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Two-level ultrasonographic assessment of aortomesenteric distances in relation to self-reported abdominal symptoms and body mass index: a single-centre exploratory cross-sectional study

In a single-centre cross-sectional study of 196 adults, shorter ultrasonographic aorta–superior mesenteric artery distances measured at both proximal and renal-artery levels were significantly associated with self-reported abdominal symptoms after adjusting for body mass index, whereas the aortomesenteric angle showed no such association.

Original authors: Lívia Mojsza-Csernus, Gyöngyi Emese Juharosi, Zita Bednárik, Tamás Schnabel, Dániel Sándor Veres, László Földvári-Nagy, Katalin Lenti

Published 2026-09-15

📖 5 min read🧠 Deep dive

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Original authors: Lívia Mojsza-Csernus, Gyöngyi Emese Juharosi, Zita Bednárik, Tamás Schnabel, Dániel Sándor Veres, László Földvári-Nagy, Katalin Lenti

Original paper licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). ✨ This is an AI-generated explanation of the paper below. It is not written or endorsed by the authors. For technical accuracy, refer to the original paper. Read full disclaimer

Inside the human abdomen, a delicate anatomical relationship exists between two major blood vessels: the aorta, the body's main highway for oxygenated blood, and the superior mesenteric artery, which branches off to feed the intestines. Between them lies a small space where the third part of the small intestine, the duodenum, passes through. In rare cases, this space can become too narrow, pinching the intestine and causing a blockage. This condition, known as superior mesenteric artery syndrome, is often linked to rapid weight loss, where the natural cushion of fat that usually keeps these vessels apart disappears. While doctors have long used high-resolution CT scans to measure the gap between these vessels and the angle they form, these machines use radiation and are not always necessary for a first look. Ultrasound offers a safer, radiation-free alternative, but interpreting the images is tricky. The size of the gap can change depending on a person's body shape, and it is not always clear if a small measurement on a screen actually explains a patient's stomach pain.

A team of researchers at Semmelweis University in Hungary set out to explore this uncertainty using a simple, non-invasive approach. They wanted to see if measuring the distance between the aorta and the superior mesenteric artery at two different levels using ultrasound could help explain why some people report abdominal symptoms. Instead of focusing only on patients already suspected of having a blockage, they invited a broad group of adults who were already scheduled for routine abdominal ultrasounds. The goal was to see if there was a connection between the physical measurements taken during the scan and a simple yes-or-no answer to whether the person was currently experiencing any abdominal discomfort.

The study involved 196 adults who agreed to participate. After their standard ultrasound exams were completed, a sonographer asked each person a single question: did they have any abdominal symptoms right now? The researchers then looked back at the images they had just taken. They measured the angle between the two blood vessels and the distance between them at two specific spots. The first spot was just below where the mesenteric artery began, and the second spot was lower down, at the level where a kidney artery branches off the main aorta. This two-level approach allowed them to see if the space between the vessels changed as it moved down the body.

The results revealed a clear pattern. Among the 196 participants, 27 people reported having abdominal symptoms. When the researchers compared the measurements of those who had symptoms to those who did not, they found a distinct difference in the distances. The group with symptoms had significantly smaller gaps between the aorta and the mesenteric artery. On average, the distance just below the artery's origin was 7 millimeters for those with symptoms, compared to 12 millimeters for those without. At the lower level near the kidney artery, the gap was 11 millimeters for the symptomatic group versus 16 millimeters for the others. The researchers calculated that for every millimeter the distance decreased, the likelihood of a person reporting symptoms increased.

Interestingly, the angle between the two vessels did not show the same connection. The size of the angle varied widely among all participants, but it did not consistently differ between the group with symptoms and the group without. This suggests that while the width of the space between the vessels matters, the sharpness of the angle might not be the primary factor in explaining these specific symptoms in this general population. The study also confirmed that body size plays a major role in these measurements. People with higher body weight and body mass index tended to have larger gaps between the vessels, likely because more fat tissue fills the space and pushes the vessels apart.

Despite these clear associations, the authors are careful not to claim that ultrasound has solved the diagnostic puzzle for this condition. The study was exploratory, meaning it looked for patterns rather than proving a cause-and-effect relationship. The symptom reported by the participants was a simple, unverified "yes" or "no" to any abdominal pain, not a confirmed diagnosis of a blockage. Therefore, finding a narrow gap on an ultrasound does not automatically mean a person has a serious obstruction or the specific syndrome. The researchers emphasize that these measurements should be viewed as pieces of a larger picture, heavily influenced by a person's body size, rather than as a standalone test that can confirm a disease.

The findings offer a promising direction for future research. By showing that measuring the distance at two different levels is feasible and correlates with how people feel, the study suggests that ultrasound could be a useful tool for gathering more detailed anatomical data without radiation. However, the authors conclude that before these measurements can be used to make clinical decisions or triage patients, more rigorous studies are needed. These future studies would need to use more precise symptom questionnaires and compare ultrasound results directly with the gold-standard CT scans to confirm if a narrow gap truly predicts a blockage. For now, the study provides a clearer map of how body size and vessel spacing relate to self-reported discomfort, reminding us that the human body's internal geometry is complex and deeply personal.

Technical Summary: Two-Level Ultrasonographic Assessment of Aortomesenteric Distances

Problem Statement
Superior mesenteric artery (SMA) syndrome is a rare cause of proximal intestinal obstruction resulting from duodenal compression between the aorta and the SMA, often associated with weight loss and depletion of mesenteric fat. While contrast-enhanced CT is the standard for diagnosis, ultrasonography offers a non-ionizing, accessible alternative. However, existing ultrasonographic evidence is limited to small, selected symptomatic cohorts, and the interpretation of measurements is complicated by body habitus. Furthermore, most studies assess only a single distance measurement and the aortomesenteric angle. There is a lack of data regarding the relationship between ultrasonography-derived aortomesenteric parameters and self-reported abdominal symptoms in heterogeneous adult populations, and no published study has specifically evaluated the left renal artery origin as a predefined landmark for a second distance measurement.

Methodology
This was a single-centre, exploratory, cross-sectional study conducted at Békés County Central Hospital, Hungary, between October 2022 and May 2024.

Population: The study initially invited 792 adults attending scheduled abdominal ultrasonography. After exclusions for consent withdrawal and technical failure (excessive bowel gas), the final analysis cohort comprised 196 participants (114 women, 82 men; median age 59.0 years).
Data Collection:
- Symptoms: Following the ultrasound, a sonographer asked a single binary question: "Do you have any abdominal symptoms?" Responses were recorded as "yes" (symptom-positive, n=27) or "no" (symptom-negative, n=169). No further details on symptom type, severity, or duration were collected.
- Ultrasound Protocol: Examinations were performed after an 8-hour fast using a 2–5 MHz convex transducer. Measurements were taken during inspiration with minimal transducer pressure.
- Measurements: Three parameters were assessed:
  1. Aortomesenteric Angle: Measured in a longitudinal plane between the aorta and proximal SMA.
  2. Proximal Distance: Measured in a longitudinal plane, 10 mm caudal to the SMA origin.
  3. Renal-Artery-Level Distance: Measured in a transverse plane at the origin of the left renal artery.
Statistical Analysis: Primary analysis involved multivariable logistic regression to assess associations between continuous ultrasound parameters and the binary symptom response, adjusted for age, sex, and BMI. Holm's procedure was used to adjust for multiple comparisons across the three primary models. Secondary analyses included Spearman's rank correlation for the relationship between the two distances and linear regression to evaluate associations with anthropometric variables (BMI, body weight).

Key Results

Symptom Associations:
- Distances: Participants reporting abdominal symptoms had significantly shorter aorta-SMA distances compared to those without symptoms.
  - Median proximal distance: 7.0 mm (symptom-positive) vs. 12.0 mm (symptom-negative) ( $p=0.001$ ).
  - Median renal-artery-level distance: 11.0 mm (symptom-positive) vs. 16.0 mm (symptom-negative) ( $p<0.001$ ).
- Regression: After adjusting for age, sex, and BMI, each 1-mm decrease in proximal distance was associated with higher odds of a positive symptom response (Adjusted OR 1.21; 95% CI 1.07–1.37; Holm-adjusted $p=0.005$ ). Similarly, each 1-mm decrease in renal-artery-level distance was associated with higher odds (Adjusted OR 1.24; 95% CI 1.10–1.41; Holm-adjusted $p=0.002$ ).
- Angle: No linear association was observed between the aortomesenteric angle and symptom status ( $p=0.614$ ). Exploratory cubic B-spline analysis suggested a possible non-linear pattern, but this remains hypothesis-generating due to the small number of symptom-positive cases.
Measurement Relationship: The two distance measurements were strongly positively correlated (Spearman's $\rho=0.839$ ). The renal-artery-level distance was greater than the proximal distance in 92.0% of participants, indicating systematic cranio-caudal variation rather than interchangeability.
Body Size Associations: All three measurements (both distances and the angle) increased with higher BMI and body weight. For instance, a 5 kg/m² increase in BMI was associated with an average increase of 1.82 mm in proximal distance and 2.30 mm in renal-artery-level distance.

Significance and Claims
The authors position this study as an exploratory association study rather than a diagnostic accuracy evaluation.

Primary Claim: Shorter aorta-SMA distances at two predefined anatomical levels (proximal and renal-artery-level) are associated with a binary self-report of abdominal symptoms in a general clinical population, independent of age, sex, and BMI.
Limitations of Claims: The authors explicitly state that these findings do not establish SMA syndrome, confirm duodenal compression, or prove clinically relevant obstruction. The study endpoint was a non-validated, binary self-report, and no objective imaging of compression was performed.
Clinical Implications: The study suggests that fixed ultrasonographic thresholds should be interpreted cautiously in the context of body size, as measurements correlate strongly with BMI. The renal-artery-level measurement requires prospective clinical and imaging validation before it can be used for diagnostic or triage purposes.
Future Directions: The authors conclude that further studies using standardized symptom assessment, objective imaging of duodenal compression, and formal reproducibility testing are necessary before the two-level protocol can be adopted for clinical decision-making.

Technical Summary: Two-Level Ultrasonographic Assessment of Aortomesenteric Distances

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