Surgical Anatomy of Anterior Abdominal Wall

SECTION 1

1General

Surgical Anatomy of Anterior Abdominal Wall

CS Ramesh Babu, Aruna Arya
Overview of Laparoscopic Entry

Artin Ternamian2

Surgical Anatomy of Anterior Abdominal WallCHAPTER 1

CS Ramesh Babu,

Aruna Arya

INTRODUCTION

Anterior abdominal wall (AAW) is a hexagonal area bounded superiorly by the xiphoid process and costal margins (formed by 7th to 10th costal cartilages), inferiorly by upper border of pubic symphysis, pubic crest, pubic tubercle, inguinal ligament and iliac crest and laterally by midaxillary lines. It consists of skin, superficial fascia, deep fascia, muscles and their aponeuroses, fascia transversalis, extraperitoneal (preperitoneal) fat, and parietal peritoneum. A thorough knowledge of anatomy of this region is most essential to surgeons and understanding of its neurovascular anatomy became imperative especially after the advent of laparoscopic surgery. In this chapter surgical anatomy of blood vessels of AAW, relevant to laparoscopic portals is discussed.

UMBILICUS

The fibrous cicatrix umbilicus represents the site of attachment of the umbilical cord. Its position is highly variable especially in multiparous obese women. It is one of the commonly used sites of laparoscopic entry because at this site skin and linea alba are in close contact with parietal peritoneum with little intervening fat. Attached to the umbilical scar are four remnants of fetal structures (1) ligamentum teres hepatis (remnant of left umbilical vein) running along the free margin of falciform ligament attached at 12 o–clock position, (2 and 3) right and left medial umbilical ligaments (remnants of umbilical arteries) attached at 4 o–clock and 8 o–clock positions, (4) median umbilical ligament (remnant of urachus) attached at 6 o–clock position.¹ During embryonic period midgut loop as physiological umbilical hernia and vitellointestinal duct extend into umbilical cord. Meckel–s diverticulum which is a remnant of vitellointestinal duct, if remains patent, opens at the umbilicus. The urachus connected to apex of urinary bladder sometimes remains patent and opens at umbilicus.4

SUPERFICIAL FASCIA

Many text books of anatomy customarily describe the superficial fascia as a single fatty layer in the supraumbilical region and as a bilaminar structure in the infraumbilical region made up of superficial fatty layer (Camper–s fascia) and a deep membranous layer (Scarpa–s fascia). A trilaminar arrangement of superficial fascia as superficial fatty layer, middle membranous layer, and a deep fatty layer with adipose tissue metabolically different from that of the superficial fatty layer has recently been suggested.^2,3 Computerized tomographic analysis has revealed that the membranous layer was observable in whole of AAW and the superficial fascia was a three layered structure.⁴

ARTERIAL SUPPLY

Arteries supplying the AAW include superficial and deep set of arteries which are branches of external iliac, femoral, subclavian, and descending aorta. The superficial set supplies the skin and subcutaneous tissues and is located between the superficial fatty layer and Scarpa–s fascia. Three superficial branches of the femoral artery supply the infraumbilical region and small arteries accompanying the cutaneous nerves and cutaneous perforating branches from deep set of arteries supply the supraumbilical region. The deep set supplies the muscles and deeper tissues and lie between the muscles.

It is convenient to divide the AAW into three zones based on the arterial supply.⁵ Zone I is the midcentral portion of supraumbilical AAW supplied by vertically oriented deep superior epigastric and inferior epigastric arteries. Zone II is the entire infraumbilical region supplied by femoral and external iliac artery branches generally oriented vertically. Zone III is the lateral parts (flank) of supraumbilical region supplied by musculophrenic, posterior intercostal, lumbar, and deep circumflex iliac arteries (Fig. 1).

Superficial inferior epigastric artery (SIEA) or simply superficial epigastric artery is a branch of common femoral artery present nearly in 85–94% cases⁶ and arises 1.0–1.5 cm below the midinguinal point (Fig. 2). Enters AAW just lateral to midinguinal point and ascends up to umbilicus to supply infraumbilical region lying 2 cm lateral to linea semilunaris. The diameter ranges from 0.6 mm to 1.5 mm.⁷
Superficial circumflex iliac artery (SCIA) arises from common femoral artery and passes obliquely parallel to inguinal ligament to reach the anterior superior iliac spine (ASIS) to supply superficial tissues anterosuperior to ASIS up to the level of umbilicus. The diameter ranges from 0.9 mm to 2 mm.⁸
Superficial external pudendal artery (SEPA) a small branch from common femoral passes medially towards pubic symphysis to supply labium majus and infraumbilical AAW.5

Fig. 1: Vascular zones of anterior abdominal wall. Deep arteries are shown on the left side.

Fig. 2: Cutaneous vessels of anterior abdominal wall. Superficial arteries on the right and veins on the left. (P: perforator).

Deep circumflex iliac artery (DCIA) is a branch arising from lateral aspect of external iliac above the inguinal ligament in 72–91% cases and in rest of the 9–28% cases from common femoral artery below the inguinal ligament.^8,9 Its diameter ranges from 1.1–3.2 mm. It passes upwards and laterally towards ASIS and gives branches to iliacus muscle and ilium. Curving posterolaterally along the iliac crest it gives off a large ascending branch which runs between internal oblique and transversus abdominis muscles to supply them and anastomose with posterior intercostal and musculophrenic arteries (Figs. 1 and 3. Ascending branch of DCIA runs more laterally in the flank region to supply zone III.6

Fig. 3: Deep arteries are shown on the left. On the right the anterior extent of three flat abdominal muscles are shown, beyond which their aponeuroses contribute to formation of rectus sheath.

Superior epigastric artery (SEA) is one of the terminal branches of internal mammary branch of subclavian artery arising in 6th intercostal space. It enters the rectus sheath to descend between the muscle and posterior rectus sheath. Generally it divides into branches to anastomose with inferior epigastric artery midway between umbilicus and xiphoid process (Figs. 1 and 3. Mean diameter of SEA at its origin is 1.6 mm.¹⁰ At the level of xiphoid process it lies at a distance of 4.0–4.5 cm and midway between umbilicus and xiphoid process at a distance of 5.3–5.5 cm from the midline.¹¹
Deep inferior epigastric artery (DIEA) or simply inferior epigastric artery is the most widely studied vessel of the AAW because of its susceptibility to injury during laparoscopic and other interventional procedures (0.3–2.5% cases). Since it is the dominant artery supplying the AAW, perforator based cutaneous and myocutaneous flaps [deep inferior epigastric artery perforator (DIEAP) flap and transverse rectus abdominis myocutaneous (TRAM) flap] are frequently used for breast reconstruction. It arises from anteromedial aspect of external iliac just above the inguinal ligament and passes superomedially along the medial margin of deep inguinal ring towards lateral border of rectus abdominis (Figs. 1 and 3. It is estimated that it arises from the external iliac in 83.6% cases but may also arise from femoral below the inguinal ligament, from obturator artery or in common with obturator from the external iliac.¹² Its origin from external iliac was above inguinal ligament in 76% cases, behind the inguinal ligament in 12% and from femoral below the ligament in 8% cases.¹³ Its origin above the inguinal ligament ranges from 0.5 cm to 2.0 cm.¹⁴7

Fig. 4: Three types of deep inferior epigastric artery. (DIEA: deep inferior epigastric artery; M: medial branch; L: lateral branch; I: intermediate branch; U: umbilical branch).

Initially it lies in the extraperitoneal tissue in the posterior wall of inguinal canal forming the lateral boundary of inguinal triangle of Hesselbach and raises a peritoneal fold named as lateral umbilical fold. Piercing the transversalis fascia it enters the rectus sheath generally at the level of arcuate line (linea semicircularis of Douglas). Length of the DIEA measured from its origin to entry into the rectus sheath was as short as 1.2 cm on the left and 3.5 cm on the right side and as long as 6.8 cm on the right side and 6.9 cm on the left.¹⁵ It ascends with in the rectus sheath posterior to the muscle and anastomoses with SEA midway between umbilicus and xiphoid process. In about 28% cases the DIEA did not reach the umbilicus.^15,16 It gives a pubic branch which anastomoses with a similar branch from obturator artery on the pelvic surface of pubis forming arteria corona mortis. Branching pattern of DIEA within the rectus sheath was classified according to number of branches into three types: Type I single artery found in 29%, Type II bifurcation into two branches in 57%, and Type III trifurcation in 14% cases (Fig. 4).¹⁰ An umbilical branch from DIEA supplies the umbilicus. It also gives muscular branches to supply rectus abdominis and perforator branches to the overlying skin. It was noted that more branches arose from the lateral aspect and were contained within the rectus sheath.¹⁶

Many cadaveric and radiological studies focused their attention to map a safety zone of entry by measuring the distance of deep epigastric arteries from midline at certain levels to avoid vascular injuries.^17–21 To minimize the risk of vascular injury, Hurd et al. (1994) suggested that the lateral trocars should be placed 8 cm lateral to midline and 5 cm above the pubic symphysis.¹⁷ Sriprasad et al. (2006) indicated that the ideal primary port entry is in the midline and the ideal lateral port entry is more than 6 cm from the midline both at the level of ASIS.²² Kulkarni et al. (2013) suggested that a zone of safety for access in the midline is 2 cm (1 cm on each side of midline) at the level of xiphoid process, 4 cm at umbilicus (2 cm on either side of midline) and 5 cm at ASIS.²³ They also 8suggested that more laterally the safe area of access is >8 cm from the midline at the level of umbilicus. It was observed that the position of deep epigastric vessels shifted more laterally after insufflation ranging from 0.6 cm to 1.1 cm.²⁴

VENOUS DRAINAGE

Veins draining the AAW accompany the corresponding arteries and are grouped into superficial and deep veins. Superficial veins drain the skin and subcutaneous tissues whereas the deep veins drain the muscles. Infraumbilical AAW is drained by three superficial veins; the superficial inferior epigastric, superficial circumflex iliac, and superficial external pudendal, which are tributaries of the great saphenous vein whereas the supraumbilical region is drained by small veins which unite to form the thoracoepigastric vein which joins the lateral thoracic vein, a tributary of the axillary vein (Fig. 2). The superficial inferior epigastric and superficial circumflex iliac veins anastomose with the thoracoepigastric vein. Thus this longitudinally arranged superficial venous system can act as a collateral channel connecting the superior vena cava with inferior vena cava. The deeper veins include deep circumflex iliac and deep inferior epigastric veins draining into external iliac vein, superior epigastric vein draining into internal mammary vein, subcostal, lower posterior intercostal, and lumbar veins draining into azygos venous system. At the umbilicus the veins of the AAW establish an important anastomosis with paraumbilical vein and smaller veins in the falciform ligament which drain into portal vein. Thus umbilicus is one of the sites of portocaval anastomosis and in cases of portal hypertension enlarged tortuous radiating veins appear around umbilicus, a condition called as “caput medusae”.

MUSCLES

There are three flat abdominal wall muscles in the flank region, the external oblique, internal oblique, and transversus abdominis which are arranged in a plane similar to that of the three intercostal muscles in the thoracic region. These muscles end in aponeuroses more medially at variable distances from the linea semilunaris and contribute to the formation of rectus sheath enclosing vertically oriented paramedian rectus abdominis and pyramidalis muscles. The aponeuroses of muscles of both sides interlace with each other at linea alba resulting in a digastric arrangement of the muscles with linea alba acting as the intermediate tendon.

Linea alba: It is a median fibrous raphe formed by the interlacement and decussation of aponeuroses of three anterolateral muscles forming the anterior and posterior rectus sheath. It extends from tip of xiphoid process to upper border of pubic symphysis. It is wider above the umbilicus than below and widest at the level of umbilicus.²⁵ The width of the linea alba indicates the inter-recti distance. A recent sonographic study in nulliparous 9women suggested that the linea alba can be considered normal up to a width of 22 mm at a point 3 cm above the umbilicus, 16 mm at a point 2 cm below the umbilicus, and 15 mm at the xiphoid process.²⁶ Linea alba is not a simple merging line of the aponeuroses of both sides forming the rectus sheath. Fibers from each layer decussate to the opposite side forming a continuous aponeurosis with the contralateral muscles. Thus linea alba acts as a central tendon for the digastric arrangement of the three flat muscles. Moreover, fibers also decussate anteroposteriorly passing from anterior sheath to the posterior sheath. Linea alba is relatively avascular and is a preferable site for various surgical approaches.

TRANSVERSALIS FASCIA

It is a thin fascial layer lining the AAW on the deep surface of the transversus abdominis and is a part of endoabdominal fascia. It is separated from the parietal peritoneum by the extraperitoneal fat. Superiorly it is continuous with the fascia on the abdominal surface of diaphragm. Posteriorly it is continuous with thoracolumbar fascia. Posteroinferiorly it is attached to iliac crest where it is continuous with the iliac and parietal layer of endopelvic fascia. Anteroinferiorly it is attached to inguinal ligament and shows a thickening called as iliopubic tract (deep crural arch), an important structure during inguinal hernia surgery. Opposite to midinguinal point it presents the deep inguinal ring through which vas deferens in male and round ligament of uterus in female enter the inguinal canal surrounded by a prolongation of the transversalis fascia named as internal spermatic fascia. Along the medial margin the deep inguinal ring it is thickened to form interfoveolar ligament. It is also prolonged around femoral vessels forming anterior wall of femoral sheath. Above the pubic symphysis and below the arcuate line the rectus abdominis muscle rests on it.

EXTRAPERITONEAL FAT

It is a loose connective tissue layer with fat separating the parietal peritoneum from the abdominal wall. Along the medial margin of the deep inguinal ring it is traversed by the deep inferior epigastric vessels. A considerable accumulation of subperitoneal fat named as “yellow island” is present at the lateral third of a line joining the ASIS with umbilicus. The “yellow island” is well developed especially in obese women and it is suggested that this site is suitable for safe introduction of ancillary trocars since vascular injury is avoided. The DIEA and other major vessels are never present in this area.^27,28

CONCLUSION

This article is not an exhaustive description of anatomy of the AAW. Its main focus is to discuss about the surgical anatomy of the AAW more relevant to 10laparoscopic gynecological surgery. Therefore the detailed anatomy of the muscles, nerves, inguinal canal, and associated structures are not discussed. In an attempt to identify a safety zone of entry, though lot of morphometric data on deep epigastric vessels was generated, there was no uniformity because different authors have used different anatomical landmarks. It will be more fruitful if both cadaveric/surgical and radiological studies employ same bony landmarks for measuring the distance of the epigastric vessels from midline. More studies on the positional anatomy of DCIA and its ascending branch are required. Similarly morphometric data on vascular anatomy in nulliparous and multiparous women and women with normal body mass index (BMI) and increased BMI are necessary. Similarly positional anatomy of the vessels in resting and insufflated abdomen is needed.

REFERENCES

Skandalakis PN, Skandalakis JE, Colborn GL, et al. Abdominal wall and hernias. In: Skandalakis JE (Ed). Surgical Anatomy: The Embryologic and Anatomic Basis of Modern Surgery. Athens: Paschalidis Medical Publications; 2004. pp. 393–492.

Rosen MJ, Petro CC, Stringer MD. Anterior abdominal wall. In: Standring S (Ed) Gray's Anatomy: The Anatomical Basis of Clinical Practice, 41st edition. Amsterdam, Netherlands: Elsevier; 2016. pp. 1069–82.

Lancerotto I, Stecco C, Macchi V, et al. Layers of the abdominal wall: anatomical investigation of subcutaneous tissue and superficial fascia. Surg Radiol Anat. 2011;33:835–42.

Chopra J, Rani A, Rani A, et al. Re-evaluation of superficial fascia of anterior abdominal wall: a computed tomographic study. Surg Radiol Anat. 2011;33:843–9.

Huger WE Jr. The anatomic rationale for abdominal lipectomy. Am Surg. 1979;45:612–7.

Rozen WM, Chubb D, Grinsell O, et al. The variability of the superficial inferior epigastric artery (SIEA) and its angiosome: A clinical anatomical study. Microsurgery. 2010;30(5):386–91.

Fathi M, Hatamipour E, Fathi HR, et al. The anatomy of superficial inferior epigastric artery flap. Acta Cirurgica Brasileira. 2008;23(5):429–34.

Penteado CV. Anatomosurgical study of the superficial and deep circumflex iliac arteries. Anat Clin. 1983;5:125–7.

Vasanthakumar T, Priyadarisini SE. A study on the variations in the origin of deep circumflex iliac artery. Int J Anat Res. 2017;5:4451–3.

Taylor GI. The angiosomes of the body and their supply to perforator flaps. Clin Plast Surg. 2003;30:331–42.

Saber AA, Meslemani AM, Davis R, et al. Safety zone for anterior abdominal wall entry during laparoscopy. Ann Surg. 2004;239:182–5.

Al-Talalwah W. The inferior epigastric artery: Anatomical study and clinical significance. Int J Morphol. 2017;35(1):7–11.

Jakubowicz M, Czarniawska-Grzesinska M. Variability in origin and topography of the inferior epigastric and obturator arteries. Folia Morphol (Warsz). 1996;55:121–6.

Anandhi V, Rajeshwari K, Jebakani CF. A study of the origin and course of the inferior epigastric artery and its significance in laparoscopic surgery. Int J Anat Res. 2016;4(3):2692–7.

11 Rao MP, Swamy V, Arole V, et al. Study of the course of inferior epigastric artery with reference to laparoscopic portal. J Min Access Surg. 2013;9:154–8.

Joy P, Pritishkumar IJ, Isaac B. Clinical anatomy of the inferior epigastric artery with special relevance to invasive procedures of the anterior abdominal wall. J Min Access Surg. 2017;13:18–21.

Hurd WW, Bude RO, De Lancey JO, et al. The location of abdominal wall blood vessels in relationship to abdominal landmarks apparent at laparoscopy. Am J Obstet Gynecol. 1994;171(3):642–6.

Joy P, Simon B, Pritishkumar IJ, et al. Topography of inferior epigastric artery relevant to laparoscopy: a CT angiographic study. Surg Radol Anat. 2016;38(3):279–83.

Andrade D, Abranches D, Souza N, et al. An analysis of the anatomical trajectory of the inferior epigastric arteries in the era of videolaparoscopic surgery: Is there in fact a ‘safety zone’ for the prevention of iatrogenic lesions? Eur J Anat. 2012;16(1):43–8.

Rahn DD, Phelan JN, Roshanravan SM, et al Anterior abdominal wall nerve and vessel anatomy: clinical implications for gynaecologic surgery. Am J Obstet Gynecol. 2010;202:234–6.

Epstein J, Arora A, Ellis H. Surface anatomy of inferior epigastric artery in relation to laparoscopic injury. Clin Anat. 2004;17:400–8.

Sriprasad S, Yu DF, Muir GH, et al. Positional anatomy of the vessels that may be damaged at laparoscopy: new access critera based on CT and ultrasonography to avoid vascular injury. J Endourol. 2006;20(7):498–503.

Kulkarni M, Ambiye M. Positional anatomy of deep epigastric arteries. Int J Biol Med Res. 2013;4(3):3350–4.

Burnett TL, Garza-Cavazos A, Groesch K, et al. Location of the deep epigastric vessels in the resting and insufflated abdomen. J Minim Invasive Gynecol. 2016;23(5):798–803.

Rath AM, Attali P, Dumas JL, et al. The abdominal linea alba: an anatomo-radiological and biomechanical study. Surg Radiol Anat. 1996;18:281–8.

Beer GM, Schuster A, Seifert B, et al. The normal width of the linea alba in nulliparous women. Clin Anat. 2009;22:706–11.

Tinelli A, Gasbarro N, Lupo P, et al. Safe introduction of ancillary trocars. JSLS. 2012;16:276–9.

Vitale SG, Gasbarro N, Lagana AS, et al. Safe introduction of ancillary trocars in gynaecological surgery: the yellow island anatomical landmark. Ann Ital Chir. 2016;87:608–11.

Chapter Notes

Surgical Anatomy of Anterior Abdominal WallCHAPTER 1