Clinical Hook

A 76-year-old man presents to the emergency department with right upper quadrant abdominal pain.

At first glance, this sounds like one of the most familiar presentations in abdominal emergency medicine: acute cholecystitis.

But the CT tells a more important story.

Along the gallbladder wall are small, unmistakably abnormal foci of gas. There is surrounding inflammatory change, and gallstones are present.

That tiny amount of gas is not an incidental detail.

It changes the diagnosis from an ordinary inflammatory gallbladder disorder to emphysematous cholecystitis, an aggressive infection in which ischemic tissue and gas-producing organisms can combine to produce necrosis, perforation, peritonitis, and sepsis.

The key lesson is deceptively simple:

When gas is identified around the gallbladder, do not stop at identifying the gas. Determine exactly where it is.

Gas confined to the lumen has a different differential diagnosis from gas embedded within the gallbladder wall. Gas extending into the pericholecystic tissues raises still another level of concern.

The case presented here involves a 76-year-old man with right upper quadrant pain. CT demonstrated gas tracking along the gallbladder wall, mild pericholecystic inflammatory change, and gallstones—findings that strongly support emphysematous cholecystitis.

This distinction matters because the radiologist is not merely naming a disease. The radiologist is communicating a potential source-control emergency.

Learning Objectives

After reading this article, the reader should be able to:

Recognize the characteristic CT appearance of emphysematous cholecystitis.
Explain why ischemia and gas-forming infection interact to produce gallbladder wall gas.
Distinguish emphysematous cholecystitis from other causes of gallbladder gas.
Identify CT findings suggesting advanced disease, necrosis, perforation, or extra-gallbladder extension.
Understand the role of CT relative to ultrasound and MRI in this emergency.
Explain how AI-assisted imaging could support—but not replace—expert interpretation.

1. Anatomy Review

The gallbladder is a pear-shaped organ situated beneath the inferior surface of the liver. It consists of the fundus, body, infundibulum, and neck, which continues into the cystic duct.

Its wall contains several histologic layers, although the gallbladder differs from the typical gastrointestinal tract because it lacks a well-developed muscularis mucosae and submucosa.

Arterial supply is predominantly derived from the cystic artery, most commonly originating from the right hepatic artery. This vascular arrangement becomes particularly important when considering emphysematous cholecystitis.

Gallbladder inflammation and increasing intraluminal pressure can compromise microvascular perfusion. Once ischemia develops, the wall becomes increasingly susceptible to bacterial invasion and tissue necrosis.

This provides the anatomical substrate for gas-forming infection.

Figure 1. Anatomical and Pathophysiological Basis of Emphysematous Cholecystitis

Schematic illustration of the gallbladder, cystic artery, gallbladder wall, lumen, surrounding liver, and pericholecystic tissues. The diagram demonstrates how cystic duct obstruction and increased intraluminal pressure can compromise gallbladder-wall perfusion, creating an ischemic environment favorable to invasive infection and gas formation.

2. Case Presentation

History

A 76-year-old man presented with right upper quadrant abdominal pain.

The source case describes the patient as belonging to a demographic group associated with increased risk for emphysematous cholecystitis. The clinical presentation may initially resemble uncomplicated acute cholecystitis.

Symptoms

The principal symptom was right upper quadrant pain.

Potential accompanying manifestations of emphysematous cholecystitis include fever, nausea, vomiting, anorexia, right upper quadrant tenderness, leukocytosis, systemic inflammation, and sepsis. Importantly, elderly or diabetic patients may have relatively subtle clinical manifestations despite substantial disease.

Physical Examination

The source material emphasizes that fever and Murphy sign may be less prominent in high-risk patients.

This is clinically important. A relatively unimpressive examination should not overrule a highly suspicious CT finding.

Clinical Question

The central diagnostic question is not simply:

“Does this patient have acute cholecystitis?”

It is:

“Is there gas within the gallbladder wall, and if so, has the infection extended beyond the gallbladder?”

Laboratory Findings

The source material identifies leukocytosis and elevated inflammatory markers as common laboratory abnormalities. Sepsis-related abnormalities may occur in advanced disease.

Specific laboratory values are not provided in the available case material and therefore should not be fabricated.

CT Findings

Axial and coronal CT demonstrated gas distributed along the gallbladder wall. Mild pericholecystic inflammatory change and gallstones were also present.

This combination is highly characteristic.

MRI Findings

MRI/MRCP may provide useful biliary and soft-tissue information, but MRI is not the preferred first-line examination when emphysematous cholecystitis is suspected in an acute setting because the immediate diagnostic priority is identifying and mapping gas.

No patient-specific MRI findings are provided in the case material.

Pathology

The pathological process is expected to involve acute inflammation, ischemic injury, bacterial infection, and potentially gangrenous necrosis.

The case material does not provide a detailed histopathology report, so specific microscopic findings should not be invented.

Final Diagnosis

Emphysematous cholecystitis.

The diagnosis is supported primarily by the presence of gas within the gallbladder wall in the appropriate clinical setting.

3. Pathophysiology: Why Does Gas Develop in the Gallbladder Wall?

Emphysematous cholecystitis is best understood as the interaction of two pathological processes:

ischemic tissue injury + gas-forming infection

The disease may begin with gallbladder inflammation and impaired drainage. Increased intraluminal pressure can compromise wall perfusion. Once microvascular perfusion falls, ischemic tissue becomes increasingly vulnerable to bacterial invasion.

Gas-producing organisms can then proliferate within the compromised tissue.

The source material identifies Clostridium perfringens as a particularly important organism and also discusses organisms such as Klebsiella pneumoniae and Escherichia coli.

The resulting sequence can be conceptualized as:

This sequence explains why a small quantity of intramural gas can have disproportionately important clinical implications.

Diabetes and Vascular Disease

Diabetes is an important risk factor because microvascular dysfunction and impaired host defense may facilitate severe infection. The source material also identifies peripheral vascular disease, immunosuppression, advanced age, and gallstones as clinically relevant risk factors.

However, the absence of diabetes does not exclude emphysematous cholecystitis.

Figure 2. Pathophysiological Cascade of Emphysematous Cholecystitis

Diagram demonstrating the progression from gallbladder obstruction and vascular compromise to ischemia, gas-producing bacterial infection, intramural gas accumulation, gangrenous necrosis, perforation, peritonitis, and systemic sepsis.

4. Epidemiology

Emphysematous cholecystitis is substantially less common than uncomplicated acute cholecystitis, but its clinical importance is disproportionate to its frequency.

The source case emphasizes a characteristic demographic pattern: older men, particularly those with diabetes or vascular disease. A male predominance of approximately 3:1 is described in the provided material.

Table 1. Epidemiologic and Clinical Risk Profile

Characteristic	Clinical Significance
Advanced age	Increased susceptibility to ischemia and severe infection
Male sex	Reported male predominance
Diabetes mellitus	Microvascular dysfunction and impaired host defense
Peripheral vascular disease	Reduced tissue perfusion
Immunosuppression	Increased risk of severe infection
Gallstones	Can contribute to cystic duct obstruction
Cardiovascular disease	May contribute to impaired tissue reserve

Exact incidence and prevalence estimates are not supplied in the case material and should therefore be obtained from population-based literature rather than inferred from this single case.

5. Clinical Presentation

The clinical presentation can be deceptively ordinary.

Typical manifestations include:

Right upper quadrant pain
Fever
Nausea
Vomiting
Anorexia
Right upper quadrant tenderness
Leukocytosis
Elevated inflammatory markers
Sepsis

The problem is that severe disease does not necessarily produce dramatic symptoms.

In elderly patients, inflammatory responses may be blunted. Diabetes can further alter the clinical presentation. The source material specifically cautions against excluding severe disease because fever or Murphy sign is absent.

Red Flags

The following combination should substantially increase concern:

Older patient + right upper quadrant pain + gallbladder inflammation + intramural gas

Additional red flags include:

Pericholecystic gas
Irregular or poorly enhancing wall
Wall discontinuity
Pericholecystic fluid collection
Abscess
Pneumoperitoneum
Systemic inflammatory response
Hemodynamic instability

6. Imaging Features: The CT Finding That Changes Everything

The most important imaging clue is gas within the gallbladder wall.

This distinction is more important than simply identifying gas somewhere near the gallbladder.

6.1 Intramural Gas

Gas may appear as:

Linear collections
Curvilinear collections
Small irregular foci
Multiple small gas locules

When these foci track within the gallbladder wall, emphysematous cholecystitis should immediately enter the differential diagnosis.

The case demonstrates precisely this pattern on axial and coronal CT.

6.2 Gas Within the Gallbladder Lumen

Luminal gas is less specific.

Possible causes include:

Recent ERCP
Biliary intervention
Enterobiliary fistula
Communication with bowel
Infection
Emphysematous cholecystitis

Therefore, the statement “gas is present in the gallbladder” is insufficient.

The radiologist must determine whether the gas is:

luminal → mural → pericholecystic

This anatomical progression has increasing clinical importance.

6.3 Pericholecystic Gas

Gas extending outside the gallbladder raises concern for more advanced infection, tissue destruction, or perforation.

The source material specifically emphasizes assessment of the progression from gallbladder wall to lumen and surrounding tissue.

6.4 Associated Findings

Additional CT findings may include:

Gallbladder distention
Wall thickening
Pericholecystic fat stranding
Gallstones
Pericholecystic fluid
Abscess
Wall irregularity
Necrosis
Perforation

The presented case demonstrates gallstones and mild pericholecystic inflammatory change in association with gallbladder wall gas.

7. Figure-by-Figure Radiologic Interpretation

Figure 2. Axial CT

Radiologic Interpretation

Axial CT demonstrates abnormal gas distributed along the gallbladder wall.

The critical observation is the mural location of the gas rather than its mere presence.

Diagnostic Pearl

Gas following the contour of the gallbladder wall should raise immediate suspicion for emphysematous cholecystitis.

Clinical Meaning

This finding should trigger communication with the treating team because the diagnosis may require urgent source-control intervention.

Figure 3. Coronal CT

Coronal reconstruction confirms the spatial relationship between the gas and gallbladder wall.

Multiplanar reconstruction is particularly useful because tiny gas collections may be difficult to localize confidently on a single axial image.

The source case specifically emphasizes the value of coronal imaging for confirming the distribution of wall gas and assessing extension into adjacent tissues.

Imaging Pitfall

A tiny gas focus may be mistaken for adjacent bowel gas when only axial images are reviewed.

This is one reason emergency abdominal CT interpretation should not be restricted to a single plane.

Figure 4. Gas Along the Gallbladder Wall

The most diagnostically significant feature is the circumferential or segmental distribution of gas along the gallbladder wall.

Once identified, the diagnostic question should immediately shift from:

“Is this acute cholecystitis?”

to:

“How advanced is the emphysematous process?”

That second question is much more clinically useful.

8. Radiologist Reading Report

Findings

The gallbladder contains gallstones with inflammatory change in the surrounding fat. Multiple foci of gas are seen tracking along the gallbladder wall on axial and multiplanar CT images. The distribution is consistent with intramural gas. Assess the gallbladder wall for discontinuity, nonenhancement, and focal perforation, and evaluate the surrounding tissues for extraluminal gas, fluid collection, or abscess.

Impression

Findings are compatible with emphysematous cholecystitis, characterized by gas within the gallbladder wall.

Given the potential for gangrenous change and perforation, urgent clinical and surgical evaluation is recommended.

9. Clinical Imaging Interpretation

The imaging findings reflect the underlying biology.

Why is gas visible on CT?

Gas has very low x-ray attenuation and therefore appears as a markedly hypodense, nearly black region on CT.

The key advantage of CT is not simply that it detects gas well. It demonstrates where the gas is located.

Why does mural gas matter?

Intramural gas suggests that gas production is occurring within diseased tissue rather than simply entering the gallbladder from an external source.

Why are multiplanar images important?

The gallbladder has a three-dimensional relationship with the liver, duodenum, colon, and adjacent peritoneal tissues. Coronal and sagittal reconstructions help determine whether gas truly lies within the wall or belongs to an adjacent bowel loop.

10. Ultrasound Versus CT Versus MRI

Ultrasound remains an important first-line examination for suspected acute gallbladder disease.

It can demonstrate:

Gallstones
Wall thickening
Gallbladder distention
Sonographic tenderness

However, gas can generate strong reflection and reverberation artifact, potentially limiting evaluation of deeper structures.

CT has a major advantage when emphysematous cholecystitis is suspected because it directly maps the extent and location of gas.

MRI/MRCP is valuable for biliary anatomy and selected diagnostic questions but is generally not the examination that should delay CT-based evaluation in an acute gas-forming infection.

Modality	Major Strength	Major Limitation	Role
Ultrasound	Gallstones and gallbladder inflammation	Gas-related artifact	Initial assessment
CT	Excellent gas detection and anatomical mapping	Ionizing radiation	Key examination for suspected emphysematous infection
MRI/MRCP	Biliary anatomy and soft-tissue characterization	Less practical in acute emergency assessment	Problem-solving / complementary imaging

11. Differential Diagnosis

Not every gallbladder containing gas has emphysematous cholecystitis.

Table 2. Imaging Differential Diagnosis

Diagnosis	CT Appearance	Key Differentiating Feature
Emphysematous cholecystitis	Intramural or intraluminal gas with inflammatory change	Gas within gallbladder wall
Ordinary acute cholecystitis	Distention, wall thickening, pericholecystic inflammation	No characteristic intramural gas
Post-ERCP state	Luminal biliary/gallbladder gas	Recent procedure
Enterobiliary fistula	Gallbladder/intestinal communication	Abnormal fistulous tract
Gangrenous cholecystitis	Irregular/nonenhancing wall	Ischemic wall destruction
Gallbladder perforation	Pericholecystic collection or extraluminal gas	Wall defect and surrounding complication
Adjacent bowel gas	Gas immediately adjacent to gallbladder	Separate bowel-wall origin

The most important discriminator is therefore not “Is there gas?” but “Where is the gas, and what anatomical structure contains it?”

12. Treatment Strategy

Emphysematous cholecystitis should not be approached as a condition suitable for prolonged observation alone.

Initial management includes:

Hemodynamic assessment
Intravenous fluids when indicated
Laboratory evaluation
Blood cultures when clinically appropriate
Broad-spectrum antimicrobial therapy
Sepsis assessment
Early source-control planning

The fundamental therapeutic objective is eradication of the infected gallbladder when the patient can safely undergo definitive intervention.

The case material identifies cholecystectomy as definitive treatment and percutaneous cholecystostomy as an option in patients with prohibitive operative risk.

The Tokyo Guidelines 2018 similarly emphasize severity assessment, early surgical management in appropriate candidates, and gallbladder drainage when early surgery is unsuitable.

Importantly, treatment should be individualized according to:

Physiologic stability
Organ dysfunction
Comorbidities
Operative risk
Local expertise
Disease extent
Availability of interventional drainage

13. Prognosis

Prognosis depends on more than the presence or absence of gallbladder inflammation.

Important prognostic factors include:

Delay in diagnosis
Sepsis
Gangrene
Perforation
Advanced age
Diabetes
Immunosuppression
Vascular disease
Extent of infection
Surgical risk

The source material notes reported mortality in the range of approximately 15–25% in some literature, emphasizing the substantially greater danger compared with uncomplicated acute cholecystitis.

These figures should be interpreted cautiously because reported mortality varies according to patient selection, disease severity, comorbidities, treatment strategy, and study design.

14. The Radiologist's Real Responsibility

A technically correct diagnosis is not necessarily a clinically complete report.

Consider the difference between:

“Emphysematous cholecystitis.”

and:

“Gas is present within the gallbladder wall, compatible with emphysematous cholecystitis. Evaluate urgently for gangrenous change or perforation. No definite pericholecystic abscess is identified.”

The second report communicates:

What was found.
What it means.
What complication needs to be assessed.
What the clinical team should do next.

This is the essence of actionable radiology.

15. Artificial Intelligence Perspective

Emphysematous cholecystitis presents an interesting problem for clinical AI because the diagnostic signal may be extremely small.

An AI system may potentially be trained to detect:

Abnormal gallbladder wall morphology
Intramural gas
Gallbladder distention
Pericholecystic inflammation
Gallstones
Extraluminal gas
Fluid collections
Possible perforation

Radiomics

Radiomics could quantify:

Texture heterogeneity
Wall thickness
Pericholecystic tissue characteristics
Spatial distribution of gas
Gallbladder shape
Inflammatory changes

However, radiomics should not be treated as a substitute for direct image interpretation.

Foundation Models

Large multimodal imaging models may eventually analyze the entire abdominal CT rather than searching for one predefined abnormality.

This is potentially important because the clinically relevant question is broader than:

“Is there gallbladder gas?”

It is:

“Does this patient have a severe gallbladder infection, and what complications are present?”

Vision-Language Models

A vision-language model could potentially combine:

CT findings
Patient age
Symptoms
Laboratory data
Clinical notes

and generate a structured clinical hypothesis.

However, the generated interpretation must remain subordinate to radiologist verification.

AI Workflow

A realistic workflow might look like:

The value of AI may therefore lie less in replacing the radiologist and more in ensuring that a subtle but critical abnormality is not overlooked during a busy emergency shift.

16. Enterprise Clinical AI Architecture

A hospital-scale implementation could integrate the model into PACS and the broader clinical infrastructure.

Interoperability can involve:

DICOM for imaging
HL7 for clinical messaging
FHIR for modern health-data exchange
PACS/RIS/EHR integration

An enterprise AI system could generate a high-priority notification when the model detects probable intramural gallbladder gas.

But an alert system must be carefully calibrated.

Too many false-positive alerts create alert fatigue.

Too many false negatives create false reassurance.

The appropriate objective is therefore not maximum sensitivity at any cost. It is clinically useful sensitivity with transparent uncertainty and human oversight.

Figure 6. AI-Enabled Emphysematous Cholecystitis Detection Workflow

17. AI Limitations

AI may fail when:

Gas collections are extremely small.
Motion artifact is substantial.
The gallbladder is poorly visualized.
Adjacent bowel gas mimics mural gas.
Surgical or endoscopic intervention has altered anatomy.
Unusual anatomical variants are present.
Training data do not represent the target population.

A model may also detect gas correctly but misinterpret its significance.

This distinction is crucial.

Detection is not diagnosis.

A clinically meaningful AI system must understand—or at least support the human interpretation of—the anatomical context.

18. Future of Precision Imaging

The future may move beyond binary detection.

Instead of simply reporting:

“Gallbladder wall gas: present.”

a multimodal AI platform could estimate:

Probability of emphysematous infection
Likelihood of gangrene
Risk of perforation
Extent of pericholecystic infection
Risk of clinical deterioration
Potential need for urgent source control

Radiogenomics may eventually explore relationships between imaging phenotypes and biological characteristics.

Federated learning could permit institutions to train models without directly pooling all patient-level data.

Synthetic imaging data may help expand rare-disease datasets.

Digital twins could theoretically model disease trajectories and treatment responses.

These technologies remain at different stages of maturity. They should therefore be distinguished carefully from currently established clinical practice.

19. Diagnostic Imaging Pearls

Gallbladder wall gas is the most important imaging clue.
Do not equate all gallbladder gas with emphysematous cholecystitis.
Always determine whether gas is luminal, mural, or pericholecystic.
Use multiplanar CT reconstructions to confirm the anatomical location of subtle gas.
Look for gallbladder wall irregularity or nonenhancement when gangrene is suspected.
Search for extraluminal gas and fluid collections indicating advanced disease.
Assess the surrounding liver and peritoneal tissues for extension.
Gallstones may coexist but are not required for the diagnosis.
Diabetes increases risk but its absence does not exclude emphysematous cholecystitis.
Elderly patients may have deceptively mild clinical symptoms.
CT is particularly valuable because it demonstrates both gas and its anatomical distribution.
A diagnosis of emphysematous cholecystitis should trigger consideration of urgent source control.
The report should communicate complications, not merely name the disease.
AI may assist detection but cannot reliably replace contextual radiologic reasoning.
The smallest gas focus may be the most clinically important finding on the entire CT examination.

Quiz

Question 1

A 76-year-old man presents with right upper quadrant pain. CT demonstrates linear gas tracking within the gallbladder wall and mild pericholecystic inflammatory change. What is the most likely diagnosis?

① Simple cholelithiasis
② Acute pancreatitis
③ Emphysematous cholecystitis
④ Gallbladder adenomyomatosis
⑤ Primary cholangitis

Answer: ③ Emphysematous cholecystitis

Explanation: Intramural gallbladder gas in the appropriate clinical setting is the key imaging feature of emphysematous cholecystitis.

Question 2

Which organism is particularly associated with gas-forming infection in emphysematous cholecystitis?

① Salmonella
② Pseudomonas aeruginosa
③ Clostridium perfringens
④ Yersinia enterocolitica
⑤ Actinomyces

Answer: ③ Clostridium perfringens

Explanation: Clostridium perfringens is a well-recognized gas-producing organism associated with emphysematous infections, including emphysematous cholecystitis.

Question 3

Which imaging feature is most important in distinguishing emphysematous cholecystitis from nonspecific gallbladder luminal gas?

① Gallstones
② Gallbladder distention
③ Intramural gas
④ Mild wall thickening
⑤ Pericholecystic fat stranding

Answer: ③ Intramural gas

Explanation: The anatomical location of the gas is critical. Gas within the gallbladder wall strongly supports emphysematous cholecystitis.

Question 4

Which imaging modality is particularly useful for demonstrating the distribution and extent of gas in suspected emphysematous cholecystitis?

① Plain radiography only
② CT
③ Mammography
④ Bone scintigraphy
⑤ Noncontrast brain MRI

Answer: ② CT

Explanation: CT provides excellent visualization of gas and allows assessment of whether it is confined to the lumen, involves the wall, or extends into surrounding tissues.

Question 5

What is the definitive treatment when a patient is an appropriate surgical candidate?

① Observation alone
② Analgesia alone
③ Antibiotics alone
④ Cholecystectomy
⑤ MRI follow-up

Answer: ④ Cholecystectomy

Explanation: Source control is central to treatment. Cholecystectomy is the definitive treatment in appropriate surgical candidates, while gallbladder drainage can be considered for patients who are poor surgical candidates.

Frequently Asked Questions

1. What is emphysematous cholecystitis?

It is a severe form of acute gallbladder infection characterized by gas formation within the gallbladder lumen, wall, or surrounding tissues.

2. What is the most important CT finding?

Gas within the gallbladder wall is the key imaging finding.

3. Does gallbladder gas always mean emphysematous cholecystitis?

No. Recent ERCP, biliary procedures, enterobiliary fistula, and other causes can introduce gas into the biliary system.

4. Why is CT important?

CT accurately identifies gas and demonstrates its anatomical distribution and complications.

5. Can ultrasound diagnose emphysematous cholecystitis?

Ultrasound can suggest the diagnosis, but gas-related reverberation artifact can limit evaluation. CT is particularly valuable for defining disease extent.

6. Is MRI required?

Usually not in the acute diagnostic setting when CT can rapidly demonstrate the critical gas pattern.

7. Is diabetes required for the diagnosis?

No. Diabetes is an important risk factor, but emphysematous cholecystitis can occur without diabetes.

8. What complications should the radiologist look for?

Gangrene, wall necrosis, perforation, abscess, pericholecystic extension, peritonitis, and sepsis.

9. Is emphysematous cholecystitis an emergency?

It should be treated as a potentially severe surgical infection requiring prompt clinical assessment and source-control planning.

10. Can AI diagnose emphysematous cholecystitis?

AI may assist with detection and triage, particularly by identifying subtle intramural gas, but definitive interpretation requires clinical and anatomical context and expert oversight.

Conclusion

Emphysematous cholecystitis illustrates one of the most important principles in emergency radiology:

A small imaging abnormality can carry enormous clinical significance.

A 76-year-old man with right upper quadrant pain may initially appear to have routine acute cholecystitis. Yet the presence of gas within the gallbladder wall fundamentally changes the diagnostic and management pathway.

The CT finding reflects an underlying pathological cascade involving ischemia, bacterial invasion, gas production, and potentially tissue necrosis.

For the radiologist, the task is therefore not simply to identify the disease.

The task is to answer three questions:

Where is the gas?

How far has the disease extended?

Is there evidence of gangrene or perforation?

The Tokyo Guidelines emphasize structured diagnosis, severity assessment, and treatment selection based on patient condition and surgical risk.

In contemporary radiology, this case also illustrates an emerging role for AI. A properly validated AI system could help flag subtle intramural gas, prioritize the examination, and integrate imaging with clinical information. But the final clinical judgment remains dependent on human interpretation.

The most important practical message is simple:

When a high-risk patient has right upper quadrant pain and CT demonstrates gas within the gallbladder wall, think beyond ordinary cholecystitis. Think emphysematous cholecystitis—and assess for complications immediately.

Final Clinical Message

The diagnosis is not “gas in the gallbladder.”

The diagnosis becomes clinically meaningful when the radiologist establishes:

gas + gallbladder wall involvement + inflammatory context + appropriate clinical setting.

In the presented 76-year-old man, that combination points toward emphysematous cholecystitis.

The next responsibility is to determine whether there is evidence of:

gangrene → perforation → abscess → peritonitis → sepsis.

That is where expert radiologic interpretation makes the difference between merely identifying an abnormality and providing clinically actionable information.

In emergency abdominal CT, the smallest pocket of gas may be the finding that matters most.

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Emphysematous Cholecystitis: When a Small Pocket of Gallbladder Wall Gas Becomes a Surgical Emergency