What additional labs, imaging, or referrals are needed to evaluate elevated liver enzymes and impaired renal function?

Workup for Elevated Liver Enzymes and Mildly Elevated BUN

For this patient with elevated ALT (108 U/L), mildly elevated total protein (8.5 g/dL), and borderline BUN (21 mg/dL) with normal creatinine and excellent GFR (121 mL/min/1.73m²), the priority is evaluating the liver enzyme elevation through risk stratification for hepatic fibrosis, followed by targeted testing based on risk factors.

Immediate Laboratory Testing Required

Hepatic Fibrosis Risk Stratification

• Calculate FIB-4 score immediately using the patient's age, ALT (108), AST (53), and platelet count (if available from the CBC) 1
  • FIB-4 <1.3 (or <2.0 if age >65): Low risk, proceed with annual monitoring 1
  • FIB-4 1.3-2.67: Indeterminate risk, requires additional testing 1
  • FIB-4 >2.67: High risk, refer to hepatology 1

Extended Liver Etiology Screen

The following tests should be ordered to identify the cause of elevated transaminases 1:

• Viral hepatitis serologies: Hepatitis B surface antigen, hepatitis B core antibody, hepatitis C antibody 1
• Autoimmune markers: Antinuclear antibody (ANA), anti-smooth muscle antibody, anti-liver kidney microsomal antibody 1
• Metabolic screening:
  • Fasting lipid panel (if not already done) 1
  • Hemoglobin A1c or fasting glucose (already done - glucose 104 mg/dL, borderline) 1
  • Iron studies: serum iron, total iron binding capacity, ferritin, transferrin saturation 1
• Additional metabolic tests: Alpha-1-antitrypsin level, ceruloplasmin (if age >3 years) 1
• Celiac disease screening: Tissue transglutaminase antibody (IgA) with total IgA level 1

Alcohol Use Assessment

• Administer AUDIT questionnaire to quantify alcohol consumption 1
  • AUDIT score >19 indicates alcohol dependency requiring referral to alcohol services 1

Imaging Studies

Abdominal Ultrasound

• Order abdominal ultrasound to evaluate for hepatic steatosis, focal liver lesions, and biliary obstruction 1
  • If hepatic steatosis is present with metabolic risk factors (borderline glucose, need to assess BMI), this supports NAFLD diagnosis 1

Vibration-Controlled Transient Elastography (FibroScan)

• If FIB-4 score is indeterminate (1.3-2.67) or high (>2.67), order liver stiffness measurement 1
  • LSM <8.0 kPa: Low risk for clinically significant fibrosis, repeat surveillance in 2-3 years 1
  • LSM 8.0-12.0 kPa: Indeterminate, refer to hepatology for consideration of liver biopsy or MRE 1
  • LSM >12.0 kPa: High risk for advanced fibrosis, refer to hepatology 1
  • LSM ≥20 kPa: Suggestive of cirrhosis, requires variceal screening 1

Renal Function Considerations

Current Renal Status

The mildly elevated BUN (21 mg/dL) with normal creatinine (0.83 mg/dL) and excellent GFR (121 mL/min/1.73m²) does not indicate renal impairment 1. This BUN elevation is likely pre-renal (dehydration, high protein intake, GI bleeding) rather than intrinsic renal disease.

Monitoring Plan

• Repeat basic metabolic panel in 2-4 weeks if liver enzymes remain elevated to monitor BUN and creatinine trends 1
• No nephrology referral is needed at this time given normal GFR and creatinine 1
• Progressive renal insufficiency would warrant nephrology referral, but this patient shows no evidence of kidney disease 1

Referrals

Hepatology Referral Indicated If:

• FIB-4 score >2.67 1
• LSM >12.0 kPa on FibroScan 1
• Persistently elevated ALT (>3-fold upper limit of normal) after repeat testing in 2-4 weeks 1
• Extended liver screen is negative and no clear etiology identified 1
• Evidence of cirrhosis or portal hypertension on imaging 1

Gastroenterology Referral for:

• Celiac disease confirmation if serology is positive (requires small bowel biopsy) 1
• Consideration of bidirectional endoscopy if iron deficiency anemia is present (not indicated from current labs) 1

Common Pitfalls to Avoid

• Do not assume NAFLD without excluding other causes - viral hepatitis, autoimmune hepatitis, hemochromatosis, and Wilson disease must be ruled out first 1
• Do not delay fibrosis assessment - early identification of advanced fibrosis significantly impacts management and prognosis 1
• Do not over-interpret the mildly elevated BUN - with normal creatinine and excellent GFR, this does not represent kidney disease 1
• Do not order bone scan or brain imaging without specific symptoms (bone pain, elevated alkaline phosphatase, neurological signs) 1