Pictorial Essay. Abdominal Wall Hernias: MDCT Findings. Diego A. Aguirre1, Giovanna Casola, Claude Sirlin

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1 Downloaded from by on 11/29/17 from IP address Copyright RRS. For personal use only; all rights reserved Pictorial Essay bdominal Wall Hernias: MDCT Findings Diego. guirre1, Giovanna Casola, Claude Sirlin bdominal wall hernias account for most external hernias [1 3]. Diagnosis is usually made at physical examination; however, clinical diagnosis can be difficult, especially in patients with obesity, pain, or abdominal wall scarring [4]. In these cases, abdominal imaging may be the first clue to the correct diagnosis. In the past, conventional radiographs or barium studies were predominantly used in confirming or excluding abdominal wall hernias; currently, CT has assumed a dominant role. dvantages of CT include more accurate identification of abdominal wall hernias and their contents, differentiation of hernias from other abdominal Fig year-old woman with cirrhosis and indirect inguinal hernia, abdominal pain, distention, and palpable mass in left groin., xial contrast-enhanced reformatted MDCT image obtained through level of symphysis pubis shows left indirect inguinal hernia containing thickened and dilated small-bowel loops (arrows) with radiating mesenteric fat stranding (arrowhead) indicative of incarceration. In this case, prominent subcutaneous collaterals related to patient cirrhosis made identification of epigastric vessels difficult., Oblique coronal 3D volume-rendered MDCT image obtained through hernia shows incarcerated smallbowel loops and ascitic fluid in hernia sac (arrows). C, Sagittal reformatted MDCT image obtained through left groin delineates size of defect and hernia sac. gain note prominent vascularity (arrows) in abdominal wall secondary to portal hypertension. C Received November 19, 2003; accepted after revision March 9, ll authors: Department of Radiology, University of California, San Diego, 200 W rbor Dr., San Diego, C ddress correspondence to D.. guirre (daguirre@ucsd.edu). JR 2004;183: X/04/ merican Roentgen Ray Society JR:183, September

2 Downloaded from by on 11/29/17 from IP address Copyright RRS. For personal use only; all rights reserved guirre et al. Fig year-old woman with direct inguinal hernia and small-bowel obstruction secondary to incarcerated left direct inguinal hernia., xial contrast-enhanced reformatted MDCT image obtained at level of symphysis pubis shows bilateral inguinal hernias containing small-bowel loops (black arrows). Note epigastric vessels (white arrows) displaced anteriorly by hernia sacs. In multiple images on monitor, hernia sacs were medial to vessels consistent with direct inguinal herniation., Coronal reformatted MDCT image shows dilation of intraabdominal loops (black arrows) with protrusion of small-bowel loops and ascitic fluid through wall defect (white arrow). Notice that left hernia sac is located medial to epigastric vessels (arrowhead), diagnostic of direct herniation. C, Sagittal oblique MDCT image obtained through left inguinal hernia shows abdominal wall defect with herniation of dilated small bowel (large arrow). Note multiple small-bowel air fluid levels (small arrows) secondary to obstruction caused by incarcerated hernia. C Fig year-old man with femoral hernia and history of rectal cancer who presented with mass in left femoral region., xial contrast-enhanced reformatted MDCT image obtained through symphysis pubis shows left femoral hernia, containing properitoneal fat (arrow) medial to femoral vessels (arrowhead) protruding into upper thigh. Compare with other side, where no hernia sac is seen. Note bulky rectal mass., Sagittal oblique reformatted MDCT image shows that defect originates in attachment of fascia transversalis to pubis (arrow). 682 JR:183, September 2004

3 Downloaded from by on 11/29/17 from IP address Copyright RRS. For personal use only; all rights reserved MDCT of bdominal Wall Hernias Fig year-old woman with cirrhosis who presented with umbilical hernia., xial volume-rendered MDCT image obtained through umbilicus shows voluminous hernia sac containing properitoneal fat and ascitic fluid (arrowhead) related to underlying cirrhosis; ascites (not shown) was also present in upper abdomen. Mass was not palpable clinically, perhaps because of thickness of subcutaneous adipose tissue., Sagittal volume-rendered MDCT reformation obtained through umbilicus shows defect in abdominal wall with protrusion of herniated sac into subcutaneous tissue (arrow). masses (tumors, hematomas, abscesses, undescended testes, and aneurysms), and detection of complications (incarceration, bowel obstruction, volvulus, and strangulation) [1 3]. CT is also useful in evaluating postsurgical patients, especially those with enlarging masses or exuberant scars. In markedly obese patients, CT helps determine the shape, location, and content of abdominal wall hernias. MDCT has the potential to further advance the preoperative assessment of these hernias. y permitting rapid acquisition of 3D image data sets and exquisite multiplanar reforma- tions, MDCT precisely delineates hernia type, location, size, and shape. In addition, because of its superior anatomic detail, MDCT may potentially detect subtle signs of strangulation, such as mesenteric stranding, poor bowel wall enhancement, wall thickening, free air, or fluid in the hernia sac. This pictorial essay reviews common abdominal wall hernias with emphasis on important pathogenic and demographic factors, characteristic CT appearance and diagnosis, and use of MDCT and multiplanar reforma- tions to aid in diagnosis and enhance communication of findings to referring physicians. MDCT Technique Supine images were acquired from the diaphragm to the pubic symphysis (table speed, 10 mm/sec; collimation, 2.5 mm) during a single breath-hold and reconstructed at 2.5-mm intervals. Multiplanar reformations were obtained on a workstation (Vitrea 2, Vital Images). Postural maneuvers (e.g., prone or lateral decubitus positioning) and maneuvers Fig year-old man with history of previously repaired paraumbilical hernia who presented with enlarging mass in umbilical area., xial contrast-enhanced reformatted MDCT image obtained through umbilicus shows diastasis and atrophy of rectus abdominis muscles with protrusion of omental fat into abdominal wall (arrowheads) on both sides of umbilicus, consistent with bilateral paraumbilical hernias., Sagittal volume-rendered MDCT image shows wall defect in umbilical area (arrow) immediately inferior to mesh in supraumbilical region (arrowheads) from previous hernia repair. JR:183, September

4 Downloaded from by on 11/29/17 from IP address Copyright RRS. For personal use only; all rights reserved guirre et al. Fig year-old obese woman with multiple previous abdominal surgeries who presented with periumbilical mass., xial contrast-enhanced reformatted MDCT image obtained immediately superior to umbilicus shows diastasis of rectus muscles and protrusion of properitoneal and mesenteric fat into subcutaneous tissue (arrow)., xial reformatted MDCT image obtained inferior to umbilicus shows separate diastasis of rectus abdominis muscles with protrusion of contrast material filled small-bowel loops into subcutaneous tissue (arrowheads). C, Sagittal 3D volume-rendered MDCT image shows complex anatomy of paraumbilical hernia, with component above umbilicus (arrow) and second component below umbilicus (arrowhead). C Fig year-old man with no previous surgeries who presented with epigastric mass., xial reformatted MDCT image obtained through level of kidneys shows midline defect in anterior abdominal wall with diastasis of rectus muscles and protrusion of omental fat (arrowheads). Note close relationship of hernia to transverse colon., Sagittal reformatted midline MDCT image shows wall defect (arrow) between xiphoid process and umbilicus (arrowhead). 684 JR:183, September 2004

5 MDCT of bdominal Wall Hernias Downloaded from by on 11/29/17 from IP address Copyright RRS. For personal use only; all rights reserved Fig year-old woman with left flank mass. xial MDCT image obtained at level below umbilicus shows protrusion of mesenteric fat through defect in left linea semilunaris, characteristic of spigelian hernia (arrowheads). Subcutaneous hernia sac can be confused with abdominal wall lipoma if muscular defect is not recognized. Clinical diagnosis is extremely difficult in these patients. Fig year-old woman with history of cholecystectomy who now has mass at incision site as spigelian incisional hernia., Oblique coronal 3D reformatted MDCT image shows abnormal protrusion of colon (arrow) and right hepatic lobe (arrowhead) through abdominal wall defect., xial MDCT image obtained at level of kidneys shows hernia sac protruding between right rectus abdominis muscle (arrow) and aponeuroses of right transversus abdominis and internal oblique muscles (arrowheads), consistent with spigelian hernia. Fig. 10. Diagram shows distribution of lumbar triangles. Coronal reformatted MDCT image obtained through dorsal aspect of abdominal wall shows superior lumbar triangle (double asterisk) bordered superiorly by 12th rib, laterally and anteriorly by internal oblique muscle (arrowhead), and posteriorly by erector spinal muscle (ES). Inferior lumbar triangle (single asterisk) is shown on right side, bordered inferiorly by iliac crest, laterally and anteriorly by external oblique muscle (arrow), and posteriorly by latissimus dorsi muscle (LD). JR:183, September

6 Downloaded from by on 11/29/17 from IP address Copyright RRS. For personal use only; all rights reserved guirre et al. Fig year-old man after motor vehicle crash., xial contrast-enhanced reformatted MDCT image obtained through lower pole of kidneys shows right perirenal hematoma (arrowheads). On left side, posterior herniation of descending colon (arrow) is noted with adjacent soft-tissue stranding, consistent with traumatic lumbar herniation., Sagittal 3D volume-rendered MDCT image reveals protrusion of descending colon into posterior abdominal wall (arrowheads) in superior lumbar triangle, characteristic of Grynfeltt Lesshaft hernia (most frequent lumbar hernia). to increase intraabdominal pressure (e.g., straining or Valsalva maneuver) were not routinely performed, although they may help depict subtle anterior hernias [5]. Groin Hernias Inguinal Hernias Indirect inguinal hernias are by far the most common abdominal wall hernias, constituting approximately 66% of surgically repaired hernias in the United States [6]. They result from herniation through a patent processus vaginalis and hence are located lateral to the inferior epigastric vessels [7]. They are responsible for almost all inguinal hernias in children and are more common in men, because the peritoneal extension accompanying the testis often fails to obliterate. In adults, they are caused by acquired weakness and dilation of the internal inguinal ring [3] (Fig. 1). In contrast, direct inguinal hernias are caused by acquired weakness of the transversalis fascia and hence are located medial to the inferior epigastric vessels. They are commonly seen in men years old and are often bilateral [7] (Fig. 2). Femoral Hernias Femoral hernias are far less frequent than inguinal hernias and are especially rare in children. They occur more commonly in women and, for unclear reasons, have a tendency to be right-sided [2]. They arise from a defect in the attachment of the transversalis fascia to the pubis and thus occur medial to the femoral vein and posterior to the inguinal ligament [7] (Fig. 3). They are difficult to differentiate from inguinal hernias and have a high tendency to incarcerate [2, 8]. Ventral Hernias Ventral hernias include all hernias through the anterior and lateral abdominal wall, apart from inguinal hernias. Midline Defects Midline defects include umbilical, epigastric, and hypogastric hernias. During the em- Fig year-old woman with previous left nephrectomy for renal cell carcinoma who presented with bulging mass in incision area as lumbar hernia., xial contrast-enhanced reformatted MDCT image obtained through lower pole of right kidney shows defect in abdominal wall at inferior lumbar triangle, with protrusion of small bowel into subcutaneous tissue (arrow)., Coronal volume-rendered MDCT image shows protrusion of small-bowel loops into inferior lumbar triangle (arrow) below 12th rib (arrowhead) through site of previous nephrectomy incision, consistent with inferior lumbar (Petit s) incisional hernia. 686 JR:183, September 2004

7 Downloaded from by on 11/29/17 from IP address Copyright RRS. For personal use only; all rights reserved MDCT of bdominal Wall Hernias Fig year-old woman with previous right nephrectomy who presented with right abdominal bulge as incisional hernia., xial contrast-enhanced reformatted MDCT image obtained through inferior pole of left kidney shows defect in right internal oblique muscle, with protrusion of contrast material filled small-bowel loops into abdominal wall (arrow)., Oblique coronal volume-rendered MDCT image shows protrusion of intraabdominal content through incisional scar into abdominal wall (arrow). bryonic period, the abdominal contents herniate through the umbilicus and normally return into the abdominal cavity by the 10th week of gestation. Closure of this physiologic abdominal wall defect may be incomplete at birth. Many neonates have a small umbilical hernia, but most of these close spontaneously during infancy or childhood. In adults, umbilical hernias are usually acquired, occur 10 times more frequently in women, and represent the second most common surgically repaired hernia in the United States [6]. Risk factors include multiple pregnancies, ascites, obesity, and large intraabdominal masses [2, 7] (Fig. 4). Umbilical hernias do not reduce spontaneously and have a high prevalence of incarceration and strangulation. lthough in some cases no bowel content is seen in the hernia sac, torsion of the fat vascular pedicle can cause acute abdominal symptoms. paraumbilical hernia is a protrusion through the linea alba in the region of the umbilicus (Fig. 5) and is usually related to diastasis of the rectus abdominis muscles [3] (Figs. 6 and 6). Hypogastric hernias occur below the umbilicus and often undergo incarceration or strangulation [9] (Fig. 6C). Epigastric hernias are uncommon. They appear on the linea alba between the umbilicus and the xiphoid process and contain properitoneal fat; vascular structures; and, uncommonly, abdominal viscera [7, 9] (Fig. 7). Epigastric hernias are usually occult in obese patients, and their symptoms may mimic peptic ulcer or gallbladder disease [9]. Lateral Defects Spigelian hernias occur through a defect in the linea semilunaris, a fibrous union of the rectus sheath with the aponeuroses of the transverse and oblique abdominal muscles that extends from the level of the ninth costal cartilage to the symphysis pubis; wall defects are often secondary to acquired weakness of the aponeurosis (Fig. 8) or surgical incisions (Fig. 9). Fig year-old man with history of partial colectomy for colon carcinoma who presented with enlarging mass next to colostomy in left flank as parastomal hernia. xial contrast-enhanced reformatted MDCT image obtained through lower abdomen shows parastomal herniation of small bowel (arrowhead) adjacent to colonic stoma (arrow). JR:183, September

8 Downloaded from by on 11/29/17 from IP address Copyright RRS. For personal use only; all rights reserved guirre et al. Fig year-old woman who presented with bulging masses in both lower quadrants., xial reformatted MDCT image obtained through subumbilical area shows bilateral defects in abdominal wall with protrusion of small-bowel loops and mesenteric fat into intermuscular plane between internal (solid arrowheads) and external oblique (open arrowheads) muscles characteristic of interparietal hernias., xial reformatted MDCT image obtained through neck of right-sided hernia shows protrusion of mesenteric fat, vessels, and bowel loops (arrow) into interparietal hernia sac. Typically, the omentum and short segments of bowel protrude through the hernia defect [1, 3] (Fig. 8) and have a high frequency of incarceration [1, 9]. They characteristically traverse the complete thickness of abdominal wall muscles, in contrast to interparietal hernias in which the hernia sac is confined between muscular layers. Posterior Defects Lumbar hernias occur spontaneously, postsurgically or secondary to trauma, especially after pelvic fracture. Herniation can occur either through defects in the lumbar muscles or the posterior fascia (transversalis or lumbodorsal) in the superior (Grynfeltt-Lesshaft) or inferior (Petit s) lumbar triangles (Fig. 10). Fig year-old man who presented with abdominal distention as Richter s-type umbilical hernia. xial contrast-enhanced reformatted MDCT image obtained through mid abdomen shows dilatation of small-bowel loops with numerous air fluid levels. t level of umbilicus, protrusion of antimesenteric wall of dilated small-bowel loop is seen (arrowheads) without involvement of opposite wall (arrows), characteristic of Richter s hernia. This patient had small-bowel obstruction caused by adhesions in distal ileum, and Richter s hernia was incidental. 688 The Grynfeltt-Lesshaft triangle is bordered by the 12th rib superiorly, the internal oblique muscle anteriorly, and the erector spinal muscle posteriorly and constitutes the most common location for lumbar hernias (Fig. 11). Petit s triangle is bordered by the external oblique muscle anteriorly, the latissimus Fig year-old woman with vague pelvic pain from pelvic floor hernia. xial CT image of lower pelvis shows bowel loops in right ischiorectal fossa (arrowheads) consistent with sciatic hernia. These rare hernias are usually caused by abnormal development or atrophy of piriform muscle. Sac may contain small bowel, urinary bladder, ovary, ureters, or colon. Sciatic hernia also is known as sacrosciatic, ischiatic, or gluteal hernia (hernia incisurae, ischiadicae, and ischiocele). JR:183, September 2004

9 MDCT of bdominal Wall Hernias Downloaded from by on 11/29/17 from IP address Copyright RRS. For personal use only; all rights reserved Fig year-old woman with abdominal distention. xial CT image obtained through pelvic floor shows artifact from bilateral hip prosthesis. Note fluid-filled bowel loops lateral to right obturator foramen (arrowhead), characteristic of obturator hernia. These rare hernias are mainly seen in older patients. dorsi muscle posteriorly, and the iliac crest inferiorly (Fig. 12). Diffuse lumbar hernias, a third type, are most often iatrogenic, usually occurring after flank incisions for kidney operations [1, 10]. owel loops, retroperitoneal fat, kidneys, or other viscera can protrude through the hernia defect. Incarceration and strangulation may occur [1]. Incisional Hernias Incisional hernias are delayed complications of abdominal surgery and occur in % of patients in reported series [4]. Most incisional hernias develop during the first months after surgery; however, 5 10% may re- main clinically silent for up to 5 years until detection [4]. These hernias are more common with vertical rather than transverse incisions, but they can also develop through small laparoscopic puncture sites [4, 7]. Risk factors for incisional hernias include old age, obesity, postoperative wound infection, chronic pulmonary disease, ascites, malignant tumor, and malnutrition (Fig. 13). Parastomal hernias are considered a form of incisional hernia. They occur adjacent to a stoma and are aggravated by factors such as obesity, malnutrition, chronic cough, or abdominal distention [9]. Clinical evaluation is difficult, and CT shows bowel loops protruding through the wall defect at the stomal site (Fig. 14). Other Hernias Less commonly encountered are interparietal, Richter s, and Littre s hernias in the abdominal wall; and sciatic, obturator, and perineal hernias in the pelvis. Interparietal or interstitial hernias (Fig. 15) are rare acquired hernias, most commonly found in the inguinal region, located in the fascial planes between the abdominal wall muscles (typically the external and internal obliques) without exiting into the subcutaneous tissue. Incarceration of herniated bowel is a common complication. In a Richter s hernia, only the antimesenteric wall of the bowel is herniated, without compromising its entire lumen (Fig. 16). Usually these cause symptoms stemming from Fig. 19. Three-dimensional maximum-intensity-projection reformations of osseous pelvis show distribution of pelvic hernias. and, nterior () and lateral () projections show distribution of perineal (vertical arrow), obturator (oblique arrow), and sciatic hernias (curved arrow). JR:183, September

10 guirre et al. Downloaded from by on 11/29/17 from IP address Copyright RRS. For personal use only; all rights reserved strangulation and occur most frequently in femoral hernias or trocar sites after laparoscopic surgery [11]. hernia containing a Meckel s diverticulum characterizes a Littre s hernia [12], also known as a persistent omphalomesenteric duct hernia, most frequently encountered in the inguinal region. Sciatic hernias pass through the greater or lesser sciatic foramen, most commonly involving the small bowel or the distal ureter (Fig. 17). Obturator hernias are rare, occur primarily in elderly women, and have high predisposition for incarceration. Protrusion of the peritoneal sac through the obturator foramen and extension between the pectineal and obturator muscles are characteristic [1] (Fig. 18). Perineal hernias are uncommon and tend to occur in older women with acquired weakness of the pelvic floor. These hernias are usually adjacent to the anus, the labia majora, or the gluteal region (Fig. 19). Conclusion Radiologists should assess the abdominal wall on all CT scans to detect clinically occult hernias. If a hernia is detected, it is important to delineate its site, size, contents, shape, and related complications. MDCT with multiplanar reformations provides a unique perspective on abdominal anatomy, shows wall defects to best advantage, and adds important information in the interpretation and planning of treatment. References 1. Miller P, Mezwa DG, Feczko PJ, Jafri ZH, Madrazo L. Imaging of abdominal hernias. RadioGraphics 1995;15: Zarvan NP, Lee FT Jr, Yandow DR, Unger JS. bdominal hernias: CT findings. JR 1995;164: Lee GH, Cohen J. CT imaging of abdominal hernias. JR 1993;161: Ghahremani GG, Jimenez M, Rosenfeld M, Rochester D. CT diagnosis of occult incisional hernias. JR 1987;148: Emby DJ, oun G. CT Technique for suspected anterior abdominal wall hernia. JR 2003;181: Rutkow IM. Demographic and socioeconomic aspects of hernia repair in the United States in Surg Clin North m 2003;83: Harrison L, Keesling C, Martin NL, Lee KR, Wetzel LH. bdominal wall hernias: review of herniography and correlation with cross-sectional imaging. RadioGraphics 1995;15: Rettenbacher T, Hollerweger, Macheiner P, et al. bdominal wall hernias: cross-sectional imaging signs of incarceration determined with sonography. JR 2001;177: Stabile Ianora, Midiri M, Vinci R, Rotondo, ngelelli G. bdominal wall hernias: imaging with spiral CT. Eur Radiol 2000;10: Goodman P, Raval. CT of the abdominal wall. JR 1990;154: Matthews D, Heniford T, Sing RF. Preperitoneal Richter hernia after a laparoscopic gastric bypass. Surg Laparosc Endosc Percutan Tech 2001;11: Lauschke H, Kaminski M, Stratmann H, Nirner. Littré s hernia: clinical aspects and review of the history [in German].Chirurg 1999;70: JR:183, September 2004