Monday, March 21, 2011

Intern Report Case Discussion 3.4


Case Presentation by Dr. Kevin Sprague



The patient is suffering from acute cholecystitis. This is caused by inflammation of the gallbladder, most commonly after a gallstone (cholelithiasis) obstructs the neck of the gallbladder or cystic duct. The obstruction causes mucus layer disruption, irritation and inflammation, which leads to dysmotility and distention. This inflammation occurs in the absence of bacterial infection. The most common type of gallstones in western civilization are cholesterol stones which occur when the cholesterol in the gallbladder exceeds the solubilizing capacity. The cholesterol will then nucleate into monohydrate crystals. These crystals cause gallbladder hypomotility which further accelerates cholesterol stone formation.

Cholesterol stones account for approximately 80% of gallstones in western civilization. The other type are designated pigment stones. These stones are a mixture of abnormal insoluble calcium salts of unconjugated bilirubin along with inorganic calcium salts. The amount of unconjugated bilirubin increases with infection of the biliary tract, and so infection with E. Coli or Ascaris lumbricoides (roundworm) increases the likelihood of pigment stone formation. These stones are radiopaque once the concentration of Ca exceeds 4%.

2-12% of cases are not caused by gallstones and are classified as acalculous. These typically occur in severely ill patients. Common scenarios are: postoperative state after major surgery, severe trauma, severe burns, multisystem organ failure, and sepsis. Diagnosing these patients is much more difficult as the onset is insidious and symptoms are obscured by the previously mentioned scenarios. The incidence of gangrene and perforation are higher in these patients. The mortality rate from acalculous cholecystitis is as high as 41%.

A differential for acute cholecystitis can include hepatitis, hepatic abscess, pyelonephritis, RLL pneumonia/pleurisy, perforated duodenal ulcer, pancreatitis, and appendicitis. Patients may have a mild fever, anorexia, nausea, vomiting, tachycardia, and diaphoresis. They may have had previous episodes of biliary pain. WBC count is normal in 27-40% of patients. Alkaline phosphatase, bilirubin, and serum aminotransferase are often within normal limits, but may be mildly elevated.

Ultrasound imaging is most commonly used in the ED as it is rapid and has good sensitivity. A gallstone or sludge may be visualized as well as gallbladder distention, gallbladder wall thickening, and pericholecystic fluid. A positive sonographic Murphy’s sign has good specificity for cholecystitis.

Treatment includes basic supportive measures, correcting fluid status and electrolyte imbalance. Emesis is managed with antiemetics and nasogastric suction. NG suction may diminish biliary secretion and excretion. Pain control may be achieved with narcotics. Antibiotics should be administered to prevent ascending infection. For uncomplicated cases, a 2nd or 3rd generation cephalosporin is recommended.

Common complications are gangrene, necrosis, and perforation. Emphysematous cholecystitis occurs in 1% of cases. This is the consequence of gas producing organisms (E. Coli, Klebsiella, C. perfringens) invading the mucosa of the gallbladder.


Answers

D. Hepatobiliary Iminodiacetic Acid (HIDA) Scan is the most sensitive at 97% for acute cholecystitis. Ultrasound is a close second at 94% sensitive. According to Rosen’s Emergency Medicine 7th Edition, CT may be 92% sensitive. However, I have also seen it reported as low as 50% sensitive. The bottom line is that CT is a much less preferable imaging modality. X-Ray will pick up 10% of gallstones, or about half of the cases of pigmented stones. I have never seen any information on MRI for acute cholecystitis, but I needed a 5th option.

E. This is sort of a cheap question. Over 90% of cases are caused by mechanical obstruction of the gallbladder neck or cystic duct by a gallstone. Even though the etiology is noninfectious, antibiotic therapy with a 2nd or 3rd generation cephalosporin is recommended. The other 4 choices are the organisms most commonly responsible for ascending cholangitis.

B. Porcelain Gallbladder is caused by calcifications within the gallbladder wall. The gallbladder may be palpable through the skin (Courvoisier’s sign). There is a high incidence of gallbladder carcinoma associated with this radiologic finding. These patients should be referred for a cholecystectomy.

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