Ascariasis is caused by Ascaris lumbricoides, the most common intestinal parasite in humans, typically transmitted via the fecal-oral route. In most cases, Ascaris infection is asymptomatic. However, factors such as starvation or reduced gastric acidity can prompt Ascaris to migrate into the biliary tract, leading to a range of clinical symptoms collectively referred to as biliary ascariasis. In recent years, improved dietary habits and sanitation have led to a significant decline in the incidence of this condition.
Etiology and Pathology
The natural burrowing behavior of Ascaris lumbricoides and its preference for an alkaline environment contribute to its pathogenesis. Altered intestinal conditions, such as gastrointestinal dysfunction, starvation, fever, pregnancy, or improper deworming, can prompt Ascaris to migrate into the duodenum. Dysfunction of the sphincter of Oddi may allow Ascaris to enter the biliary tract, where its mechanical stimulation of the sphincter can cause spasms, leading to biliary colic or even acute pancreatitis. Intestinal bacteria or fungi carried by Ascaris may infect the biliary system, potentially causing acute suppurative cholangitis or liver abscesses in severe cases. Migration through the cystic duct into the gallbladder may even result in gallbladder perforation. Ascaris within the biliary tract may be solitary or multiple, and prolonged sphincter spasms can cause the worms to die, leaving behind carcasses that can act as nuclei for the formation of bile duct stones.
Clinical Manifestations
The hallmark of biliary ascariasis is severe abdominal pain with disproportionately mild physical findings, commonly described as a "mismatch between symptoms and signs." Patients often experience sudden, excruciating, colicky pain under the xiphoid process that worsens intermittently. The pain causes severe restlessness, groaning, and profuse sweating, and may be accompanied by nausea, vomiting, or the expulsion of worms. The pain is often referred to the right scapular region or back. Episodes of abdominal pain may resolve abruptly, leaving the patient symptom-free between attacks. Recurrences vary in frequency and duration. If cholangitis accompanies the condition, symptoms resemble those of acute cholangitis, with severe cases presenting as obstructive suppurative cholangitis.
Physical examination often reveals mild tenderness in the right upper quadrant or below the xiphoid process. If cholangitis, pancreatitis, or a liver abscess is present, corresponding physical signs may also be observed.
Auxiliary Examinations
Ultrasound is the preferred diagnostic modality and is often sufficient for diagnosis. Imaging findings may include parallel echogenic bands within the bile ducts, with a central hypoechoic area, and occasionally the movement of worms within the ducts. CT imaging may show smooth, curved, elongated hypodense structures within the gallbladder or bile ducts. MRCP and ERCP can reveal the position of the worms within the biliary tree.
Diagnosis
The diagnosis is generally straightforward based on symptoms, physical findings, and imaging studies but should be differentiated from cholelithiasis.
Treatment
Non-surgical treatment forms the mainstay of management, while surgical intervention may be considered for complications.
Non-Surgical Treatment
Antispasmodics and Pain Relief
Administration of 33% magnesium sulfate and antispasmodic medications can relieve sphincter spasms of Oddi. Severe pain can be managed with anticholinergic drugs such as atropine or anisodamine (654-2), and pethidine may be used if necessary.
Choleretics and Anti-Parasitics
An acidic environment disrupts Ascaris activity, which can be achieved using vinegar or sour plum soup, helping immobilize the worms and reduce irritation, thereby alleviating pain. Administration of oxygen via a gastric tube may also aid both in immobilizing worms and providing pain relief. Once symptoms subside, anti-parasitic treatment is initiated, using commonly prescribed medications such as albendazole, mebendazole, ivermectin, or levamisole. Continued choleretic medication following deworming may facilitate the expulsion of worm remnants.
Antibiotics
Antibiotics targeting intestinal bacteria are used to prevent and control infection.
Duodenoscopic Worm Removal
During ERCP, identified worms protruding from the duodenal papilla can be mechanically extracted. For pediatric patients, special consideration is given to preserving sphincter of Oddi function, and sphincterotomy is performed with caution.
Surgical Treatment
Surgical intervention may be indicated when non-surgical measures fail to relieve symptoms or when complications such as bile duct stones, acute obstructive suppurative cholangitis, liver abscesses, or severe pancreatitis are present. Common bile duct exploration with T-tube drainage can be performed. During surgery, a choledochoscope may be used to remove worm remnants. Postoperatively, anti-parasitic medications remain necessary to prevent recurrence of biliary ascariasis.