The abdominal wall

Abdominal wall, congenital defect, layers, incision, laparoscopic approach

1. THE ABDOMINAL WALL Dr Rajeev Kumar Pandit FCPS 1 st Yr Surgery Resident Manmohan Memorial Medical College Swoyambhu , Nepal

2. Embryology The abdominal wall begins to develop from the lateral plate of the embryonic mesoderm By the end of the third month of gestation, the body wall has closed, except at the umbilical ring.

3. Anatomy Nine layers to the abdominal wall: Skin Subcutaneous tissue Superficial fascia External oblique muscle Internal oblique muscle Transversus abdominis muscle Transversalis fascia Preperitoneal adipose Areolar tissue Peritoneum

4. Subcutaneous Tissues There is no deep fascia over the trunk, only the superficial fascia The subcutaneous tissue consists of Camper and Scarpa fasciae. Camper fascia is the more superficial adipose layer that contains the bulk of the subcutaneous fat, whereas Scarpa fascia is a deeper, denser layer of fibrous connective tissue contiguous with the fascia lata of the thigh. Approximation of Scarpa fascia aids in the alignment of the skin after surgical incisions in the lower abdomen . Fibrous layer blends with the deep fascia of the upper thigh, extends into the penis and scrotum (or labia majora) and into the perineum as Colles ’ fascia.

5. Muscle External oblique Muscle Origin - outer surfaces of the lower eight ribs Insertion - xiphoid, linea alba, the pubic crest, pubic tubercle and the anterior half of the iliac crest. From the pubic tubercle to the anterior superior iliac spine its lower border forms the aponeurotic inguinal ligament of Poupart. Internal oblique muscle Origin - lumbar fascia, the anterior two‐thirds of the iliac crest and the lateral two‐thirds of the inguinal ligament. Insertion - lowest six costal cartilages, linea alba and the pubic crest Transversus abdominis Origin - lowest six costal cartilages (interdigitating with the diaphragm), the lumbar fascia, the anterior two thirds of the iliac crest and the lateral one‐third of the inguinal ligament Insertion - linea alba and the pubic crest. Rectus abdominis Origin - 5th, 6th and 7th costal cartilages Insertion – pubic crest three constant transverse tendinous intersections the rectus muscle is completely free behind At each intersection, vessels from the superior epigastric artery and vein pierce the rectus.

6. RECTUS SHEATH Formed by the aponeuroses of external oblique, internal oblique and the transversus abdominis anterior sheath posterior sheath The rectus sheaths fuse in the midline to form the linea alba Arcuate line - point midway between umbilicus and pubis Linea semilunaris - The lateral border of the rectus muscles has a curved shape identifiable as the surface landmark, the

7. Transversalis fascia Covers the deep surface of the transversus abdominis muscle and, with its various extensions, Forms a complete fascial envelope around the abdominal cavity. This fascial layer is regionally named for the muscles that it covers, for example, iliopsoas fascia, obturator fascia, and inferior fascia of the respiratory diaphragm. The transversalis fascia binds together the muscle and aponeurotic fascicles into a continuous layer and reinforces weak areas where the aponeurotic fibers are sparse. This layer is responsible for the structural integrity of the abdominal wall, and by definition, a hernia results from a defect in the transversalis fascia.

8. Vessels the last six intercostals and four lumbar arteries, superior and inferior epigastric arteries, and deep circumflex iliac arteries The inferior epigastric vessels arising from the external iliac, passes medial to the deep inguinal ring as it runs upwards and medially on the deep aspect of the abdominal wall musculature and enters the rectus sheath at the arcuate line. The companion vein joins the external iliac vein. The smaller superior epigastric artery terminal branch of the internal thoracic artery enters the sheath from under the costal margin. The two vessels have anastomotic connections within the belly of the muscle. It is this vascular arrangement that enables the surgeon to use the rectus muscle as a reconstructive flap, which can be swung cranially or caudally

9. VENOUS DRAINAGE Supraumbilicus empty into the superior vena cava by way of the internal mammary, intercostal, and long thoracic veins. Infraumbilicus —the superficial epigastric, circumflex iliac, and pudendal veins—converge toward the saphenous opening in the groin to enter the saphenous vein and become a tributary to the inferior vena cava

10. Lymphatic drainage Supraumbilical region drain into the axillary lymph nodes, Infraumbilical region drain toward the superficial inguinal lymph nodes. The lymphatic vessels from the liver course along the ligamentum teres to the umbilicus to communicate with the lymphatics of the anterior abdominal wall. It is from this pathway that carcinoma in the liver may spread to involve the anterior abdominal wall at the umbilicus ( Sister Mary Joseph node or nodule ).

11. Nerves lower five intercostals, the subcostal, the iliohypogastric and the ilioinguinal. All except for the last two enter the rectus sheath and pierce the rectus to end as cutaneous branches.

12. Preperitoneal Space Lies between the transversalis fascia and parietal peritoneum. Contains adipose and areolar tissue. Coursing through the preperitoneal space are the following: Inferior epigastric artery and vein. Medial umbilical ligaments, which are the vestiges of the fetal umbilical arteries Median umbilical ligament, which is a midline fibrous remnant of the fetal allantoic stalk or urachus Falciform ligament of the liver, extending from the umbilicus to the liver The round ligament, or ligamentum teres, is contained within the free margin of the falciform ligament and represents the obliterated umbilical vein, coursing from the umbilicus to the left branch of the portal vein.

13. Congenital Abnormalities Umbilical hernias - classified into three distinct forms: omphalocele and gastroschisis, infantile umbilical hernia, and acquired umbilical hernia.

14. Omphalocele Defect in the central abdomen through which the viscera protrude into the base of the umbilical cord. It is caused by failure of the abdominal wall musculature to unite in the midline during fetal development. The umbilical vessels may be splayed over the viscera or pushed to one side. In larger defects, the liver and spleen may lie within the cord, along with a major portion of the bowel. There is no skin covering these defects, only peritoneum and, more superficially, amnion. Of infants who are born with an omphalocele, 50% to 60% will have concomitant congenital anomalies of the skeleton, gastrointestinal (GI) tract, nervous system, genitourinary system, or cardiopulmonary system.

15. Gastroschisis Congenital defect of the abdominal wall in which the umbilical membrane has ruptured in utero, allowing the intestine to herniate outside the abdominal cavity. The defect is almost always to the right of the umbilical cord. The intestine is not covered with skin or amnion. Typically, the intestine has not undergone complete mesenteric rotation and fixation; hence, the infant is at risk for mesenteric volvulus, with resultant intestinal ischemia and necrosis. Concomitant congenital anomalies occur in about 10% of these

16. Infantile umbilical hernia Appears within a few days or weeks after the stump of the umbilical cord has sloughed. It is caused by a weakness in the adhesion between the scarred remnants of the umbilical cord and umbilical ring. In contrast to omphalocele, the infantile umbilical hernia is covered by skin. In general, these small hernias occur in the superior margin of the umbilical ring. They are easily reducible and become prominent when the infant cries. Most of these hernias resolve within the first 24 months of life, and complications such as strangulation are rare. Operative repair is indicated for those children in whom the hernia persists beyond the age of 3 or 4 years.

17. Acquired umbilical hernia This hernia occurs most commonly at the upper margin of the umbilicus Results from weakening of the cicatricial tissue that normally closes the umbilical ring. This weakening can be caused by excessive stretching of the abdominal wall, which may occur with pregnancy, vigorous labor, or ascites. In contrast to infantile umbilical hernias, acquired umbilical hernias do not spontaneously resolve but gradually increase in size. The dense fibrous ring at the neck of this hernia makes strangulation of herniated intestine or omentum an important complication.

18. Abnormalities resulting from persistence of the omphalomesenteric duct During fetal development, the midgut communicates widely with the yolk sac through the vitelline or omphalomesenteric duct. As the abdominal wall components approximate one another, the omphalomesenteric duct narrows and comes to lie within the umbilical cord. Over time, communication between the yolk sac and intestine becomes obliterated, and the intestine resides free within the peritoneal cavity. Persistence of part or all of the omphalomesenteric duct results in a variety of abnormalities related to the intestine and abdominal wall.

19. Meckel’s diverticulum Persistence of the intestinal end of the omphalomesenteric duct. These true diverticula arise from the antimesenteric border of the small intestine, most often the ileum. A rule of 2s 2% of the population, within 2 feet of the ileocecal valve, 2 inches in length, and contain 2 types of ectopic mucosa (gastric and pancreatic). Meckel’s diverticula may be complicated by inflammation, perforation, hemorrhage, or Obstruction(intussusception or volvulus around an abnormal fibrous connection between the diverticulum and posterior aspect of the umbilicus) GI bleeding is caused by peptic ulceration of adjacent intestinal mucosa from hydrochloric acid secreted by ectopic parietal cells within the diverticulum

20. Abnormalities resulting from persistence of the allantois The allantois is the cranialmost component of the embryologic ventral cloaca. The intra-abdominal portion is termed the urachus and connects the urinary bladder with the umbilicus, whereas the extra-abdominal allantois is contained within the umbilical cord. At the end of gestation, the urachus is converted into a fibrous cord that courses between the extraperitoneal urinary bladder and umbilicus as the median umbilical ligament. Persistence of part or all of the urachus may result in the formation of a vesicocutaneous fistula, with the appearance of urine at the umbilicus, An extraperitoneal urachal cyst presenting as a lower abdominal mass, or a urachal sinus with the drainage of a small amount of mucus. Because of the risk of complications including transformation into malignancy, treatment is excision of the urachal remnant with closure of the bladder, if necessary.

21. Acquired Abnormalities Diastasis recti. Thinning of the linea alba in the epigastrium Manifested as a smooth midline protrusion of the anterior abdominal wall. The transversalis fascia is intact, and hence this is not a hernia. There are no identifiable fascial margins and no risk for intestinal strangulation. The presence of diastasis recti may be particularly noticeable to the patient on straining or when lifting the head from the pillow. Appropriate treatment consists of reassurance of the patient and family about the innocuous nature of this condition

22. Rectus Sheath Hematoma Hemorrhage from the network of collateralizing vessels within the rectus sheath and muscles can result in a rectus sheath hematoma. Causes Trauma Sudden contraction of the rectus muscles with coughing, sneezing, or any vigorous physical activity Spontaneous rectus sheath hematomas ( elderly and in those on anticoagulation therapy) Clinical features Sudden onset of abdominal pain, which may be severe and is often exacerbated by movements requiring contraction of the abdominal wall Tenderness over the rectus sheath, often with voluntary guarding Abdominal wall mass Abdominal wall ecchymosis, including periumbilical ecchymosis (Cullen sign) and blue discoloration in the flanks (Grey Turner sign) Fothergill’s sign is a palpable abdominal mass that remains unchanged with contraction of the rectus muscles and is classically associated with rectus hematoma

23. Investigation Hematocrit level may fall, Ultrasonography or CT will confirm Tx Rest and analgesics and, if necessary, blood transfusion Correction of coagulopathies Angiographic embolization of the bleeding vessel Surgical therapy ( failed angiographic treatment or hemodynamic instability )

24. The anatomy of abdominal incisions Maximum access Minimal scar Minimal damage to the muscles & nerve supply.

25. Midline incisions Made through the linea alba. Made of fibrous tissue so almost bloodless. Disadvantage Crosses the natural crease lines of the skin Hypertrophic scar is common, especially in young children Burst abdomens and incisional hernia were a relatively common complication of midline wounds Suprapubic incisions Pfannenstiel incisions

26. Paramedian incisions Vertical incision placed 2.5 cm (1 in) to 4 cm (1.5 in) lateral, and parallel, to the midline; the anterior rectus sheath is opened, the rectus displaced laterally and the posterior sheath, together with peritoneum, then incised. less destructive to tissue but offers more limited exposure This incision has the advantage that, on suturing the peritoneum, the rectus slips back into place to cover and protect the peritoneal scar. Closure of a paramedian incision is undertaken in two layers. The paramedian skin incision avoids the challenges posed by the umbilicus, and is deepened down to the fascia of the anterior layer of the rectus sheath.

27. Muscle-splitting incisions Muscle-splitting incisions provide limited access but sufficient for an appendicectomy, as the appendix and part of the caecum can be delivered out through the incision The gridiron and Lanz incisions

28. Muscle-cutting incisions Muscle bellies are divided in line with a transverse or oblique skin incision Long transverse muscle-cutting incision, either just above or below the umbilicus, provides good access to most of the abdomen. Access is superior in those with a short wide abdomen and a wide costal angle Postoperative pain is restricted to fewer dermatomes The final transverse scar is unobtrusive Access to the oesophageal hiatus and the pelvis is, however, usually inferior to that obtained with a long midline incision In infants, transverse incisions are preferable to midline incisions. The abdominal muscle bulk is small, the abdomen is short and wide and the costal angle is obtuse, allowing easy access to the diaphragm.

29. Oblique subcostal muscle-cutting incisions provide good access on the right for liver, biliary and renal surgery, and on the left for splenic and renal surgery. The angulation of the incision overcomes the limitations imposed by a narrow costal angle, but several abdominal nerves are divided. A bilateral subcostal (chevron or rooftop) incision is in essence a modification of a transverse incision and gives excellent access to the upper abdomen, although many of the advantages of a transverse incision at the level of the umbilicus are lost.

30. Loin incisions are posterior oblique muscle-cutting incisions. Posteriorly, latissimus dorsi, serratus posterior inferior and quadratus lumborum replace the external and internal oblique muscles of the more anterior incision. Subcostal incision posterior division of the renal fascia gives access to the retroperitoneal fat A supracostal incision along the superior border of the 10th, 11th or 12th rib will usually give good access to the kidney or adrenal. Lumbotomy vertical incision is made from the lowest rib to the iliac crest along the lateral border of erector spini , and deepened through muscles and fascia into the retroperitoneal space.

31. Anterior thoracoabdominal incisions classic thoracoabdominal incision the oblique, muscle-cutting abdominal incision crossed the costal margin and continued along the 8th interspace.

32. LAPAROSCOPIC ACCESS INTRAPERITONEAL LAPAROSCOPIC SURGERY safe establishment of access to the peritoneal cavity The initial port is frequently inserted at the umbilicus, but it may be situated elsewhere if no umbilical port is required for the procedure or to stay clear of adhesions from previous surgery. Left upper quadrant placement of the first port may be useful, as this area often has few adhesions and fewer vulnerable intra-abdominal structures Pneumoperitoneum is created by insufflation of CO2 to a specified pressure. Usually, 12 mmHg is sufficient to give a working space in a fully relaxed patient and while higher pressures are used, they can interfere with ventilation.

33. Open and Closed techniques Closed technique By using veress needle Open technique the umbilicus is grasped at its base and everted. A 1–2-cm incision is created in the umbilical pit that allows the linea alba to be picked up with artery forceps. The linea alba and peritoneum are then opened by the same technique that is used for an open laparotomy. The first port trocar is introduced and used to insufflate CO2. Insertion of a transparent trocar, within which the laparoscope can be used to give a direct view of the progress of the trocar through the tissues of the abdominal wall, is an alternative method for initial port placement and may be particularly useful in obese patients.

34. EXTRAPERITONEAL LAPAROSCOPIC SURGERY for most retroperitoneal structures A balloon technique to create a larger, more localised space can be used Groin access for extraperitoneal inguinal hernia repair through an initial 10-mm port established by a 1–2-cm transverse incision just below the umbilicus. A transverse incision is then made in the anterior rectus sheath just to one side of the midline. The medial edge of the rectus muscle is retracted laterally to expose the fibres of the posterior sheath. The laparoscope is inserted under the rectus muscle and gas insufflation commenced. The laparoscope is then introduced and advanced. The posterior sheath forms a barrier to inadvertent deep insertion until the laparoscope emerges into the true extraperitoneal space below the arcuate line. Two further 5-mm ports are then established

35. COMPLICATIONS FROM ABDOMINAL WOUNDS Wound infections reduced by the administration of prophylactic antibiotics. Burst abdomen At around 7–10 days postoperatively, leakage of clear or serosanguineous fluid from the wound is the first ominous sign of incipient dehiscence Incisional herniae

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