Variant hepatic arterial anatomy

Variation in hepatic arterial anatomy is seen in 40-45% of people. Classic branching of the common hepatic artery from the celiac artery, and the proper hepatic artery into right and left hepatic arteries to supply the entire liver, is seen in 55-60% of the population. 

Terminology

An accessory hepatic artery is one which arises from an anomalous origin and supplies a portion of the liver along with another artery.

A replaced hepatic artery is one which arises from an anomalous origin and supplies a portion of the liver solely. 

Variant anatomy

In general, the common hepatic artery may arise from the abdominal aorta or superior mesenteric artery (SMA) and all or part of the right and left hepatic arteries may arise from (be replaced to) other vessels.  

The two most common variants are:

• replaced right hepatic artery arising from the SMA
• replaced left hepatic artery arising from the left gastric artery

Another common finding, though not considered a variant by many authors, is trifurcation of the common hepatic artery into the right hepatic artery, left hepatic artery and gastroduodenal artery (GDA). With this branching pattern, there is no proper hepatic artery (PHA).

Common hepatic artery (CHA)

• from aorta: 2%
• from SMA: 2%
• trifurcation into RHA, LHA and GDA: ~6% (range 4-8%)

Right hepatic artery (RHA)

• from celiac artery: ~2.5% (range 1-4%)
• from SMA: ~12.5% (range 9-15%)
• accessory RHA from SMA: ~4% (range 1-7%)

Left hepatic artery (LHA)

• from left gastric artery (LGA): ~7.5% (range 4-11%) 
• accessory LHA from LGA: ~7.5% (range 4-11%)

Right and left hepatic arteries

• RHA from SMA and LHA from LGA: ~1% (range 0.5-2%)
• accessory RHA and LHA: 1%

Middle hepatic artery (MHA)

• MHA usually arises from the left hepatic artery
• it may arise from the right hepatic artery
• it may arise as a trifurcation of the PHA in the porta hepatis
• in patients with a replaced left hepatic artery, the MHA arises from the right hepatic artery
• in patients with a replaced right hepatic artery, the MHA arises from the left hepatic artery
• if the bifurcation of the PHA is low within the porta hepatic, then the MHA may have an extrahepatic course and traverse Calot's triangle

​Classification

A classification method was described by Michel et al. in 1955 ⁶

• I: standard anatomy ~60% (range 55-61%)
• II: replaced LHA ~7.5% (range 3-10%)
• III: replaced RHA ~10% (range 8-11 %)
• IV: replaced RHA and LHA  ~1%
• V: accessory LHA from LGA ~10% (range 8-11%)
• VI: accessory RHA from SMA ~5% (range 1.5-7%)
• VII: accessory RHA and LHA ~1%
• VIII: accessory RHA and LHA and replaced LHA or RHA ~2.5%
• IX: CHA replaced to SMA ~3% (range 2-4.5%)
• X: CHA replaced to LGA ~0.5%
• unclassified
  • CHA separate origin from aorta ~2%
  • double hepatic artery ~4%
  • PHA replaced to SMA; GDA origin from aorta <0.5%

See also

• variant hepatic venous anatomy
• anatomic variants