Gastric Ascariasis on CT: An Unexpected Cause of Right Upper Quadrant Pain and the Rare Possibility of Cerebral Migration

A Worm on CT? The Hidden Diagnosis Behind Persistent Right Upper Quadrant Pain

Keywords: Gastric ascariasis, Ascaris lumbricoides, abdominal CT, liver lesions, parasitic infection, intestinal helminths, emergency radiology, AI radiology, abdominal pain diagnosis, medical imaging AI

How CT Imaging Revealed Gastric Ascariasis, Hepatic Involvement, and the Rare Risk of Brain Migration

Clinical Hook

A 32-year-old previously healthy woman arrived at the emergency department after nearly ten days of worsening right upper quadrant pain. The discomfort intensified during deep inspiration but did not radiate elsewhere. She also reported a persistent cough, reduced appetite, and generalized fatigue. Routine laboratory studies were largely unremarkable, making the diagnosis initially elusive. Physical examination demonstrated decreased breath sounds over the right lower lung and tenderness in the right upper abdomen.

The turning point occurred when contrast-enhanced CT unexpectedly demonstrated a dilated stomach containing a long tubular intraluminal structure consistent with Ascaris lumbricoides, together with several low-density hepatic lesions suggestive of biliary involvement. Subsequent antiparasitic treatment resulted in the passage of adult worms and complete clinical recovery.

This case illustrates how modern cross-sectional imaging can identify uncommon parasitic diseases before serious complications occur and highlights the emerging role of artificial intelligence in detecting subtle imaging abnormalities.

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Learning Objectives

After completing this article, readers should be able to:

• Recognize CT manifestations of gastric ascariasis.
• Understand the life cycle of Ascaris lumbricoides.
• Identify hepatic and biliary complications.
• Explain why abdominal CT may establish the diagnosis when laboratory findings are nonspecific.
• Discuss uncommon extraintestinal migration, including cerebral involvement.
• Apply differential diagnosis strategies for tubular intraluminal filling defects.
• Appreciate the future role of AI-assisted abdominal imaging.

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Anatomy Review

Figure 1. Normal Gastrointestinal Route of Ascaris lumbricoides

This schematic emphasizes why abdominal imaging alone may not reveal the full biological behavior of the parasite.

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Anatomy Overview

The stomach normally serves only as a transient passage for swallowed parasites. Adult Ascaris lumbricoides typically inhabit the jejunum and ileum, where they survive by absorbing intestinal contents. Under stressful physiological conditions—including fever, anesthesia, pregnancy, or heavy worm burden—the parasites may migrate into atypical locations such as the stomach, biliary tree, pancreas, appendix, or even the upper airway.

Understanding these migration pathways is essential because imaging findings often reflect aberrant parasite movement rather than primary gastric disease.

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Case Presentation

Patient

32-year-old woman

Previously healthy

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Chief Complaint

Progressively worsening right upper quadrant pain lasting approximately ten days.

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Clinical History

The patient described localized right upper abdominal pain that became significantly worse during deep inspiration. She denied radiation of pain but reported several constitutional symptoms, including:

• Persistent irritating cough
• Decreased appetite
• General fatigue

No previous gastrointestinal disease or chronic medical illness was documented.

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Physical Examination

Important examination findings included:

• Decreased breath sounds over the right lower lung field
• Tenderness on palpation of the right upper abdomen
• No obvious peritoneal irritation

Routine hematologic investigations were essentially normal despite an active parasitic infection.

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Clinical Question

Could an uncommon parasitic infection explain persistent right upper quadrant pain despite essentially normal laboratory findings?

This diagnostic dilemma illustrates one of the greatest strengths of modern radiology: revealing unexpected pathology when clinical presentation is nonspecific.

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CT Findings

Figure 2. Contrast-enhanced axial abdominal CT

 Figure 2. Contrast-enhanced axial abdominal CT demonstrates a markedly dilated stomach containing a long tubular intraluminal structure (arrow), compatible with Ascaris lumbricoides. Multiple hypoattenuating hepatic lesions are also identified, suggesting hepatobiliary involvement. These imaging findings established the diagnosis of gastric ascariasis and guided subsequent antiparasitic treatment.

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MRI Considerations

MRI was not performed in this patient.

However, MRI may become valuable when:

• biliary obstruction is suspected
• hepatic abscess requires characterization
• pancreatic duct invasion is possible
• neurological symptoms suggest cerebral migration

Particularly, contrast-enhanced brain MRI would be the preferred modality for evaluating rare intracranial involvement by migrating larvae, complementing CT findings when neurological manifestations develop.

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Final Diagnosis

Gastric Ascariasis (Ascaris lumbricoides infection) with hepatic involvement and awareness of the rare potential for cerebral larval migration.

The patient was treated successfully with mebendazole, subsequently passed adult worms in the stool, and remained symptom-free with negative stool examinations at two-month follow-up.

6. Imaging Pearls

Unlike many abdominal emergencies, gastric ascariasis often presents with minimal laboratory abnormalities despite conspicuous imaging findings. In the present case, routine blood tests were essentially normal, emphasizing that radiologic evaluation rather than laboratory screening established the diagnosis.

Imaging Pearl 1

A long, smooth tubular intraluminal structure within the stomach or bowel should immediately suggest a parasitic infestation, particularly in endemic regions.

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Imaging Pearl 2

Unlike neoplastic lesions, adult Ascaris lumbricoides demonstrates:

• uniform caliber
• sharply defined margins
• absence of mural destruction
• elongated configuration

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Imaging Pearl 3

CT frequently identifies secondary complications rather than the parasite itself.

Examples include:

• biliary obstruction
• hepatic abscess
• pancreatitis
• intestinal obstruction
• bowel perforation

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Imaging Pearl 4

Migration into the biliary tree may produce:

• intrahepatic duct dilatation
• cholangitis
• hepatic inflammatory lesions

before worms are directly visualized.

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Imaging Pearl 5

Dynamic imaging occasionally demonstrates subtle movement of intraluminal worms between serial examinations.

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Imaging Pearl 6

Ultrasound may demonstrate the classic:

• Inner tube sign
• Strip sign
• Spaghetti sign

whereas CT better depicts extraintestinal complications.

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Imaging Pearl 7

MRI contributes little to uncomplicated intestinal disease but becomes valuable for:

• biliary complications
• pancreatic involvement
• cerebral migration
• spinal infection

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Imaging Pearl 8

Normal eosinophil counts do not exclude ascariasis.

Radiologists should therefore avoid dismissing parasitic disease solely because laboratory studies appear reassuring.

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7. Pathophysiology

Figure 3. Life Cycle and Organ Migration of Ascaris lumbricoides

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Biological Mechanism

Human infection begins after ingestion of embryonated eggs from contaminated food or water. Once inside the small intestine, larvae hatch and penetrate the intestinal mucosa before entering the bloodstream. They subsequently migrate through the liver and lungs, ascend the bronchial tree, are swallowed, and mature into adult worms within the small intestine.

Although this pulmonary-hepatic migration is a normal component of the parasite's life cycle, adult worms occasionally leave the intestine and migrate into abnormal anatomical locations.

Potential migration sites include:

• stomach
• biliary tract
• gallbladder
• pancreatic duct
• appendix
• upper airway

Extremely rarely, larvae may reach the central nervous system through hematogenous dissemination. Proposed mechanisms include passage across the blood–brain barrier after systemic circulation, although this remains incompletely understood. Neurological manifestations may include headache, seizures, altered mental status, focal deficits, or coma.

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8. Epidemiology

Table 1. Epidemiologic Features of Ascariasis

Feature	Summary
Organism	Ascaris lumbricoides
Transmission	Fecal–oral route
Reservoir	Humans
Major Risk	Poor sanitation
Global Burden	One of the most common helminth infections worldwide
Endemic Areas	Asia, Africa, Latin America
Pediatric Predominance	Yes
Extraintestinal Migration	Uncommon
Brain Involvement	Extremely rare

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Global Perspective

Ascariasis remains among the world's most prevalent parasitic infections despite major improvements in sanitation.

Hundreds of millions of people continue to be infected annually, particularly in tropical and subtropical regions where:

• inadequate sanitation
• contaminated water
• poor hygiene

facilitate transmission.

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9. Clinical Manifestations

Clinical manifestations vary according to:

• parasite burden
• migration phase
• affected organ

Intestinal Phase

• abdominal discomfort
• nausea
• anorexia
• intestinal obstruction

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Pulmonary Phase (Löffler Syndrome)

• cough
• wheezing
• transient pulmonary infiltrates
• eosinophilia

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Hepatobiliary Disease

• right upper quadrant pain
• cholangitis
• liver abscess
• biliary colic

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Pancreatic Disease

• acute pancreatitis

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Rare Neurological Disease

Although gastrointestinal and hepatobiliary involvement represent the most common manifestations of Ascaris lumbricoides, migration to the central nervous system is exceedingly rare. When cerebral involvement occurs, patients may present with headache, seizures, altered mental status, focal neurological deficits, or coma. Neuroimaging plays a crucial role in excluding alternative diagnoses and evaluating intracranial complications.

Figure 4. Axial Brain CT

Figure 4. Axial brain CT illustrating cerebral involvement associated with ascariasis. Although central nervous system involvement is exceedingly rare, brain CT is an important first-line imaging modality for evaluating acute neurological symptoms and excluding alternative intracranial pathologies. MRI may provide additional characterization when cerebral involvement is suspected.

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10. Differential Diagnosis

Table 2. Differential Diagnosis of Tubular Intraluminal Gastric Lesions

Disease	CT Appearance	Distinguishing Feature
Gastric Ascariasis	Long tubular structure	Smooth worm morphology
Bezoar	Mottled intraluminal mass	Air bubbles
Food residue	Variable density	Changes after fasting
Gastric neoplasm	Wall thickening	Enhancing mass
Blood clot	Hyperdense filling defect	Trauma or bleeding history
Foreign body	Variable attenuation	Clinical history

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Diagnostic Strategy

Radiologists should evaluate:

Morphology

• tubular
• linear
• folded
• mobile

Location

• stomach
• duodenum
• jejunum
• biliary tree

Associated Findings

• biliary dilatation
• hepatic lesions
• bowel obstruction
• pancreatitis

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11. Clinical Management

The cornerstone of treatment is anthelmintic therapy.

Common medications include:

• Albendazole
• Mebendazole

The present patient received mebendazole, successfully expelled adult worms in the stool, and became symptom-free. Follow-up stool examinations two months later were negative for parasites.

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Management Algorithm

Mild Disease

• oral antiparasitic therapy
• hydration
• follow-up stool examination

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Moderate Disease

• abdominal imaging
• hepatobiliary evaluation
• laboratory monitoring

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Severe Complications

Consider:

• ERCP for biliary obstruction
• surgery for intestinal perforation
• drainage of hepatic abscess
• intensive neurologic management when cerebral involvement occurs

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Prognosis

Most uncomplicated infections have an excellent prognosis when diagnosed early.

Delayed recognition, however, may lead to:

• bowel obstruction
• biliary sepsis
• pancreatitis
• hepatic abscess
• rare neurological complications

Consequently, radiologists play a pivotal role in early diagnosis, especially when imaging reveals unexpected tubular intraluminal structures despite nonspecific clinical findings.

12. Artificial Intelligence Perspective

Why AI Matters in Parasitic Imaging

Parasitic diseases have traditionally been considered "low-volume" radiology cases compared with stroke, trauma, or cancer. Consequently, many radiologists encounter only a limited number of confirmed cases during training.

This rarity creates an ideal opportunity for artificial intelligence—not to replace radiologists, but to function as a clinical decision support system (CDSS) that improves the detection of uncommon imaging patterns.

In gastric ascariasis, AI can assist by:

• Detecting elongated tubular intraluminal structures
• Differentiating parasites from food residue or bezoars
• Identifying subtle biliary abnormalities
• Quantifying secondary inflammatory changes
• Alerting radiologists to unusual migration pathways

Rather than making an autonomous diagnosis, AI provides probability-based pattern recognition that supports expert interpretation.

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Figure 5. Enterprise AI Workflow for Gastric Ascariasis

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AI-Assisted Image Interpretation

Modern deep-learning algorithms excel at recognizing geometric structures.

Adult Ascaris lumbricoides demonstrates several features particularly amenable to machine learning:

• elongated morphology
• homogeneous diameter
• smooth contour
• intraluminal location
• characteristic attenuation
• predictable anatomical course

Segmentation networks can isolate these structures automatically, while classification models estimate the likelihood of parasitic infestation.

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Foundation Models in Radiology

Large multimodal foundation models represent one of the most important recent advances in medical imaging.

Unlike conventional AI systems trained for a single disease, foundation models learn general imaging representations from millions of radiologic images.

Potential applications include:

• CT interpretation
• MRI interpretation
• Chest radiography
• Ultrasound
• PET/CT
• Multimodal clinical reasoning

For parasitic infections, foundation models may eventually integrate:

• CT appearance
• laboratory findings
• epidemiologic exposure
• travel history
• symptoms
• previous examinations

to generate differential diagnoses ranked by probability.

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Radiomics

Radiomics converts medical images into quantitative biomarkers.

Instead of relying solely on visual inspection, radiomics analyzes:

• texture
• intensity
• entropy
• shape
• edge characteristics
• spatial heterogeneity

For gastric ascariasis, radiomics could distinguish:

Imaging Feature	Potential Radiomic Marker
Worm	Linear shape signature
Food residue	Irregular texture
Bezoar	High heterogeneity
Tumor	Surface irregularity
Blood clot	Density variation

Future radiomics research may enable automated discrimination between parasitic infestation and other intraluminal lesions with greater reproducibility than subjective visual assessment.

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Clinical Decision Support Systems (CDSS)

Clinical decision support combines imaging AI with patient-specific clinical information.

Example Workflow

Such systems reduce diagnostic delay while preserving physician oversight.

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Integration with PACS, RIS, and Electronic Health Records

Enterprise deployment requires seamless interoperability.

A future AI platform could integrate with:

• PACS (Picture Archiving and Communication System)
• RIS (Radiology Information System)
• EMR/EHR
• HL7 messaging
• FHIR APIs
• Clinical dashboards

This architecture allows imaging findings to be combined with laboratory results, medication history, microbiology reports, and epidemiologic information, creating a comprehensive clinical context for decision-making.

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AI Limitations

Despite rapid progress, several limitations remain.

Limited Training Data

Parasitic infections are uncommon in many countries, resulting in relatively small annotated imaging datasets.

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Geographic Bias

Algorithms trained primarily on datasets from high-income countries may underperform in tropical regions where parasitic diseases are more prevalent.

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False Positives

Potential mimics include:

• food residue
• gastric folds
• intraluminal tubes
• postoperative material
• bezoars

Human review remains essential.

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Explainability

Clinical adoption requires AI systems that provide transparent reasoning rather than opaque probability scores.

Explainable AI techniques such as attention maps and lesion localization improve clinician trust.

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13. Future of Precision Imaging

Digital Twin Technology

Digital twins represent virtual patient models that continuously integrate:

• imaging
• laboratory values
• genomics
• microbiology
• treatment response

In parasitic diseases, digital twins may simulate:

• parasite migration
• treatment response
• risk of biliary obstruction
• probability of complications

Before clinical deterioration occurs.

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Federated Learning

Privacy regulations often prevent hospitals from sharing imaging data directly.

Federated learning addresses this challenge by allowing AI models—not patient images—to be shared between institutions.

Benefits include:

• improved privacy
• larger training populations
• better algorithm generalization
• reduced institutional bias

This approach is particularly valuable for rare diseases such as cerebral ascariasis, where individual hospitals encounter very few confirmed cases.

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Synthetic Medical Imaging

Generative AI can produce realistic synthetic CT and MRI datasets that preserve imaging characteristics without exposing patient identities.

Applications include:

• AI training
• resident education
• algorithm validation
• multicenter benchmarking

Synthetic images may substantially expand datasets for rare parasitic infections, accelerating the development of robust diagnostic algorithms.

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Precision Medicine

Future imaging systems will combine:

• Radiology
• Pathology
• Genomics
• Clinical biomarkers
• AI prediction models

to personalize diagnosis and therapy.

Rather than treating all patients identically, precision imaging aims to estimate each individual's risk of complications and tailor management accordingly.

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Key Takeaways from the AI Perspective

• AI enhances—but does not replace—expert radiologic interpretation.
• Foundation models may improve recognition of rare parasitic diseases by integrating multimodal clinical information.
• Radiomics offers quantitative characterization of intraluminal lesions beyond visual assessment.
• Federated learning enables collaborative AI development while preserving patient privacy.
• Synthetic imaging and digital twins have the potential to transform education, research, and precision medicine for uncommon infections.

14. Clinical Pearls

Pearl 1

Persistent right upper quadrant pain with normal laboratory findings does not exclude significant abdominal pathology.

Pearl 2

Adult Ascaris lumbricoides typically appears on CT as a long, smooth, tubular intraluminal structure.

Pearl 3

CT is superior to plain radiography for detecting extraintestinal migration and associated complications.

Pearl 4

Biliary ascariasis should be considered in patients with biliary colic living in or returning from endemic regions.

Pearl 5

Routine laboratory tests may remain normal despite active infection.

Pearl 6

Ultrasound is useful for detecting motile worms within the biliary tract, whereas CT better evaluates surrounding organs.

Pearl 7

MRI becomes valuable when neurological symptoms raise concern for rare cerebral migration.

Pearl 8

Radiologists should evaluate the entire abdomen for secondary inflammatory complications rather than focusing solely on the parasite.

Pearl 9

Early diagnosis prevents unnecessary surgery in many patients.

Pearl 10

Anthelmintic therapy is highly effective for uncomplicated disease.

Pearl 11

Migration rather than worm burden often determines clinical severity.

Pearl 12

Artificial intelligence can improve detection consistency but should complement—not replace—expert interpretation.

Pearl 13

Radiomics may provide objective differentiation between parasites, bezoars, and intraluminal tumors.

Pearl 14

Structured reporting improves communication between radiologists, gastroenterologists, and surgeons.

Pearl 15

Every confirmed parasitic case enriches AI training datasets for future diagnostic systems.

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15.Quiz

Question 1

Which imaging modality established the diagnosis in this case?

A. Plain radiography

B. Ultrasound

C. Contrast-enhanced CT

D. PET/CT

✅ Answer: C

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Question 2

The typical life cycle of Ascaris lumbricoides includes migration through which organ?

A. Kidney

B. Lung

C. Thyroid

D. Spleen

✅ Answer: B

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Question 3

Which CT feature most strongly suggests ascariasis?

A. Calcified mass

B. Ring-enhancing lesion

C. Smooth tubular intraluminal structure

D. Gas-filled cyst

✅ Answer: C

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Question 4

Which medication was successfully used in this patient?

A. Vancomycin

B. Ciprofloxacin

C. Mebendazole

D. Amphotericin B

✅ Answer: C

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Question 5

Which complication is exceptionally rare?

A. Appendicitis

B. Pancreatitis

C. Cerebral migration

D. Cholangitis

✅ Answer: C

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16. Frequently Asked Questions (FAQ)

Can CT identify intestinal parasites?

Yes. Modern multidetector CT can directly visualize adult worms and detect secondary complications.

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Is eosinophilia always present?

No. Laboratory findings may be normal despite active infection.

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Can parasites reach the brain?

Although extremely uncommon, hematogenous larval migration has been reported and may produce neurological symptoms.

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Is surgery usually required?

Most patients respond to medical therapy unless complications such as obstruction or perforation develop.

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Will AI replace radiologists in diagnosing parasitic disease?

Current evidence supports AI as a decision-support tool rather than an autonomous diagnostic system.

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17. Conclusion

This case demonstrates that uncommon parasitic infections may masquerade as routine abdominal pain while routine laboratory studies remain unrevealing. Cross-sectional CT imaging provided the decisive diagnosis by identifying a gastric Ascaris lumbricoides worm and associated hepatic abnormalities, enabling prompt treatment and complete clinical recovery.

Beyond the individual case, it highlights the expanding role of artificial intelligence, radiomics, and multimodal clinical integration in supporting radiologists faced with rare diseases. As enterprise imaging platforms evolve, AI-assisted recognition of atypical parasitic infections may reduce diagnostic delay, improve reporting consistency, and strengthen precision medicine without replacing expert clinical judgment.

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18. Continue Learning

Recommended next topics:

1. Biliary Ascariasis: Imaging Features and Management
2. CT Diagnosis of Hepatic Parasitic Diseases
3. Neuroparasitic Infections on MRI
4. Emergency Abdominal CT: Unexpected Infectious Findings
5. AI-Assisted Detection of Gastrointestinal Diseases

Medical Disclaimer

This article is intended for educational purposes only and does not constitute medical advice. Patients should consult qualified healthcare professionals for diagnosis and treatment.

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About the Author

Author

Dr. SangBock Lee
Founder, ScholarGen Inc.
Medical AI Researcher and Radiology Educator

Co-Author

Dr. H. J. Lee, Professor

Director, ScholarGen Inc.