hypertriglyceridemia: Plasma triglycerides >=150 mg/dL (1.70 mmol/L) or lipid-lowering treatment.
  5. Low HDL Cholesterol: Plasma HDL-C <40 mg/dL (1.0 mmol/L) in men, <50 mg/dL (1.3 mmol/L) in women, or specific drug therapy.
• Alcohol Consumption Thresholds:
  • MASLD strictly requires alcohol consumption to be <20 g/day for women (<1.5 standard US drinks daily) and <30 g/day for men (<2 standard drinks daily).
  • Patients with hepatic steatosis who meet cardiometabolic criteria but consume higher amounts of alcohol (20 to 50 g/day for women, 30 to 60 g/day for men) are classified as having MetALD (Metabolic and Alcohol-Related Liver Disease), recognizing the synergistic hepatotoxic effect of metabolic dysfunction and alcohol.

Histopathologic Spectrum: Steatosis vs. Steatohepatitis (MASH)

• Simple Steatosis (MASL): Triglyceride accumulation within the cytoplasm of >5% of hepatocytes without significant hepatocellular injury or inflammation. Carries a low rate of fibrotic progression.
• MASH (Steatohepatitis): Steatosis accompanied by lobular inflammation and hepatocyte ballooning degeneration (cytoskeletal swelling and disruption by Mallory-Denk bodies). Hepatocyte lipotoxicity activates immune cascades and hepatic stellate cells, driving progressive perisinusoidal, "chicken-wire" fibrosis that advances from Stage F0 (no fibrosis) to F1 (perisinusoidal), F2 (perisinusoidal and periportal), F3 (bridging fibrosis), and F4 (frank cirrhosis).

Non-Invasive Fibrosis Risk Assessment: The FIB-4 Index & Elastography Algorithms

In MASLD, long-term liver-related morbidity, cardiovascular events, and all-cause mortality are dictated almost exclusively by the stage of hepatic fibrosis, rather than the absolute quantity of liver fat. Because liver biopsy carries procedural risks and sampling error, multi-society clinical practice guidelines mandate non-invasive fibrosis risk stratification for all patients with MASLD in primary care.

First-Line Screening: The Fibrosis-4 (FIB-4) Index

The FIB-4 Index is calculated using four universally accessible clinical parameters: $\text{FIB-4} = \frac{\text{Age (years)} \times \text{AST (U/L)}}{\text{Platelet Count } (10^9/\text{L}) \times \sqrt{\text{ALT (U/L)}}}$

                     PRIMARY CARE FIB-4 RISK STRATIFICATION

   FIB-4 Score Range      Fibrosis Risk Tier   Clinical Interpretation & Actionable Pathway
   ═════════════════════════════════════════════════════════════════════════════════════════════════
   < 1.30                 LOW RISK             High Negative Predictive Value (>90-95%) for
   (< 2.0 in age >=65)                         advanced fibrosis (F3-F4). Excludes advanced disease.
                                               • Manage in primary care with lifestyle counseling
                                               • Optimize diabetes, hypertension, and lipids
                                               • Repeat FIB-4 every 2 to 3 years

   1.30 to 2.67           INTERMEDIATE /       Indeterminate score; advanced fibrosis cannot be
                          INDETERMINATE RISK   excluded.
                                               • Reflex to secondary non-invasive testing:
                                                 Vibration-Controlled Transient Elastography (VCTE)
                                                 OR Enhanced Liver Fibrosis (ELF) serum test

   > 2.67                 HIGH RISK            High Positive Predictive Value for advanced fibrosis
                                               (F3) or cirrhosis (F4).
                                               • Expedited referral to Gastroenterology / Hepatology
                                               • Screen for portal hypertension and cirrhosis
                                               • Initiate biannual HCC surveillance if cirrhotic
   ═════════════════════════════════════════════════════════════════════════════════════════════════
   *Age Adjustment: In patients aged >=65 years, physiological shifts alter transaminases; the lower cutoff
   is adjusted upward to <2.0 to prevent excessive false-positive results.

Secondary Non-Invasive Testing: Transient Elastography (VCTE / FibroScan)

Patients in the intermediate-risk tier (or high-risk tier for staging confirmation) undergo secondary non-invasive evaluation with Vibration-Controlled Transient Elastography (VCTE / FibroScan), which measures shear-wave velocity to quantify liver stiffness in kilopascals (kPa):

• Liver Stiffness < 8.0 kPa: Low risk of advanced fibrosis (F0-F1). Patient can remain in primary care for ongoing metabolic optimization and repeat elastography in 3 years.
• Liver Stiffness 8.0 to 12.0 kPa: Moderate/advanced fibrosis (F2-F3). Referral to hepatology for disease-modifying therapy and clinical trial consideration.
• Liver Stiffness >= 12.0 to 15.0 kPa: Advanced fibrosis to cirrhosis (F3-F4). High risk of portal hypertension; mandates hepatology co-management, variceal screening, and HCC surveillance.
• Enhanced Liver Fibrosis (ELF) Score: A proprietary serum test measuring hyaluronic acid, procollagen III N-terminal peptide, and tissue inhibitor of metalloproteinase 1. An ELF score <7.7 indicates low risk, 7.7 to 9.8 intermediate risk, and >=9.8 indicates advanced fibrosis.

Evidence-Based Pharmacotherapy & Management for MASLD/MASH

1. Lifestyle Interventions & Weight Loss Targets:
   • A direct, dose-dependent relationship exists between the magnitude of weight loss and histologic liver improvement:
     • >=3% to 5% weight loss: Achieves significant reduction in hepatic steatosis.
     • >=7% to 10% weight loss: Induces resolution of steatohepatitis (MASH) and halts or reverses hepatic fibrosis in up to 50% to 80% of patients.
   • Dietary Pattern: The Mediterranean diet—rich in monounsaturated fatty acids, omega-3 fatty acids, fresh vegetables, legumes, and extra-virgin olive oil, while severely restricting ultra-processed foods, saturated fats, and high-fructose corn syrup beverages—is the gold standard.
   • Exercise: At least 150 minutes per week of moderate-intensity aerobic exercise paired with resistance training.
2. Resmetirom (Rezdiffra):
   • The first FDA-approved medication for non-cirrhotic MASH with moderate-to-advanced liver fibrosis (stages F2-F3), used as an adjunct to diet and exercise.
   • Mechanism of Action: A liver-directed, oral thyroid hormone receptor-beta (THR-beta) agonist. THR-beta is the predominant thyroid hormone receptor subtype in hepatocytes. By selectively stimulating hepatic THR-beta without activating cardiac or bone THR-alpha receptors, resmetirom increases hepatic mitochondrial fatty acid beta-oxidation, decreases toxic lipotoxic intermediates, promotes MASH resolution, and reverses fibrosis.
   • Dosing: Weight-based: 80 mg PO once daily for body weight <100 kg, and 100 mg PO once daily for body weight >=100 kg.
   • Safety Pearls: Most common adverse effects are transient diarrhea and nausea; monitor for drug-drug interactions with statins (increases statin exposure; cap rosuvastatin at 20 mg daily).
3. Incretin Mimetics (GLP-1 Receptor Agonists & Dual Incretins):
   • Semaglutide (and tirzepatide) produces robust, sustained weight reduction (10% to 20%), drives resolution of steatohepatitis, and reduces major adverse cardiovascular events (MACE). Although FDA approvals have primarily focused on diabetes and obesity, current guidelines strongly endorse GLP-1 RAs as preferred cardiometabolic therapy in patients with MASLD/MASH.
4. Pioglitazone:
   • A peroxisome proliferator-activated receptor-gamma (PPAR-gamma) agonist (30 to 45 mg daily) that enhances peripheral and hepatic insulin sensitivity. Proven in biopsy-controlled trials to improve steatosis and lobular inflammation in patients with type 2 diabetes or prediabetes. Adverse effects include weight gain, fluid retention/peripheral edema, heart failure precipitation, and decreased bone density.
5. Vitamin E (Alpha-Tocopherol):
   • An antioxidant (800 IU daily) that improves liver histology in non-diabetic adults with biopsy-proven MASH (PIVENS trial). Not recommended for diabetic patients or without biopsy confirmation; long-term use warrants caution regarding potential modest increases in all-cause mortality, prostate cancer, and hemorrhagic stroke.

Cirrhosis & Portal Hypertension: Staging, Scoring & Pathophysiology

Cirrhosis is the histopathological end stage of chronic liver disease, defined by diffuse architectural disruption, regenerative parenchymal nodules, and dense bands of bridging fibrous septa.

Pathophysiology of Portal Hypertension

Portal hypertension is defined as a hepatic venous pressure gradient (HVPG) >5 mmHg; clinical complications emerge when the HVPG reaches >=10 mmHg (clinically significant portal hypertension, CSPH):

1. Increased Intrahepatic Vascular Resistance: Structural distortion from dense extracellular collagen deposition and vascular remodeling. In addition, activated hepatic stellate cells and sinusoidal endothelial cells demonstrate functional deficiency of endogenous vasodilator nitric oxide (NO) and hyperresponsiveness to vasoconstrictors (endothelin-1), increasing sinusoidal tone.
2. Hyperdynamic Splanchnic Circulation: Severe shear stress and localized inflammation trigger massive release of splanchnic vasodilators (predominantly nitric oxide). This results in profound arteriolar vasodilation throughout the mesenteric and splanchnic arterial beds.
3. Splanchnic Inflow & Arterial Underfilling: Massive splanchnic arterial inflow floods into the portal vein against elevated intrahepatic resistance, creating high portal pressures. Systemically, splanchnic pooling causes effective arterial hypovolemia, triggering reflex compensatory hyperactivation of the renin-angiotensin-aldosterone system (RAAS), the sympathetic nervous system, and non-osmotic release of antidiuretic hormone (ADH), driving renal sodium and water retention.

Prognostic Staging Systems: Child-Pugh & MELD-Na

                    THE CHILD-PUGH CLASSIFICATION SYSTEM

   Clinical / Laboratory Variable   1 Point        2 Points       3 Points
   ═════════════════════════════════════════════════════════════════════════════
   Serum Total Bilirubin (mg/dL)   < 2.0          2.0 to 3.0     > 3.0
   Serum Albumin (g/dL)            > 3.5          2.8 to 3.5     < 2.8
   Prothrombin Time INR            < 1.7          1.7 to 2.2     > 2.2
   Ascites Severity                None           Mild / Med     Moderate to Severe
                                                  controlled     (refractory)
   Hepatic Encephalopathy          None           Grade 1-2      Grade 3-4
                                                  (mild/asterixis) (severe/coma)
   ═════════════════════════════════════════════════════════════════════════════
   Child-Pugh Class A:  5 to 6 points   | Well-compensated disease; 1-yr survival ~100%
   Child-Pugh Class B:  7 to 9 points   | Significant functional compromise; 1-yr survival ~80%
   Child-Pugh Class C:  10 to 15 points | Decompensated end-stage disease; 1-yr survival ~45%

• Model for End-Stage Liver Disease - Sodium (MELD-Na):
  • An objective mathematical model incorporating four laboratory parameters: Serum Total Bilirubin, INR, Serum Creatinine, and Serum Sodium (with adjustments for patients receiving hemodialysis).
  • Scores range from 6 to 40, accurately calculating objective 90-day mortality risk in patients with end-stage liver disease. MELD-Na serves as the universal legal metric for deceased-donor liver organ allocation via UNOS/OPTN throughout the United States. Patients with MELD-Na >=15 should be formally evaluated for liver transplantation.

Evidence-Based Management of Cirrhotic Complications

Decompensation transforms compensated cirrhosis into a multi-system, life-threatening disorder. The development of variceal hemorrhage, ascites, spontaneous bacterial peritonitis, or hepatic encephalopathy marks a dramatic decrease in median survival.

                   EVIDENCE-BASED MANAGEMENT OF CIRRHOTIC COMPLICATIONS

   Complication          Diagnostic Criteria               First-Line Therapeutic Management
   ═════════════════════════════════════════════════════════════════════════════════════════════════════
   Gastroesophageal      Screening EGD at cirrhosis        Primary Prophylaxis: Non-selective beta-blocker
   Varices               diagnosis (or defer if VCTE       (Carvedilol 6.25-12.5 mg daily preferred; or
                         <20 kPa and platelets >150k)      Nadolol/Propranolol) OR Endoscopic Variceal
                                                           Ligation (EVL / banding)

   Ascites               Ultrasound / paracentesis;        • Sodium restriction: 2,000 mg/day (88 mmol/d)
                         SAAG >= 1.1 g/dL indicates        • Dual diuretics: Spironolactone + Furosemide
                         portal hypertension                 (100 mg : 40 mg ratio; max 400 mg : 160 mg)
                                                           • Large-volume paracentesis (>5 L): 6-8 g
                                                             IV albumin per liter removed

   Spontaneous           Ascitic fluid absolute PMN        • IV Ceftriaxone 2 g daily for 5 days
   Bacterial             count >= 250 cells/mm³            • IV Albumin: 1.5 g/kg within 6 hours,
   Peritonitis (SBP)     (neutrophils)                       followed by 1.0 g/kg on Day 3
                                                           • Secondary prophylaxis: lifelong daily oral
                                                             TMP-SMX DS (1 tab daily) or Ciprofloxacin

   Hepatic               West Haven criteria;              • Lactulose titrated to 2 to 3 soft stools/day
   Encephalopathy (HE)   asterixis, cognitive change;      • Add Rifaximin 550 mg PO twice daily for recurrence
                         identify precipitants             • DO NOT restrict dietary protein (1.2-1.5 g/kg/d)

   Hepatocellular        All cirrhotic patients            Abdominal Ultrasound with or without serum
   Carcinoma (HCC)       regardless of etiology            Alpha-Fetoprotein (AFP) every 6 months
   ═════════════════════════════════════════════════════════════════════════════════════════════════════

1. Gastroesophageal Varices & Primary Prophylaxis

• Screening: All patients with newly diagnosed cirrhosis should undergo screening EGD. Under Baveno VII criteria, screening EGD may be safely deferred if liver stiffness on transient elastography is <20 kPa AND platelet count is >150,000/mcL.
• Indications for Primary Prophylaxis: Medium-to-large varices (>=5 mm), small varices with red wale markings, or Child-Pugh Class C cirrhosis with any varices.
• Non-Selective Beta-Blockers (NSBB):
  • Carvedilol (6.25 mg daily titrated to 12.5 mg daily) is the preferred NSBB: provides combined $\beta_1/\beta_2$ blockade plus intrinsic $\alpha_1$-adrenergic antagonism, which dilates intrahepatic sinusoids while constricting splanchnic arteries, achieving greater portal pressure reduction than traditional agents.
  • Traditional NSBBs: Nadolol (20 to 40 mg daily) or Propranolol (20 to 40 mg BID), titrated to achieve a resting heart rate of 55 to 60 bpm with systolic blood pressure maintained >=90 mmHg. Mechanism: $\beta_1$ blockade reduces cardiac output, while $\beta_2$ blockade produces unopposed splanchnic $\alpha_1$ vasoconstriction, reducing portal inflow.
  • Endoscopic Variceal Ligation (EVL): Recommended for patients with contraindications, intolerance, or hypotension preventing NSBB therapy.

2. Ascites & Large-Volume Paracentesis

• Diagnostic Paracentesis: Mandatory in all patients presenting with new-onset ascites, hospital admission with cirrhosis, or acute clinical deterioration.
• Serum-Ascites Albumin Gradient (SAAG): Calculated as: $\text{SAAG} = \text{Serum Albumin} - \text{Ascitic Fluid Albumin}$.
  • SAAG >= 1.1 g/dL (High Gradient): Indicates portal hypertension with 97% accuracy. Causes include cirrhosis (ascitic total protein <2.5 g/dL), congestive heart failure / constrictive pericarditis (ascitic total protein >=2.5 g/dL), and Budd-Chiari syndrome.
  • SAAG < 1.1 g/dL (Low Gradient): Indicates non-portal causes (no capillary hydrostatic hypertension). Causes include peritoneal carcinomatosis, tuberculous peritonitis, nephrotic syndrome, and pancreatic ascites.
• Medical Management:
  • Dietary Sodium Restriction: Strictly limited to 2,000 mg/day (88 mmol/day). Extreme fluid restriction (<1.5 L/day) is NOT indicated unless profound hypervolemic hyponatremia (serum Na <120 to 125 mEq/L) is present.
  • Dual Diuretic Therapy: Spironolactone (aldosterone antagonist) + Furosemide (loop diuretic) administered in a fixed single morning ratio of 100 mg : 40 mg. This specific ratio maintains normokalemia and targets a urinary Na/K ratio >1. Dosages can be titrated stepwise every 3 to 5 days up to a maximum of 400 mg spironolactone and 160 mg furosemide daily.
• Large-Volume Paracentesis (LVP > 5 Liters):
  • When removing >5 liters of ascitic fluid, administration of intravenous albumin (20% or 25% formulation) at a dose of 6 to 8 grams per liter of ascites removed is mandatory.
  • Clinical Rationale: Prevents Paracentesis-Induced Circulatory Dysfunction (PICD)—a catastrophic syndrome characterized by severe peripheral vasodilation, rapid decline in effective circulating arterial volume, activation of the RAAS, acute kidney injury (hepatorenal syndrome), and early mortality.

3. Spontaneous Bacterial Peritonitis (SBP)

• Pathogenesis: Translocation of enteric Gram-negative bacilli (Escherichia coli, Klebsiella pneumoniae) or streptococci across a permeable intestinal wall into ascitic fluid lacking adequate opsonic activity.
• Diagnostic Threshold: Ascitic fluid Absolute Neutrophil Count (ANC / PMN count) >= 250 cells/mm³ (calculated as total fluid WBC $\times$ % neutrophils). Treatment must begin immediately based on PMN count without waiting for culture results.
• Antimicrobial Therapy: Empiric IV third-generation cephalosporin (Ceftriaxone 2 g IV every 24 hours or Cefotaxime 2 g IV q8h) for 5 days.
• Mandatory IV Albumin Infusion: Administer IV albumin at 1.5 g/kg within 6 hours of diagnosis, followed by 1.0 g/kg on Day 3. Landmark trials demonstrate this protocol reduces the incidence of hepatorenal syndrome from 33% to 10% and cuts in-hospital mortality from 29% to 10%.
• Lifelong Secondary Prophylaxis: All patients recovering from an episode of SBP mandate indefinite oral prophylaxis with Trimethoprim-Sulfamethoxazole (one DS tablet daily) or Ciprofloxacin (500 mg daily).

4. Hepatic Encephalopathy (HE)

• Pathogenesis: Portosystemic shunting and impaired hepatic urea synthesis allow neurotoxins, predominantly ammonia ($NH_3$), to cross the blood-brain barrier. Astrocytes metabolize ammonia to glutamine, producing cerebral edema, neurosteroid dysregulation, and GABAergic neuroinhibition.
• Clinical Manifestations: Inversion of sleep-wake cycle, cognitive slowing, irritability, lethargy, marked confusion, and asterixis (bilateral, asynchronous flapping tremor elicited on wrist dorsiflexion with arms extended).
• Identifying Triggers: Encephalopathy is almost invariably precipitated by an acute intercurrent event. Always identify and treat the underlying trigger: Infection (SBP, UTI, pneumonia), Gastrointestinal bleeding (digested blood acts as a massive protein load), Constipation, Hypokalemia and metabolic alkalosis (promotes conversion of uncharged $NH_3$ that crosses the blood-brain barrier), Dehydration, or Sedating medications.
• Medical Therapy:
  • Lactulose: First-line. A non-absorbable disaccharide. Colonic bacteria ferment lactulose into lactic and acetic acid, acidifying the colonic lumen (pH <5.0). Acidification protonates ammonia ($NH_3$) into unabsorbable ammonium ($NH_4^+$), trapping it in the stool ("ammonia trapping"), while exerting an osmotic laxative effect. Titrate to achieve 2 to 3 soft bowel movements per day.
  • Rifaximin (550 mg PO twice daily): A minimally absorbed oral rifamycin antibiotic that suppresses gut urease-producing bacteria, decreasing intestinal ammonia generation. Adding rifaximin to lactulose significantly reduces recurrent encephalopathy hospitalizations and mortality.
  • Dietary Counseling: Strict dietary protein restriction is harmful and contraindicated! Cirrhotic patients are in a state of accelerated starvation; skeletal muscle is the primary alternative site for ammonia detoxification. Patients must maintain a high-protein diet (1.2 to 1.5 g/kg/day) to preserve muscle mass and prevent sarcopenia.

5. Hepatocellular Carcinoma (HCC) Surveillance

Cirrhosis of any etiology is the single greatest risk factor for hepatocellular carcinoma. Current AASLD and EASL practice guidelines mandate surveillance with abdominal ultrasound with or without serum Alpha-Fetoprotein (AFP) every 6 months for all patients with cirrhosis (Child-Pugh A, B, or C awaiting transplant). Any newly detected solid liver nodule >=1.0 cm requires dynamic multi-phase contrast-enhanced CT or MRI applying Liver Imaging Reporting and Data System (LI-RADS) diagnostic criteria.