Multi-slice computed tomography diagnosis of pneumatosis cystoides intestinalis with pneumoperitoneum in high-altitude regions: preventing unnecessary laparotomies

Introduction

Pneumatosis cystoides intestinalis (PCI) is a rare condition characterized by multiple air-filled cysts in the submucosal or serosal layers of the gastrointestinal tract (1). Depending on the location and pattern of free air accumulation in the extraluminal digestive tract, PCI is also referred to as pneumatosis intestinalis (PI), intraluminal bowel gas, or pneumatosis coli (2).

First described in 1730, PCI was initially confused with its clinical manifestations. However, the detection rate of PCI has increased significantly in recent decades, primarily due to the widespread use and enhanced resolution of multi-slice computed tomography (MSCT) imaging (3). Typically, PCI appears as gas-filled cysts along the gastrointestinal wall, ranging from the esophagus to the rectum, with a predominance in the small and large intestines (4). PCI may be confined to the mucosa, submucosa, or subserosa, or extend across multiple layers.

The pathogenesis of PCI is thought to involve three primary mechanisms (5): (I) mechanical factors, whereby an increase in intraluminal pressure causes mechanical damage and mucosal rupture of the intestinal wall, leading to the migration of gas from the gastrointestinal cavity to the intestinal wall; (II) pulmonary causes, such as chronic obstructive pulmonary disease (COPD), asthma, or interstitial pneumonia, where alveolar rupture permits gas to travel along vascular sheaths to the intestinal wall; and (III) bacterial involvement, in which gas-producing microorganisms penetrate the mucosa and generate intramural gas through fermentation.

Historically, pneumatosis was considered a hallmark of intestinal ischemia that necessitated emergency surgery, with reported mortality rates as high as 44% (6). However, recent evidence indicates that early surgical intervention may be unnecessary—and potentially harmful—in cases of benign pneumoperitoneum (6). In PCI, free intraperitoneal gas often results in cyst rupture, which can mimic gastrointestinal perforation and lead to misdiagnosis. Therefore, accurate differentiation is critical. Radiologists play a vital role in detecting clinically significant pneumoperitoneum, alerting treating physicians, and assisting in evaluating its clinical relevance.

This study aimed to investigate PCI with pneumoperitoneum in high-altitude regions through MSCT. By retrospectively analyzing PCI with pneumoperitoneum clinical and imaging features, we sought to improve understanding and the diagnostic accuracy of this condition. We present this article in accordance with the STROBE reporting checklist (available at https://qims.amegroups.com/article/view/10.21037/qims-2025-1451/rc).

Methods

Study cohort

This study was conducted in accordance with the Declaration of Helsinki and its subsequent amendments. The Ethics Committee of Dege County People’s Hospital in China approved this study (No. 2025-YNYJ-02) and waived the requirement of informed consent due to the retrospective nature of this study.

Between March 1, 2024, and May 31, 2025, abdominal and pelvic computed tomography (CT) scans were performed on all patients with PCI with pneumoperitoneum who were treated at Dege County People’s Hospital. Dege County People’s Hospital is situated on the southeastern edge of the Qinghai-Tibet Plateau, with a relative altitude of 3,188 meters and an average altitude of 4,235 meters. To identify eligible cases, CT reports containing the term “pneumoperitoneum” were retrospectively reviewed. The study inclusion criteria were: (I) availability of an abdominal and pelvic CT scan; and (II) the presence of PCI in any part of the intestinal wall, from the stomach to the sigmoid colon. The exclusion criteria included the absence of PCI (n=57), and cases in which PCI was detected only on thoracic CT scan (n=14).

The clinical characteristics, symptoms, and laboratory data were collected retrospectively from electronic medical records at the time of the CT examination. Ultimately, 15 patients met the study inclusion criteria and were included in the analysis (Figure 1). All the patients had complete clinical data, underwent MSCT examinations, and were followed up via CT or telephone.

Figure 1 Flow chart of patient enrollment. CT, computed tomography; PCI, pneumatosis cystoides intestinalis.

MSCT protocol

All MSCT scans were performed using a 40-detector row CT scanner (uCT 530, United Imaging Healthcare, Shanghai, China). Patients were positioned supine with their arms raised above their head. The scans extended from the apex of the diaphragm to the inferior margin of the pubic symphysis. Breath-hold scanning was conducted after deep inhalation. The scanning parameters were as follows: tube voltage, 120 kV; tube current, 200–400 mA (automatically adjusted); slice thickness and spacing, 5.0 mm; and thin-slice reconstruction, 1.0 mm.

Imaging analysis

All the MSCT images were transferred to the picture archiving and communication system and independently reviewed by three radiologists specializing in abdominal imaging. The review team included one resident radiologist with 5 years of general diagnostic imaging experience, responsible for compiling the clinical data (including age, sex, symptoms, laboratory examination, and medical history), and two senior abdominal radiologists with 21 and 7 years of experience, respectively. Any discrepancies in image interpretation were resolved through consensus discussion. Multiplanar reconstruction was applied to all scans, with the window width and level adjusted as needed. Lesion characteristics—such as the anatomical location, number of lesions, and extent of intestinal involvement—were systematically assessed.

Results

Frequency of PCI with pneumoperitoneum

Among 86 patients with pneumoperitoneum, 29 were diagnosed with PCI, resulting in a prevalence rate of 33.7%. However, 14 patients were excluded, as they only had chest CT scans available. Thus, ultimately, 15 patients were enrolled in this cohort study over a period of 18 months.

Clinical characteristics, symptoms and laboratory data

The mean age of the patients was 57.3±12.6 years (range, 37–82 years), and seven patients were male and eight were female. All patients were of Tibetan ethnicity and had been residing in high-altitude areas. The clinical data and presentations of the patients are summarized in Table 1.

Among the 15 patients, five (5/15; 33.3%) with PCI and pneumoperitoneum reported abdominal pain. Of these, three had concurrent acute appendicitis, and one had cholecystitis, while one had no additional comorbidities. Six patients (6/15; 40.0%) had pneumonia, one (1/15; 6.7%) had secondary pulmonary tuberculosis, and one (1/15; 6.7%) reported lower back pain, and was diagnosed with lumbar disc herniation. Additionally, one (1/15; 6.7%) patient had a neck abscess, and one (1/15; 6.7%) was diagnosed incidentally at a routine medical examination. The duration of symptoms varied from one day to two months.

Follow-up was performed using CT and telephone interviews. Four patients; completed CT follow-up (3–12 months), among whom, three showed pneumoperitoneum absorption, while one patient exhibited persistent PCI with pneumoperitoneum on CT scan 6 months later. All 15 patients completed the telephone follow-up (3–12 months), which was conducted to inquire about symptoms and any surgical interventions. Except for three patients who underwent surgery for acute appendicitis, none of the remaining patients reported abdominal abnormalities or underwent surgical treatment.

The symptoms and laboratory findings for PCI with pneumoperitoneum are detailed in Table 2. All the patients were generally in good health, and many showed no signs of peritonitis. Abdominal tenderness was observed in five patients, including three with appendicitis and one with cholecystitis. Mildly increased abdominal tension was observed in two patients. Although leukocytosis was absent in several cases, the C-reactive protein levels of the patients were found to be elevated.

CT findings when PCI with pneumoperitoneum was detected

All the included patients with PCI and pneumoperitoneum underwent abdominal and pelvic MSCT scans. Free gas in the abdominal cavity was predominantly concentrated in the mesenteric region surrounding the PCI, as well as around the liver and spleen. In three patients, the free gas in the abdominal cavity was absorbed over time, while in one patient, the free gas persisted for more than 3 months.

Lesion involvement was confined to the colon in all cases. Thirteen patients (13/15; 86.7%) presented with multisegmental involvement (Figure 2), while two patients (2/15; 13.3%) had lesions limited to the ascending colon (Figures 3,4). Notably, one patient demonstrated involvement of the entire colon. The specific segmental involvement included: the ascending colon in 12 patients (12/15; 80.0%); the hepatic flexure in 11 patients (11/15; 73.3%), the transverse colon in 13 patients (13/15; 86.7%), the splenic flexure in four patients (4/15; 26.7%), the descending colon in three patients (3/15; 20.0%), and the sigmoid colon in four patients (4/15; 26.7%). Detailed CT findings are summarized in Table 3. Apart from three cases of acute appendicitis with surrounding exudation, classic signs of acute bowel disease or perforation—such as bowel wall discontinuity, segmental wall thickening, perivisceral fat stranding, and abscess formation—were absent in all patients. Further, no portal vein gas was detected in any case.

Figure 2 Abdominal CT showing. (A) PCI of the transverse colon combined with pneumoperitoneum. (B) PCI of the colon with multisegmental involvement. (C) PCI of the colon with multisegmental involvement combined with pneumoperitoneum from the coronal view. The red arrows indicate pneumoperitoneum; the yellow arrows indicate PCI. CT, computed tomography; PCI, pneumatosis cystoides intestinalis.

Figure 3 Abdominal CT showing PCI with pneumoperitoneum. The red arrows indicate pneumoperitoneum; the yellow arrows indicate PCI. CT, computed tomography; PCI, pneumatosis cystoides intestinalis.

Figure 4 Abdominal CT showing PCI with pneumoperitoneum; PCI is limited to the ascending colon. The red arrows indicate pneumoperitoneum; the yellow arrows indicate PCI. CT, computed tomography; PCI, pneumatosis cystoides intestinalis.

Discussion

PCI is a rare condition with an unclear etiology. Autopsy studies report a prevalence of approximately 0.03% in the general population, although its true incidence remains uncertain (7). In rare cases, PCI can lead to benign pneumoperitoneum characterized by free air in the peritoneal cavity (8). In the small intestine, PCI typically involves subserosal cysts, whereas in the colon, it more frequently affects the submucosal layer (4,6). Pneumoperitoneum in PCI results from the rupture of subserosal cysts (9), which may explain why all the PCI-associated pneumoperitoneum cases identified in our study were located in the colon. The detection of free gas in the colon wall and adjacent mesenteric area can help localize PCI lesions.

The incidence of PCI is not well-defined, but with the increasing use of CT scans, detection rates have risen significantly (10). CT is particularly valuable in diagnosing PCI, as it can be used to identify free intraperitoneal air, which occurs in approximately 2% of colonic and 15% of small intestinal cases (11). Adachi et al. (9) identified pneumoperitoneum with PCI in 0.12% of all abdominal CT examinations. PCI was observed in 24.7% of cases of extraluminal free air without iatrogenic causes. In the present study, which was conducted in a high-altitude plateau region, PCI with pneumoperitoneum occurred in 33.7% of all pneumoperitoneum cases. Adachi et al.’s study included patients at Fujimi-Kogen Hospital in Nagano, Japan, located at an average altitude of approximately 1,132 meters. Conversely, the patients in the present study were situated at an average altitude of approximately 4,235 meters. Thus, the incidence of pneumoperitoneum in PCI was higher in the present study than in Adachi et al.’s study; however, we cannot definitively conclude that altitude alone increases the incidence of pneumoperitoneum in PCI.

It may be that the combination of PCI with pneumoperitoneum is more common in high-altitude regions. Wu et al. (12) systematically analyzed PCI cases reported in Chinese literature and found that 66.9% originated from highland areas. High-altitude environments may exacerbate factors contributing to PCI, such as mechanical stresses including hypoxia and increased abdominal pressure, which can damage the intestinal mucosa. For instance, studies have shown that high-altitude hypobaric hypoxia worsens ulcerative colitis severity in mouse models by upregulating T helper 1 and T helper 17 lymphocytes (13). Spontaneous mediastinal emphysema frequently occurs when individuals from low-altitude areas adapt to high-altitude environments characterized by cold, low pressure, and hypoxia, with gas sometimes escaping into the abdominal cavity (14). Additionally, gut microbiota may undergo adaptive changes to high altitude (15,16). Therefore, PCI might not be as rare in plateau regions as previously thought, and could be related to the prolonged hypoxia affecting the intestinal mucosa. Nevertheless, further studies are required to explore its specific causes.

PCI is classified as primary (15%) and secondary (85%). Secondary PCI arises from underlying conditions such as gastrointestinal obstruction, COPD, abdominal trauma or surgery, and malnutrition (5). Besides gastrointestinal disorders and emphysema, PCI has been associated with rare conditions such as the use of alpha-glucosidase inhibitors, sunitinib therapy, lung transplantation, bone marrow transplantation, systemic lupus erythematosus, systemic sclerosis, multiple myeloma, and granulomatosis with polyangiitis (5). Iatrogenic injuries from procedures like colonoscopy and biopsy can also contribute to PCI by allowing gas to enter the intestinal mucosa.

Although most pneumoperitoneum cases with PCI in our study had comorbidities, no specific shared comorbidities were found. The clinical presentation of primary PCI was nonspecific, with abdominal pain (59%), diarrhea (53%), nausea and vomiting (14%), mucus in stool (12%), and hematochezia (12%) being the most common symptoms. Secondary PCI typically retains the clinical features of the underlying primary disease. Approximately 3% of PCI patients develop complications such as pneumoperitoneum, volvulus, intestinal obstruction, or intestinal ischemia (5,12,17).

A prospective study by Knechtle et al. (18) found no sex-based differences in the incidence of PCI. While PCI was traditionally thought to be more prevalent in the small intestine, recent studies using barium enema and colonoscopy indicate greater involvement of the colon (12). Morris et al. (19) reported that 46% of lesions occurred in the colon, 27% in the small intestine, 7% in both the colon and small intestine, and 5% in the stomach. Wu et al.’s (12) study of a Chinese cohort reported distinct epidemiological patterns, a male-to-female ratio of 2.4:1, and a mean age of 45.3±15.6 years. In this cohort, PCI predominantly affected the colon rather than the small intestine (1.3:1 ratio), and the combined involvement of both the colon and small intestine was rare (2.9%) (12). We found that PCI primarily affected the ascending colon, hepatic flexure, and transverse colon. Previous studies have similarly reported a higher prevalence of PCI in the right colon (1,20,21). This distribution may reflect anatomical differences, as the right colonic wall is thinner than the left. Additionally, variations in bacterial phenotypes between different regions of the colon may influence gas formation (22).

Laboratory tests and pathological biopsies for PCI lack specificity, and diagnosis primarily relies on imaging techniques such as colonoscopy, CT, radiography, and ultrasound. Due to the limited clinical recognition of the condition, PCI is frequently misdiagnosed as intestinal polyps, cancer, inflammatory bowel disease, or necrotizing enterocolitis, even when colonoscopy and biopsy are performed (5). Clinicians frequently encounter patients presenting with pneumoperitoneum who undergo unnecessary surgery after being misdiagnosed with gastrointestinal perforation. In China, the extremely high surgical resection rate of 40.6% reflects this lack of realization and misdiagnosis; however, many PCI cases can recover with nonoperative management (12).

Imaging studies are essential for diagnosing PCI, typically revealing intramural air and radiolucent shadows along the bowel lumen on conventional radiographs. Plain films may also show gas outlining both the luminal and extraluminal bowel walls, a characteristic finding called the double-wall (Rigler) sign (23). However, CT is more accurate than plain radiography in the diagnosis of PCI and its complications.

Abdominal CT typically shows grape-like or honeycomb radiolucencies along the intestinal wall, which are characteristic of PCI (12,21,24). In CT scans of PCI with pneumoperitoneum, classic signs of acute bowel disease or perforation—such as bowel wall discontinuity, segmental wall thickening, perivisceral fat stranding, and abscesses—were absent in all cases. Consequently, the lack of CT signs suggesting peritonitis, combined with infrequent ascites, represents characteristic radiological findings in these cases (9). CT is considered the definitive modality for confirming PCI, offering superior diagnostic accuracy and the ability to identify additional abdominal abnormalities. Contrast-enhanced CT can also help assess the likelihood of PCI accompanied by intestinal ischemia (3). Dual-energy CT may further elucidate the relationship between bowel wall enhancement and ischemia (25).

Pneumoperitoneum is a critical indicator of severe intra-abdominal pathology, although not all cases require laparotomy, as free air alone does not always signify life-threatening perforation. PCI can cause pneumoperitoneum without peritonitis through ruptured intramural blebs, representing a non-surgical cause of free air in the abdomen (23). Even minimal PCI can produce substantial extraluminal free air with both the air and the lesions typically resolving rapidly. Distinguishing between benign and life-threatening PCI cases in patients with pneumoperitoneum is crucial, as extraluminal free air alone has limited diagnostic value (9).

Most asymptomatic patients recover without intervention. For symptomatic patients, conservative management, including gastrointestinal decompression, bowel rest, parenteral nutrition, and electrolyte correction, is often effective (12). Despite the pioneering use of oxygen therapy by Forgacs et al. (26) in 1973, its optimal concentration, duration, and clinical effects remain undefined, and it carries potential pulmonary toxicity risks (1). Nonetheless, PCI with pneumoperitoneum has been reported to be successfully treated with conservative methods, including hyperbaric oxygen therapy (27,28).

Conservative treatment is appropriate for PCI caused by benign factors; however, emergency surgery is necessary if bowel perforation, ischemia, or necrosis is suspected. Greenstein et al. (29) reported a 20% in-hospital mortality rate and a 35% surgical intervention rate among PCI patients. Graber et al. (30) showed that the localization of PCI in the colon, elevated blood aspartate aminotransferase levels, and perfusion abnormalities in abdominal organs, particularly the liver and spleen, independently predicted short-term mortality in this patient cohort. Clinicians should recognize that conservative management suffices for cases without life-threatening complications, as intraperitoneal free air alone does not confirm perforation.

This study had several limitations. First, the sample size was small, particularly in terms of cases of life-threatening PCI. As a result, while we were able to characterize benign PCI, we could not reliably define the features of life-threatening cases. In addition, CT enhancement data for PCI with pneumoperitoneum were unavailable due to technical constraints. Second, although all the participants lived in high-altitude regions, they were exclusively of Tibetan ethnicity, which limits the generalizability of our findings to more diverse populations. Future research should involve larger, multicenter cohorts with broader demographic representation to validate and expand upon these results.

Conclusions

PCI, as demonstrated by CT findings of pneumoperitoneum, is prevalent in highland regions. In cases of pneumoperitoneum caused by PCI, which does not typically require urgent surgery, CT clearly identifies the site and extent of the lesions, as well as any intestinal and extra-intestinal complications. However, emergency surgery is essential when bowel perforation, ischemia, or necrosis is suspected.

Acknowledgments

None.

Footnote

Reporting Checklist: The authors have completed the STROBE reporting checklist. Available at https://qims.amegroups.com/article/view/10.21037/qims-2025-1451/rc

Data Sharing Statement: Available at https://qims.amegroups.com/article/view/10.21037/qims-2025-1451/dss

Funding: None.

Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://qims.amegroups.com/article/view/10.21037/qims-2025-1451/coif). The authors have no conflicts of interest to declare.

Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. This study was conducted in accordance with the Declaration of Helsinki and its subsequent amendments. The Ethics Committee of Dege County People’s Hospital in China approved all of the procedures of this study (No. 2025-YNYJ-02). This study was a retrospective analysis and the ethics committee waived the requirement for patients to provide informed consent.

Open Access Statement: This is an Open Access article distributed in accordance with the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License (CC BY-NC-ND 4.0), which permits the non-commercial replication and distribution of the article with the strict proviso that no changes or edits are made and the original work is properly cited (including links to both the formal publication through the relevant DOI and the license). See: https://creativecommons.org/licenses/by-nc-nd/4.0/.

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