Appendectomy

Published on 16/04/2015 by admin

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Chapter 19

Appendectomy

Mark L. Manwaring

Introduction

More than 280,000 appendectomies are performed annually in the United States. First described as a treatment for appendicitis by Reginald Fitz in 1886, appendectomy has become the standard of care because of its efficacy and low morbidity. Thorough knowledge of the diagnostic evaluation, preoperative considerations, operative decision making, anatomy, and technique for appendectomy is critical for every trainee and abdominal surgeon.

Anatomic Principles of Diagnosis and Evaluation

There is considerable variation in the clinical presentation of appendicitis. The classic patient presents with several hours of periumbilical pain that “migrates” to the right lower abdomen, with associated anorexia. The migration of the pain is mediated by the separate innervation of visceral and parietal tissues. Appendiceal obstruction and inflammation, which occur early in the process, cause irritation of autonomic visceral afferent nerves of the superior mesenteric ganglion that result in a nonspecific, poorly localized epigastric or periumbilical pain, secondary to the location and lack of specificity of the autonomic ganglion (Fig. 19-1). Ileus, nausea, anorexia, and diarrhea may also be mediated in this manner. Once inflammation reaches parietal surfaces of the peritoneum (e.g., through perforation), somatic sensory fibers create localized pain in the right lower quadrant (RLQ) with findings of peritonitis, including rigidity, distention, and hyperesthesia.

FIGURE 19–1 Autonomic innervation of the intestine.
Symp., Sympathetic; T11, 11th thoracic.

Examination of the patient with appendicitis may further localize inflammation and determine the stage of the diagnosis. Tenderness in the RLQ at McBurney’s point is typical. Well-recognized signs include RLQ pain on palpation of the left abdomen (Rovsing’s sign) and internal rotation of the right hip resulting in motion of deep pelvic musculature, which can cause pain in the case of pelvic appendicitis (obturator sign). Pain with extension of the right hip is caused by motion of the psoas muscle posterior to the cecum (psoas sign) (Fig. 19-2, A).

FIGURE 19–2 Cross-sectional periappendicular anatomy.
CT, Computed tomography; S1, 1st sacral vertebra.

Although the diagnosis of appendicitis may often be made with physical examination alone, computed tomography (CT) has been increasingly used for the evaluation of patients with appendiceal pathology because of its high sensitivity and specificity. Coronal and sagittal reconstructions provide excellent anatomic detail that is useful in surgical planning (Fig. 19-2, B and C).

Surgical Principles

Exposure

When the laparoscopic approach is used, placing the patient in a left-side down, Trendelenburg position aids laparoscopic visualization by employing gravity to retract intestinal structures away from the RLQ and cecum. The small intestine can be manipulated manually into the left upper quadrant to prevent injury and aid in visualization. The greater omentum often wraps the ileocecal area, localizing the infectious process to the right lower quadrant. Blunt dissection using an atraumatic laparoscopic instrument with gentle traction can mobilize the omentum away from the cecum, revealing the appendix. The challenges of dissection in appendectomy are typically related to inflammatory changes that make the appendix adherent to inflamed surrounding tissues. Again, blunt dissection in this setting is most effective for safely separating inflamed tissues. If a neoplastic process is suspected, however, an en bloc open resection is indicated.

In the open setting, incision length and type should allow adequate visualization of the critical anatomy. The choice of incision should be based on the patient’s body habitus, previous surgical sites, physical examination findings, preoperative imaging, and surgeon preference. Use of small, handheld Richardson or appendiceal retractors is standard practice when an RLQ Rocky-Davis (transverse) or McBurney (oblique) incision is used. Retrocecal appendicitis may also be approached in this manner, although a somewhat longer incision is often required to mobilize the cecum adequately for appendectomy. When the surgeon uses an open approach, patients with perforated appendicitis, generalized peritonitis, or those with suspected neoplastic processes may best be approached with the use of a standard midline laparotomy.

Operative Anatomy

The appendix is a tubular organ located at the base of the cecum; it begins invariably at the fused origin of the taenia coli. The appendix varies considerably in length and orientation relative to the cecum (Figs. 19-3 and 19-4). The appendix receives its blood supply from the appendiceal artery, a terminal branch of the ileocolic pedicle supplied by the superior mesenteric artery. The appendiceal artery travels posterior to the terminal ileum and into the mesoappendix (Fig. 19-5).

FIGURE 19–3 Ileocecal region.

FIGURE 19–4 Vermiform appendix.

FIGURE 19–5 Variations in cecal and appendicular arteries.

The terminal ileum joins the cecum at the ileocecal valve and generally lies medial to the appendiceal base (Fig. 19-6, A). The ureter lies within the retroperitoneum and is usually located medial to the appendix, although it must be considered when dissection in the region is performed. The appendix often courses over the right iliac vessels into the pelvis (Fig. 19-6, B). Laparoscopically, relational anatomy must be conceptualized because wide visualization can be limited; Figure 19-7 shows a laparoscopic depiction of the relevant anatomy.

FIGURE 19–6 Ileocecal region and iliac vessels.

FIGURE 19–7 Right lower quadrant anatomy: laparoscopic view.

Identification of the appendiceal base and full resection of length of the appendix are critical to avoid partial appendectomy. Complete appendectomy prevents recurrent infection of the appendiceal stump. In addition, ligation in an area of healthy tissue away from appendiceal inflammation is necessary to ensure safe closure of the cecum. Full dissection of the appendix along its course, followed by firm but atraumatic traction on the appendix, can aid in directing dissection to allow visualization of the base of the appendix. Before division, the terminal ileum, base of the cecum, and retroperitoneum should be identified and preserved.

Surgical Technique

Laparoscopic Approach

Midline umbilical access is accomplished by using the open Hassan technique, and pneumoperitoneum is established. Next, using laparoscopic assistance and avoiding the inferior epigastric vessels, the surgeon places a 12-mm port in the left lower quadrant, which allows use of a stapling device and provides an aperture for specimen removal at the conclusion of the procedure. A third suprapubic port offers a good cosmetic option but is not always appropriate, depending on the patient’s anatomy. Alternative approaches include use of a periumbilical port for stapling and specimen removal.

The patient is placed in the Trendelenburg position, and the operating table is “airplaned” to the left. This arrangement facilitates exposure of the right lower quadrant. Initial exploration includes retraction of the omentum, evaluation for abscesses or collections, and evaluation of the adnexa laparoscopically.

The tip of the appendix is identified and dissected, with care taken to preserve periappendiceal structures, which can include adnexa, gonadal vessels, and ureter. Once freed, the appendix is grasped and elevated by using an atraumatic grasper. An aperture in the mesoappendix is created bluntly at its base along the wall of the appendix using a Maryland dissector. This window is widened to admit a bowel grasper to identify the cecal-appendiceal junction clearly. The mesoappendix is then ligated with a vascular stapler load, or alternatively the appendiceal artery may be dissected and clipped. An endoloop or laparoscopic tissue stapler is then used to ligate or divide the appendiceal base. This procedure is performed at a site where tissue quality is adequate for the technique. If there is any doubt about tissue quality, the stapler may be applied slightly onto the base of the cecum.

The appendix is placed in a specimen bag and removed through the 12-mm port in the left lower quadrant. Any abscess or fluid collections can be irrigated before closure. If needed, a Jackson-Pratt drain can be left in place at the site of an abscess.

Open Technique

An open incision is made at McBurney’s point, located one-third the distance between the anterior superior iliac spine and the umbilicus (see Fig. 19-4). This area generally corresponds to the location of the base of the appendix. Subcutaneous tissues are opened to the level of the external oblique muscle by using electrocautery, and its fascia is incised parallel to its fibers. External oblique fibers run inferomedially and are separated along their length, exposing the internal oblique muscle and then the transversus abdominis muscle. These muscles also are preserved and separated through blunt retraction along their length. The peritoneum is opened sharply, with caution taken to avoid injury to underlying viscera.

The right lower quadrant is explored to identify the pathology. A finger sweep can be used to identify an inflamed appendix, which typically feels firm and indurated, revealing its location. Alternatively, identification of the decussation of the taenia coli can be used to identify the base of the appendix. The appendix should be followed to the tip to ensure complete resection. In the case of a retrocecal appendix, the cecum may need to be mobilized fully for adequate exposure (see Fig. 19-4).

After identification and mobilization, the base of the cecum and appendix can be flipped up into the wound. While holding traction on the appendiceal tip with the aid of a moist sponge or Babcock clamp, the surgeon sequentially divides the mesoappendix and appendiceal artery from distal to proximal to the base, freeing the appendix to be drawn out to length. Mesenteric attachments should be taken with fine clamps and ties to avoid hemorrhage when the mesentery retracts into the abdominal cavity.

Once the appendiceal base is visible, the appendix is clamped at its base; an absorbable tie is used to ligate the base. It is divided sharply distal to the tie, and the appendix is passed off the field and sent for pathologic review. Some surgeons invert the appendiceal stump by using a purse-string suture. Although its necessity has not been proved, this step may be used provided that tissue quality is appropriately pliant. The peritoneum may be closed with a running absorbable suture, and the fascia and skin are closed routinely.