ANATOMIC BASES OF MEDICAL, RADIOLOGICAL AND SURGICAL TECHNIQUES

MDCT of abdominal wall lumbar hernias: anatomical review,pathologic findings and differential diagnosis

Joaquın Martın • Jose Marıa Mellado •

Susana Solanas • Nerea Yanguas • Javier Salceda •

Marıa Rosa Cozcolluela

Received: 24 November 2011 / Accepted: 13 January 2012 / Published online: 4 February 2012

� Springer-Verlag 2012

Abstract

Purpose To review the anatomical landmarks of the

abdominal wall lumbar region and its normal appearance

on multidetector computed tomography (MDCT) and to

briefly describe the MDCT features of lumbar hernias.

Methods We performed a retrospective search of the

imaging report database from November 2007 to October

2011. We retrieved the clinical data and MDCT studies of

patients suffering from abdominal wall lumbar hernias. We

reviewed the imaging features of abdominal lumbar hernias

and compared those with the normal appearance of the

lumbar region in asymptomatic individuals.

Results We classified lumbar wall hernias as diffuse,

superior (or Grynfelt–Lesshaft) and inferior (or Petit)

lumbar hernias. We briefly describe the imaging features of

each subtype and review the anatomy and MDCT appear-

ance of normal lumbar region.

Conclusions Currently available MDCT provides an

excellent opportunity for reviewing the normal anatomy of

the wall lumbar region and may be considered a useful

modality for evaluating lumbar hernias.

Keywords Abdominal wall � Lumbar region � Lumbar

hernia � Computed Tomography � MDCT

Introduction

Lumbar hernias (LH) are rare defects of the dorsolateral

abdominal wall. They are defined as protrusions of extra-

peritoneal fat, with or without peritoneum and visceral

contents. Specific sites of anatomical weakness within the

lumbar region are particularly predisposed to the formation

of LH. These are the superior (Grynfelt-Lesshaft) and

inferior (Petit) lumbar triangles. According to their etiol-

ogy, LH may be congenital or acquired. Congenital LH

appear during infancy and associate with other malforma-

tions. Acquired LH may be spontaneous, posttraumatic or

postoperative. According to their contents, LH may be

extraperitoneal, paraperitoneal or intraperitoneal [10].

Lumbar hernias (LH) may remain asymptomatic or

cause pain and palpable lump. Gastrointestinal symptoms

and urinary obstruction may occur, posing a significant

challenge on clinical diagnosis [7, 11]. In the past, com-

puted tomography (CT) was found useful for depiction of

LH [4–6, 9]. More recently, multidetector computed

tomography (MDCT) has become the modality of choice

for evaluating abdominal wall hernias [1, 2] and may be

particularly helpful for assessing LH.

Consequently, our purpose is to review the anatomical

landmarks of the lumbar region and its normal appearance

on MDCT studies. We also review the MDCT features of

LH and their differential diagnosis.

Materials and methods

We performed a retrospective search of our imaging report

database from November 2007 to October 2011 and

reviewed those MDCT studies of patients suffering

abdominal wall lumbar hernias.

J. Martın (&) � J. M. Mellado � S. Solanas � N. Yanguas �J. Salceda � M. R. Cozcolluela

Department of Radiology, Hospital Reina Sofıa,

Ctra Tarazona km 3, 31500 Tudela, Navarra, Spain

e-mail: jmcuar@hotmail.com

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Surg Radiol Anat (2012) 34:455–463

DOI 10.1007/s00276-012-0937-8

All of our studies were performed in a 64-slice MDCT

(Aquilion 64, Toshiba Medical Systems), using a conven-

tional contrast-enhanced abdominal protocol. Acquisition

was performed in a craniocaudal direction after IV

administration of 90–120 ml of non-ionic contrast medium

at flow rate of 3 ml/seg, using a power injector.

Volume data set were acquired with configuration of

64 9 0.5 mm, and reconstructions were obtained with a

slice thickness of 1 mm and reconstruction interval of

0.8 mm. Subsequently, thin-section multiplanar reforma-

tions, including orthogonal and oblique views, and volu-

men-rendered images were evaluated in a dedicated

workstation.

Anatomical review of the lumbar region

In applied surgical anatomy the term lumbar region refers

to a particularly weak area of the dorsolateral abdominal

wall, containing the superior and inferior lumbar triangles

(Fig. 1a). The lumbar region is bordered superiorly by the

12th rib, inferiorly by the iliac crest, medially by the

erector spinae muscles and laterally by the external oblique

muscle [10].

The superior lumbar triangle is an inverted triangle

(Fig. 1b). It is bordered superiorly by the 12th rib and the

serratus posterior inferior muscle, posteromedially by the

erector spinae and quadratus lumborum muscles and

anterolaterally by the internal oblique muscle. Its floor is

formed by the transversalis fascia and other fasciae. The

superior lumbar triangle is superficially covered by the

latissimus dorsi muscle and is pierced by the subcostal

neurovascular pedicle [10].

The inferior lumbar triangle is upright, smaller, more

lateral and less constant than its superior homologue

Fig. 1 Lumbar region. Schematic diagrams based on posterior

coronal volumen-rendered MDCT images show anatomical land-

marks of lumbar region (a), superior lumbar triangle (b) and inferior

lumbar triangle (c). eom external oblique muscle, esm erector spinae

muscle, iom internal oblique muscle, it inferior lumbar triangle, ldmlatissimus dorsi muscle, lr lumbar region, qlm quadratus lumborum

muscle, spim serratus posterior inferior muscle, st superior lumbar

triangle, tlf thoracolumbar fascia

Fig. 2 Lumbar region. Diagram shows cross-sectional structure of

lumbar region (yellow shadow). At its mid-portion, structures of upper

lumbar region, such as 12th rib and serratus posterior inferior muscle,

and elements of caudal lumbar region, such as iliac crest, are not seen.

atlf anterior thoracolumbar fascia, eom external oblique muscle, esmerector spinae muscle, iom internal oblique muscle, ldm latissimus

dorsi muscle, lr lumbar region, mtlf middle thoracolumbar fascia,

p peritoneum, pm psoas muscle, ptlf posterior thoracolumbar fascia,

qlm quadratus lumborum muscle, sk skin, ssf superficial subcutaneous

fascia, st superior lumbar triangle, tam transversus abdominis muscle,

tf transversalis fascia

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(Fig. 1c). It is bordered inferiorly by the iliac crest, ante-

rolaterally by the external oblique muscle and posterome-

dially by the latissimus dorsi muscle, which merges with

the thoracolumbar fascia. Its floor is formed by the thora-

columbar fascia and other fasciae. The inferior lumbar

triangle is not covered by muscles and is not pierced by any

neurovascular structures [8, 10].

The lumbar region shows great anatomical variability.

A tall, thin person with angulated 12th ribs will have a

narrow superior triangle. Conversely, a medial origin of the

latissimus dorsi muscle will cause a wide inferior triangle

[10]. Besides, the inferior triangle may reach a very

anterior position in the vicinity of the mid-axillary line [8].

Knowledge of the cross-sectional structure of the lumbar

region (Fig. 2) and familiarity with its variability are

required for understanding the MDCT appearance of the

lumbar region.

MDCT appearance of the lumbar region

On MDCT the muscles bellies of the lumbar region are

found to diverge from each other, get slender or fade away.

The small gap in between is filled up with normal fatty

Fig. 3 Lumbar region. Posterior coronal (a) and oblique lateral

(b) volume-rendered MDCT images show approximate contour of

lumbar region (dotted area), containing superior (inverted) and

inferior (upright) triangles. Note the proximity of superior triangle to

12th rib (white arrowhead in a), and of inferior triangle to iliac crest

(black arrowhead in b). Distance between inferior triangle and mid-

axillary line (dotted line in b) averages 5.8 cm [8]

Fig. 4 Superior lumbar triangle. Axial MDCT images show upper

limit (a) and mid-portion (b) of superior triangle. Upper limit is

formed by 12th rib and serratus posterior inferior muscle (a). Both

structures are no longer seen at mid-portion of superior triangle (b),

where transversalis fascia is more easily identified, and latissimus

dorsi progressively merges with posterior thoracolumbar fascia. ldmlatissimus dorsi muscle, ptlf posterior thoracolumbar fascia, spimserratus posterior inferior muscle, qlm quadratus lumborum muscle, tftransversalis fascia, 12th twelfth rib

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Fig. 5 Superior lumbar triangle. Sagittal MDCT image shows

anatomical landmarks of superior triangle. Note straight contour or

slight anterior convexity of fascial floor. ldm latissimus dorsi muscle,

spim serratus posterior inferior muscle, tf transversalis fascia, 12th

twelfth rib, eom external oblique muscle

Fig. 6 Superior lumbar triangle. Coronal MDCT image shows

inverted configuration of superior triangles (arrowheads), filled up

with normal fatty tissue and covered by latissimus dorsi muscles

(arrows). Note mild asymmetry of superior triangles

Fig. 7 Inferior lumbar triangle. Axial (a), sagittal (b) and coronal

(c) MDCT images show anatomical landmarks of inferior triangle.

Note vagueness of its medial margin (latissimus dorsi muscle),

normal straight contour of fascial floor on axial and sagittal views and

striking appearance on coronal reformation (which may falsely

suggest muscle tear). eom external oblique muscle, ldm latissimus

dorsi muscle, tlf thoracolumbar fascia, ic iliac crest

Fig. 8 Spontaneous superior LH in 68-year-old man with long-

standing painful lump. Axial (a) and sagittal (b) MDCT images show

left superior LH. Note the protrusion of extraperitoneal fat (star)

through pierced fascial floor (arrows), under 12th rib (blackarrowhead in b), leading to abnormal interposition of fat (circle)

between fascial floor and latissimus dorsi muscle (white arrowhead).

On sagittal view, protruded fat cranially exceeds upper limit of

superior triangle and distally fails to reach caudal limit of inferior

triangle

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tissue. Posterior coronal (Fig. 3a) and oblique lateral

(Fig. 3b) volume-rendered MDCT views provide a pano-

ramic approach to the evaluation of the normal lumbar

region. However, its anatomical landmarks are more easily

characterized on standard axial views and multiplanar

reconstructions. The MDCT appearance of the lumbar

Fig. 9 Spontaneous superior LH in 64-year-old man. Axial (a) and

coronal (b) MDCT images show left superior LH. Note protrusion of

extraperitoneal fat through fascial floor (thin arrow) under 12th rib

(black arrowhead), leading to abnormal interposition of fat (circle)

between fascial floor, 12th rib, intercostal muscle (thick arrow) and

latissimus dorsi muscle (white arrowhead), approaching subcutaneous

planes (dotted arrows). Following surgical repair, axial MDCT image

(c) shows restoration of anatomical landmarks within left superior

lumbar triangle

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region is influenced by the age and body habitus of the

patient. In young well-fit individuals close apposition of

muscle bellies may difficult identification of the lumbar

triangles, which are more evident in obese or elderly

patients.

On axial MDCT images, the upper limits of the superior

triangle, namely the 12th rib and the serratus posterior

inferior muscle, are easily identified (Fig. 4a). At more

caudal axial views (Fig. 4b), these structures are no longer

seen, and the latissimus dorsi muscle gets slender and fuses

Fig. 10 Traumatic inferior LH in 31-year-old man involved in car

accident. Axial (a) and sagittal (b) MDCT images show protrusion of

extraperitoneal fat (circle) through fascial floor of inferior triangle.

Note protruded fat has convex posterior contour and is laterally

contained by external oblique muscle (arrowhead). Small hematoma

within subcutaneous tissue (arrow in a) is seen. Coronal MDCT

image (c) shows abdominal active extravasation (dotted arrow),

reflecting mesenteric laceration which required prompt surgery

Fig. 11 Spontaneous diffuse LH in 78-year-old woman with constitutional syndrome. Axial (a) and sagittal (b) MDCT images show diffuse LH

(arrowheads), involving superior and inferior triangles. Note fascial floor on both axial and sagittal views is hard to identify

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with the thoracolumbar fascia. Also at distal axial views,

the fascial floor, represented by a single laminar structure,

becomes more evident. However, the inferior corner of the

inverted triangle is hard to define. On sagittal MDCT

views, the normally flat or anteriorly convex fascial floor is

readily evaluated (Fig. 5). On coronal MDCT views, the

Fig. 12 Superior postoperative LH in 74-year-old woman with

history of left nephroureterectomy. Axial (a) and coronal

(b) MDCT images show protrusion of extraperitoneal fat (circle),

spleen (star in a) and small-bowel (arrowhead in b) through fascial

floor of superior triangle. Note absence of left kidney

Fig. 13 Inferior postoperative LH in 44-year-old woman who

underwent iliac crest harvesting. Axial (a) and coronal volume-

rendered (b) MDCT images show postoperative defect of left iliac

crest (arrowheads). Protrusion of bowel loop (arrow in 13a) through

iliac crest defect is located slightly medial to inferior lumbar triangle

(dotted arrow)

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inverted configuration of the superior triangle becomes

evident and is found to contain mildly asymmetric amounts

of normal fatty tissue (Fig. 6).

On axial MDCT images the inferior triangle should be

searched for lateral to the most superior aspect of the

iliac crest, and medial to the external oblique muscle

(Fig. 7a). At this region, the latissimus dorsi muscle is

very thin and merges with the thoracolumbar fascia.

Consequently, both the internal margin and the fascial

floor of the inferior triangle may be hard to identify on

axial MDCT views. On sagittal MDCT views, the nor-

mally flat contour of the fascial floor is more easily

evaluated (Fig. 7b). On coronal MDCT views, the open

interval between the external oblique muscle and the

iliac crest may falsely suggest abnormal muscle desin-

sertion (Fig. 7c).

MDCT features of LH

MDCT studies should be able to identify the LH, assess its

size and anatomical relationships and characterize it as

superior, inferior or diffuse. MDCT should be able to

depict the internal contents and complications of the LH

and occasionally suggest its etiology. MDCT may also be

used for evaluating muscle atrophy or coexistent defects

within the abdominal wall. Finally, MDCT may be helpful

for surgical planning or postoperative follow-up [1, 4, 5, 9,

10].

The following MDCT criteria for diagnosing LH have

been suggested: First, protrusion of extraperitoneal fat and/

or viscera through the fascial floor plane should be seen on

axial or sagittal views. Such protrusion typically modifies

the normal contour of the extraperitoneal fat and may

associate with a visible tear of the fascial floor [4]. Second,

abnormal separation between muscle and fascial layers of

the lumbar region is a predictable consequence of the

protrusion. This is particularly useful for early detection of

small fatty protrusions, because LH have a natural history

of a gradual increase in size over time [14]. And third, the

protrusion causes an abnormal bulge within the abdominal

flank, usually in asymmetric fashion [4]. However, LH may

be bilateral, and normal lumbar regions may also have

slightly asymmetric contour.

LH of the superior lumbar triangle typically emerge

right under the 12th rib and are commonly spontaneous.

They usually impinge on the inner aspect of the latissimus

dorsi muscle (Fig. 8) and may anteriorly reach

Fig. 14 Pseudohernia in 71-year-old man with history of left

nephroureterectomy. Axial MDCT image show mild bulging of

atrophic dorsolateral left abdominal wall (arrows) secondary to

surgery. Note that there is no muscle or fascia disruption

Fig. 15 Axial MDCT images in three different patients with palpable lump within dorsolateral abdominal wall show differential diagnosis of

LH, which includes intercostal hernia (arrow in a), subcutaneous hematoma or degloving injury (arrowhead in b) and lipoma (circle in c)

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subcutaneous planes (Fig. 9). LH of the inferior lumbar

triangle are usually found right on top of the lateral iliac

crest and are frequently traumatic [9]. Traumatic LH are

commonly associated with flank hematomas, lumbar frac-

ture, jejunal perforation or mesenteric laceration. They may

be part of the seat-belt syndrome, and their occurrence

should warn about the possibility of life-threatening inter-

nal damage (Fig. 10) [15]. Diffuse LH typically involve the

superior and inferior lumbar triangles (Fig. 11). Diffuse LH

are usually found after lumbotomy [12, 13]. However,

incisional LH may also cause selective involvement of

the superior triangle (Fig. 12) or involve an area contigu-

ous to the inferior triangle after iliac crest harvesting

(Fig. 13) [3, 16].

Differential diagnosis of LH

Following lumbotomy, mild bulging of atrophic dorsolat-

eral abdominal wall, a normal postoperative finding is hard

to distinguish from true postoperative LH. This has been

termed pseudohernia [10] and may be readily characterized

with MDCT (Fig. 14). In addition, MDCT may prove

useful for characterizing other potential mimickers of LH,

such as intercostal hernias (Fig. 15a), subcutaneous

hematomas, long-standing degloving injuries (Fig. 15b),

abscesses or soft-tissue tumors (Fig. 15c) [3].

Conclusion

Radiologists should be able to recognize abdominal wall

lumbar hernias, their types and anatomical details. Multi-

planar capabilities of MDCT provide an excellent oppor-

tunity for studying the normal anatomy and herniations of

the lumbar region. It also is useful for evaluating their

complications and for differentiating them from other sit-

uations that mimic abdominal wall lumbar hernias.

Conflict of interest The authors declare that they have no conflict

of interest.

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