Appendix and abdominal abscess

Published on 15/04/2015 by admin

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Appendix and abdominal abscess

D.E. Whitelaw and N.J. Ward

CONTENTS

Open appendicectomy

Laparoscopic appendicectomy

Appendix mass

Subphrenic and subhepatic abscess

OPEN APPENDICECTOMY

Appraise

1. Acute appendicitis is essentially a clinical diagnosis. A detailed history and careful examination of the patient carry more weight in making the diagnosis than embarking on radiological investigations, although these investigations can be useful to rule out alternative diagnoses.

2. Although appendicectomy is still the most common reason for laparotomy, remember the following:

Young children and the elderly may have atypical presentations of appendicitis and also have a higher mortality and morbidity from this condition.¹

Female patients may have a gynaecological cause for pain and tenderness in the right iliac fossa rather than appendicitis. Order a pelvic ultrasound scan and consider carrying out a diagnostic laparoscopy in such cases.

There is good evidence that in female patients, appendicitis, even when perforated, does not adversely affect fertility, so you need not perform a mandatory appendicectomy in equivocal cases.²

Although elderly patients do develop appendicitis, consider other pathology such as perforating carcinoma of the caecum and diverticulitis, which may mimic its presenting features. In case of doubt, use a midline incision so you can carry out a full examination of the peritoneal cavity.

Computed tomography (CT) is the most sensitive imaging technique for diagnosing appendicitis.³ In view of the radiation dose, reserve this investigation for those in whom a negative laparotomy represents an unjustifiable risk.

3. Tend to treat conservatively a patient with symptoms for 5 or more days in whom you find a mass in the right iliac fossa. Give a 7-day course of intravenous antibiotics such as co-amoxiclav and metronidazole, withhold oral feeding and replace fluid intravenously. Mark the extent of the mass on the abdominal wall. Perform an ultrasound or CT scan to exclude the presence of a large abscess that can be drained percutaneously. Carefully monitor the patient and perform an operation only if:

The mass increases in size despite antibiotics

The patient develops features of bowel obstruction or peritonitis

The patient develops worsening toxaemia or septic shock.

As a rule, in patients over the age of 40 years, order a barium enema X-ray, CT colography or colonoscopy when the mass has settled to exclude caecal carcinoma. It has been conventional practice to re-admit patients for ‘interval’ appendicectomy 1–2 months later, but the number of patients developing recurrent appendicitis is small, so it may be justifiable to defer operation indefinitely, but warn the patient to seek medical attention if symptoms recur.

4. Some surgeons carry out diagnostic laparoscopy whenever they suspect appendicitis, proceeding to laparoscopic appendicectomy if the diagnosis is confirmed.

5. Avoid removing a normal appendix incidentally during other operations, such as cholecystectomy. It is a possible cause of complications such as wound infection and subsequent adhesive intestinal obstruction.

PREPARE

1. Wound infection is the most common complication following operation for acute appendicitis, so routinely give 500 mg of metronidazole and a broad-spectrum antibiotic (e.g. co-amoxiclav) intravenously at induction of anaesthesia.

2. In patients with clinically severe acute appendicitis who are demonstrating signs of systemic sepsis, commence intravenous metronidazole and a broad-spectrum antibiotic as soon as the decision to operate is made.

3. Patients who have a perforated appendix require a full 5-day course of broad-spectrum antibiotic and metronidazole.

KEY POINTS

Antibiotic usage

Where the diagnosis of appendicitis is equivocal, avoid starting antibiotic therapy, as this will mask developing signs and symptoms of the disease, thus making surgical exploration mandatory. Antibiotics should only be commenced once the decision to operate has been made.

Traditionally, cephalosporins have been combined with metronidazole for treatment of intra-abdominal sepsis. They have, however, been linked with antibiotic-associated infective colitis and many hospitals have now developed guidelines discouraging the widespread use of cephalosporins. Always use local prescribing guidelines when choosing antibiotic therapy, or consult with a microbiologist.

KEY POINT

Re-examine the abdomen when the patient is anaesthetized

Always re-examine the abdomen when the patient is anaesthetized. You may feel the inflamed appendix in the relaxed abdomen, which was impalpable beforehand. This is a valuable general rule before any abdominal operation, and may help you determine the best site for the incision.

Access

1. As a routine employ a Lanz incision in a skin crease. This modification of the gridiron incision transversely crosses McBurney’s point – the junction of the middle and outer thirds of a line joining the anterior superior iliac spine and the umbilicus. The incision starts 2 cm below and medial to the right anterior, superior iliac spine and extends medially for 5–7 cm. It may be possible to site it lower in a young girl so that the scar lies below the waistline of a bikini.

2. Alternatively, use the traditional gridiron incision, 5–8 cm long, in line with the external oblique fibres if you anticipate the need to extend the exposure (Fig. 7.1). The incision crosses McBurney’s point at right-angles to the spino-umbilical line, one-third above, two-thirds below. If necessary, the external oblique muscle and aponeurosis can be split in both directions and the internal oblique and transversus muscles can be cut to convert the incision into a right-sided Rutherford Morrison incision.

Fig. 7.1 Gridiron incision for appendicectomy. In the Lanz modification the skin incision is transverse but the abdominal muscles are similarly split in the line of their fibres.

3. If appendicitis is one of a number of likely diagnoses, opt for a lower midline incision.

Opening the abdomen

1. Incise the skin cleanly with the belly of the knife. Divide the subcutaneous fat, Scarpa’s fascia and subjacent areolar tissue to expose the glistening fibres of the external oblique aponeurosis. In the gridiron approach these fibres run parallel to the skin incision.

2. Stop the bleeding. Incise the external oblique aponeurosis in the line of its fibres. Start with a scalpel, then use the partly closed blades of Mayo’s scissors (Fig. 7.2) while your assistant retracts the skin edges.

Fig. 7.2 Appendicectomy. Regardless of which skin incision is used, the external oblique aponeurosis is split by pushing partly closed scissors in the line of the fibres.

3. Retract the external oblique aponeurosis to display the fibres of the internal oblique muscle, which run at right-angles. Split internal oblique and transversus abdominis muscles, using Mayo’s straight scissors (Fig. 7.3). Open the blades in the line of the fibres and use both index fingers to widen the split. Provided the scissors are not thrust in violently, the transversalis fascia and peritoneum are pushed away unopened.

Fig. 7.3 Appendicectomy. The internal oblique muscle is split by opening Mayo’s straight scissors in the line of the fibres.

4. Stop the bleeding. Have the muscles retracted firmly to display the fused transversalis fascia and peritoneum.

5. Pick up a fold of peritoneum with toothed dissecting forceps and grasp the tented portion with artery forceps. Release the dissecting forceps and take a fresh grasp to ensure that only the peritoneum is held. Make a small incision through the peritoneum with a knife. Allow air to enter the peritoneal cavity, so that the viscera fall away. Use scissors to enlarge the hole in the line of the skin incision. Now protect the wound edges with swabs or skin towels.

Assess

1. Look. Is there any free fluid or pus? If so, take a specimen for microscopy and culture.

2. Find the caecum, identify a taenia and follow it distally to the base of the appendix. Insert a finger and lift out the appendix by pushing from within, not by pulling from without.

KEY POINT

Manipulate the inflamed appendix with care

Never pull on the appendix if the distal end is stuck. If it is gangrenous it will tear and release infected material into the peritoneal cavity. Improve your view if necessary by extending the incision.

3. If the appendix is not evident, push your index finger posteriorly until it comes to lie on the peritoneum over the psoas muscle. Then, maintaining contact with the posterior peritoneum, draw your finger to the right until it can go no further. The caecum should now lie between the ‘hook’ of your finger and the right limit of the iliac fossa, and may be gently pushed out onto the surface. In some cases you may need to mobilize the caecum by incising the parietal peritoneum in the paracolic gutter, in order to raise the caecum on its mesentery, especially if the appendix is adherent retro-caecally. If the caecum is not evident, remember that it sometimes lies quite high, under the right lobe of the liver.

DIFFICULTY

There is no appendix? In a small number of patients there is no appendix, either because it did not develop or because it has been digested or has atrophied as a result of previous inflammatory disease. In this case, what is the cause of the patient’s symptoms? Carry out a search for disease of nearby organs (see below).

4. Confirm the diagnosis: the appendix, or more usually its tip, is swollen, congested, inflamed, even gangrenous, often with fibrin deposition, turbid fluid or frank pus.

DIFFICULTY

1. If the appendix is not inflamed, examine its tip to exclude a neuroendocrine (carcinoid) tumour, which usually manifests as a yellowish swelling at the tip; such tumours are common, with low malignant potential, and appendicectomy may well be curative. Adenocarcinoma of the appendix, however, demands a right hemicolectomy.

2. Examine the caecum, since an ulcer, inflammation or cancer may present as appendicitis. Pass the distal 1.5 m of the ileum and its mesentery through your fingers to exclude mesenteric adenitis, Crohn’s disease or Meckel’s diverticulum. Palpate the posterior abdominal wall, ascending colon, liver edge and gallbladder fundus and the lower pole of the right kidney. Now feel below into the right rim of the pelvis, the bladder fundus, right iliac vessels and right inguinal region. In females examine the right ovary and fallopian tube, and attempt to feel the uterus and left ovary and tube.

3. Look for features of a distant cause such as bile-stained fluid tracking down from a perforated peptic ulcer, an inflamed gallbladder or gynaecological pathology. Be prepared to close a standard Lanz incision and make a fresh, well-placed incision, rather than struggle to deal with the problem by extending or stretching the incision in the right iliac fossa. The presence of free purulent fluid is an indication to embark on wider examination of the abdominal contents.

Action

1. Mobilize the appendix from base to tip by gently moving or peeling away adherent structures. Remember that the artery enters from the medial aspect. If the tip is adherent, improve the view. Do not dissect blindly. If necessary, extend the incision. Apply Babcock’s tissue forceps to enclose, but not grasp, an uninflamed portion of the appendix, to hold it so you can view the mesentery against the light and identify the artery.

2. Pass one blade of the artery forceps through the mesoappendix and clamp the vessels (Fig. 7.4). If it is thickened, take the mesoappendix in two bites. Divide the mesoappendix distal to the clamp and ligate the vessel gently but firmly with 2/0 Vicryl or similar material, ignoring the slight back bleeding from the distal cut end.