Abdomen contouring

The central hepatobiliary tract is the region at the hilum of the liver where the main bile ducts leave the liver alongside the portal vein.

It is built rather than drawn. Toesca 2017 defined it as uniform expansions of the portal vein, testing 5, 10, 15, 20 and 25 mm, and found the 15 mm expansion a suitable surrogate. Check the definition your protocol uses.

The common bile duct carries bile from the liver and gallbladder into the duodenum.

Jabbour 2014:

• The common bile duct (usually 8–10 cm long and 5–6 mm wide) is formed by the cystic duct from the gallbladder and the common hepatic duct.
• Top: the contour starts at the first bifurcation, or where the duct enters the portal triad.
• It runs down behind and medial to the duodenum, joins the pancreatic duct, and drains into the second part of the duodenum at the ampulla of Vater. The consensus contour was extended down to the level of the second part of the duodenum.

Agreement between experts was only moderate for this structure in the consensus work, so take care with it.

The duodenum is the first part of the small intestine; bile and pancreatic juice enter it to digest food.

Jabbour 2014 traces its four parts:

• First part (about 5 cm): starts just below the pylorus, with the common bile duct, portal vein and IVC behind it.
• Second part (descending): attached to the head of the pancreas, to the right of L1–L3 and of the IVC.
• Third part: turns toward the midline at L3 and crosses to the left, in front of the aorta and IVC and behind the superior mesenteric artery and vein.
• Fourth part: rises to the left of L3 toward the pancreatic body and ends at the duodenojejunal junction (ligament of Treitz). The inferior mesenteric vein is a useful landmark for that junction.

Coronal views help, especially for the third part. In the consensus work the fourth part was often missed.

Timmerman 2022 (Tables 8–11, written for its SBRT dose tables): the entire duodenal wall and lumen from the pylorus to the duodenojejunal flexure.

The gallbladder stores and concentrates bile from the liver and releases it into the duodenum after meals.

Both Jabbour 2014 and Timmerman 2022 exclude the gallbladder from the liver contour. Neither gives written boundaries for the gallbladder itself. Written boundaries from an open published source: verified source required.

The kidneys filter the blood to make urine and help control blood pressure and red blood cell production.

Jabbour 2014: the renal pelvis is generally included in the kidney contours for upper-abdominal treatment.

Timmerman 2022 (Tables 8–11, written for its SBRT dose tables) splits the kidney into two structures:

• Renal cortex: right and left kidneys as one structure, all kidney tissue excluding the renal hilum/vascular trunk.
• Renal hilum/vascular trunk: each side separately, including the major calyces, renal pelvis and the proximal renal artery medial to the aorta.

Check whether your limit refers to whole kidneys, the cortex or the hilum.

The large intestine absorbs water and salts and stores stool.

Gay 2012:

• Colon: the large bowel continuing above where the anus–rectum–rectosigmoid (AnoRectumSig) contour ends. Depending on the volume treated, it includes part or all of the ascending, transverse, descending and sigmoid colon.
• Sigmoid (used in GYN cases): the bowel continuing above the anorectum, stopping before it joins the ascending colon at the side.

Timmerman 2022 (Tables 8–11, written for its SBRT dose tables): one structure, wall and contents, from 10 cm above to 10 cm below the PTV. Jabbour 2014 recommends tracking large bowel slice by slice in the upper abdomen.

CORSAIR's contouring table defines both a sigmoid and a large bowel structure, with the large bowel ending at the bottom at the rectosigmoid junction. Make the sigmoid–rectum boundary match how the rectum was contoured, so no segment is counted twice or missed.

The liver filters the blood, makes bile and many proteins, stores energy and clears drugs and toxins.

Jabbour 2014 (RTOG upper abdominal consensus):

• Exclude the gallbladder.
• Exclude the inferior vena cava where it is separate from the liver.
• Portal vein: exclude it only where the caudate lobe (segment I) lies behind it; include it where segment I lies to its left. Branches of the portal vein and other vessels inside the liver are included.

Timmerman 2022 (Tables 8–11, written for its SBRT dose tables): right and left lobes as one structure, all liver tissue minus the GTV, the major draining ducts, the portal vein outside the liver, and the gallbladder.

The small intestine absorbs most of the nutrients from food.

Sources use two different approaches:

• Individual loops. Gay 2012: oral contrast (given about 30 minutes before the scan) is encouraged so small bowel can be told from large bowel; the small bowel is outlined as the loops containing contrast. Jabbour 2014 recommends tracking the loops slice by slice.
• Bowel bag. Gay 2012 also defines a "BowelBag": the abdominal contents (excluding muscle and bone) from the lowest small or large bowel loop or the top of the rectum, whichever is lower, with other organs subtracted. Jabbour 2014 does not recommend the bowel bag in place of individual loops for upper-abdominal planning.

Timmerman 2022 (Tables 8–11, written for its SBRT dose tables): all loops of small bowel within 10 cm of the PTV in any direction, as one structure.

A limit written for loops does not apply to a bowel bag, or the reverse — match the structure to your source.

The spleen filters the blood, removes worn-out red blood cells and is part of the immune system.

The RTOG upper abdominal atlas (Jabbour 2014) shows the spleen among its consensus contours on the atlas images, but it does not give written boundaries for it. Written boundaries from an open published source: verified source required.

The stomach holds swallowed food and starts breaking it down with acid and enzymes.

Jabbour 2014:

• Oral contrast is recommended to show the stomach wall.
• Contour the stomach as one organ — cardia, fundus, body, antrum and pylorus.
• The cardia begins below the gastroesophageal junction; the fundus is the highest part, against the left hemidiaphragm.

Timmerman 2022 (Tables 8–11, written for its SBRT dose tables): the entire stomach wall and its contents, from the gastroesophageal junction to the start of the duodenum at the pylorus.