ABDOMINAL WALL MASS

Hisham AlKhatib, M.D.Consultant Radiologist

الحمد هلل والصالة والسالم على رسول هللا وعلى اله •

وصحبه وسلّم اجمعين

اللهم انفعني بما علمتني وعلمني بما ينفعني وزدني علما ، •

انك العليم الحكيم

• Praise be to Allah and prayers be upon the Messenger of Allah and his family and companions.

• Oh God, give me the benefit of what you have taught me and teach me what benefits me.

DIFFERENTIAL DIAGNOSIS

Common Causes

• Inguinal Hernia

• Ventral Hernia

• Umbilical Hernia

• Spigelian Hernia

• Femoral Hernia

• Lumbar Hernia

• Abdominal Wall Abscess

• Sebaceous Cyst

• Lipoma

• Keloid

• Hematoma

• Paraumbilical Varices

• Muscle Asymmetry

• Injection Site

Key Differential Diagnosis Issues

• Physical exam and CT are key in distinguishing among hernias and various abdominal wall masses

• Most masses have characteristic appearance on CT

– Some nonspecific "soft tissue density“ masses require biopsy or excision

Helpful Clues for Common Diagnoses

Inguinal Hernia

• Contains fat and/or bowel; may extend into scrotum or labia

Ventral Hernia

• Through midline (linea alba); most common after surgery

• May be off midline at site of incision

Umbilical Hernia

• Through umbilical ring; common in patients with ascites

Spigelian Hernia

• Through defect lateral to rectus sheath

• Often covered by external oblique muscle and aponeurosis

Femoral Hernia

• Medial to and compresses femoral vein; likely to strangulate

Lumbar Hernia

• Through defect where abdominal wall muscles insert on iliac crest or thoracolumbar fascia (inferior lumbar triangle)

• Defect in oblique and transverse abdominal muscles, often covered by latissimus dorsi muscle

Abdominal Wall Abscess

• Encapsulated ± gas = abscess

• Diffuse, nonencapsulated = cellulitis

• Also consider enterocutaneous fistula (e.g., from diverticulitis)

Sebaceous Cyst

• Common, usually small spherical or oval, well-encapsulated

• Low density, non-enhancing contents without surrounding infiltration

Lipoma

• Common in subcutaneous tissues and between muscle planes

• Uniform fat density with no visible blood vessels

• Liposarcoma

– More complex appearing with visible blood vessels

– May be of near water attenuation (myxoid elements of tumor)

Keloid

• Overgrowth of scar tissue at site of cutaneous injury

• More common in African-Americans

Hematoma

• Heterogeneous, relatively high density focal mass (becomes more uniformly low density as it lyses)

• More diffuse, without mass effect = ecchymosis

• In response to focal trauma or anticoagulation (look for fluid level within hematoma)

Parumbilical Varices

• Common in severe cirrhosis with portal hypertension

• Serpiginous enhancing structures that connect to falciform ligament

Muscle Asymmetry

• Common after surgery, paralysis, polio

Injection Site

• Common in subcutaneous tissues of anterior abdominal wall and buttocks

• May contain gas, soft tissue density; may calcify (injection site granuloma)

Less Common Causes

• Endometriosis

• Calcinosis Syndromes

• Metastases

• Lymphoma and Leukemia

• Desmoid

• Sarcoma

• Rhabdomyolysis

Helpful Clues for less Common Diagnoses

Endometriosis

• May implant in abdominal wall at site of prior Cesarian section or hysterectomy

• Ask about history of cyclical pain and swelling at site of mass

Calcinosis Syndromes

• Dystrophic: Response to tissue injury, such as implanted medical device; or connective tissue diseases (scleroderma, dermatomyositis, CREST); or severe pancreatitis with fat necrosis (most often in breasts)

Calcinosis Syndromes

• Metastatic: I n patients with calcium-phosphate imbalance (renal failure, milk-alkali syndrome)

• Tumoral calcification: Large globular deposits near joints

Metastases

• Melanoma + renal cell most common

• Mass(es) in subcutaneous fat or muscle

• Often subtle or overlooked on CT; more apparent on PET CT

• May occur at site of surgery (e.g., for gallbladder, renal or colon cancer)

Lymphoma and Leukemia

• Cutaneous T cell lymphoma (also known as mycosis fungoides or Sezary syndrome)

– Skin second most common site of extra nodal lymphoma (after GI tract)

• Leukemia cutis (also known as chloroma, or granulocytic sarcoma)

Desmoid

• Also known as fibromatosis; histologically benign but very aggressive growth

• May occur sporadically, but more often in association with Gardner syndrome

Sarcoma

• Rare; heterogeneous vascular tumor with foci of necrosis

Rhabdomyolysis

• Muscle necrosis in response to crush injury, seizures, statin medications

• Poorly defined and minimally enhancing lesion within skeletal muscle

• Commonly leads to severe renal damage due to release of myoglobin into bloodstream

THANK YOU