Enterocutaneous fistula resulting from the drainage of a contained appendiceal perforation secondary to a partially obstructing low-grade appendiceal mucinous neoplasm

Abstract

We report a case of an enterocutaneous fistula resulting from drainage of a contained appendiceal perforation secondary to an obstructing appendiceal mucinous neoplasm. A 66-year-old otherwise healthy female patient proceeded to laparoscopic appendicectomy with resection of the fistula tract. Histopathology demonstrated a mid-appendiceal mucinous neoplasm, with a benign enterocutaneous fistula tract communicating with the distal, non-malignant portion of the appendix. We provide an overview of the literature and highlight the need to consider appendiceal mucinous neoplasm as a differential in the management of spontaneous right iliac fossa collections and fistulae.

Background

We present the rare case of an enterocutaneous fistula resulting from the drainage of a contained appendiceal perforation secondary to an obstructing low-grade appendiceal mucinous neoplasm (LAMN). Fistulation due to malignant invasion and perforation due to luminal obstruction are well-documented complications of appendiceal mucinous neoplasms. To our knowledge, this is the first report of benign fistulation secondary to appendicitis resulting from an obstructing mid-appendiceal tumour.

Case presentation

A 66-year-old woman was referred for management of an enterocutaneous fistula on a background of a known recurrent superficial pelvic collection, identified 12 months prior. She initially presented with a tender superficial supra-pubic mass located at the rightmost lateral margin of a Pfannenstiel scar, associated with dysuria, fevers and unexpected weight loss. Computed tomography (CT)imaging at the time demonstrated a heterogeneous partially cystic collection located in the pre-vesical space of the pelvis and intimately related to the appendix, small bowel and bladder. The collection was drained percutaneously, and the patient managed on antibiotics. Microbiological analysis of aspirated fluid demonstrated mixed growth of Escherichia coli and Bacteroides fragilis, with no malignant cells identified on cytology. Colonoscopy and cystoscopy at the time failed to identify a cause for the abscess.

Recurrence of the collection with abdominal skin breakdown at 9 months resulted in repeat cystoscopy, as well as a CT sinogram, all of which failed to identify an underlying visceral communication.

Aside from well-controlled hypertension (perindopril 2.5 mg daily) and two previous caesarean section deliveries via Pfannenstiel incision, the patient had no other significant medical history.

Investigations

Due to 3 months of persisting abdominal wound discharge, the patient was examined under anaesthesia, which revealed a tract extending 20 mm into the abdominal cavity. A repeat CT sinogram (figure 1) demonstrated a fistula tract with contrast tracking into the caecum via the tip of the appendix, associated with reactive bladder wall thickening, but no contrast was flowing into the bladder itself. There was no extravasation of contrast and no appendiceal mass identified, although no intravenous contrast was administered.

Figure 1.

Coronal view (i) and axial series (ii) of CT sinogram demonstrating contrast (green arrow) tracking through a superficial abdominal wall collection (A) into the caecal pole (B) via the appendix (C). Right hip joint (D); bladder (E); sacrum (F).

Treatment

The patient underwent diagnostic laparoscopy, during which it was noted that there was a mid-appendiceal tumour, with distal appendiceal adherence to the anterior abdominal wall but no mucinous contamination of the abdomen. The decision was thus made to proceed with laparoscopic appendicectomy with resection of the fistula tract. An en bloc approach was attempted but was not achieved due to friability of the fistulating tissue. Histopathology revealed a grade 1, stage 0 (TisN0M0) LAMN in the mid-appendix with clear proximal and distal margins (figure 2) but no mucin on the serosal surface of the appendix. The enterocutaneous fistula tract showed giant cell reaction to acellular material that was only weakly positive for mucin stains but had no features of malignancy.

Figure 2.

Macroscopic and microscopic appearance of appendiceal neoplasm (i and iii, respectively) and cutaneous aspect of fistula tract (ii and iv, respectively). Neoplasm (A); appendiceal mucosa; epithelial surface of skin (C).

Outcome and follow-up

Repeat CT at 3 months and 12 months following resection showed no recurrence of the appendiceal malignancy, pelvic abscess or fistula tract.

Discussion

Primary malignancies of the vermiform appendix are rare. Mucinous tumours account for approximately 1 in 400 appendiceal neoplasms and are classified as low grade or high grade based on cytological atypia and invasion beyond the muscularis mucosa.^{1 2} LAMNs are well-differentiated, slow-growing tumours that usually result in mucocele formation or gradual obstruction of the appendiceal orifice with subsequent appendicitis.³ They are most commonly found incidentally on unrelated cross-sectional abdomino-pelvic imaging or discovered in histopathological specimens following appendicectomy for appendicitis.⁴ When symptomatic, appendiceal mucinous neoplasms typically present with right lower quadrant pain with or without a palpable lump.^{5 6} Occasionally, they can have a mass effect which can precipitate bowel obstruction.⁴ Intraperitoneal rupture of the tumour, termed pseudomyxoma peritonei (PMP), is a feared complication, leading to mucinous ascites and peritoneal tumour dissemination. PMP is present in 50% of cases at diagnosis and confers a poor prognosis.^{1 4}

Cross-sectional imaging of the abdomen and pelvis, most commonly with CT, is required prior to resection, with the primary goal of staging and differentiating ruptured versus contained LAMN.⁷

Curative resection of contained appendiceal mucinous neoplasm can be achieved with simple appendicectomy. However, failure to obtain negative margins necessitates caecectomy. In the rare case of nodal disease, formal right hemicolectomy is recommended. A laparoscopic approach can be considered, provided that regional lymph nodes can be adequately resected and that there is negligible risk of converting a contained neoplasm into a perforated one. Perforation warrants the use of heated intraperitoneal chemotherapy (HIPEC) with or without cytoreductive surgery.⁴ The presence of mucin on the appendix’s serosal surface (staged T4a) results in higher rates of recurrence. There is some debate regarding optimal management for these patients. Formal right hemicolectomy can be performed, although this provides no clear survival benefit compared with appendicectomy.⁸ Alternatively, either a high frequency surveillance strategy can be adopted for early detection of disease progression, or pre-emptive HIPEC and cytoreductive surgery can be offered.⁹

In general, iatrogenic enterocutaneous fistulae can arise secondary to an anastomotic leak, missed enterostomy or mesh-induced bowel wall erosion.¹⁰ Spontaneous enterocutaneous fistulae arise secondary to foreign bodies, radiation, inflammation/infection, epithelialisation, neoplasia or distal obstruction (FRIEND).¹¹ The acronym FRIEND is commonly used memory aid.

There are several case reports documenting fistula formation secondary to LAMN. These include a handful of cases of enterocutaneous fistulae, some of which occurred at previous surgical sites.^12–16 In these cases, LAMNs were locally invasive, with the migration of neoplastic cells along the fistula tract or the presence of mucin on the serosal surface of the appendix. Accordingly, these tumours were staged T4a or T4b and would warrant further management given the associated poorer survival. In contrast, there were no invasive features in our case, and appendiceal perforation was the consequence of mechanical obstruction and not direct invasion of the abdominal wall. Expert pathologist opinion was sought for this case, and it was postulated that an enlarging, but not invading, tumour in the mid-appendix caused partial luminal obstruction with subsequent distal appendicitis with perforation. Percutaneous drainage of the contained perforation resulted in enterocutaneous fistula formation. This hypothesis is supported by the absence of malignant cells in the fistula tract and distal appendix. There are no similar cases reported in the literature.

Despite previous publications, appendiceal mucinous neoplasms continue to be overlooked as a differential in managing spontaneous abdominal wall collections. As such, this case serves as a prudent reminder to consider appendiceal mucinous neoplasms in instances of unexplained collections and non-healing sinuses/fistulae located in the right iliac fossa or right flank.

Learning points.

• This is the first documented case of benign perforation and subsequent fistulation secondary to distal appendicitis resulting from an obstructing mid-appendiceal tumour.

• Appendiceal mucinous neoplasms should be considered as differential diagnoses for spontaneous ride-sided enterocutaneous fistulae.

• Not all fistulae arising in the context of appendiceal mucinous neoplasms should be considered invasive.

Ethics statements

Patient consent for publication

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