According to "Harrison's Principles of Internal Medicine 17th Edition," gallstones affect 20 percent of women and 8 percent of men over 40 years of age and increases in incidence to 40 percent in women over 65 years of the age. Gallstones are categorized based upon their primary composition as cholesterol or pigmented stones. The cholesterol type occurs more commonly in the United States and forms primarily in the gallbladder in association with obesity and high-cholesterol diets. Pigmented stones occur in patients with chronic hemolytic disease and primarily form in the biliary ducts. Despite the stone composition and origin, gallstones cause biliary colic, cholecystitis and choledocholithiasis.
Biliary Colic
According to "Harrison's Principles of Internal Medicine 17th Edition," the gallbladder is connected to a network of ducts by a short cystic duct that normally drains bile from the gallbladder into the duodenum, the first segment of the small intestine. Cholesterol stones of varying sizes can migrate from the gallbladder into the cystic duct and may become stuck inside the lumen, causing partial or complete obstruction. In either case, as the gallbladder contracts, bile is squeezed forward against an obstructing stone, which impedes the flow of bile and increases the pressure within the cystic duct and gallbladder, causing pain. In the scenario of a partially obstructed duct, bile can leak past the stone, reducing the pressure and associated pain. Increased biliary pressure may reoccur after consuming a fatty meal, which causes the secretion of cholecystokinin, a hormone that stimulates gallbladder contraction. Patients usually complain of repeated pain attacks separated by a period of wellness. This is the clinical picture of biliary colic.
Characteristically, pain begins suddenly in the abdomen in the area of the right upper quadrant and becomes severe, aching and constant, lasting anywhere from 30 minutes up to 5 hours. The pain may radiate to the right shoulder or upper back and may diminish either gradually or quickly. If the cystic duct becomes completely obstructed, then pain persists and biliary colic progresses to a more severe condition called acute cholecystitis.
Acute Cholecystitis
According to Harrison's, acute cholecystitis is an inflamed gallbladder that typically follows the obstruction of the cystic duct. The so-called mechanical inflammation occurs from increased pressure that distends the gallbladder and reduces blood supply, causing damage to the gallbladder cells. With a bleak and fickle blood supply, the gallbladder begins to die, which is evidenced by thickening walls, exuding fluid and air formation within the lumen and walls of the gallbladder. In 50 to 85 percent of patients, gallbladder inflammation is secondary to bacterial infection.
The pain attack in acute cholecystitis is similar to biliary colic with the occurrence of a sudden pain in the right upper quadrant that may radiate to the right shoulder or upper back. However, the pain attack progressively gets worse increasing in frequency and intensity lasting longer than five hours. Pain is accompanied by gastrointestinal symptoms including loss of appetite, nausea and vomiting. Infection of the gallbladder will result in a low-grade fever and chills.
The classic triad of sudden right upper quadrant pain, fever and a lab test indicating inflammation or leukocytosis strongly suggests an impending acute cholecystitis.
Choledocholithiasis
According to Harrison's, cholesterol gallstones from the gallbladder can migrate past the cystic duct and enter the common bile duct, or CBD. A stone in the CBD is called choledocholithiasis. The stone may go unnoticed and pass into the duodenum without symptoms or complications. The most common scenario, however, is the stone is too large to pass and remains stuck within the CBD causing partial or complete obstruction. Depending on the level of obstruction, a variety of complications may occur including cholangitis, obstructive jaundice, pancreatitis and secondary biliary cirrhosis.
A common bile duct obstruction prevents bile from properly draining into the duodenum and increases pressure within the biliary system. Bile and its components, primarily conjugated bilirubin and bile salts, will backflow into systemic circulation causing jaundice from increased conjugated bilirubin and itching from bile salt deposition under the skin. Because bile cannot enter the duodenum, light or clay color stool is observed, and fever develops in the presence of infection.
References
- "Harrison's Principles of Internal Medicine 17th Edition"; Fauci, et al.; 2008
