Introduction

Necrotizing fasciitis (NF) is an extremely virulent form of infectious fasciitis. It affects the skin, subcutaneous fat, and superficial and deep muscular fascia by rapidly progressive necrosis. Expeditious diagnosis and radical debridement are necessary to prevent the onset of sepsis, multisystem organ failure, and possible death. Perforated rectal cancer resulting in NF can spread to the perineum and genitals known as Fournier gangrene. This case describes an unusual case of NF of the right thigh secondary to rectal cancer perforation.

This case highlights the need for prompt diagnosis, urgent aggressive surgical debridement, and consideration of a rare underlying cause in the management of necrotizing fasciitis.

Case report

A 61-year-old woman presented acute proctalgia and right thigh pain. She had a locally advanced rectal cancer and had recently completed neoadjuvant chemoradiotherapy.

In the emergency room, she was hemodynamically unstable and septic. On examination, she had functional impotence of the right leg and there was a large tender swelled area on the posterior thigh. Blood tests revealed elevated acute phase reactants (C-reactive protein 315 mg/L and procalcitonin 5.25 ng/mL), leukopenia, acute kidney failure, and metabolic acidosis.

The computed tomography (CT) scan showed ulcerated and perforated rectal neoplasm with a presacral abscess extending through the sciatic foramen and pyomyositis of the right leg muscles with gas around the femoral vessels and sciatic nerve (Fig. 1).

Figure 1 Computed tomography scan of the thigh, demonstrating gas around the left femoral vessels with associated pyomyositis. 

A laparoscopic diverting loop colostomy was performed, as well as debridement of the extensive pyomyositis. Intraoperatively, there was an offensive gas-forming infection of the deep fascia extending between the muscles of the posterior thigh, which was focused on the sciatic nerve (Fig. 2). All of the involved skin, fascia, and muscle were excised. Following the sciatic nerve proximally, the pus extended above the greater sciatic foramen.

Figure 2 Intraoperative photograph of debridement. Exploration of the left leg revealed severe soft-tissue infection involving the skin, subcutaneous fat, and fascia; the femoral vein and nerve were covered in infected fascia. 

Postoperatively, the patient was transferred to the Intensive Care Unit, and she underwent five further debridements in the theater. A negative pressure dressing was applied for 12 days until the skin defect was covered with skin grafts.

She was discharged after 2 months with neuropathic pain treated with morphic. Additional staging CT was performed with disease progression and the case was discussed at a multidisciplinary meeting where the decision was made to aim for palliative chemotherapy.

Discussion

Necrotizing fasciitis is a potentially life-threatening surgical emergency and can be difficult to recognize in the early stages. It is a rapidly progressive soft-tissue infection, and mortality rates are between 25 and 35%¹. Mortality is related to the degree of sepsis and the general condition of the patient at the time of diagnosis. The infection is usually polymicrobial. Clinical findings include swelling, rapidly spreading cellulitis, severe pain, and palpable crepitus; the patient may be in septic shock.

NF can be difficult to recognize in the early stages, so a high index of suspicion is needed when confronted with rapidly spreading erythema or subcutaneous crepitus. Skin necrosis and blistering are late signs. When NF of the abdominal wall or thigh is not associated with an obvious cutaneous portal of entry, an intra-abdominal cause should be sought.

Treatment is mainly surgical, involving early aggressive debridement in conjunction with high-dose intravenous antibiotics and intensive care support². The goal of the debridement is to remove all necrotic tissues, to stop the progressive infection, and to reduce systemic toxicity. Debridement should be repeated when necessary. In cases of rectal perforation, fecal diversion is recommended³.

There are very few reported cases of perforation of a rectal malignancy leading to NF of the thigh. There are several possible routes of entry for fecal matter and infection to invade the thigh: Femoral sheath, femoral canal, psoas sheath, sciatic notch, and the obturator foramen.

However, rectal perforation should always be ruled out, especially in patients with a prior history of rectal disease³-⁵. In this patient, the femoral canal provided a channel for the intra-abdominal infection to invade the thigh.

Conclusion

NF is a rare condition that demands prompt diagnosis and surgical treatment is the aggressive debridement to healthy tissue. NF of the thigh secondary to rectal cancer perforation is unusual. Our case highlights the sciatic foramen as a channel for the spread of pelvic infection into the thigh. The loop colostomy promotes wound healing by protecting it from fecal matter.

In addition, NF is a very severe complication that can delay and hinder the definitive treatment of the cancer.