A Lump in the Groin: The Diagnostic Dilemma

Authors: Molly L. Tolins, MD and Sachita Shah, MD (Division of Emergency Medicine, Department of Medicine, University of Washington, Seattle WA) // Edited by: Alex Koyfman, MD (@EMHighAK, EM Attending Physician, UTSW / Parkland Memorial Hospital) and Brit Long, MD (@long_brit)

The Case: Groin Pain

A 53-year-old male with a history of IV drug use presents to your emergency department with swelling and pain in his right groin. He shoots in his bilateral groins and says his last injection in the right groin was about a week ago; he noticed the swelling and pain over the last few days. He denies fevers, chills, malaise, lower extremity weakness, numbness, or swelling. His vitals are normal, and on your exam he has an indurated mass, approximately 4 cm in diameter, in his right groin just below the inguinal ligament, tender to palpation, with minimal overlying erythema. He also has several track marks in bilateral groin regions. What do you want to do next? Labs? Ultrasound? CT scan? Call a friend? Discharge with PCP follow up?

Groin Mass: The Differential

The differential for a groin mass in someone who injects in their groin is long. Abscess, of course, is high on the differential. However, not all hoof beats are horses, and before you go incising that mass, you have to consider alternatives. These include entities such as retained foreign bodies (broken needle tips), reactive adenopathy, suppurative lymphadenitis, DVT, superficial thrombophlebitis, cellulitis, and femoral artery pseudoaneurysm.

These diagnoses require very different management, and so differentiating them is critical. Luckily, bedside ultrasound is the quickest and best modality for assessment in most cases. In this patient’s case, you decide to do a quick bedside ultrasound, and find this:

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Figure 1. Bedside ultrasound, 2-dimensional gray scale, with the common femoral artery on the left of the screen in cross-section, demonstrating a large fluid-filled mass.

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Figure 2. Same view bedside ultrasound, with color Doppler applied, demonstrating bidirectional flow within the mass.

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Figure 3. Pulsed wave Doppler overlying the neck of the mass on bedside ultrasound showing pulsatile flow.


This patient has an infected right common femoral artery (CFA) pseudoaneurysm. CTA confirms the bedside ultrasound findings (Fig. 4).

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Figure 4. CTA Pelvis with new right CFA irregular pseudoaneurysm measuring 4.3 x 2.2 cm. There is soft tissue attenuation stranding around the aneurysm sac suggesting infection/mycotic aneurysm.


Traumatic arterial injury is the most common cause of pseudoaneurysms. Infected femoral artery pseudoaneurysm is one of the most common arterial complications of repeated non-sterile punctures in injection drug users. 1  Femoral pseudoaneurysms are also reported to occur in 1% of diagnostic arterio-grams and up to 8% of therapeutic endovascular interventions.2


Pseudoaneurysms follow arterial damage, allowing blood to escape into surrounding tissue, with a fibrin wall gradually forming, resulting in a false aneurysm.3,4  The natural history of a pseudoaneurysm is to grow gradually over time; an abrupt increase in size should raise concern for a ruptured aneurysm.

Most patients present with masses and can have leg swelling or limitation of activity of their leg. Some patients with a ruptured pseudoaneurysm will present with active bleeding. A femoral pseudoaneurysm can masquerade as an abscess, as both often present with groin pain and swelling, and not all pseudoaneurysms will be pulsatile.2 Mistaking the two can be catastrophic.

Work Up

The diagnosis of a pseudoaneurysm may be confirmed with color Doppler ultrasonography, computed tomography, or angiography.There are 3 classic signs of a pseudoaneurysm in sonography: a communication between the artery and the pseudoaneurysm (Fig.1); a yin-yang sign, which indicates bidirectional flow because of the swirling of blood within the pseudoaneurysm cavity (Fig. 2); and a “to-and-fro” on pulsed wave doppler within the neck, indicating reversal of flow in the neck during diastole (Fig. 3).  Bedside ultrasonography has a sensitivity and specificity of 94% and 94%-97%, respectively in the evaluation of possible vascular injury causing pseudoaneurysm,6 and should be performed prior to consideration of incision and drainage of what might otherwise appear to be an abscess.

Computed tomography angiography (CTA) is also a valuable diagnostic tool, allowing assessment of the pseudoaneurysm, surrounding structures, arterial inflow, and distal run-off of the leg.6   This can be especially helpful when an infected pseudoaneurysm is suspected, and for surgical planning.


Approach to the management of a pseudoaneurysm depends on its anatomical location. Potential treatment modalities include radiological management, including ultrasound guided compression repair (UGCR); endovascular management, with the usage of embolization, perfusion balloons, and placement of covered stents/endoluminal prostheses; and open surgical management with ligation.2

Infected femoral artery pseudoaneurysms in IV drug users should not be managed expectantly. The mass will inevitably grow and rupture, and thus surgical therapy and vascular consultation should be pursued as soon as possible. If grafts are placed, these patients are at higher risk for infection of their grafts and need of a second surgery for graft removal.6

When there is evidence that the femoral pseudoaneurysm is ruptured, such as active bleeding or rapid expansion, emergent surgery is the cornerstone of treatment.Hemodynamic support with product resuscitation and vasopressors may be necessary until definitive treatment can be provided. Active external bleeding from the site should be stopped with direct pressure and/or packing.8

In all cases of infected femoral artery pseudoaneurysms, there is a high risk of infection both pre- and post-operatively. Thus, all patients with a suspected infected CFA pseudoaneurysm should be covered with broad-spectrum antibiotics.9


  • Consider pseudoaneurysm in your differential for groin, axilla, and other lumps before proceeding down an abscess treatment algorithm
  • Your physical exam will not always give you the diagnosis
  • Bedside ultrasonography has a sensitivity and specificity of 94% and 94%-97%, respectively, in the evaluation of pseudoaneurysm
  • Femoral artery pseudoaneurysm requires surgical consultation, and surgical management is the mainstay of treatment
  • Administer broad spectrum antibiotics in septic patients or those with evidence of infected pseudoaneurysm


References / Further Reading

  1. Qiu, W. Zhou, W. Zhou, X. Tang, Q. Yuan, X. Zhu, Y. Yang, J. Xiong. The Treatment of Infected Femoral Artery Pseudoaneurysms Secondary to Drug Abuse: 11 Years of Experience at a Single Institution. Annals of Vascular Surgery, 2016; 36: 35–43
  2. Petrou, I. Malakos, S. Kampanarou, N. Doulas, V. Voudris. Life-threatening rupture of a femoral pseudoaneurysm after cardiac catheterization. Open Cardiovasc Med J. 2016; 10: 201-204.
  3. Gudena, N. Khetan. Swelling of volar aspect of the wrist. Postgrad Med J, 81 (2005) e9, e11
  4. L. Zitsman. Pseudoaneurysm after penetrating trauma in children and adolescents. J Pediatr Surg, 33 (1998), pp. 1574–1577
  5. Goksu, E., Yuruktumen, A., and Kaya, H. Traumatic pseudoaneurysm and arteriovenous fistula detected by bedside ultrasound. J Emerg Med. 2014; 46: 667–669
  6. Gullo, J., Singletary, E.M., and Larese, S. Emergency bedside sonographic diagnosis of subclavian artery pseudoaneurysm with brachial plexopathy after clavicle fracture. Ann Emerg Med. 2013; 61: 204–206
  7. Etemad-Rezai R., Peck D.J. Ultrasound-guided thrombin injection of femoral artery pseudoaneurysms. Can. Assoc. Radiol. J. 2003;54(2):118–120.
  8. Li Q., Shu C., Jiang X., Li M., Li X., He H. Surgical management of infected pseudoaneurysms of femoral artery caused by narcotics injection.Zhong Nan Da Xue Xue Bao Yi Xue Ban. 2009;34(6):476–480
  9. Salimi J, Shojaeefar A, Khashayar P. Management of infected femoral pseudoaneurysms in intravenous drug abusers: a review of 57 cases.Archives of Medical Research. 2008;39(1):120–124.

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