1207 CT of the Abdominal Wall PhilipGoodma& 2 and Bharat Raval1 CT is an excellent method for evaluating the abdominal wall. Various abnormalities including hernia, hematoma, abscess, tumor, and neuromuscular disease are easily detected and assessed by CT. Examples of common and uncommon diseases illustrate the value of CT in the diagnosis of abdominal wall diseases. Normal Anatomy The abdominal wall consists of skin, subcutaneous tissues, and a muscular layer that is divided into anterior, anterolateral, and posterior groups (Fig. 1). The anterior group consists of rectus abdominis muscles lying within the rectus sheath. The anterolateral group is formed by external and internal oblique and transversus abdominis muscles. Latissimus dorsi, quadratus lumborum, and paraspinal muscles make up the posterior group. The abdominal wall is separated from the peritoneum by the transversalisfascia and extrapentoneal fat [1]. Hernia Abdominal wall hernias may be difficult to diagnose clinically inobese patientsor in those who have acute abdominal pain and distensionor when the hernia is located in an uncommon site. CT readily detects the size, location, and content of paraumbilical, incisional, spigelian, and lumbar hernias (Figs. 2-4) [2]. CT may be used in the symptomatic patient for preoperative planning. Hematoma Pictorial Essay Abdominal wall hematomas may be associated with trauma, anticoagulation therapy, or blood dyscrasia or may occur spontaneously because of muscular strain. These commonly involve the anterior or anterolateral muscle groups and may dissect along fascial planes or involve the muscle itself. Acute hematomas are hyperdense because of clot formation, and attenuation values decrease with time as breakdown of blood products occurs (Figs. 5 and 6) [3]. Fig. 1.-Drawing shows axial section of normal anatomy of abdominal wall. Received December 11, 1989; accepted after revision January 22, 1990. Department of Radiology, The University of Texas Medical School at Houston, 6431 Fannin, 2134 MSMB, Houston, TX 77030. 2Prcoent address: Department of Radiology, University of Texas Medical Branch, Galveston, IX 77550. Address reprint requests to P. Goodman. AJR 154:1207-1211, June 1990 0361-803X/90/1 546-1 207 American Roentgen Ray Society
1208 GOODMAN AND RAVAL AJR:154, June 1990 Fig. 2.-Large incisional ventral hernia con- Fig. 3.-Hemiation of colon through right pos- Fig. 4.-Large spigelian hernia containing taming opacified bowel loops (arrows). terolateral abdominal wall incisional hernia (ar- bowel and Intraperitoneal fat (arrows), adjacent rows). to inferolateral aspect of right rectus abdominis muscle. Fig. 5.-Left rectus abdominis hematoma (straight arrows) In patient whose hemoglobin level dropped after cardiopulmonary resuscitation. Low-density area within hematoma represents clot lysls (curved arrow). Fig. 6.-Large abdominal wall hematoma occurred spontaneously In this patient on anticoagulant therapy. Fluid-fluid level representing hematocrlt effect Is present within hematoma (arrow). Fig. 7.-Large complex mass (arrow) is present adjacent to transplanted kidney. Patient had fever and chills that resolved after pus was drained from abdominal wall abscess. Fig. 8.-Low-density abscess (straight arrow) In right flank displaces right kidney. Increased density in adjacent subcutaneous fat represents Inflammatory edema (curved arrow). Fig. 9.-Long gas-fluid level (arrow) lies just deep to mesh graft In patient with postsurgical abscess after ventral hernia repair.
AJR:154, June 1990 CT OF THE ABDOMINAL WALL 1209 Fig. 10.-Well-defined low-density mass be- Fig. 11.-A and B, CT scans before (A) and after (B) administration of contrast material show tween left external and internal oblique muscles is enhancing soft-tissue mass (arrows) extending deep into subcutaneous tissues in child with hemana iipoma (arrow). gloma of the back. Fig. 12.-Diffuse infiltration of left rectus abdominis muscle by desmold tumor (arrows). Fig. 13.-Metastatic subcutaneous nodule In anterior abdominal wall from adenocarcinoma of the lung (arrow). Fig. 14.-irregular soft-tissue mass (straight arrows) in anterior abdominal wall adjacent to lowdensity area in liver (curved arrow). Subxiphold mass resected from this area 1 year caner was metastatic colonic carcinoma. Fig. 15.-Diffuse soft-tissue mass involving subcutaneous tissues and right paraspinal muscles is direct extension of sacral chordoma (arrows).
1210 GOODMAN AND RAVAL AJR:154, June 1990 Fig. 16.-Diffuse muscular atrophy with fatty Fig. 17.-Marked asymmetry of right flank In Fig. 18.-Irregular soft-tissue mass of left recreplacement (arrows) in patient with long history patient with previous massive soft-tissue injury tus sheath and adjacent subcutaneous tissue Is of limb-girdle muscular dystrophy. of the right flank and subsequent reconstructive endometriosis In a surgical scar (arrow). surgery. irregular posttraumatlc caicifications involve posterior abdominal wall (arrow). Fig. 19.-Diffuse streaky soft-tissue densities indicate edema in subcutaneous tissues associated with congestive heart failure. Abscess Inflammatory disease of the abdominal wall commonly resuits from postsurgical wound infection or extension of an intraabdominal abscess. Usually it involves the subcutaneous tissues or the muscular layer. When the usefulness of physical examination is limited, particularly in obese patients, CT is the method of choice to evaluate suspected abdominal wall infection.the CT findingsinclude diffuseedema with cellulitis or discrete fluidcollectionswhen abscess formation has occurred (Figs.7-9). Gas or gas-fluidlevelshave been reported to be present inapproximately 30% of abscesses [3,4]. Tumor Commonly encountered benign neoplasms of the abdominal wall include lipoma, hemangioma, and neurofibroma (Figs. Fig. 20.-Midline anterior abdominal wall kebid (asterisk). Fig. 21.-Tubular structure (arrow) In right anterolateral muscle group Is axiliofemoral bypass graft (confirmed by digital anglogram).
AJR:154, June 1990 CT OF THE ABDOMINAL WALL 1211 Fig. 22.-A and B, Extravasation of contrast material deep and superficial to abdominal wall muscles from extraperltoneal rupture of bladder. 1 0 and 1 1). Primary malignant lesions are rare and include soft-tissue sarcoma and lymphoma. Desmoid tumor, though histologically benign, is often locally aggressive (Fig. 12). Secondary malignancies of the abdominal wall occur as subcutaneous nodules by hematogenous spread. These are well visualized on CT because of contrast with adjacent fat (Fig. 1 3). Contiguous spread of a primary or metastatic lesion to the abdominal wall may cause infiltration of muscles and loss of adjacent fat planes (Figs. 14 and 15). These tumors usually arise in superficial organs such as the transverse colon, gallbladder, urinary bladder, and omentum. This is sometimes difficult to distinguish from extension of an intraabdominal abscess and may require percutaneous biopsy. CT is the method of choice for staging and follow-up of malignancies involving the abdominal wall and for directing percutaneous biopsy and placing radiotherapy ports [3, 4]. Miscellaneous Other abnormalities of the abdominal wall detected by CT are shown in Figures 16-22. REFERENCES 1. Fisch AE, Brodey PA. Computed tomography of the anterior abdominal wall: normal anatomy and pathology. J Comput Assist Tomogr 1981: 5:728-733 2. Wechsler RJ, Kurtz AB, Needleman L, et al. Cross-sectional imaging of abdominal wall hernias. AiR 1989:153:517-521 3. Heiken JP. Abdominal wall and pentoneal cavity. In: Lee JKT, Sagel SS, Stanley RJ, eds. Computed body tomography with MRI correlation. New Vork: Raven, 1989:661-705 4. Pandolfo I, Biandino A, Gaeta M, Racchiusa S, Chirico G. CT findings in palpable lesions of the anterior abdominal wall. J Comput Assist Tomogr 1986;10:629-633