Rectus diastasis is characterized by a thinning of the linea alba so that the distance between the rectus muscles is increased. There is no defect in the underlying aponeurosis and transversalis fascia; thus, there is no actual hernia. The patient may have a midline bulge as a result of this diastasis that is often mistaken as a hernia (Fig. 6.2). Management usually entails reassurance to the patient. If surgical correction is desired by the patient, abdominoplasty techniques are utilized. Ultrasound has been shown to be an accurate method of measuring the supraumbilical and periumbilical diastasis for the purposes of operative planning [8].

Hematomas within the rectus sheath are uncommon. They may develop spontaneously, yet, they often are associated with traumatic injury, pregnancy, coughing, or the use of anticoagulation therapy. They present with an acute onset of abdominal pain and tenderness that may be mistaken for peritonitis. In advanced cases, there may also be periumbilical or flank ecchymosis. Abdominal ultrasonography and CT scan aid in identifying the extent of a hematoma. The sonographic appearance of a rectus sheath hematoma varies with the age and location of the hematoma (Fig. 6.7). Above the arcuate line, the hematoma will have a lens-shaped appearance, whereas below the arcuate line, it may be more extensive, even crossing the midline or compressing the bladder [1]. Hematomas are primarily hypoechoic but can have septal or cystic components with echogenic borders [9]. Varying echogenicities within the hematoma represent different states of organized clot formation [10, 11]. Acute hematomas are homogenous and echogenic, while late-stage hematomas can be anechoic [10].

Management is usually conservative involving bed rest, analgesics, correction of coagulopathies, and blood transfusions as needed. If persistent bleeding is suspected, angiographic embolization of the bleeding of the vessel may be warranted, and if this is not available or successful, operative hemostasis and hematoma evacuation may be necessitated. Ultrasonography can be utilized to screen for hematomas that may require surgical intervention. Hematomas that are larger in diameter and demonstrate the presence of intra-abdominal free fluid on ultrasound are more likely to benefit from surgical exploration [12]. Ultrasonographic treatment of rectus sheath hematomas, where repeated sessions of nonthermal pulsed sonography are employed, has also been reported in the physical therapy literature [13].

Abdominal wall fluid collections include cysts, hematomas, seromas, and abscesses. Ultrasonography is a useful modality in identifying a fluid collection and its characteristics. Hematomas may be spontaneous, postsurgical, or related to anticoagulation therapy or traumatic injury. If warranted, hematomas may be drained with image guidance. Abscesses have a variable appearance on ultrasound. They are typically irregular fluid collections containing septations and fluid debris and may have air-fluid levels (Fig. 6.8). They may also exhibit peripheral hyperemia with Doppler evaluation [10]. If gas bubbles are present with the abscess, they will be echogenic and demonstrate acoustic shadowing [14]. Seromas are usually more homogenous anechoic or hypoechoic fluid collections on ultrasound (Fig. 6.9). They are usually encountered following an abdominal operation, particularly following ventral hernia repairs. The development of postoperative seromas may be prevented with the use of pressure dressings and abdominal binders. If there is no evidence of superinfection, it is acceptable to observe a seroma without intervention, as there is a risk of introducing infection with needle aspiration. If a seroma or hematoma appears infected or an abdominal wall abscess is identified, operative drainage or needle drainage with image guidance is warranted in addition to antibiotic therapy. For larger fluid collections that are percutaneously drained, a drain may be left in place to facilitate additional drainage (Figs. 6.10 and 6.11).

Abdominal wall neoplasms present as painless palpable masses. Primary lesions may arise from any of the abdominal wall components: connective tissue, muscle, fat, blood vessels, or lymphoid tissue. These include benign soft-tissue neoplasms such as lipomas and desmoid tumors as well as malignant neoplasms such as sarcomas. Desmoid tumors and sarcomas are the most common primary malignancies of the abdominal wall. Metastatic neoplastic lesions may also be found in the abdominal wall, which often is associated with transperitoneal seeding of the abdominal wall by intra-abdominal malignancies (Fig. 6.12). Ultrasound examination permits precise definition of the mass as well as accurate biopsy. A diagnostic dilemma frequently occurs with these incisional wall masses where a recurrent tumor implant, a hernia, or a fluid collection could be found (Fig. 6.13). Ultrasound guidance is of value in obtaining a diagnostic biopsy of small nodules in the abdominal wall that are concerning for metastases (Table 6.3).

Lipomas, neurofibromas, and hemangiomas are the most common benign neoplasms of the abdominal wall. Lipomas are well-circumscribed mobile lesions. On ultrasound, they will have a variable echogenicity that is discrete from the surrounding fat and muscle, and they may have an echogenic capsule [15] (Fig. 6.14). Hemangiomas are typically very small in diameter (millimeters) and on ultrasound will have multiple hypoechoic or anechoic cystic areas within an echogenic hypervascular background [10].

Desmoid tumors, or aggressive fibromatosis, are rare neoplasms that arise from fibroblast cells in either fascia or muscle. They may be intra-abdominal (pelvic and mesenteric), extra-abdominal (shoulder girdle or extremities), or abdominal wall tumors. When the tumor is superficial, it arises from the fascia and typically is slow growing in nature and of small size. These lesions are commonly referred to as Dupuytren’s fibromatosis. Deeper lesions arise from the musculoaponeurotic tissues and are usually more aggressive in growth rate and size. Although these tumors do not metastasize and are thus considered benign lesions, they are locally aggressive and often recur following resection.

Additional characteristics of the mass and the extent of involvement may be delineated with the use of an ultrasound. If the lesion is solid, hypoechoic, and abutting fascial planes or muscular tissue, one should be suspicious for a desmoid lesion. If an ultrasound is inadequate, further extent of the lesion may be defined with the use of MRI. The lesion requires biopsy for diagnosis, which may be obtained with a core needle or as an incisional biopsy under ultrasound guidance.

The treatment of abdominal wall desmoids involves surgical resection with tumor-free margins. Local recurrence rate of these tumors can be as high as 40 % [16], and these recurrent tumors will also require resection. If a lesion is unresectable, primary radiation treatment may be considered as well as palliative chemotherapy with antiproliferative cytotoxic agents.

The most common primary malignant neoplasm involving the abdominal wall is a sarcoma. These sarcomas, depending on what layers and cell types of the abdominal wall soft tissue are involved, can be of several subtypes: liposarcoma, fibrosarcoma, leiomyosarcoma, rhabdomyosarcoma, and malignant fibrous histiocytoma. The clinical progression of these tumors is reflective of their histology, size, and location.

These abdominal wall sarcomas can present as painless abdominal wall masses. Suspicion for malignancy arises with masses that are solid, large, fixated, and fast growing. On ultrasound, a sarcomatous lesion will be a hypoechoic solid lesion that may have localized areas of necrosis or fluid [10]. MRI can also be used to further delineate extent of disease. These lesions require guided biopsies, either incisional or percutaneous, to confirm their pathological diagnosis.

Transperitoneal, hematogenous, lymphatic seeding of intra-abdominal carcinomas or melanomas may result in metastatic lesions in the abdominal wall (Fig. 6.15). Cases of port-site seeding after laparoscopic surgery have also been reported in the literature, particularly following laparoscopic cholecystectomy where the cancer diagnosis was unknown at the time of operation. A metastatic deposit at the umbilicus is known as a Sister Mary Joseph’s nodule. These lesions may be characterized and biopsied with sonographic guidance and are typically treated with surgical resection and radiation as needed. Ultrasound has also been reported to be of use in guiding insertion of applicator needles that can administer brachytherapy to abdominal wall metastases from colorectal cancer [17].