A thorough understanding of the indications and local anatomy are important for successful removal of the axillary and superficial inguinal lymph nodes. This article provides anatomic landmarks for the axillary and superficial inguinal lymph nodes, reviews the surgical approach to removal of these lymph nodes, and discusses surgical considerations and complications.<\/p>\n
Take-Home Points<\/strong><\/p>\n <\/div><\/div><\/p>\n The axillary and superficial inguinal lymph nodes are important drainage centers for tumors of the forelimbs, ventral abdomen, mammary glands, scrotum, and pelvic limbs yet are often not sampled cytologically when they are normal sized.<\/span>1-4<\/sup><\/span> The inguinal lymph node sits within the inguinal fat pad and can often be 5 mm or less in diameter, making visualization and removal difficult without guidance, while the axillary lymph node is in a challenging anatomic location. Knowledge of lymph node drainage patterns is important for surgical planning, and removal of draining lymph nodes should be considered for staging if the lymph node is normal on palpation or for treatment if the lymph node is metastatic.<\/span>5<\/sup><\/span><\/p>\n In normal animals, the axillary and inguinal lymph nodes should not be palpable on physical examination; therefore, additional techniques, such as sentinel lymph node (SLN) mapping, may be needed to help in identification.<\/span>3,4<\/sup><\/span> SLN mapping is a technique that involves visual identification of the first draining lymph node through the local injection of dyes or contrast agents, and SLN mapping techniques were described in a previous Today\u2019s Veterinary Practice<\/i> article.<\/span>6<\/sup><\/span> This complementary article describes the anatomic landmarks of the axillary and superficial inguinal lymph nodes and discusses the surgical approach to lymphadenectomy and its associated complications. For descriptions of approaches to the removal of additional peripheral lymph nodes (mandibular, medial retropharyngeal, superficial cervical, and popliteal), see <\/span>go.navc.com\/4d7bNW0<\/span><\/a>. <\/span><\/p>\n Moderately to markedly enlarged axillary and inguinal lymph nodes can often be palpated externally, and surgical approaches can be based on palpation and direct incision over the lymph node, which can be removed using the information provided below. The necessary equipment is listed in <\/span>BOX 1<\/b><\/span>.<\/span><\/p>\n If the lymph node is not palpable, SLN mapping via radiographic lymphography using iodinated contrast can be useful to identify the location of the primary draining lymph node for surgical planning and preparation.<\/span>6<\/sup><\/span> However, SLN mapping is reserved for cases in which the lymph node has subclinical disease. It may not work if the lymph node is completely effaced with tumor cells.<\/span>7<\/sup><\/span> If available, a computed tomography (CT) lymphangiogram can also be considered.<\/span><\/p>\n Fine-needle aspiration, either of palpably enlarged lymph nodes or via ultrasound guidance, and cytology can help to determine if there is evidence of lymph node metastasis. Depending on the tumor type, additional staging to assess the patient for metastasis may include 3-view thoracic radiography, abdominal ultrasonography, and CT, depending on availability and the expected metastasis patterns.<\/span><\/p>\n The axillary lymph node is located medial to the shoulder and ranges from 0.3 to 5 cm in size.<\/span>3<\/sup><\/span> It is adjacent to the teres major muscle laterally and deep pectoral (pectoralis profundus) muscle medially. The caudal pectoral nerve is typically located medial or ventral to the lymph node, with the thoracodorsal artery and vein running dorsal to it (<\/span>FIGURE 1<\/b><\/span>).<\/span>3,8<\/sup><\/span> Lymphatic drainage to the axillary lymph node is from the thoracic wall, cranioventral abdominal wall, thoracic limb, and mammary glands.<\/span>2,3<\/sup><\/span> This lymph node is usually singular; however, an accessory counterpart has been reported.<\/span>3,8<\/sup><\/span> Unless it is enlarged, peripheral palpation of the axillary lymph node during a physical examination should not be possible.<\/span><\/p>\n Figure 1. Illustration of the pertinent anatomic landmarks for axillary and accessory lymph node extirpation. a\u2009=\u2009artery; m\u2009=\u2009muscle; n\u2009=\u2009nerve; v\u2009=\u2009vein. Illustration: Kip Carter<\/p><\/div>\n Figure 2. Positioning of a dog in lateral recumbency for left axillary lymphadenectomy with the head to the left of the image and left forelimb abducted and pulled forward.<\/p><\/div><\/li>\n Figure 3. Surgical approach to the axillary lymph node. The physical depression is palpated and an incision is made on the medial aspect of the limb. The dog is positioned in lateral recumbency with the head to the left of the image and left forelimb abducted and pulled forward.<\/p><\/div><\/li>\n Figure 4. Blunt dissection is continued through the subcutaneous tissue to identify the boundaries of the latissimus dorsi muscle ventrally and deep pectoralis muscle medially.<\/p><\/div><\/li>\n Figure 5. Dissection is continued between muscle planes into the axillary region, where the lymph node can be identified. Army\u2013Navy or Senn retractors are used to aid in visualization. The pectoralis muscle is visible within the medial aspect of the incision (arrow).<\/p><\/div><\/li>\n Figure 6. The right axillary lymph node is visualized within the deep fat (arrow).<\/p><\/div><\/li>\n Figure 7. The right axillary lymph node is grasped and removed using a combination of sharp and blunt dissection. (A) The vascular bundle (arrow) is located caudally. The dog is positioned in dorsal recumbency with the head to left of the image and right forelimb abducted and pulled forward.<\/p><\/div>\n Figure 7B. The removed right axillary lymph node is seen on clean gauze.<\/p><\/div><\/li>\n Figure 8. The accessory axillary lymph node (tip of forceps) is visible superficially and caudal to the axilla. The axillary lymph node is within the fat at the tip of the Metzenbaum scissors.<\/p><\/div><\/li>\n The superficial inguinal lymph node is located cranial to the pubis and dorsolateral to the penis (in males) or the mammary glands (in females).<\/span>4,9<\/sup><\/span> It has been reported to be 0.5 to 6.8 cm in size (although in the authors\u2019 experience is typically closer to 0.5 cm in size) and is surrounded by the gracilis muscle and the aponeurosis of the external abdominal oblique muscle.<\/span>4<\/sup><\/span> The external pudendal artery and vein are located lateral to the superficial inguinal lymph node, when singular, or between the lymph nodes when there are 2 (FIGURE<\/b><\/span><\/span>\u00a09<\/b><\/span>).<\/span>4<\/sup><\/span> Lymphatic drainage to the superficial inguinal lymph node is from the ventral abdominal wall, skin of the prepuce and scrotum, mammary glands, and pelvic limb. There can be 1 to 3 lymph nodes in this location per side.<\/span>4,10\u00a0<\/sup><\/span><\/p>\n Figure 9. Illustration of the pertinent anatomic landmarks for superficial inguinal lymph node extirpation. a\u2009=\u2009artery; m\u2009=\u2009muscle; n\u2009=\u2009nerve; v\u2009=\u2009vein. Illustration: Kip Carter<\/p><\/div>\n Figure 10. Intraoperative radiograph of an aseptically prepared and draped dog showing staples (arrowheads) at the level of the inguinal lymph nodes. The dog is positioned in dorsal recumbency with its head to the top of the image.<\/p><\/div><\/li>\n Figure 11A. Surgical marker showing the planned incision to access the inguinal lymph node in an aseptically prepared and draped female patient.<\/p><\/div>\n Figure 11B. The borders of the gracilis muscle and mammary gland are palpated and an incision made in a craniolateral to caudodorsal direction. The dog is positioned in dorsal recumbency with the head to the top of the image and pelvic limbs abducted.<\/p><\/div><\/li>\n\n
Preoperative Planning and Diagnostic Testing<\/h2>\n
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Axillary Lymph Node<\/h2>\n
Anatomy<\/h3>\n
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<\/a>Surgical Technique for Removal<\/h3>\n
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<\/a>Superficial Inguinal Lymph Node<\/h2>\n
Anatomy<\/h3>\n
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<\/a>Surgical Technique for Removal<\/h3>\n
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