When should an ultrasound be ordered?

When to Order Ultrasound: Evidence-Based Guidelines

Ultrasound should be ordered based on specific clinical indications, patient age, and suspected pathology, following established clinical guidelines for each body system and clinical scenario.

Breast Imaging

Palpable Breast Mass

• For women ≥30 years with a palpable breast mass, both diagnostic mammogram and ultrasound are recommended for accurate diagnosis 1
• For women <30 years with a palpable breast mass, ultrasound is the preferred initial imaging modality due to its sensitivity in detecting breast abnormalities 1, 2
• For men ≥25 years with pathologic nipple discharge, mammography/digital breast tomosynthesis should be performed initially, with ultrasound added as indicated 2

Nipple Discharge

• Physiologic nipple discharge does not require diagnostic imaging 2
• For pathologic nipple discharge in women ≥40 years, mammography or digital breast tomosynthesis should be the initial examination, usually complemented by ultrasound 2
• For women 30-39 years with pathologic discharge, either mammogram or ultrasound may be used as the initial examination based on institutional preference 2
• For women <30 years with pathologic discharge, ultrasound should be the initial examination 2

Breast Implant Evaluation

• For asymptomatic patients with breast implants (any age), imaging is not recommended 2
• For patients with suspected saline implant complications and equivocal clinical findings:
  • <30 years: ultrasound is the examination of choice 2
  • 30-39 years: either mammography/digital breast tomosynthesis or ultrasound may be used 2
  • ≥40 years: mammography/digital breast tomosynthesis is recommended 2
• For patients with suspected silicone implant complications:
  • <30 years: MRI without contrast or ultrasound is used 2
  • 30-39 years: MRI without contrast, mammography/digital breast tomosynthesis, or ultrasound may be used 2
  • ≥40 years: MRI without contrast or mammography/digital breast tomosynthesis is used 2

Venous Thrombosis Evaluation

• All patients should be evaluated for pretest probability of deep venous thrombosis (DVT) using clinical decision rules such as the Wells score 2
• For patients with low (unlikely) pretest probability of DVT, obtaining a high-sensitivity D-dimer is appropriate before considering ultrasound 2
• Ultrasound is appropriate for patients with:
  • Likely pretest probability of DVT 2
  • Unlikely pretest probability of DVT with a positive D-dimer 2
  • Cases where pretest probability was not assessed 2

Gynecologic Imaging

Abnormal Uterine Bleeding

• Combined transabdominal and transvaginal ultrasound of the pelvis with Doppler is the most appropriate initial imaging study for patients with abnormal uterine bleeding 2
• If the uterus is incompletely visualized with the initial ultrasound, MRI of the pelvis without and with contrast is the next appropriate imaging study 2
• If a polyp is suspected on the original ultrasound, sonohysterography can be performed 2, 1

Early Pregnancy Evaluation

• For stable patients in the first trimester of pregnancy with abdominal pain or vaginal bleeding, ultrasound is indicated 2
• For patients with a β-hCG level below the discriminatory threshold (typically 1,500 mIU/mL), ultrasound may still be beneficial:
  • Sensitivity for diagnosing intrauterine pregnancy is approximately 33% 2
  • Specificity is approximately 98% 2
• The decision to perform ultrasound should consider the patient's ability to arrange appropriate follow-up 2

Liver Imaging

Surveillance for Hepatocellular Carcinoma

• Ultrasound every 6 months is universally recommended for hepatocellular carcinoma (HCC) surveillance in at-risk populations 2
• Target populations for surveillance include:
  • Cirrhotic patients with varying etiology 2
  • Chronic HBV or HCV carriers (specific recommendations vary by guideline) 2
• Some guidelines recommend combining ultrasound with alpha-fetoprotein (AFP) measurement every 6 months 2
• CT or MRI may be used in select patients with a high likelihood of having an inadequate ultrasound 2

Pitfalls and Considerations

• Ultrasound availability may be limited during "off hours" (evenings, nights, and weekends), potentially affecting clinical decision-making 3
• The sensitivity and specificity of ultrasound vary by body system, clinical indication, and operator experience 4
• For follow-up of probably benign findings (BI-RADS 3), ultrasound every 6 months for 1-2 years is recommended 1
• Routine ultrasound during pregnancy before 24 weeks may reduce short-term maternal anxiety and improve detection of major fetal abnormalities, but may not alter other important maternal or fetal outcomes 5

Special Populations

• For pregnant women with isolated soft markers on previous ultrasound (such as choroid plexus cysts), no further ultrasound evaluation is needed if serum or cfDNA screening results are negative 1
• For transfeminine (male-to-female) patients, mammography/DBT and ultrasound are useful due to the increased incidence of breast cancer 2