Raised AFP: When You Need an Abdominal Scan

Alpha-fetoprotein (AFP) is a protein normally produced by a developing foetus. After birth, AFP levels drop to very low levels in healthy adults. When AFP is raised in a non-pregnant adult, it can indicate liver disease, certain cancers, or other conditions. Abdominal MRI is usually the next step to find out what's driving the elevation.

What's a Normal AFP Level?

In healthy, non-pregnant adults:

• Normal: Less than 10 ng/mL (some labs use less than 7 or less than 8.1)
• Mildly elevated: 10–100 ng/mL — warrants investigation but has multiple possible causes
• Moderately elevated: 100–400 ng/mL — suspicious for significant liver disease or malignancy
• Highly elevated: Greater than 400 ng/mL — strongly associated with hepatocellular carcinoma (HCC) or germ cell tumours

The level alone doesn't make a diagnosis, but the degree of elevation helps guide which conditions to investigate first.

Why AFP Rises

Liver-related causes

• Hepatocellular carcinoma (HCC): Primary liver cancer is the most important cause of significantly raised AFP. About 60–70% of HCCs produce AFP, and levels above 400 ng/mL in the context of known liver disease are highly suspicious.
• Chronic hepatitis: Both hepatitis B and hepatitis C can raise AFP mildly to moderately, especially during active infection or flares.
• Cirrhosis: AFP can be mildly elevated in cirrhosis from any cause — alcohol, fatty liver disease, autoimmune hepatitis.
• Acute hepatic injury: Severe, acute liver damage (from medications, toxins, or acute viral hepatitis) can cause a temporary AFP spike as the liver regenerates.

Non-liver causes

• Germ cell tumours: Testicular cancer (particularly non-seminomatous germ cell tumours), ovarian germ cell tumours, and extragonadal germ cell tumours can produce AFP.
• Pregnancy: AFP is naturally high during pregnancy — maternal serum AFP (MSAFP) is used as a screening test for certain foetal abnormalities.
• Gastric cancer: A minority of stomach cancers produce AFP (AFP-producing gastric cancer is a specific subtype).

Why Abdominal MRI Is the Key Investigation

When AFP is raised and the cause isn't immediately apparent, abdominal MRI is typically the most informative single investigation. Here's why:

Liver assessment

MRI is the best imaging modality for characterising liver lesions. It can:

• Detect hepatocellular carcinoma. HCC has a characteristic appearance on MRI — it enhances intensely in the arterial phase of contrast injection and washes out in later phases. This pattern is so specific that in the context of cirrhosis, MRI can diagnose HCC without needing a biopsy (following LI-RADS criteria).
• Differentiate HCC from benign lesions. The liver frequently has benign masses — haemangiomas, focal nodular hyperplasia (FNH), hepatocellular adenomas, and cysts. MRI characterises these far better than CT or ultrasound.
• Assess background liver disease. MRI shows cirrhosis, fatty liver, iron overload, and fibrosis — the soil in which HCC typically grows.
• Stage the cancer. If HCC is found, MRI shows its size, number of lesions, vascular invasion (tumour growing into blood vessels), and involvement of surrounding structures — all critical for treatment planning.

Broader abdominal assessment

An abdominal MRI also evaluates:

• Kidneys: Renal masses and cysts
• Pancreas: Pancreatic masses and cysts
• Adrenal glands: Adrenal masses
• Lymph nodes: Enlarged abdominal lymph nodes that might indicate metastatic disease
• Retroperitoneum: Germ cell tumours can arise in the retroperitoneum (the space behind the abdominal organs)

The Surveillance Context

For people at high risk of liver cancer — those with cirrhosis from any cause, chronic hepatitis B, or certain other liver conditions — regular surveillance with ultrasound and AFP every 6 months is the standard recommendation (NICE, AASLD, and EASL guidelines).

When surveillance ultrasound detects something suspicious, or when AFP rises during surveillance, MRI is the next step. It provides the detail needed to confirm or rule out HCC and plan treatment if cancer is found.

AFP as a Tumour Marker: Limitations

AFP is useful but imperfect as a tumour marker:

• Not all HCCs produce AFP — about 30–40% of liver cancers have normal AFP
• AFP can be raised without cancer — chronic liver disease, hepatitis flares, and pregnancy can all cause elevation
• AFP level doesn't perfectly correlate with tumour size or prognosis
• Very early-stage HCC may not raise AFP above the detection threshold

This is precisely why imaging is essential when AFP is elevated. A raised AFP is a signal that something may be happening in the liver — MRI determines whether that something is cancer, benign disease, or nothing structurally visible.

Blood Tests to Combine

When AFP is raised, the following additional tests provide important context:

• Liver function tests: ALT, AST, GGT, ALP, bilirubin, albumin — assessing overall liver health
• Hepatitis serology: Hepatitis B surface antigen, hepatitis C antibody — screening for viral causes
• Full blood count: Low platelets can indicate liver disease and portal hypertension
• Coagulation screen: INR/PT — assessing liver synthetic function
• AFP-L3 and DCP (Des-gamma-carboxyprothrombin): Additional tumour markers that can improve the specificity of AFP testing — not universally available but increasingly used
• hCG and LDH: If a germ cell tumour is suspected (particularly in younger men with testicular symptoms)

When to Investigate Raised AFP

• AFP above 10 ng/mL on a routine blood test: Repeat in 4–6 weeks. If persistent, investigate with liver function tests, hepatitis serology, and abdominal imaging.
• AFP above 20 ng/mL with known liver disease: Warrants prompt MRI to assess for HCC.
• AFP above 100 ng/mL: Warrants urgent abdominal MRI regardless of other factors.
• AFP above 400 ng/mL: Highly suspicious for malignancy. Urgent specialist referral alongside imaging.
• Rising AFP over serial measurements: A rising trend is more concerning than a single elevated result. Even modest rises over time warrant imaging.

A raised AFP isn't a diagnosis — it's an alert. Abdominal MRI provides the structural detail needed to determine whether that alert points to something that needs treatment, something that needs monitoring, or something that can be safely explained by a benign cause.