Should I order an ultrasound for a patient with a pea-sized lump in the right groin that has doubled in size and is difficult to palpate?

Ultrasound Evaluation for Right Groin Lumps

For a patient with pea-sized lumps in the right groin that have doubled in size and are difficult to palpate, an ultrasound should be ordered as the initial imaging study. 1, 2

Rationale for Ultrasound as First-Line Imaging

• Ultrasound is the most appropriate initial imaging modality for evaluating superficial soft tissue masses and groin lumps for several reasons:
  • High sensitivity (94.1%) and specificity (99.7%) for superficial soft tissue masses 1
  • Ability to differentiate solid from cystic lesions 1
  • Can visualize soft tissue structures distinctly in the groin region 3
  • Allows for dynamic evaluation during Valsalva maneuver to assess for hernias 2
  • Non-invasive and does not expose the patient to radiation

Ultrasound Protocol for Groin Evaluation

When ordering the ultrasound, specify that it should include:

1. Grayscale imaging of the entire groin region
2. Color Doppler assessment to evaluate vascularity
3. Dynamic evaluation during Valsalva maneuver to assess for potential hernias
4. Examination in two orthogonal planes to avoid diagnostic pitfalls 2
5. Assessment of adjacent structures including lymph nodes and musculature

Differential Diagnosis to Consider

The ultrasound will help differentiate between:

• Inguinal or femoral hernia
• Enlarged lymph nodes
• Lipoma or other soft tissue tumors
• Vascular abnormalities (aneurysm, pseudoaneurysm)
• Endometrioma (in female patients) 4
• Abscess or inflammatory conditions
• Rare conditions like Kikuchi-Fujimoto disease 5

Management Algorithm Based on Ultrasound Findings

If Ultrasound Shows Simple Cyst:

• If asymptomatic: Routine follow-up
• If symptomatic: Consider therapeutic aspiration 1

If Ultrasound Shows Complicated Cyst:

• Options include aspiration or short-term follow-up with physical examination and ultrasound every 6-12 months for 1-2 years 1
• If the cyst increases in size on follow-up, tissue biopsy should be performed 1

If Ultrasound Shows Solid Mass:

• For small, superficial lesions with benign characteristics: Follow-up in 6-12 months
• For larger masses or those with concerning features: Consider biopsy or surgical referral 1

If Ultrasound Shows Hernia:

• Surgical consultation for potential repair

If Ultrasound is Indeterminate:

• Consider MRI for further characterization, especially for soft tissue masses 1
• CT is typically not recommended as initial imaging due to suboptimal soft tissue discrimination in the groin region 1

Common Pitfalls to Avoid

1. Failing to perform dynamic evaluation during Valsalva maneuver, which can miss intermittent hernias
2. Not documenting findings in two orthogonal planes, which can lead to misdiagnosis
3. Overlooking small lymph nodes or vascular structures
4. Misinterpreting normal anatomical structures as pathological

Follow-Up Recommendations

• If ultrasound findings are benign and image-concordant: Physical examination with or without repeat ultrasound every 6-12 months for 1-2 years 1
• If the mass increases in size: Repeat imaging and consider biopsy
• If the mass remains stable: Return to routine screening

Ultrasound has proven to be a valuable diagnostic tool for groin pathology, with studies showing correct prediction of surgical findings in 68 out of 70 patients with operative verification 3.