Pylephlebitis and Acalculous Cholecystitis
Related narrative: Pylephlebitis
Portal pylephlebitis is by definition an infection of the portal vein, usually manifested radiographically by air in the portal vein. Although portal venous infection occurs more frequently than the demonstration of portal venous air, the latter complication is usually lethal. Pylephlebitis is a likely cause of hepatic abscess; multiple, microscopic hepatic abscesses are often found at autopsy in patients dying of sepsis with portal pylephlebitis. More abscesses occur in the right than in the left lobe. This is probably due to preferential laminar drainage of the superior mesenteric vein to the right lobe.
Clinical features are unexplained sepsis with few early localizing signs, then rapid progression to gangrene and perforation of the gallbladder. Physical examination may show fever, but right upper quadrant tenderness is only present in about 25%. Leukocytosis and hyperamylasemia may be present. Pylephlebitis usually occurs secondary to infection in the region drained by the portal venous system. A review of 19 cases identified infection (most commonly diverticulitis) in 13 (68%) of the cases. Bacteremia was present in 88% of the patients, and the most common isolate was Bacteroides fragilis. Overall mortality was 32%, but most of the patients who died had severe sepsis prior to the initiation of antibiotic therapy. In no case was improvement in a patient's clinical status clearly attributable to the use of heparin, but some beneficial effect of anticoagulation could not be ruled out. If the underlying etiology is cholecystitis, urgent cholecystectomy should be performed or emergency cholecystectomy for gangrene or perforation. Prognosis is poor, with a mortality ranging from 10 - 50%.
ACUTE ACALCULOUS CHOLECYSTITIS
Acute acalculous cholecystitis is acute inflammation of the gallbladder in the absence of stones.
Epidemiology and Risk Factors
Acalculous cholecystitis occurs in approximately 5 - 15% of patients with cholecystitis, but in postoperative patients and children, the estimates are as high as 87% and 50%, respectively. It can be caused by a variety of conditions, including (1) cardiac events, (2) surgery, (3) sickle cell disease, and (4) diabetes melitus. In AIDS patients, infections resulting from cytomegalovirus, cryptosporidiosis, or microsporidiosis can lead to cholecystitis. But, infection of the gallbladder mucosa with bacteria is thought to be a secondary event in acute acalculous cholecystitis, following rather than causing the initial injury in most cases. Although in most patients the pathogenesis is unclear and is likely multifactorial in origin, the process is believed to be one of secondary infection in a functionally obstructed gallbladder. Pancreatic cancer or gallbladder cancer can present as an obstruction; torsion of the gallbladder caused by lost fixation can also prevent the normal outflow of bile and therefore resemble an obstruction.
Patients with acute acalculous cholecystitis are more likely to be male and old than are patients with cholecystitis that is caused by stones, which clusters in younger women. Acalculous cholecystitis is a disease of immobilized and critically ill patients. Other risk factors include pre-exisiting atherosclorosis, recent surgery, and hemodynamic instability. Less often, acute acalculous cholecystitis may occur in the absence of antecedent trauma or stress, especially in children, elderly patients with coexisting vascular disease, and patients with AIDS.
Because the disease often occurs in a group of debilitated patients and because the clinical course is fulminant with rapid, early complications, the mortality of acute acalculous cholecystitis is very high, ranging from 10 - 50%, which is far in excess of the expected 1% mortality seen in patients with calculous cholecystitis.
The clinical features of acute acalculous cholecystitis differ from that resulting from stone disease. Although right upper quadrant pain, fever, localized tenderness overlying the gallbladder, and leukocytosis may be evident, these features are frequently lacking in elderly, postoperative patients. Often, unexplained fever or hyperamylasemia is the only clue. Symptoms or signs referable to the right upper quadrant are initially absent in three fourths of cases. The clinical course of acute acalculous cholecystitis is more fulminant than ordinary cholecystitis. By the time the diagnosis has been made, at least half of patients have already experienced a complication, such as gangrene or a confined perforation of the gallbladder. Empyema and ascending cholangitis may further complicate cases in which bacterial superinfection of the gallbladder has occurred.
Diagnosis and Treatment
Patients may become bacteremic and septic if the condition is not treated promptly. The rapid development of complications in acute acalculous cholecystitis makes early diagnosis critical in avoiding excessive mortality; unfortunately, the lack of specific findings implicating the gallbladder combined with a confusing clinical picture related to antecedent surgery or trauma makes an early diagnosis very difficult. Delays in diagnosis or treatment have led to a high incidence of complications (e.g., gangrene, empyema, perforation) before surgery. For elderly patients at risk, a high index of suspicion for biliary tract sepsis is the best hope for early recognition. The mortality rate may be at least twice as high in acalculous cholecystitis as in calculous disease because of the high incidence of comorbid conditions and the delay in diagnosis.
In evaluating patients with suspected acute acalculous cholecystitis, sonography offers the advantage of being widely available and easily transportable to the bedside. Computed tomography (CT) findings suggestive of cholecystitis include wall thickening (>4 mm), pericholecystic fluid, subserosal edema, intramural gas, and sloughed mucosa. An advantage to CT compared with sonography is that it is superior at detecting pathology elsewhere in the abdomen that could be the cause of the patient's fever or pain. The disadvantage of CT is that it cannot be applied at the bedside, which is necessary for many critically ill patients.
Supportive medical care should include restoration of hemodynamic stability and antibiotic coverage for gram-negative enteric flora and anaerobes if biliary tract infection is suspected. Optimal treatment is emergency cholecystectomy, but a percutaneous cholecystostomy is alternative therapy in patients with extremely high surgical risk.
Approximately 500,000 cholecystectomies are performed annually in the U.S. Although gallstones cause the majority of these cases, between 5% and 10% of cholecystectomies are performed for the treatment of acalculous disease. In cholecystectomies performed on postoperative patients or on hospitalized patients recovering from trauma or burns, more than half of the gallbladders are resected because of acalculous disease.
Acute Acalculous Cholecystitis in Childhood
In childhood, acute acalculous cholecystitis has been associated with Rocky Mountain spotted fever and a variety of bacterial infections from Salmonella and Shigella organisms. Similar to adults, young patients usually present with right upper quadrant pain that radiates through to the back and may be associated with fever, nausea, and vomiting. Jaundice occurs in up to one third of patients.
A study of 12 children with acute acalculous cholecystitis noted that almost all had fever, abdominal pain, and tenderness. Other symptoms included vomiting (75%) and jaundice (41%). Results of laboratory tests showed leucocytosis (83%) and abnormal liver function (66%). Three patients (25%) had previous operations (2 perforated appendicitis and 1 osteomylitis), and 4 (33%) had a previous blunt abdominal trauma. Five patients (41%) had underlying infectious disease.
Diagnosis was suspected clinically and confirmed by ultrasonography. In nine patients, daily ultrasound showed progressive improvement. They were treated nonoperatively and recovered fully. In the other three, daily ultrasound found a progressive increase in gallbladder wall thickness and distension or appearance of nonshadowing echogenic materials or sludge and pericholecystic fluid. Cholecystectomy was performed in these patients. The authors suggested that initial nonoperative treatment of acute acalculous cholecystitis in children is usually effective.
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