Ross
254 lines
22 KiB
Markdown
254 lines
22 KiB
Markdown
---
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title: "Abdominal Wall Mass"
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docid: "d51e2268-67b6-4a60-9222-f5a86f61ddec"
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authors:
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- key: "c1df94ab-4a9f-44c4-add7-1f174fb9ac45"
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value: "Siva P. Raman, MD"
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breadcrumbs:
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-
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name: "Gastrointestinal"
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slug: "gastrointestinal"
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treeNodeId: "b52263f7-5978-4a22-a17d-7260e0033943"
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-
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name: "Differential Diagnosis"
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slug: "differential-diagnosis"
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treeNodeId: "a0fd80ff-6231-49d3-94b8-ea083449979d"
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-
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name: "Abdominal Wall"
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slug: "abdominal-wall"
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treeNodeId: "08db01f7-2961-47f7-954d-2a5fca7e707d"
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-
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name: "Anatomically Based Differentials"
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slug: "anatomically-based-differentials"
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treeNodeId: "1525b44f-9d47-4ff4-8330-693211bd5eb5"
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-
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name: "Abdominal Wall Mass"
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slug: "abdominal-wall-mass"
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treeNodeId: null
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category: "Gastrointestinal"
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documentVersionId: "258ccc6a-0370-4b08-adc4-dfc3ef9a1ce6"
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imageCount: 18
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lastUpdated: "07/15/22"
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pageDescription: "Abdominal Wall Mass"
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pageKeywords: "Gastrointestinal, Differential Diagnosis, Abdominal Wall, Anatomically Based Differentials, Abdominal Wall Mass"
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pageTitle: "Abdominal Wall Mass | STATdx"
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enhancedTitle: "Abdominal Wall Mass"
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type: "DDX"
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references: true
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breadcrumbs:
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- "Gastrointestinal"
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- "Differential Diagnosis"
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- "Abdominal Wall"
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- "Anatomically Based Differentials"
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- "Abdominal Wall Mass"
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---
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# ESSENTIAL INFORMATION
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- ## Key Differential Diagnosis Issues
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- Given limitations of clinical examination, imaging plays important role in differentiating true soft tissue masses from hernias, vascular abnormalities, and normal variants
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- Most soft tissue masses have nonspecific appearance and may require biopsy or excision for diagnosis
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- ## Helpful Clues for Common Diagnoses
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- **Abdominal Wall Hernias**
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- **Inguinal hernia**
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- Most common external hernia, which extends into groin anterior to horizontal plane of pubic tubercle
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- Divided into direct (arises anteromedial to inferior epigastric vessels) and indirect (arises superolateral to inferior epigastric vessels) subtypes
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- **Ventral hernia**
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- Broad term describing acquired or congenital hernias through anterior and lateral abdominal wall
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- Midline hernias include epigastric (above umbilicus) and hypogastric (below umbilicus) hernias
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- Incisional hernias occur at prior surgical incision sites
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- **Umbilical hernia**
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- Hernias arising at midline in upper 1/2 of umbilical ring, which can be congenital or acquired
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- Very common incidental finding on imaging, although usually small and asymptomatic
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- **Spigelian hernia**
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- Hernia through defect lateral to rectus sheath (inferior and lateral to umbilicus) often covered by external oblique muscle and aponeurosis
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- **Femoral hernia**
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- Groin hernia extending medial to femoral vessels with frequent compression of femoral vein
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- Most common in older female patients with very high risk of strangulation and incarceration
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- **Lumbar hernia**
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- Hernia through defect in lumbar muscle or thoracolumbar fascia
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- Can be congenital or acquired with many acquired due to incisions in flank region for renal surgery
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- **Abdominal Wall Abscess**
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- Loculated fluid collection (± internal gas) with peripheral enhancement and surrounding edema/fat stranding
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- Differentiate drainable abscess from diffuse, nondrainable edema/fluid (cellulitis/phlegmon)
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- Presence of gas-containing abdominal wall abscess in close contiguity with bowel tethered to abdominal wall raises possibility of enterocutaneous fistula
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- **Sebaceous Cyst**
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- Common incidental finding, appearing as small, round/oval, well-encapsulated cyst near skin surface
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- Should be low density and nonenhancing without surrounding subcutaneous edema/fat stranding
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- **Lipoma**
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- Common incidental mass in subcutaneous tissues and between muscle planes, demonstrating uniform fat density with no internal soft tissue component
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- Differentiate from liposarcoma, which demonstrates internal complexity and soft tissue component
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- Confident diagnosis may be difficult on US, but mass should have similar echogenicity to subcutaneous fat
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- **Keloid**
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- Benign fibrotic scar tissue or tissue overgrowth at site of soft tissue injury (i.e., surgical incision or trauma)
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- Usually asymptomatic but can be painful or pruritic
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- No clear imaging features to allow differentiation of large keloid from other soft tissue masses
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- **Hematoma**
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- Heterogeneous, high-density blood products, which gradually evolve and become lower in density over time
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- More diffuse subcutaneous blood products may reflect subcutaneous ecchymosis
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- **Paraumbilical Varices**
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- Common portosystemic collaterals in patients with severe cirrhosis and portal hypertension
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- Serpiginous enhancing structures that connect to recanalized paraumbilical vein near falciform ligament
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- May be visible/palpable at skin (i.e., caput medusae)
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- **Injection Site**
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- Common incidental finding usually secondary to injection of heparin, insulin, or other medications
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- Small nodular foci with ectopic gas, blood, or fluid
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- May chronically evolve into injection granulomas, appearing as rounded or linear foci of soft tissue or calcification (most common in buttocks)
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- **Calcified Scar**
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- Heterotopic ossification (myositis ossificans traumatica) can occur at abdominal incision sites and is most common in linear alba after midline abdominal incision
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- Ossified scar in incision can resemble rib (with both cortex and medulla)
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- **Muscle Asymmetry (Mimic)**
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- May be mistaken for mass and are common secondary to prior surgery, paralysis, myopathy, etc.
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- **Melanoma**
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- 5th most common new cancer in US, but imaging typically not utilized for diagnosis of primary tumor
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- Most commonly multiple small subcutaneous nodules, although rarely presents as solitary abdominal wall mass
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- Homogeneous enhancement ± hyperintense on T1 MR
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- ## Helpful Clues for Less Common Diagnoses
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- **Endometriosis**
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- Endometriosis implants may be seen within incision sites after prior C-section or hysterectomy
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- Typically appears as solid, spiculated subcutaneous mass with variable enhancement (usually hypointense on T1 and hyperintense on T2 MR)
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- May be associated with clinical history of cyclical pain (corresponding with menstruation) at incision site
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- **Calcinosis Syndromes**
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- Dystrophic: Calcifications may be due to tissue injury response, such as implanted medical device, connective tissue diseases (scleroderma, dermatomyositis, CREST), severe pancreatitis, or fat necrosis
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- Metastatic: Most often in patients with calcium-phosphate imbalance (renal failure, milk-alkali syndrome)
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- Tumoral calcification: Large globular deposits of calcification near joints
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- **Soft Tissue Metastases**
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- Most common malignancies to metastasize to soft tissues are melanoma and renal cell carcinoma
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- Soft tissue nodule or mass(es) in subcutaneous fat or muscle with enhancement similar to primary tumor
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- Easily overlooked on CT if careful survey of soft tissues not undertaken, but often more apparent on PET
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- Tumor may also be implanted at site of surgery (probably more common with laparoscopic surgery) or biopsy
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- Surgical seeding can also occur with benign lesions, including uterine fibroids and ectopic splenic tissue
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- **Lymphoma and Leukemia**
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- Cutaneous T-cell lymphoma (a.k.a. mycosis fungoides or Sézary syndrome)
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- Skin 2nd most common site of extranodal lymphoma (after GI tract)
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- Skin involvement may be difficult to appreciate on imaging unless unusually nodular or mass-like
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- Subcutaneous panniculitis-like T-cell lymphoma
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- Manifests as site of soft tissue induration/infiltration or as discrete nodules
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- Leukemia cutis (i.e., chloroma or granulocytic sarcoma)
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- Primary B-cell cutaneous lymphomas more likely to present as solitary isolated skin lesion
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- Posttransplant lymphoproliferative disorders (PTLD) can rarely manifest in subcutaneous soft tissues
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- **Desmoid**
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- Benign locally aggressive neoplasm, which can be intraabdominal or extraabdominal (e.g., abdominal wall)
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- Abdominal wall lesions most frequently arise from rectus or oblique muscles, especially at incision sites
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- Major risk factors include prior surgery, trauma, Gardner syndrome, and familial adenomatous polyposis
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- Variable appearance but typically solid, well-defined, hypoenhancing, heterogeneously high signal on T2 and low signal on T1 MR
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- **Sarcoma**
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- Malignant mesenchymal soft tissue tumors, which encompass wide range of different histologic subtypes
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- May be difficult to differentiate from other soft tissue masses based on imaging alone, although most sarcomas tend to be larger and more heterogeneous with frequent necrosis (± distant metastatic disease)
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- Different subtypes of sarcomas cannot be differentiated on imaging with any accuracy
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- **Rhabdomyolysis**
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- Muscle necrosis in response to wide variety of causes, including crush injury, seizures, statin medications, etc.
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- Involved muscles on CT generally appear either normal or abnormally hypodense (due to edema)
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- MR more sensitive, with muscles demonstrating T2 hyperintensity and enlargement, as well as hyperenhancement (can appear ring-like or mass-like)
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- Commonly leads to severe renal damage due to release of myoglobin into bloodstream
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- **Pancreatic Panniculitis**
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- Subcutaneous fat necrosis seen with pancreatitis and pancreatic adenocarcinoma (due to ↑ serum lipase)
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- Manifest as small nodular foci of predominantly fat density on CT and hyperechoic on US
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- **Kaposi Sarcoma**
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- Most common AID-related vascular neoplasm in Western world, presenting as either diffuse infiltration of skin or discrete subcutaneous nodules
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## References
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# Selected References
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1. [Ballard DH et al: Imaging of abdominal wall masses, masslike lesions, and diffuse processes. Radiographics. 40(3):684-706, 2020](http://www.ncbi.nlm.nih.gov/pubmed/?term=32330085%5Bpmid%5D)
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1. [Draghi F et al: Abdominal wall sonography: a pictorial review. J Ultrasound. 23(3):265-78, 2020](http://www.ncbi.nlm.nih.gov/pubmed/?term=32125676%5Bpmid%5D)
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1. [Kania LM et al: Interpreting body MRI cases: classic findings in pelvic MRI. Abdom Radiol (NY). 45(9):2916-30, 2020](http://www.ncbi.nlm.nih.gov/pubmed/?term=32607649%5Bpmid%5D)
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1. [Mao A et al: Post-cesarean section abdominal wall endometrioma. Cureus. 12(8):e10088, 2020](http://www.ncbi.nlm.nih.gov/pubmed/?term=33005511%5Bpmid%5D)
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1. [Youssef AT: The ultrasound of subcutaneous extrapelvic endometriosis. J Ultrason. 20(82):e176-80, 2020](http://www.ncbi.nlm.nih.gov/pubmed/?term=33365153%5Bpmid%5D)
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1. [Hensen JH et al: Abdominal wall endometriosis: clinical presentation and imaging features with emphasis on sonography. AJR Am J Roentgenol. 186(3):616-20, 2006](http://www.ncbi.nlm.nih.gov/pubmed/?term=16498086%5Bpmid%5D)
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1. [Zafar HM et al: Anterior abdominal wall hernias: findings in barium studies. Radiographics. 26(3):691-9, 2006](http://www.ncbi.nlm.nih.gov/pubmed/?term=16702448%5Bpmid%5D)
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1. [Aguirre DA et al: Abdominal wall hernias: imaging features, complications, and diagnostic pitfalls at multi-detector row CT. Radiographics. 25(6):1501-20, 2005](http://www.ncbi.nlm.nih.gov/pubmed/?term=16284131%5Bpmid%5D)
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1. [Shadbolt CL et al: Imaging of groin masses: inguinal anatomy and pathologic conditions revisited. Radiographics. 21 Spec No:S261-71, 2001](http://www.ncbi.nlm.nih.gov/pubmed/?term=11598262%5Bpmid%5D)
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## Images
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### Selected Images
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**Abdominal Wall Hernias**
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*Axial CECT shows a right inguinal hernia <img src='img/arrows/WS.png'/> containing loops of nonobstructed small bowel.*
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**Abdominal Wall Hernias**
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*Axial CECT shows a right inguinal hernia <img src='img/arrows/WS.png'/> containing loops of nonobstructed small bowel.*
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**Sebaceous Cyst**
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*Axial CECT shows an encapsulated, near water density mass <img src='img/arrows/WS.png'/> in the left buttock. Sebaceous cysts are a common incidental finding and, when demonstrating a classic appearance, do not require further follow-up or evaluation.*
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**Lipoma**
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*Coronal CECT shows a large, fat-containing mass <img src='img/arrows/WS.png'/> within the right lateral abdominal wall, compatible with a simple lipoma. Note the absence of any complexity or soft tissue component within the mass.*
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**Hematoma**
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*Axial CECT shows an acute, high-density subcutaneous hematoma <img src='img/arrows/WS.png'/> in a patient with recent trauma.*
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**Hematoma**
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*Axial CECT in a patient with cirrhosis and portal hypertension shows subcutaneous varices <img src='img/arrows/WS.png'/> overlying the anterior abdominal wall, representing a caput medusae.*
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**Paraumbilical Varices**
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*Axial T1 C+ MR shows an enhancing mass <img src='img/arrows/WS.png'/> in the left anterior pelvic wall, found to represent a scar endometrioma in this patient status post prior laparoscopic pelvic surgery.*
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**Endometriosis**
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*Sagittal CECT shows a soft tissue mass <img src='img/arrows/WS.png'/> intimately associated with the umbilicus, ultimately found at biopsy to represent endometriosis.*
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**Soft Tissue Metastases**
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*Axial CECT shows a hypodense mass <img src='img/arrows/WS.png'/> in the midline anterior abdominal wall, proven to represent a metastasis from the patient's known primary colon cancer.*
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**Soft Tissue Metastases**
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*Axial CECT shows a hypodense mass <img src='img/arrows/WS.png'/> in the abdominal wall musculature, representing a metastasis from the patient's known colon cancer.*
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**Lymphoma and Leukemia**
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*Axial CECT shows a biopsy-proven chloroma <img src='img/arrows/WS.png'/> in the right anterior abdominal wall in a patient with known leukemia.*
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**Desmoid**
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*Axial CECT shows multiple large, hypodense masses <img src='img/arrows/WS.png'/> in the pelvic subcutaneous soft tissues in a patient with known familial polyposis, representing desmoid tumors.*
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**Desmoid**
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*Axial CECT shows a hypodense mass <img src='img/arrows/WS.png'/> in the right anterior abdominal wall, ultimately found to represent a desmoid tumor.*
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**Sarcoma**
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*Axial CECT shows a large, rapidly growing mass <img src='img/arrows/WS.png'/> in the left anterior abdominal wall, representing a primary soft tissue sarcoma (malignant fibrous histiocytoma).*
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**Sarcoma**
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*Axial T1 C+ FS MR shows a highly invasive, large tumor in the buttock <img src='img/arrows/WS.png'/>, which enhances significantly. This lesion proved on biopsy to be a high-grade epithelioid sarcoma.*
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### Additional Images
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**Paraumbilical Varices**
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*Axial CECT shows a colostomy <img src='img/arrows/WC.png'/> with extensive varices <img src='img/arrows/WO.png'/> in the parastomal region. These develop in patients with portal hypertension (e.g., following colectomy for primary sclerosing cholangitis with cirrhosis).*
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**Paraumbilical Varices**
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*Axial CECT shows prominent parastomal varices <img src='img/arrows/WO.png'/>.*
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**Paraumbilical Varices**
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*Axial CECT shows a cirrhotic liver and a large parumbilical varix <img src='img/arrows/WS.png'/>.*
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**Paraumbilical Varices**
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*Axial CECT shows continuation of the parumbilical varix with collaterals in the rectus muscles and subcutaneous fat <img src='img/arrows/WS.png'/> (caput medusae).*
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