Appendicular Mass

An appendicular mass is a localised inflammatory phlegmon surrounding an inflamed or perforated appendix. It usually develops after several days of untreated appendicitis when the omentum, caecum and adjacent small bowel contain the inflammatory process.

The mass is predominantly inflamed adherent tissue rather than a mature pus collection. This distinction matters because an appendicular abscess may be suitable for image guided drainage, whereas a phlegmon usually is not.

The main surgical problem is that the appendix may be densely adherent to the caecum, terminal ileum and mesentery. Immediate dissection can therefore convert a contained process into bowel injury, faecal fistula, caecal resection or ileocaecal resection.

Current surgical guidance accepts both operative and nonoperative approaches for complicated appendicitis. SAGES generally favours operative treatment, but recognises that a mature inflammatory mass, prolonged symptoms and severe caecal inflammation may favour initial conservative management.

Presentation is typically later than uncomplicated appendicitis, often after several days of symptoms.

The usual pattern is:

• Persistent right iliac fossa pain that may be less intense than at initial onset
• Fever, anorexia and malaise
• Localised tenderness and guarding
• A firm, tender, poorly defined right iliac fossa mass
• Mild abdominal distension or local ileus in more advanced inflammation

The patient may appear surprisingly stable because contamination has been contained.

Features suggesting progression beyond a stable phlegmon include increasing pain, spreading tenderness, persistent tachycardia, recurrent fever, vomiting, worsening ileus, sepsis or haemodynamic instability.

Generalised guarding or rigidity means the process is no longer adequately contained and should not be managed as a simple appendicular mass.

Older adults require particular caution because caecal carcinoma, appendiceal neoplasia and inflammatory bowel disease may present as an apparent appendicular inflammatory mass.

Contrast enhanced CT of the abdomen and pelvis is the preferred investigation in adults. It establishes whether the lesion is predominantly phlegmonous or contains a drainable abscess and can identify perforation, bowel obstruction, appendicolith or alternative pathology. Current IDSA guidance favours CT as the initial imaging modality for suspected appendicitis in nonpregnant adults.

Typical CT findings include:

• Inflamed appendix embedded within inflammatory tissue
• Dense periappendiceal fat stranding
• Thickening of adjacent caecum or terminal ileum
• Matted bowel loops
• Omental inflammatory change
• No dominant fluid cavity suitable for drainage

Check full blood count, C reactive protein, renal function and electrolytes. Obtain lactate and blood gas if there is sepsis, poor perfusion or significant physiological derangement.

Blood cultures are most useful when fever is accompanied by hypotension, tachypnoea, delirium or concern for resistant organisms. They are not routinely required in a stable uncomplicated presentation.

A physiologically stable patient with a well localised appendicular mass, no diffuse peritonitis and no drainable abscess can undergo initial nonoperative management.

Keep the patient fasting initially if significant pain, vomiting or possible intervention is anticipated. Correct dehydration with balanced crystalloid, provide analgesia and monitor abdominal findings and physiological parameters serially.

For a stable adult with community acquired infection:

Ceftriaxone 2 g IV every 24 hours plus metronidazole 500 mg IV or orally every 12 hours.

Ceftriaxone does not usually require renal adjustment. Metronidazole at this dose is appropriate for intra abdominal infection.

In severe infection, recent healthcare exposure or substantial risk of resistant Gram negative organisms:

Piperacillin tazobactam 4.5 g IV loading dose over approximately 30 minutes, then 4.5 g IV every 8 hours infused over 4 hours.

Adjust piperacillin tazobactam for significant renal impairment. Prolonged beta lactam infusion is preferred in sepsis because it improves pharmacodynamic exposure.

Clinical improvement should be evident over the next 24 to 72 hours, with decreasing pain and tenderness, improving temperature and pulse, improving oral intake and a downward inflammatory marker trend. The palpable mass may take considerably longer to disappear.

A patient who does not improve requires reassessment rather than simply more antibiotics.

Escalate for:

• New generalised peritonitis
• Persistent or worsening sepsis
• Haemodynamic deterioration
• Progressive obstruction or ileus
• Increasing pain or tenderness
• Development of a drainable abscess
• Failure of clinical improvement despite appropriate treatment

Repeat CT is appropriate when deterioration suggests abscess formation, perforation or another diagnosis.

Early laparoscopic appendicectomy is an alternative when advanced laparoscopic expertise is available. Surgery should prioritise safe source control. Dense inflammatory tissue should not be forcibly separated merely to complete a conventional appendicectomy. Severe caecal destruction may occasionally require limited caecal or ileocaecal resection, but this should not result from unnecessarily aggressive dissection.

If conservative management succeeds, the need for interval appendicectomy should be individualised. Current SAGES guidance conditionally favours interval appendicectomy in adults after successful nonoperative treatment of complicated appendicitis, although the certainty of evidence is low. Concern is greater in adults over approximately 40 years because occult appendiceal neoplasia is more frequent in this group.

Colonic evaluation and interval cross sectional imaging should be strongly considered in older adults or when imaging is atypical.