What are the appropriate ICD‑10 codes for mild hepatomegaly (correlate with liver function tests), a hypodense gallbladder focus (possible non‑calcified stone or biliary sludge), bilateral renal cortical cysts, and an enlarged prostate with heterogeneous density (correlate with prostate‑specific antigen)?

ICD-10 Coding for CT Abdomen Findings

For the four findings described, assign the following ICD-10 codes: R16.0 (hepatomegaly), K82.4 (cholelithiasis or biliary sludge), N28.1 (renal cyst), and N40.0 (benign prostatic hyperplasia without lower urinary tract symptoms) or N40.1 (with LUTS if clinically present).

1. Mild Hepatomegaly (Correlate with Liver Function Tests)

Primary Code: R16.0 (Hepatomegaly, not elsewhere classified) 1

• Use R16.0 when hepatomegaly is identified on imaging but the underlying etiology has not been definitively established 1
• The American College of Radiology recommends correlating hepatomegaly with liver function tests to determine the underlying cause, which may include hepatocellular injury patterns (elevated ALT/AST) or cholestatic patterns (elevated alkaline phosphatase/GGT) 1
• Once liver function tests and additional workup establish a specific diagnosis (e.g., K76.0 for fatty liver, K74.60 for cirrhosis, K75.9 for inflammatory liver disease), replace R16.0 with the definitive diagnosis code 1
• Body surface area-normalized liver volume (H-score) >0.92 L/m² defines mild hepatomegaly and >1.08 L/m² defines massive hepatomegaly, though visual assessment by radiologists has only 56.7% sensitivity for mild hepatomegaly 2

Additional Considerations:

• If diabetes is present with hepatomegaly and elevated transaminases, consider E11.69 (Type 2 diabetes with other specified complication) as glycogenosis causes reversible hepatomegaly in poorly controlled diabetics 3
• Document associated findings such as splenomegaly (R16.1), ascites (R18.8), or portal hypertension signs, as these modify coding and clinical management 4

2. Hypodensity Within Gallbladder (Noncalcified Stone vs. Biliary Sludge)

Primary Code: K82.4 (Cholelithiasis of gallbladder with other cholecystitis) or K80.20 (Calculus of gallbladder without cholecystitis without obstruction) 1

• For noncalcified gallstones without acute inflammation, use K80.20 1
• For biliary sludge without acute cholecystitis, use K82.4 1
• Ultrasound is superior to CT for distinguishing stones from sludge, as CT has limited sensitivity for non-calcified gallbladder pathology 1
• Gallbladder wall thickening >5.2 mm on imaging predicts severe hepatobiliary disease and should prompt additional coding for cholecystitis (K81.9) if present 5

Clinical Pitfall:

• Do not code as K80.80 (other cholelithiasis) without specifying location, as this reduces coding specificity 1
• If the patient has primary sclerosing cholangitis or other biliary tract disease, gallbladder abnormalities occur in up to 41% of cases and may require additional codes 1

3. Bilateral Renal Cortical Hypodensities (Differential: Cortical Cysts)

Primary Code: N28.1 (Cyst of kidney, acquired) 1

• Use N28.1 for simple renal cortical cysts identified on imaging without evidence of polycystic kidney disease 1
• If multiple bilateral cysts are present with family history or other features suggesting autosomal dominant polycystic kidney disease (ADPKD), use Q61.2 (Polycystic kidney, adult type) instead 1
• The KDIGO 2025 guidelines emphasize that ADPKD diagnosis requires appropriate imaging criteria (modified Piscaglia criteria for ultrasound or Ravine criteria for CT/MRI) and should not be coded based on isolated bilateral cysts alone 1
• Document cyst characteristics: simple cysts (anechoic/hypodense, thin-walled, no enhancement) versus complex cysts (septations, calcifications, enhancement) which require Bosniak classification 1

Additional Considerations:

• If renal function is impaired, add N18.x codes for chronic kidney disease stage 1
• Hepatic cysts may coexist in 50-70% of ADPKD patients, supporting Q61.2 coding if both organs are involved 1

4. Enlarged Prostate with Heterogeneous Density (Correlate with PSA)

Primary Code: N40.0 (Benign prostatic hyperplasia without lower urinary tract symptoms) or N40.1 (Benign prostatic hyperplasia with lower urinary tract symptoms) 6, 7

• Use N40.0 for imaging-detected prostatic enlargement without documented urinary symptoms 6
• Use N40.1 if the patient reports hesitancy, frequency, nocturia, weak stream, or incomplete emptying 6
• Heterogeneous density on CT is nonspecific and occurs in both benign prostatic hyperplasia (BPH) and prostate cancer 6
• PSA density (PSAD = serum PSA ÷ prostate volume) improves discrimination: PSAD <0.05 strongly suggests BPH, PSAD 0.05-0.1 is indeterminate, and PSAD >0.1 raises concern for malignancy 6
• No patient with BPH in validation studies had PSAD >0.117, while 33 of 34 patients with PSAD ≥0.1 had prostate cancer 6

Critical Coding Decision Points:

• Do NOT code C61 (malignant neoplasm of prostate) based on imaging heterogeneity alone—this requires biopsy confirmation 6
• If PSA is elevated (>4.0 ng/mL) with PSAD >0.1, add R97.20 (elevated PSA) as a secondary code to document the indication for further urologic evaluation 6
• If prostate volume cannot be calculated from CT, recommend transrectal ultrasound for accurate volume measurement and PSAD calculation 6