# Ultrasonography of the Equine Abdomen: Indications and Findings


## Key Takeaways

- Transabdominal ultrasonography is a critical diagnostic tool for equine abdominal pain, offering real-time assessment of peritoneal fluid, gastrointestinal wall thickness and motility, and solid organ architecture to differentiate medical from surgical conditions.
- Specific sonographic findings, such as distended and nonmotile small intestinal loops, are statistically associated with strangulating obstructions requiring surgical intervention, while increased free peritoneal fluid and thickened intestinal loops indicate significant small intestinal disease.
- Equipment selection is crucial, with 3.0-3.5 MHz curvilinear transducers recommended for adult abdomens and higher frequency linear transducers (6-13 MHz) for body wall and neonates, optimizing image resolution based on target depth.
- Physiological factors like fasting and sedation significantly influence gastrointestinal motility and visibility; fasting enhances jejunal visualization but reduces motility, and xylazine sedation further depresses motility in fasted horses, necessitating careful interpretation within this context.
- A standardized examination sequence, proceeding systematically from ventral to lateral and cranial to caudal regions in both transverse and sagittal planes, is essential to reduce the risk of overlooking clinically significant findings and to allow for meaningful serial comparisons.
- Diagnostic failure can occur, particularly false-negatives in small intestinal obstruction due to gas, deep conformation, or patient fractiousness; therefore, ultrasound findings must always be integrated with physical examination, laboratory data, and clinical response to therapy.

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Transabdominal ultrasonography has become a standard component of the diagnostic evaluation for horses presenting with acute abdominal pain, and it offers comparable value in the assessment of chronic gastrointestinal disease, hepatic disorders, and renal dysfunction. The modality provides real-time information about peritoneal fluid volume and character, gastrointestinal wall thickness and motility, and the architecture of solid organs, all of which can refine the differential diagnosis and guide decisions between medical management, surgical exploration, and further diagnostic testing. This article serves the practicing equine clinician who needs a structured approach to performing and interpreting abdominal ultrasound in the field or hospital setting, with emphasis on the colic workup and on distinguishing findings that mandate surgical referral from those that can be managed medically.

The evidence base for equine abdominal ultrasonography has grown substantially over the past two decades. Studies correlating ultrasonographic findings with definitive diagnoses in horses with acute abdominal pain have demonstrated that specific sonographic abnormalities, particularly distended and nonmotile small intestinal loops, are statistically associated with strangulating obstructions requiring surgery [Is there a statistical correlation between ultrasonographic findings and definitive diagnosis in horses with acute abdominal pain?](https://pubmed.ncbi.nlm.nih.gov/21790762/). However, the technique is operator-dependent and heavily influenced by patient preparation, transducer availability, and the complexity of the underlying disorder [Ultrasound of the equine acute abdomen](https://pubmed.ncbi.nlm.nih.gov/25016496/). The sections that follow establish the physical and physiological principles that underpin image interpretation, then build toward a systematic examination protocol and a catalogue of clinically significant findings.

## At a Glance

| Parameter | Clinical Relevance | Key Considerations |
|---|---|---|
| Transducer selection | 3.0 to 3.5 MHz curvilinear for adult abdomen, 6 to 13 MHz linear for body wall and neonates | Lower frequency penetrates to deep viscera, higher frequency improves near-field resolution [Understanding abdominal ultrasonography in horses: which way is up?](https://pubmed.ncbi.nlm.nih.gov/21993992/) |
| Patient preparation | Fasting increases jejunal visibility and decreases gastrointestinal motility | Feeding status must be interpreted alongside sonographic findings [Evaluation of gastrointestinal activity patterns in healthy horses using B mode and Doppler ultrasonography](https://pubmed.ncbi.nlm.nih.gov/15825515/) |
| Sedation | Xylazine decreases jejunal and cecal activity in fasted horses | Minimal effects in fed horses, document sedation status in the record |
| Small intestine wall thickness | Normal jejunum measures less than 3 mm | Thickened loops correlate with inflammatory or ischemic small intestinal disease |
| Small intestine motility | Normal jejunum shows 3 to 6 contractions per minute | Absent motility with distension suggests strangulating obstruction |
| Peritoneal fluid | Normal volume is scant, abnormal volume or echogenicity indicates peritonitis or bowel compromise | Increased free fluid is associated with small intestinal disease categories |
| Stomach position | Normally dorsal, caudal to the liver | Ventral displacement occurs with gastric distension or fasting |

## Physical Principles and Image Orientation

Ultrasound image interpretation depends on understanding the relationship between transducer orientation, tissue interfaces, and the projected image. The transducer face is the top of the image, and depth is displayed downward. The left side of the monitor corresponds to the side of the transducer marked by the indicator, which may be a notch, dot, or raised line. For a transverse orientation, the indicator is directed to the patient's right, for a sagittal orientation, it is directed cranially. Consistent application of this convention prevents the common error of misattributing a finding to the wrong side of the abdomen [Understanding abdominal ultrasonography in horses: which way is up?](https://pubmed.ncbi.nlm.nih.gov/21993992/).

Tissue interfaces produce echoes based on differences in acoustic impedance. Fluid-filled structures appear anechoic with distal acoustic enhancement, while gas-filled bowel produces reverberation artifact and shadowing that obscures deeper structures. The equine abdomen presents a particular challenge because of its size, the depth of the viscera, and the presence of gas within the large colon and cecum. The examiner must work within the constraints of acoustic windows, typically the ventral abdomen, the right and left paralumbar fossae, and the caudal thorax. Hair clipping is not always necessary, soaking the hair with isopropyl alcohol can provide adequate contact for a preliminary survey, although clipping improves image quality for detailed assessment [Understanding abdominal ultrasonography in horses: which way is up?](https://pubmed.ncbi.nlm.nih.gov/21993992/).

## Physiological Influences on Gastrointestinal Sonography

Interpretation of gastrointestinal motility and visibility requires knowledge of normal physiological variation. In healthy adult horses, transabdominal ultrasonography can quantitatively assess jejunal, cecal, and colonic activity. Fasting increases jejunal visibility and decreases motility in all three gastrointestinal compartments. The stomach is displaced ventrally during fasting and is visualized ventral to the costochondral junction. Nasogastric intubation in fasted horses moves the stomach dorsally but has no observable effect on gastrointestinal activity. Xylazine sedation in fed horses has minimal effects on motility, but in fasted horses it significantly decreases jejunal and cecal activity [Evaluation of gastrointestinal activity patterns in healthy horses using B mode and Doppler ultrasonography](https://pubmed.ncbi.nlm.nih.gov/15825515/).

These findings carry direct clinical implications. A horse that has been fasted for several hours before examination will show reduced motility that could be misinterpreted as pathological ileus. Similarly, sedation administered before ultrasound can suppress motility and mimic a surgical lesion. The clinician should record the duration of fasting and the timing and type of any sedative drugs, then interpret motility findings in that context. Doppler techniques can provide a quantitative measure of jejunal peristaltic activity and correlate strongly with B mode assessment, offering a potential adjunct for equivocal cases [Evaluation of gastrointestinal activity patterns in healthy horses using B mode and Doppler ultrasonography](https://pubmed.ncbi.nlm.nih.gov/15825515/).

## Study Design and Evidence Interpretation

The clinical literature on equine abdominal ultrasonography consists largely of retrospective case series and prospective observational studies. A representative study reviewed medical records of 158 horses undergoing surgery or post mortem examination for colic, then used logistic regression to identify associations between ultrasonographic findings and disease categories. Distended and nonmotile small intestinal loops were associated with strangulating obstruction, while increased free peritoneal fluid, completely distended small intestinal loops with abnormal motility, and thickened loops were associated with definitive diagnoses involving the small intestine [Is there a statistical correlation between ultrasonographic findings and definitive diagnosis in horses with acute abdominal pain?](https://pubmed.ncbi.nlm.nih.gov/21790762/). These associations are statistically robust but do not establish causality, and the sensitivity and specificity of individual findings vary with the examiner and the disease population.

The practical consequence is that ultrasonographic findings should be integrated with physical examination, laboratory data, and response to medical therapy instead of used in isolation. A thickened, nonmotile small intestinal loop in a horse with severe pain and tachycardia supports a surgical diagnosis, but the same finding in a quiet, comfortable horse warrants serial re-evaluation. The evidence base also reflects the referral hospital population, where the prevalence of surgical lesions is higher than in first-opinion practice. Clinicians working in the field should expect a lower pretest probability of strangulating obstruction and adjust their interpretation accordingly.

## Equipment Selection and Examination Environment

Portable ultrasound machines with curvilinear transducers in the 3.0 to 3.5 MHz range are adequate for most adult equine abdominal examinations. Higher frequency linear transducers, typically 6 to 13 MHz, are useful for evaluating the body wall, the neonatal abdomen, and superficial structures such as the bladder and umbilical remnants [Ultrasonographic Examination of the Equine Neonate: Thorax and Abdomen](https://pubmed.ncbi.nlm.nih.gov/26612746/). The examination environment should allow safe restraint of the horse, adequate lighting for machine operation, and a power source for recharging batteries. In field settings, a generator or vehicle inverter may be necessary, and the machine should be protected from dust and moisture.

The neonate presents specific considerations. The smaller body mass allows higher frequency transducers and more complete evaluation of the abdominal viscera. Ultrasonography is not affected by intracavitary fluid accumulation, making it particularly valuable in septic or premature foals where peritoneal effusion may obscure radiographic detail [Ultrasonographic Examination of the Equine Neonate: Thorax and Abdomen](https://pubmed.ncbi.nlm.nih.gov/26612746/). The same physical principles apply, but the examiner must adapt the examination to the smaller field of view and the different distribution of normal findings.

## Standardized Examination Sequence

A consistent, repeatable scanning sequence reduces the risk of overlooking clinically significant findings and allows meaningful comparison between serial examinations. Begin with the most painful or unstable patient regions only after stabilization, and defer complete evaluation until the patient tolerates handling.

The examination proceeds from the ventral abdomen cranially to caudally, then laterally on both sides. The ventral midline is scanned first with the transducer oriented transversely, from the xiphoid to the prepubic tendon. This identifies the ventral colon, cecum, and any small intestinal loops that have migrated ventrally. The liver is then evaluated from the right cranial abdomen, followed by the right kidney, duodenum, and right dorsal colon. The left side is examined for the spleen, left kidney, stomach, and large colon. The stomach is visualized from the left cranial abdomen, often requiring a dorsal approach between the ribs.

Each region is assessed in both transverse and sagittal planes. The transducer is moved in a grid pattern to ensure complete coverage instead of relying on a single window. For the small intestine, the examiner should document the location of each loop, its diameter, wall thickness, motility, and luminal content. The large colon is assessed for wall thickness, sacculation, and the presence of gas or ingesta. The cecum is identified by its characteriztic haustra and is evaluated for wall thickness and content.

Free peritoneal fluid is assessed in the most dependent regions, typically the ventral midline and the caudoventral abdomen. The volume, echogenicity, and character of the fluid are recorded. A small volume of anechoic fluid is normal in many horses, but increased volume or altered echogenicity warrants cytological analysis.

## Organ-Specific Assessment

### Stomach

The stomach is visualized from the left cranial abdomen, caudal to the spleen and dorsal to the liver. The normal gastric wall is approximately 3 to 5 mm thick, and the lumen contains gas, fluid, or ingesta depending on feeding status. Gastric distension is identified when the stomach extends beyond the costal arch or when the wall appears thin and stretched. In horses with gastric outflow obstruction or ileus, the stomach may be markedly distended with fluid, which appears as an anechoic to hypoechoic luminal content with dependent hyperechoic particles.

The position of the stomach varies with feeding and fasting. In fasted horses, the stomach is displaced ventrally and may be visualized ventral to the costochondral junction, whereas nasogastric intubation moves the stomach dorsally. This positional variation must be considered when interpreting gastric findings.

### Small Intestine

The duodenum is identified from the right side, ventral to the right kidney and liver, as a tubular structure with a thick muscular wall. The normal duodenal wall is approximately 3 to 4 mm thick, and the lumen contains fluid or small amounts of gas. The jejunum is more variable in location and is typically found in the ventral abdomen, often to the left of midline.

Small intestinal diameter is the most clinically useful measurement. Normal jejunal loops measure less than 3 cm in diameter. Loops measuring 3 to 5 cm with reduced or absent motility suggest functional ileus or early obstruction. Loops greater than 5 cm in diameter with absent motility are strongly associated with strangulating obstruction. Wall thickness greater than 5 mm indicates edema, inflammation, or ischemia, and when combined with distension and reduced motility, supports a surgical lesion.

Motility is assessed qualitatively by observing the frequency and amplitude of peristaltic contractions over 2 to 3 minutes. Doppler ultrasound can provide a quantitative assessment of jejunal peristaltic activity, and B mode and Doppler activity are strongly correlated. Sedation with xylazine decreases jejunal and cecal activity in fasted horses, so the sedation status must be recorded and considered when interpreting motility findings.

### Large Intestine

The large colon is identified by its sacculated appearance and is typically found in the ventral and lateral abdomen. The ventral colon is visualized from the ventral midline, while the right dorsal colon is assessed from the right side, medial to the liver and kidney. The normal large colon wall is approximately 2 to 3 mm thick.

The large colon is evaluated for wall thickness, sacculation, and luminal content. Thickening of the colonic wall may indicate inflammation, edema, or ischemia. Displacement or volvulus may be suspected when the colon is absent from its normal position or when the sacculated appearance is lost. The cecum is identified by its prominent haustra and is assessed from the right caudal abdomen.

### Liver

The liver is evaluated from the right cranial abdomen, caudal to the diaphragm and cranial to the right kidney. The normal liver has a homogeneous echotexture with visible portal vessels and hepatic veins. The hepatic parenchyma is slightly more echogenic than the renal cortex and less echogenic than the spleen.

Liver size is assessed subjectively by the extent of the liver beyond the costal arch and the position of the caudal margin relative to the right kidney. Hepatomegaly may be identified when the liver extends caudally beyond the right kidney or when the caudal margin is rounded. The biliary system is evaluated for distension of the bile ducts, which may indicate cholestasis or cholelithiasis.

### Kidneys

The right kidney is visualized from the right paralumbar fossa, cranial to the tuber coxae, and the left kidney from the left paralumbar fossa. The normal kidney has a distinct cortex and medulla, with the cortex being slightly less echogenic than the spleen. Renal size, contour, and pelvic dilation are assessed.

Renal pelvic dilation, urolithiasis, and parenchymal changes such as nephrolithiasis or chronic renal disease may be identified. The left kidney also serves as a landmark for the nephrosplenic space, which is relevant in horses with suspected nephrosplenic entrapment of the large colon.

## Peritoneal Fluid and Other Findings

Free peritoneal fluid is a common finding in horses with colic. The volume and echogenicity of the fluid provide diagnostic information. A small volume of anechoic fluid is normal. Increased volume with anechoic fluid suggests transudate, which may occur with early obstruction or medical colic. Echogenic fluid, particularly with swirling particles, suggests hemorrhage, peritonitis, or intestinal rupture. The presence of gas echoes within the fluid is an ominous finding that may indicate intestinal rupture.

Ultrasonography can also identify masses, abscesses, and other abnormalities that may be the cause of colic. These include intraabdominal masses, urolithiasis, cholelithiasis, and thoracic or cardiac lesions that may be discovered incidentally during the abdominal examination.

## Decision Points and Interpretation

The ultrasonographic findings must be integrated with the clinical examination, laboratory data, and response to initial therapy. The key decision is whether the lesion is medical or surgical.

| Finding | Medical Colic | Surgical Colic | Action |
|---|---|---|---|
| Small intestinal diameter | < 3 cm | > 5 cm | Surgical if > 5 cm with reduced motility |
| Small intestinal motility | Present, regular | Absent or severely reduced | Surgical if absent with distension |
| Wall thickness | < 5 mm | > 5 mm | Surgical if thickened with distension |
| Peritoneal fluid | Small volume, anechoic | Increased volume, echogenic | Abdominocentesis, cytology |
| Large colon position | Normal | Absent from normal position | Surgical exploration |
| Stomach distension | Mild, resolves with decompression | Marked, persistent | Nasogastric decompression, reassess |

The presence of distended and nonmotile small intestinal loops is associated with strangulating obstruction, while increased free peritoneal fluid, completely distended loops with abnormal motility, and thickened loops are associated with definitive small intestinal disease. These findings support early surgical intervention.

Patient status changes the approach. In neonatal foals, the examination is performed with higher frequency transducers, and the normal measurements differ from adults. Foals with sepsis, systemic inflammatory response syndrome, or prematurity may have sonographic changes in the lungs and abdomen that require a different interpretive framework. The examination environment also matters. In the field, clipping is not always necessary, and soaking the hair with isopropyl alcohol allows adequate image quality with a 3.0 to 3.5 MHz curvilinear transducer. In a hospital setting, clipping provides superior image quality and is preferred for detailed assessment.

## Documentation and Reporting

The ultrasound report should include the patient signalment, the indication for the examination, the sedation and analgesic drugs administered, and the transducer and frequency used. Each organ system is described with specific measurements and motility assessments. The location and character of free peritoneal fluid are recorded, along with the results of any abdominocentesis performed under ultrasound guidance.

Serial examinations are often more informative than a single study. The report should note the time of each examination relative to the onset of colic, the administration of drugs, and the response to therapy. This allows the clinician to track progression or resolution of findings. The report should also state the ultrasonographic diagnosis or differential diagnoses and recommend further diagnostic steps or surgical intervention when indicated.

## Recognized Complications and Failure Modes

Transabdominal ultrasonography in horses carries few direct patient risks, but diagnostic failure can delay surgical intervention in horses with strangulating lesions. The most consequential failure mode is the false-negative examination in a horse with small intestinal obstruction. Gas-filled loops, deep body conformation, and a fractious patient can obscure the duodenum or jejunum entirely. A normal study does not exclude surgical disease, and the examination must be interpreted within the full colic workup, including heart rate, peritoneal fluid analysis, and response to analgesia.

A second failure mode is overinterpretation of wall thickness. The jejunal wall is measured in the near field with the transducer perpendicular to the loop. Oblique imaging artificially increases wall thickness and can lead to a diagnosis of enteritis or ischemia when none exists. Conversely, a thickened loop deep in the abdomen may be missed when the examiner relies on a single imaging plane. The corrective action is systematic: identify each loop in two orthogonal planes, measure the wall at the point of maximal clarity, and compare serial loops instead of a single segment.

A third failure mode is misclassification of peritoneal fluid. Free fluid is an expected finding in many horses with colic, and the volume, echogenicity, and distribution matter more than its presence. An anechoic effusion with a small volume may reflect simple obstruction, whereas a large volume of echogenic fluid with fibrin tags suggests strangulation or peritonitis. The examiner must document the character of the fluid and correlate it with abdominocentesis results instead of treating fluid as a binary finding.

| Observation | Likely cause | Discriminating check |
|---|---|---|
| No duodenum visualized in right cranial quadrant | Gas overlay, deep patient, or examiner inexperience | Reposition patient, use lower frequency transducer, re-scan after 10 minutes |
| Apparent jejunal wall thickening | Oblique transducer angle | Re-image loop perpendicular to the wall in two planes |
| Large anechoic fluid volume | Simple obstruction, uroperitoneum, or normal variation | Abdominocentesis, fluid analysis, and repeat scan after decompression |
| Reduced or absent motility | Sedation, fasting, or genuine ileus | Review sedation history and fasting status before concluding pathology |
| Stomach not visualized | Gas cap, or stomach displaced by distended colon | Scan from left side at the costochondral junction, consider nasogastric decompression |

## Common Errors and Corrective Actions

Less experienced examiners frequently begin scanning before adequate patient preparation. Clipping is not always required, and isopropyl alcohol alone can provide adequate acoustic coupling in many horses, but the image quality degrades rapidly with heavy hair coats or dirt. The corrective action is to clip when the image is suboptimal instead of persisting with a poor study.

A second recurring error is failure to account for physiological state. Fasting increases jejunal visibility and decreases jejunal, cecal, and colonic activity, and xylazine sedation further depresses jejunal and cecal motility in fasted horses. An examiner who interprets reduced motility as pathological in a fasted, sedated horse will overcall ileus. The corrective action is to record fasting and sedation status on the worksheet and interpret motility in that context.

A third error is the omission of the left kidney and spleen from the routine scan. These structures anchor the examination and provide a reference for the stomach and small intestine. Missing them leaves the examiner without a spatial frame for the left cranial abdomen. The corrective action is to follow a fixed sequence that includes the left kidney in every study, regardless of the presenting complaint.

## Limitations of the Current Evidence

The evidence base for equine abdominal ultrasonography rests largely on retrospective and observational studies. The correlation between ultrasonographic findings and definitive diagnosis in horses with acute abdominal pain has been examined in a cohort of 158 horses, in which distended and nonmotile small intestinal loops were associated with strangulating obstruction and increased free peritoneal fluid with small intestinal disease [Beccati et al., 2011](https://pubmed.ncbi.nlm.nih.gov/21790762/). These associations are useful but do not establish sensitivity or specificity across the broader colic population, and the study population was limited to horses undergoing surgery or post mortem examination, which introduces selection bias.

Expert opinion still differs on several points. The threshold for calling a small intestinal loop abnormally distended varies between published sources, and the clinical significance of mild duodenal thickening without motility changes remains contested. The role of Doppler assessment of jejunal activity is promising, with B mode and Doppler activity strongly correlated in healthy horses, but its diagnostic value in diseased horses has not been established [Mitchell et al., 2005](https://pubmed.ncbi.nlm.nih.gov/15825515/). The effect of patient preparation on image quality is well recognized, but standardized protocols for clipping, sedation, and fasting have not been validated across practice settings [le Jeune and Whitcomb, 2014](https://pubmed.ncbi.nlm.nih.gov/25016496/).

## Referral, Consultation, and Reporting

Referral is indicated when the ultrasonographic findings are equivocal but the clinical picture suggests surgical disease, when the examiner cannot visualize key structures, or when the study reveals a mass, abscess, or urolith that requires advanced imaging or surgical planning. Specialist consultation with a boarded radiologist or surgeon is appropriate when the findings do not match the clinical progression, when serial examinations are needed, or when the practitioner lacks experience with a particular region such as the neonatal abdomen [Sprayberry, 2015](https://pubmed.ncbi.nlm.nih.gov/26612746/).

Laboratory involvement is complementary instead of optional. Peritoneal fluid analysis, hematology, and serum biochemistry should be interpreted alongside the ultrasound findings, and the ultrasonographic character of the fluid should be compared with the cytological results. Regulatory reporting is rarely triggered by abdominal ultrasound findings in horses, but practitioners should be aware of reportable diseases that may present with abdominal signs and should consult [WOAH terrestrial animal health standards](https://www.woah.org/en/what-we-do/standards/codes-and-manuals/terrestrial-code-online-access/) and [AVMA practice resources](https://www.avma.org/resources-tools) for current requirements in their jurisdiction.

## Frequently Asked Questions

### How much does abdominal ultrasonography cost in equine practice, and how should I justify it to a client?

Costs vary widely by region, practice type, and whether the examination is performed in the field or at a referral hospital. Portable equipment has made transabdominal ultrasonography feasible in ambulatory practice, which reduces hospitalization and transport costs for the client [ACVR professional resources](https://acvr.org/). For the colic patient, the examination can directly inform surgical versus medical decision-making, and the cost is often small relative to the expense of delayed referral or unnecessary surgery. Frame the discussion around diagnostic value: ultrasonography can identify strangulating small intestinal lesions, gastric distension, or free peritoneal fluid that would otherwise be missed on rectal palpation alone. When the client declines imaging, document that discussion and the physical examination findings that supported proceeding without it.

### What can I do when a high-quality ultrasound machine is not available?

A 3.0 to 3.5 MHz curvilinear transducer is the minimum practical tool for adult equine abdominal work, and soaking the hair with isopropyl alcohol can often eliminate the need for clipping [understanding abdominal ultrasonography in horses](https://pubmed.ncbi.nlm.nih.gov/21993992/). If only a higher-frequency linear probe is available, limit the examination to superficial structures such as the abdominal wall, peritoneal fluid, and the ventral colon in small patients. Do not attempt to interpret deep intestinal loops with an inadequate transducer, as this invites false-negative conclusions. In the field, a focused examination targeting the most diagnostically impactful questions, such as small intestinal diameter and motility, gastric distension, and free fluid, is more reliable than a complete survey performed with suboptimal equipment. Referral for a full study remains appropriate when findings are equivocal.

### How does the examination differ in neonatal foals compared with adult horses?

Neonatal foals present a smaller acoustic window and higher heart rates, but the same fundamental technique applies. The thinner body wall and smaller abdominal volume allow higher-frequency transducers, typically 5 to 10 MHz, to provide superior resolution of intestinal layers and organ architecture [ultrasonographic examination of the equine neonate](https://pubmed.ncbi.nlm.nih.gov/26612746/). Foals tolerate dorsal recumbency more readily than adults, which facilitates a systematic ventral approach. Indications differ as well: neonatal colic often arises from meconium impaction, enteritis, or congenital anomalies instead of large colon displacement, and urinary tract disorders are more commonly interrogated sonographically in this age group. Sedation requirements are lower, but restraint must account for the foal's fragility. Normal intestinal wall thickness and luminal diameters are smaller than in adults, so reference values from adult horses should not be applied directly.

### What documentation should I include in the medical record for an abdominal ultrasound?

Record the transducer type and frequency, patient preparation, sedation used, and the specific regions examined. For each organ system, document whether it was visualized and describe wall thickness, luminal diameter, motility, and echogenicity using objective measurements where possible. Include representative images with labels and a clear statement of the sonographic diagnosis or differential list. Note any factors that limited the study, such as gas artefact, patient intolerance, or poor acoustic windows, as these directly affect interpretation [ultrasound of the equine acute abdomen](https://pubmed.ncbi.nlm.nih.gov/25016496/). If the examination was performed in the field and the horse is referred, provide the images and a written summary to the receiving clinician. The record should support the reasoning behind subsequent decisions, including surgery or medical management.

### How should I communicate equivocal or negative ultrasound findings to a referring veterinarian or owner?

A negative abdominal ultrasound does not exclude surgical disease, particularly in the early stages of obstruction when intestinal distension has not yet developed. State this limitation explicitly when reporting findings. Describe what was seen, what was not seen, and what structures could not be adequately evaluated. For example, a normal duodenum and jejunum on one examination does not rule out a strangulating lesion that develops over the following hours. Advise that repeat examination is indicated if clinical signs persist or progress, and provide a timeline for re-evaluation. When findings are equivocal, recommend referral for serial examinations and continuous monitoring instead of a single definitive judgment. This approach aligns with evidence that ultrasonographic findings correlate with disease categories but do not replace surgical exploration when clinical signs demand it [statistical correlation between ultrasonographic findings and definitive diagnosis](https://pubmed.ncbi.nlm.nih.gov/21790762/).

### How do sedation and fasting status affect my interpretation of intestinal motility?

Fasting increases jejunal visibility and decreases jejunal, cecal, and colonic activity, while xylazine sedation in fasted horses further suppresses jejunal and cecal motility [gastrointestinal activity patterns in healthy horses](https://pubmed.ncbi.nlm.nih.gov/15825515/). In fed horses, xylazine has minimal effects on motility. These factors matter clinically: a horse that has been fasted for 12 hours and sedated with an alpha-2 agonist may show reduced intestinal motility that is physiological instead of pathological. Record the fasting duration and all sedatives administered before the examination, and interpret motility in that context. If reduced motility is the only abnormal finding in a fasted, sedated horse, consider repeating the assessment after the effects of sedation have waned or after feeding if the patient's condition permits.

## Related Clinical & Scientific Guides

* [MRI Monitoring of Brain Tumor Response to Therapy in Dogs](/knowledge/veterinary-medicine/diagnostic-imaging/mri-monitoring-brain-tumor-response-therapy-dogs)
* [Ultrasound-Guided Drainage of Abscesses in Small Animals](/knowledge/veterinary-medicine/diagnostic-imaging/ultrasound-guided-drainage-abscesses-small-animals)
* [Radiographic Monitoring of Total Hip Replacement in Dogs](/knowledge/veterinary-medicine/diagnostic-imaging/radiographic-monitoring-total-hip-replacement-dogs)


## References and Further Reading

- [Is there a statistical correlation between ultrasonographic findings and definitive diagnosis in horses with acute abdominal pain?](https://pubmed.ncbi.nlm.nih.gov/21790762/). 2011.
- [Ultrasound of the equine acute abdomen.](https://pubmed.ncbi.nlm.nih.gov/25016496/). 2014.
- [Evaluation of gastrointestinal activity patterns in healthy horses using B mode and Doppler ultrasonography.](https://pubmed.ncbi.nlm.nih.gov/15825515/). 2005.
- [Ultrasonographic Examination of the Equine Neonate: Thorax and Abdomen.](https://pubmed.ncbi.nlm.nih.gov/26612746/). 2015.
- [Understanding abdominal ultrasonography in horses: which way is up?](https://pubmed.ncbi.nlm.nih.gov/21993992/). 2011.
- [Transversus abdominis plane block in ponies: a preliminary anatomical study.](https://pubmed.ncbi.nlm.nih.gov/29559203/). 2018.
- [American College of Veterinary Radiology Resources](https://acvr.org/). American College of Veterinary Radiology.
- [MSD Veterinary Manual, Professional Edition](https://www.msdvetmanual.com/). MSD Veterinary Manual.
- [American Veterinary Medical Association Practice Resources](https://www.avma.org/resources-tools). American Veterinary Medical Association.

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> This article is educational professional reference material for veterinary audiences. It is not a substitute for veterinary diagnosis, individual clinical judgment, current product labeling, or applicable regulatory requirements.