What Does “Suboptimal” Mean on an Ultrasound?

“Suboptimal” on an ultrasound report means the images obtained were not as clear or complete as the sonographer and radiologist needed them to be. It is not a diagnosis, and it does not mean something is wrong with you or your baby. The word flags a technical limitation: some part of the anatomy could not be seen well enough to evaluate fully, often because of factors like body composition, the position of the organ or fetus being imaged, or intestinal gas blocking the sound waves. Understanding why this label appears and what typically happens next can save you a lot of unnecessary worry.

Why Ultrasound Reports Use This Word

Ultrasound works by sending high-frequency sound waves into the body and building an image from the echoes that bounce back. When something interferes with those echoes, whether by scattering them, absorbing them, or blocking them entirely, the resulting image degrades. A radiologist reviewing blurry or incomplete images cannot make confident assessments of the structures they are supposed to evaluate, so they note this in the report. “Suboptimal,” “limited,” “technically difficult,” and “inadequate” are all terms you might see, and they all convey roughly the same thing: the scan did not give the interpreting physician everything they needed.

This matters for legal and clinical reasons. Radiologists have a professional duty to communicate the quality of the images they are interpreting, and failure to note limitations can create both diagnostic and medicolegal problems down the line. If a report says “the gallbladder was well visualized and appears normal,” that carries a very different weight than “the gallbladder was suboptimally visualized; no definite abnormality seen.” The second statement is the radiologist being honest that they could not see the organ clearly enough to rule things out with confidence. That honesty protects you, because it tells your referring doctor that further investigation might still be warranted.

The Most Common Reasons a Scan Comes Back Suboptimal

Several factors can degrade an ultrasound image, and most of them have nothing to do with operator error or equipment failure. They fall into a few broad categories.

Body composition: Fatty tissue between the ultrasound probe and the organ of interest scatters and absorbs sound waves before they can reach their target and return. The thicker this tissue layer, the worse the image quality. Research consistently shows a direct, linear relationship between increasing body size and decreasing visualization on ultrasound, and this is one of the most frequently cited causes of suboptimal scans in both obstetric and general abdominal imaging.¹
Bowel gas: Air and gas are ultrasound’s worst enemy. When sound waves hit a tissue-air interface, they reflect almost completely, creating a bright echo at the surface and a dark shadow behind it that obscures everything deeper. This is why abdominal scans sometimes cannot visualize the pancreas, parts of the liver, or the aorta: loops of gas-filled bowel sit in the way.²
Fetal position: In obstetric scans, the baby’s position can make certain views impossible to obtain. If the fetus has its spine facing outward, for example, the bony spine blocks sound waves from reaching the heart. If the baby’s face is pressed against the uterine wall, you cannot get a good profile or check the facial structures. No amount of technical skill can overcome a fetus that will not cooperate.³
Patient positioning and cooperation: In echocardiography (heart ultrasound), the patient ideally lies on their left side with the left arm raised to widen the rib spaces and give the probe a clear window. Patients in intensive care units who are on ventilators or who cannot be repositioned often produce suboptimal studies because the sonographer cannot get the probe into the right spot. Conditions like COPD, which trap air in the lungs, also create poor acoustic windows to the heart.⁴
Organ depth and probe selection: Lower-frequency probes penetrate deeper but show less fine detail, while higher-frequency probes show exquisite detail but cannot reach deep structures. Sometimes the organ of interest sits at an awkward depth where neither frequency is ideal, and the images suffer as a result.⁵

Operator experience also plays a role. Ultrasound is one of the most operator-dependent imaging modalities in medicine. Two sonographers scanning the same patient can produce very different image quality, and a more experienced operator can sometimes find acoustic windows and troubleshoot problems that a less experienced one cannot. Studies of pancreatic ultrasound, for example, have found that diagnostic performance varies greatly depending on the operator’s skill and the patient’s condition.⁶

Suboptimal Obstetric Scans and What They Mean for Your Pregnancy

If you are pregnant and your anatomy scan (the detailed mid-pregnancy ultrasound, usually done between 18 and 22 weeks) comes back labeled suboptimal, the most common reason is one of the two causes already described: fetal position or maternal body composition. The two problems often overlap. A review of obstetric imaging found that the combination of larger body size and sound-wave distortion by overlying fatty tissue is the primary driver of incomplete pregnancy scans.³ Research on prenatal ultrasound quality has also found that incomplete exams are more common with maternal obesity, prior cesarean delivery, maternal age under 35, and when the scan is performed before 19 weeks of gestation.⁷

The practical consequence of a suboptimal obstetric ultrasound is reduced ability to detect structural abnormalities, particularly cardiac defects. The fetal heart is small, deep within the abdomen, and surrounded by other structures, making it one of the hardest things to image clearly. Studies consistently show that the detection rate for congenital anomalies drops as maternal body size increases, with heart defects being the most affected category.¹ This does not mean the baby has a problem; it means the scan was unable to confirm that certain structures look normal.

When key views are missing from an anatomy scan, you will almost always be brought back for a follow-up ultrasound. Sometimes a couple of weeks of fetal growth and a different baby position are all it takes. In other cases, your provider might recommend a targeted scan at a maternal-fetal medicine specialist’s office, where more advanced equipment and more experienced sonographers can often get what is needed. Appropriate counseling for patients with difficult imaging should include a frank discussion of the lower sensitivity of the tests and the potential need for additional procedures.⁸

Abdominal Scans and the Role of Preparation

For non-obstetric abdominal ultrasounds, such as scans of the gallbladder, liver, kidneys, or pancreas, one of the biggest controllable factors in image quality is how well you prepared beforehand. You have probably been told to fast before an abdominal ultrasound, and there is a reason for that instruction, even if the evidence is more nuanced than you might expect.

Fasting serves two purposes. First, it keeps the gallbladder distended with bile, making it easier to spot gallstones or wall thickening. If you eat before the scan, the gallbladder contracts and becomes much harder to evaluate. Second, fasting is traditionally thought to reduce bowel gas, since eating stimulates digestion and gas production. Intestinal gas causes artifacts and degrades image quality, which is why preparation guidelines commonly instruct patients to fast for around eight hours and eat a light meal the evening before.⁹

That said, one randomized study found that the technical success of abdominal ultrasound performed by radiologists blinded to whether the patient had fasted did not differ significantly between fasting and non-fasting groups, leading the authors to conclude that routine fasting before abdominal ultrasound may not be strictly necessary.¹⁰ The clinical reality is that most departments still recommend fasting as a precaution, particularly when the gallbladder is a structure of interest. A quality improvement project at one hospital found that only about a fifth of patients were arriving appropriately prepared for abdominal scans, and that standardizing preparation instructions improved that rate substantially while also reducing unnecessary fasting time from nearly 11 hours to about 6 hours.¹¹

If your abdominal scan comes back suboptimal because of bowel gas, following the preparation instructions more carefully on a repeat visit can sometimes make a difference. But if the issue is body habitus or the location of the organ relative to gas-filled bowel, no amount of fasting will solve it, and your doctor will likely order a different imaging modality such as CT or MRI instead.

Suboptimal Does Not Mean Useless

A common misconception is that a suboptimal scan provides no information at all. In practice, even a technically limited study usually provides some useful data. The sonographer may have been able to visualize seven out of eight required views on a fetal anatomy scan, or the radiologist may have seen the kidneys and liver clearly but not the pancreas. The suboptimal label tells the interpreting physician (and your referring doctor) which parts of the exam fell short, not that the entire study was worthless.

Your report will typically specify what was and was not adequately seen. You might read something like “the fetal heart was suboptimally visualized due to fetal position; the remaining anatomy appeared normal” or “the gallbladder was obscured by overlying bowel gas; the liver, kidneys, and spleen were well visualized.” These statements are your radiologist giving a granular account of what they could and could not assess, which is exactly the information your doctor needs to decide what to do next.

Reading Your Report Without Panicking

If you have access to your ultrasound results through a patient portal, seeing the word “suboptimal” or “limited” can trigger real anxiety, especially during pregnancy. Research on patient access to radiology reports has found that the language used in these reports is often not easily understood by patients, and that physicians worry about the anxiety that can result when patients read technical reports without context.¹²

A few things to keep in mind when reading your own report. “Suboptimal” is a quality descriptor for the images, not for your body or your health. “Limited evaluation” means the radiologist could not fully assess a structure, not that they found something concerning. “Recommend follow-up imaging” after a suboptimal scan is standard protocol, not an alarm bell. It means they want another chance to see what they missed this time.

The language that should get your attention is different. Words like “suspicious,” “concerning for,” “cannot exclude,” or “biopsy recommended” are clinical assessments, not image-quality notes. If your report contains those terms alongside “suboptimal,” the suboptimal label is the radiologist flagging that their assessment was made under less-than-ideal conditions, which is actually a sign of careful, honest reporting.

What You Can Do Before Your Scan

Some causes of suboptimal imaging are completely outside your control. You cannot change your body composition in time for next week’s ultrasound, and you certainly cannot convince a fetus to roll into a better position. But there are things within your control that can help.

Follow prep instructions exactly: If you are told to fast, fast for the recommended duration but not dramatically longer. One quality improvement effort found that patients were fasting for nearly 11 hours on average when 6 was sufficient, causing unnecessary discomfort without improving image quality.¹¹
Hydrate well: For pelvic ultrasounds, a full bladder acts as an acoustic window that displaces bowel gas and provides a clear path to the uterus and ovaries. Drinking the recommended amount of water before your scan and resisting the urge to empty your bladder can make the difference between a diagnostic and a non-diagnostic study.
Wear loose clothing: This has no direct effect on image quality, but it makes it easier and faster for the sonographer to access the scanning area, which means more time spent actually imaging and less time on logistics.
Ask about timing: For obstetric anatomy scans, imaging slightly later in the recommended window (closer to 20-22 weeks rather than 18 weeks) can improve visualization simply because the baby is larger and the structures are easier to see. As noted earlier, scans performed before 19 weeks have higher rates of incomplete exams.⁷

When a Different Imaging Test Is the Better Option

Sometimes the factors causing suboptimal ultrasound are not going to change on a repeat visit, and your doctor will recommend a different type of imaging altogether. This is not a failure of ultrasound as a modality; it is your care team choosing the right tool for the situation.

CT scans use X-rays and are not significantly affected by body composition or bowel gas, making them the go-to alternative when an abdominal ultrasound cannot adequately evaluate a structure. MRI uses magnetic fields rather than sound waves and provides excellent soft-tissue contrast without radiation, making it particularly useful as a follow-up for suboptimal obstetric ultrasounds when detailed fetal anatomy needs to be assessed. Fetal MRI has become increasingly common as a complement to ultrasound when critical structures like the brain or heart cannot be adequately evaluated on sonography.

For echocardiography, when standard transthoracic images are poor, the options include using contrast agents (tiny microbubbles injected into the bloodstream that dramatically improve image quality) or switching to transesophageal echocardiography, where the probe is passed into the esophagus to get closer to the heart without ribs and lungs in the way. In ICU patients with poor acoustic windows, contrast echocardiography has been shown to significantly improve diagnostic yield.⁴

Intraoperative Ultrasound and the Standoff Technique

One area where “suboptimal” takes on a slightly different flavor is intraoperative ultrasound, where surgeons use small ultrasound probes directly on or near organs during surgery. Here, one surprising cause of poor imaging is being too close to the target. Structures in the “near field,” right next to the probe surface, can appear blurry or unresolvable because the transducer needs a minimum distance to form a clear image. Surgeons work around this by using a “standoff” technique: placing a fluid-filled glove or saline-filled pad between the probe and the tissue surface, which moves the probe a centimeter or two away and dramatically improves resolution of superficial structures.¹³

This is a useful reminder that “suboptimal” in ultrasound is almost always a physics problem, not a medical one. Sound waves have physical properties that dictate what they can and cannot do, and every ultrasound exam is a negotiation between the operator, the equipment, and the patient’s anatomy. When those factors align well, ultrasound is fast, cheap, radiation-free, and remarkably informative. When they do not, the honest label is “suboptimal,” and the honest next step is either trying again under better conditions or using a different tool entirely.

1
Sonography. The effect of increased maternal body habitus on image quality and ability to identify fetal anomalies at a routine 18‐20‐week morphology ultrasound scan: a narrative review
2
PubMed. Differentiation of acoustic shadowing due to calculi and gas collections
3
PubMed Central. Helping expectant mothers understand inadequate ultrasound images
4
Chest. Contrast Microbubbles Improve Diagnostic Yield in ICU Patients With Poor Echocardiographic Windows
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PubMed Central. Utility of high-frequency ultrasound: moving beyond the surface to detect changes in skin integrity
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PubMed Central. The Role of Transabdominal Ultrasound in the Diagnosis of Early Stage Pancreatic Cancer: Review and Single-Center Experience
7
PubMed Central. Quantitative Approach to Quality Review of Prenatal Ultrasound Examinations: Incomplete Detailed Fetal Anatomy Exams
8
PubMed. Challenges of prenatal diagnosis in obese pregnant women
9
PubMed Central. Effect of adding a capsule with activated charcoal to abdominal ultrasound preparation on image quality
10
PubMed Central. Is fasting a necessary preparation for abdominal ultrasound?
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PubMed Central. Reducing prolonged fasting for abdominal ultrasound scans
12
PubMed Central. Full Radiology Report through Patient Web Portal: A Literature Review
13
Surgery Open Science. The nuts and bolts of HPB surgical ultrasound: A necessary skill for the surgeon