AJR 2001; 176:1233-1239
© American Roentgen Ray Society
Cross-Sectional Imaging of Abnormalities of the Abdominal Wall in Pediatric Patients
Lane F. Donnelly1 and
Donald P. Frush2
1
Department of Radiology, Children's Hospital Medical Center, 3333 Burnet Ave.,
Cincinnati, OH 45229-3039.
2
Department of Radiology, Duke University Medical Center, Durham, NC
27710.
Received August 23, 2000;
accepted after revision September 20, 2000.
Address correspondence to L. F. Donnelly.
Introduction
Cross-sectional imaging with CT or MR imaging has been shown to be helpful
in depicting pathologic processes involving the abdominal wall
[1,2,3].
Primarily, CT and MR imaging may be performed to evaluate palpable lesions of
the abdominal wall [2]. In
addition, accurate identification of abnormalities of the anterior abdominal
wall may provide important diagnostic clues when imaging studies are performed
in a patient during an examination for intraabdominal disease. We review the
cross-sectional imaging features of pathologic processes of the abdominal wall
that we have encountered in our practice of pediatric body imaging. Processes
reviewed are grouped by causality—congenital, inflammatory, traumatic,
neoplastic, and vascular.
Congenital Lesions
Congenital abnormalities of the anterior abdominal wall include
omphalocele, gastroschisis, and bladder extrophy. These severe abnormalities
are obvious during the physical examination of a patient and are surgically
repaired. Postnatal cross-sectional imaging does not play a primary role in
the examination of these patients. However, these abnormalities may be
encountered when CT is performed to check for a potential intraabdominal
process after surgery (Fig.
1A,1B).
View larger version (120K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 1A. —Congenital anomalies of abdominal wall are revealed on CT
scans. Omphalocele in 8-day-old male neonate who underwent CT to be evaluated
for abscess after surgery. CT scan shows liver (L) protruding through defect
(arrows) in anterior abdominal wall.
|
|
View larger version (97K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 1B. —Congenital anomalies of abdominal wall are revealed on CT
scans. Infected urachal remnant in 4-year-old girl who underwent CT to
determine cause of abdominal pain and fever. CT scan shows heterogeneous mass
(arrows) in midline anterior to bladder. Note peripheral enhancement
and central low attenuation within mass.
|
|
One congenital lesion that may initially be detected on cross-sectional
imaging is a urachal abnormality. The urachus is an embryologic canal that
connects the apex of the bladder and the umbilicus. Normally, this canal
closes by the time of birth. If any portion of this embryologic structure
remains patent, a urachal abnormality results. The portion of the urachus that
remains patent determines the type of the urachal anomaly present. If the
urachus remains patent only at its mid portion and is closed both at its
umbilical and bladder ends, a urachal cyst is formed. Patients with urachal
cysts may present with a palpable mass, abdominal pain, tenderness, and fever,
or with symptoms of a urinary tract infection. When CT is performed to
determine the cause of the patient's abdominal pain, a cystic mass
anterosuperior to the bladder dome is revealed at the midline (Fig.
1A,1B).
MR imaging has been recommended as an aid in planning surgery for infants
with positive findings for prune-belly syndrome at examinations of their
abdominal walls [4].
Prune-belly syndrome, or Eagle-Barrett syndrome, is the name given to the
triad of hypoplasia of the abdominal muscles, cryptorchidism, and
abnormalities of the urinary tract system. The syndrome can be incomplete
(pseudo-prune-belly syndrome) occurring unilaterally or in girls. Determining
the extent of abdominal wall hypoplasia and contents of the eventration with
MR imaging has been advocated as being helpful in ascertaining the
practicality of cosmetic repair, particularly in patients with the incomplete
syndrome [4] (Fig.
2A,2B).
View larger version (141K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 2A. —Unilateral abdominal wall hypoplasia (pseudo-prune-belly
syndrome) in 2-week-old girl. Coronal T1-weighted MR image (TR/TE, 500/11)
shows outpouching (arrows) of abdominal wall in region of hypoplasia
of abdominal musculature. Vertebral anomalies are also visible.
|
|
View larger version (79K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 2B. —Unilateral abdominal wall hypoplasia (pseudo-prune-belly
syndrome) in 2-week-old girl. Axial T1-weighted MR image (500/11) shows
hypoplasia (arrows) of abdominal musculature and subcutaneous fat.
Note normal thickness of right abdominal muscles and subcutaneous fat.
|
|
Inflammatory Processes
Inflammation of the subcutaneous tissue and muscle of the abdominal wall
most commonly occurs after surgery or penetrating trauma
[5]. In children, the wound
infection is most commonly encountered after surgery for a ruptured appendix
(Fig.
3A,3B).
Wound infection may appear as a phlegmon, showing poorly defined areas of
soft-tissue attenuation within the subcutaneous fat and poorly defined
muscular borders, or the infection may appear as a discrete abscess, showing a
well-defined fluid collection often with enhancing margins
[6] (Fig.
3A,3B).
View larger version (93K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 3A. —CT scans reveal manifestations of wound infections. Wound
abscess in 14-year-old boy 12 days after surgery for ruptured appendix. CT
scan shows focal area of low attenuation (arrow) within subcutaneous
fat at surgical incision. Enhancing rim and gas within lesion are consistent
with abscess. Also note several intraabdominal inflammatory fluid collections
(arrowheads).
|
|
View larger version (163K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 3B. —CT scans reveal manifestations of wound infections.
Cellulitis without discrete abscess revealed in 14-year-old girl experiencing
pain and fever 10 days after surgical removal of ovarian cyst. CT scan shows
poorly defined soft-tissue attenuation (arrows) within subcutaneous
fat surrounding previous midline incision. No drainable fluid collection is
seen.
|
|
Inflammation may also extend into the abdominal wall from extension of
intraabdominal disease. In children, there may be abdominal inflammation
caused by perforative appendicitis, typhlitis, Crohn's disease
(Fig. 4), or pancreatitis. In
patients with pancreatitis, CT may reveal abdominal wall involvement as an
extension of inflammation and hemorrhage into the periumbilical area
(Grey-Turner's sign at physical examination) (Fig.
5A,5B,5C),
as an extension of inflammation into the flanks (Cullen's sign at physical
examination), or as areas of subcutaneous fat necrosis (Fig.
5A,5B,5C).
We have also seen dystrophic muscular calcification occurring in the abdominal
wall of children after episodes of extensive abdominal wall inflammation
(Fig. 6).
View larger version (100K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 4. —CT scan shows extension of inflammation into abdominal wall
from Crohn's disease and abscess in 15-year-old girl. Marked thickening of
descending colon (arrowhead) with surrounding phlegmon and abscess
are revealed. Note asymmetric thickening of left external abdominal oblique,
internal abdominal oblique, and transversus abdominis muscles (arrow)
compared with those on right.
|
|
View larger version (137K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 5A. —CT scans reveal abdominal wall manifestations of
pancreatitis. CT scan shows Grey Turner's sign in 15-year-old boy with
pancreatitis with extension of inflammation into transverse mesocolon and
thickening of colonic wall (arrows). Soft-tissue stranding in
subcutaneous fat of overlying abdominal wall (arrowheads) is
consistent with extension of inflammation.
|
|
View larger version (128K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 5B. —CT scans reveal abdominal wall manifestations of
pancreatitis. CT scan obtained at level just above umbilicus in same patient
as in A reveals extension of inflammation (arrow) to
periumbilical area.
|
|
View larger version (120K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 5C. —CT scans reveal abdominal wall manifestations of
pancreatitis. CT scan shows presumed subcutaneous fat necrosis in 16-year-old
boy with pancreatitis. Multiple areas of soft-tissue attenuation
(arrows) within subcutaneous fat of anterior and posterior abdominal
wall.
|
|
View larger version (102K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 6. —CT scan reveals abdominal wall calcifications formed after
inflammation from colitis (presumed typhlitis) in 6-year-old boy. Marked
thickening and calcifications involving right rectus abdominis, external
abdominal oblique, internal abdominal oblique, and transversus abdominis
muscles are identified by arrows. Residual thickening of hepatic flexure and
transverse colon (arrowheads) is present from previous episode of
colitis.
|
|
Primary infection of the abdominal wall is rare. However, necrotizing
myofascitis can occur, particularly in children with compromised immune
systems. It is a rapidly progressive soft-tissue infection characterized by
wide-spread necrosis. MR imaging is the modality of choice for the evaluation
of the extent of inflammation. When the infection involves the abdominal wall,
the patient may present with symptoms mimicking those of an acute abdomen, and
CT may be performed [6]. CT
shows soft-tissue density within muscle planes
(Fig. 7), low attenuation and
swelling of muscles, and, at times, soft-tissue gas. Without aggressive
treatment, the disease can result in death.
View larger version (108K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 7. —CT scan depicts necrotizing myofascitis in 15-year-old
immunocompromised boy who presented with acute abdominal pain and tenderness.
Fluid attenuation (arrows) surrounding left rectus abdominis,
external abdominal oblique, internal abdominal oblique, and transversus
abdominis muscles is visible. Note replacement of surrounding subcutaneous fat
with soft-tissue attenuation and similar but less prominent inflammation on
right side.
|
|
Traumatic Abnormalities
Traumatic injury can result in a number of abdominal wall abnormalities
that can be detected on CT, including laceration (Fig.
8A,8B,8C,8D),
hematoma, and contusion [1,
3]. Abdominal wall trauma may
be seen on imaging when CT is performed for evaluation of intraabdominal
injury after blunt trauma, distribution of injury in penetrating trauma (Fig.
8A,8B,8C,8D),
or other abdominal symptoms in patients for whom the history of trauma is
occult (abuse or spontaneous hematoma). One of the more common causes of
abdominal wall trauma in children is lap belt injury. In addition to
intraabdominal manifestations such as bowel injury, lap belt injuries can
cause contusion or hematoma of the anterior abdominal wall or transection of
the musculature [7] (Fig.
8A,8B,8C,8D).
Rectus sheath hematoma may occur spontaneously or after minor trauma, and its
manifestations may be occultly present, with the patient reporting abdominal
pain and tenderness [3]. The
diagnosis may not be considered clinically, and the lesion may be first
identified when the patient undergoes CT
(Fig. 9). Traumatic injury may
also be iatrogenic (Fig.
10A,10B).
Causes of abdominal wall abnormalities after surgery include hematoma, edema,
or hernia [5] (Fig.
10A,10B).
View larger version (113K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 8A. —CT scans reveal manifestations of abdominal wall trauma.
Degloving injury of abdominal wall in 12-year-old boy after trauma from lap
belt. CT scan shows absence of portion of subcutaneous tissues that extends to
level of abdominal musculature (arrow). Underlying structures appear
to be uninvolved.
|
|
View larger version (106K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 8B. —CT scans reveal manifestations of abdominal wall trauma.
Penetrating injury from gunshot in 14-year-old boy. CT scan reveals
subcutaneous gas, abnormal soft-tissue density replacing subcutaneous fat, and
metal density fragments within subcutaneous tissues of left abdominal wall
(arrows). There was no evidence of involvement of peritoneal
cavity.
|
|
View larger version (125K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 8C. —CT scans reveal manifestations of abdominal wall trauma.
Transection of abdominal musculature in 10-year-old boy after lap belt injury.
CT scan shows marked thickening and indistinctness (arrows) of right
rectus abdominis, external abdominal oblique, internal abdominal oblique, and
transversus abdominis muscles compared with musculature on left. Muscles are
discontinuous from anterior to posterior with gap containing herniated fat
(arrowheads). Note large surrounding hematoma.
|
|
View larger version (124K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 8D. —CT scans reveal manifestations of abdominal wall trauma. CT
scan more inferior in same patient as in C reveals areas of high
attenuation (arrows) consistent with active arterial extravasation
into region of hematoma.
|
|
View larger version (144K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 10A. —CT scans reveal iatrogenic causes of abdominal wall
abnormalities Anterior abdominal pain in 12-year-old girl undergoing
peritoneal dialysis was caused by leaking dialysis fluid. CT scan shows poorly
defined soft-tissue attenuation (arrows) in subcutaneous fat in right
anterior abdominal wall. Note dialysis catheter (arrowhead).
|
|
View larger version (128K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 10B. —CT scans reveal iatrogenic causes of abdominal wall
abnormalities Postsurgical hernia in 8-year-old boy with remote history of
splenectomy. CT scan shows lateral hernia (arrows) containing
bowel.
|
|
Neoplastic and Vascular Masses
A number of benign and malignant masses can involve the abdominal wall. We
typically use MR imaging to examine a patient with a palpable mass. One of the
most common benign masses to involve the abdominal wall in children is a
hemangioma or vascular malformation. Hemangiomas are the most common
soft-tissue mass seen in children. MR imaging of proliferating hemangiomas
(Fig.
11A,11B)
typically shows a discrete lobulated mass that is hyperintense on T2-weighted
MR images and typically enhances diffusely with the administration of
gadolinium [8]. There may be
large draining veins. Other vascular malformations that involve the abdominal
wall are typically lowflow vascular malformations, such as venous or lymphatic
malformations. The appearance of a low-flow vascular malformation on MR images
depends on the composition of lymphatic and venous components
[8] (Fig.
11A,11B).
Other benign masses encountered in children include lipomas and neurofibromas
(Fig.
12A,12B).
With type I neurofibromatosis, numerous neurofibromas may be present in the
abdominal wall of patients (Fig.
12A,12B).
View larger version (64K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 11A. —MR images reveal vascular malformations causing focal
abdominal wall masses in children. Axial gadolinium-enhanced fat-saturated
T1-weighted MR image (TR/TE, 600/11) shows hemangioma presenting as palpable
mass in 3-month-old female infant. Plaquelike mass (arrow) showing
diffuse enhancement is confined to subcutaneous tissues.
|
|
View larger version (107K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 11B. —MR images reveal vascular malformations causing focal
abdominal wall masses in children. Axial T1-weighted MR image (666/12) shows
lymphatic malformation involving abdominal wall of 1-year-old boy.
Multiloculated mass involves subcutaneous tissues of right posterior abdominal
wall. Note overlying skin thickening (arrows). Lesion is confined to
subcutaneous tissues. T2-weighted image (not shown) revealed mass
(arrows) to be diffusely high in signal intensity.
|
|
View larger version (94K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 12A. —CT scan and MR image of other causes of benign abdominal wall
lesions. CT scan of 5-year-old girl with lipoma shows asymmetric thickening of
subcutaneous fat (L) consistent with lipoma.
|
|
View larger version (94K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 12B. —CT scan and MR image of other causes of benign abdominal wall
lesions. Axial T2-weighted MR image (TR/TE, 5000/90) shows multiple
high-signal-intensity masses (arrows)—multiple
neurofibromas—within abdominal wall in 16-year-old girl with
neurofibromatosis. Note paraspinal masses (arrowheads).
|
|
In children, malignant lesions of the abdominal wall may be primary
soft-tissue malignancies such as rhabdomyosarcoma (Fig.
13A,13B,13C,13D)
or may represent metastatic disease. The most common cause of metastasis to
the soft tissues in children is neuroblastoma (Fig.
13A,13B,13C,13D).
View larger version (107K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 13A. —MR images and CT scan of malignant abdominal wall lesions.
Axial T1-weighted MR image (TR/TE, 600/11) shows well-defined round mass
(arrow) within subcutaneous fat posterior to right iliac wing in
15-year-old girl with undifferentiated sarcoma. Mass is slightly higher in
signal intensity than adjacent muscle.
|
|
View larger version (101K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 13B. —MR images and CT scan of malignant abdominal wall lesions.
Axial T2-weighted fat-saturated MR image (2000/80) of same patient as in
A shows mass (arrow) to be heterogeneously high in signal
intensity.
|
|
View larger version (123K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 13C. —MR images and CT scan of malignant abdominal wall lesions.
Axial T2-weighted MR image (2000/80) obtained with fat saturation shows
multiple high-signal-intensity masses (arrows) involving right
lateral abdominal wall adjacent to large adrenal mass (M) in 2-year-old girl
with neuroblastoma involving abdominal wall.
|
|
View larger version (111K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 13D. —MR images and CT scan of malignant abdominal wall lesions. CT
scan shows unsuspected soft-tissue density mass (arrow) within
subcutaneous tissues of posterior abdominal wall in 16-year-old boy with
metastatic rhabdomyosarcoma to abdominal wall.
|
|
Other Vascular-Related Abnormalities
Other abnormalities that may be found within the abdominal wall during
imaging include those of vascular etiology. In case of inferior vena cava
obstruction or portal hypertension, collateral veins may be seen within the
abdominal wall (Fig.
14A,14B).
The identification of the vessels may aid in differentiating a thrombosed
inferior vena cava from a nonopacified, nonobstructed inferior vena cava on
contrast-enhanced CT scans. The abdominal wall may also show signs of
anasarca, or edema, from any of a number of vascular causes (Fig.
14A,14B).
This edema will appear as replacement of the subcutaneous fat with soft-tissue
attenuation, often more prominent in the posterior, dependent portions of the
abdominal wall. Diffuse muscular atrophy caused by neurologic deficits may
also be evident on cross-sectional imaging
(Fig. 15).
View larger version (105K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 14A. —CT scans of abdominal wall abnormalities with vascular
causes. CT scan shows venous collaterals within abdominal wall of 8-year-old
girl with thrombosis of inferior vena cava. Multiple enhancing venous
collaterals (arrows) within subcutaneous tissues of abdominal wall
are visible. Clot is identified in inferior vena cava
(arrowhead).
|
|
View larger version (134K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 14B. —CT scans of abdominal wall abnormalities with vascular
causes. CT scan reveals marked subcutaneous edema in 5-year-old girl with
Henoch-Schönlein purpura. Soft-tissue
attenuation consistent with fluid adjacent to abdominal wall musculature can
be seen in reticular pattern throughout subcutaneous tissues. Edema is most
prominent in dependent posterior positions (arrows).
|
|
View larger version (156K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 15. —CT scan obtained to evaluate renal calculi in 14-year-old
girl with muscular atrophy and history of myelomeningocele shows marked
atrophy of the abdominal wall and paraspinal musculature. Note spinal
dysraphism (arrow).
|
|
In summary, a number of abnormalities can occur in the abdominal wall of
children. Accurate identification of abnormalities of the anterior abdominal
wall is important when imaging is performed to evaluate either abdominal wall
or intraabdominal lesions.
References
-
Stamm ER, Pretorius DH, Olson LK. Abdominal wall CT: a pictorial
essay. Comput Radiol
1985;9:271
-278[Medline]
-
Pandolfo I, Blandino 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[Medline]
-
Goodman P, Raval B. CT of the abdominal wall.
AJR
1990;154:1207
-1211[Free Full Text]
-
Donnelly LF, Johnson JF III. Unilateral abdominal wall hypoplasia:
radiographic findings in two infant girls. Pediatr
Radiol 1995;25:278
-281[Medline]
-
Donnelly LF, Frush DP, O'Hara SM, Bisset GS III. Necrotizing
myofasciitis: an atypical cause of "acute abdomen" in an
immunocompromised child. Pediatr Radiol
1998;28:109
-111[Medline]
-
Ghahremani GG, Gore RM. CT diagnosis of postoperative abdominal
complications. Radiol Clin North Am
1989;27:787
-804[Medline]
-
Hayes CW, Conway WF, Walsh JW, Coppage L, Gervin AS. Seat belt
injuries: radiologic findings and clinical correlation.
RadioGraphics
1991;11:23
-36[Abstract]
-
Meyer JS, Hoffer FA, Barnes PD, Mulliken JB. Biological
classification of soft-tissue vascular anomalies: MR correlation.
AJR
1991;157:559
-564[Free Full Text]
CiteULike 
Complore 
Connotea 
Del.icio.us 
Digg 
Reddit 
Technorati What's this?
This article has been cited by other articles:
|
|
|
|
 
D. J. Emby and G. Aoun
CT Technique for Suspected Anterior Abdominal Wall Hernia
Am. J. Roentgenol.,
August 1, 2003;
181(2):
431 - 433.
[Full Text]
[PDF]
|
|
|
Top
Introduction
Congenital Lesions
