Right Upper Quadrant
In this article we will describe the anatomy of the right upper quadrant, what lies below this area of the abdominal wall, and which are the potential causes of pain in the right upper quadrant.
As a healthcare professional, you need to examine the abdomen of a patient very often because this can help establish a preliminary diagnosis in many clinical situations. Abdominal examination starts from the observation; skin colour, any bulge or distension, abdominal respiration, bruising, scars, herniae and any visible peristalsis are noted. Later steps are palpation, percussion and auscultation. In order to perform a comprehensive examination and to understand any abdominal pathology, it is essential to have proper knowledge of the relevant anatomy and the relationship of the internal structures to the surface markings on the exterior.
Because the anterior and lateral walls of the abdomen do not have any bony landmarks (like those we see around the neck and hips, for example), clinicians often make reference to imaginary lines drawn on the abdomen. For general clinical descriptions, a four-quadrant model is used which describes a right upper, right lower, left upper, and left lower quadrant. These quadrants are defined by one imaginary line drawn horizontally across the belly button and one drawn vertically down the midline of the body. More specifically, the transumbilical plane passes through the umbilicus and the intervertebral disc between the third and fourth lumbar vertebrae and the median plane passes superoinferiorly through the midline of the body, dividing it into right and left halves.
The right upper quadrant will be discussed in detail in the following article. It extends from the midline of the body to the right side of the abdomen, and from the umbilical plane to the right ribcage superiorly.
Viscera in Right Upper Quadrant
The various viscera found in the right upper quadrant are:
- Right lobe of the liver
- Pylorus of stomach
- Head of pancreas
- Right kidney with right suprarenal gland
- Right colic flexure
- Superior part of ascending colon
- Right half of transverse colon.
The most clinically relevant organs that manifest themselves as symptomatic in a patient reporting right upper abdominal pain are the liver, gallbladder, duodenum and head of the pancreas. The liver and gallbladder, along with the biliary tree, occupy the majority of the region and will be the main focus of this article. We will also discuss common clinical conditions that lead to patients’ complaints of abdominal pain in the right upper quadrant, often abbreviated to RUQ pain.
The Hepatobiliary System
Pain in the right upper quadrant (RUQ) can be caused by a wide variety of medical conditions. The hepatobiliary system is the term used to refer to how the liver and gallbladder organs work together to make and transport bile. It is often the culprit of RUQ pain.
The liver occupies the upper part of the abdominal cavity just beneath the diaphragm. Its convex superior surface is molded to the under surface of the domes of the diaphragm muscle, and it extends from the right fifth intercostal space down to the right costal margin. Grossly, the liver is divided into right, left, caudate, and quadrate lobes due to peritoneal and ligamentous attachment. The larger right and smaller left lobes are demarcated by the falciform ligament. The quadrate lobe exists between the gallbladder and round ligament. In turn, inferior vena cava, ligamentum venosum, and porta hepatis make the boundaries of caudate lobe.
The porta hepatis, or hilus of the liver, is a deep fissure in the inferior surface of the organ. It contains the hepatic ducts and branches of the portal vein and hepatic artery. The circulatory system of the liver is unlike that seen in any other organ. Roughly 75% of the blood entering the liver is venous blood from the portal vein, while the remaining 25% of the blood supply to the liver is arterial blood from the hepatic artery. Within the liver, the portal vein divides into right and left branches and then further into smaller channels (clinical fun fact: these smaller channels help define the liver segments used in surgical resections). On the other hand the hepatic arterial tree, that is often a branch of the celiac trunk, terminates in two plexuses: peribiliary plexus, which supports the functions of the biliary epithelium of the bile ducts and the periportal plexus that supplies the portal canals and drains into periportal sinusoids.
Recall that the liver microanatomy is based on the concept of the liver lobule. The liver lobule is a hexagonal prism of liver tissue with a central vein and six portal canals located at the angles of the hexagon. Sinusoids are the largest microvascular circulation of the liver, conducting nutrients, hormone-rich portal venous blood, and highly oxygenated arterial blood slowly past the liver cells, i.e.: hepatocytes. The sinusoids of the liver drain directly into the central veins, which are the smallest branches of the efferent vasculature (blood leaving the liver to return to the heart). The central veins coalesce to form large right, middle and left hepatic veins, which empty into the inferior vena cava, just beneath the right atrium of the heart.
Liver performs multiple functions which can be summarised as
- clearance of toxins, bacteria and bilirubin
- storage of glycogen, vitamin and essential elements
- metabolism of carbohydrates, amino acids and lipids
- synthesis of albumin, clotting factor and anticoagulants
It is present underneath the right lobe of the liver and consists of the neck, body, and fundus. It collects, concentrates, and secretes bile salts from the liver into the duodenum. The liver synthesizes bile salts and refluxes them into the gallbladder through the cystic duct. The stimulation of the gallbladder leads to its contraction and bile salts are secreted into the duodenum via the cystic duct into the common bile duct. These bile salts help to emulsify fats into globules that can be digested chemically.
Pancreas and Duodenum
The head of the pancreas is found in the right upper quadrant within the curvature of the duodenum. It is the thickest and broadest part of the pancreas. Anteriorly it is covered by peritoneum and is related to the origin of the transverse mesocolon, while its posterior surface is mainly related to inferior vena cava.
The duodenum forms the first ten inches of the small intestine and is mostly a retroperitoneal organ. It begins at the pylorus of the stomach and ends at the jejunum (the second portion of the small intestine) at the ligament of Treitz. The four anatomical parts of the duodenum are superior, descending, inferior, and ascending.
Apart from its digestive function, the endocrine role is also provided by the epithelium through the secretion of secretin and cholecystokinin. These hormones stimulate the liver, gallbladder, and pancreas to secrete bile, lipases, proteases, amylase, and bicarbonate.
Pain in the Right Upper Quadrant
There are many potential causes for right upper quadrant abdominal pain. It could be due to the organs found in the region, or might be due to the other abdominal organs. Sometimes non abdominal causes like pulmonary, cardiac or musculoskeletal ones are the reasons. To diagnose the associated pathology, a detailed examination with a proper history is required. Along with this, some lab tests are recommended to support the particular diagnosis. Elevation of white blood cells, though nonspecific but suggestive of infection, platelet disorders, coagulopathies, and derangements in aminotransferase levels could be indicative of liver dysfunction. Serum amylase and lipase levels are usually obtained in pancreatitis.
Imaging tools like ultrasound, CT scans and MRI are sometimes used to further explore the conditions.
The following conditions are a few that might cause right upper quadrant abdominal pain:
- Liver abscess (pus-filled pocket in the liver)
- Liver cancer
- Liver hemangioma
Gallbladder and biliary tree
- Pancreatic cancer
- Peptic ulcer disease