23 Perianal necrotising fasciitis: challenges, troubleshooting and the role of negative pressure wound therapy with installation (NPWTi)
Authors: Kovacs Luca , Johnston Magnus , Damaskos Dimitrios , Zanellato Artur 
Published: February 2025

Introduction

Necrotising fasciitis is a rare disease with a significant mortality rate worldwide. Treatment entails urgent and serial debridement alongside antibiotic therapy however management is often complicated by the anatomical wound location and contamination risk posing extra challenges. This case details how leak of bowel content into the wound even with Negative Pressure Wound Therapy with installation (NPWTi) can result in severe sepsis.

Case Report

A 79-year-old woman was brought via ambulance having been found at home following a fall and long lie. Past medical history included T2DM, hypertension, a previous transient ischaemic attack, and uterine neoplasm. On examination, the patient was very unwell, apyrexial with fast atrial fibrillation, hypotension, cool peripheries, and urinary retention. GCS was 14. A blood gas revealed significant metabolic acidosis with ketosis, hyperglycaemia (20 mmol/l), leukocytosis (25.1 × 10^9/l), neutrophilia (23.05 × 10^9/l), and an elevated C-reactive protein (417 mg/l). Initially suspected to be diabetic ketoacidosis, management was commenced with analgesia, catheterisation, intravenous fluid resuscitation and Co-amoxiclav. Due to vasoplegia, Metaraminol 35 ml/hr was administered. An urgent CT abdomen showed a large gas and fluid containing presacral collection, extending perianally and laterally through the left greater sciatic foramen across fascial planes, with extensive soft tissue gas. Once confirmed as necrotising fasciitis, urgent wound exploration and debridement of all skin and soft tissue necrosis was performed, with a large amount of pus being drained. NPWTi (Veraflo@) was used. Pus and tissue were sent for microbiology whilst antibiotics were commenced as per local guidelines (Metronidazole, Clindamycin, Flucloxacillin, Gentamicin). On day four of admission, vasopressors were weaned completely, and the patient was extubated and was allowed to eat. On day five, the patient suddenly deteriorated due to faecal contamination, requiring urgent reassessment in theatre. Although further but minimal debridement of tissue was required, notably fresh and large amount of faeces was causing gross contamination. Fistula from rectum was excluded with methylene blue test. Defunctioning loop colostomy with rectal tube and closure of the anal verge with pursue string tie was also performed to prevent leak into the large cavity. Following tissue microbiology results, the patient’s antibiotics were rationalised to Metronidazole, Tazocin and Gentamicin. Further VAC-dressing changes took place on days 6, 12, 16, 19, 23, 27, 31, 35. The NPWTi was discontinued after 39 days. Not surprisingly for her age, a few complications extended her hospital stay, however her large perineal wound and deep cavities were notably well-healed at her time of discharge 15weeks following admission.

Educational Highlights

Gross contamination of open wound by faeces can rapidly develop septic shock. Methylene blue test was adequate to clarify fistula. Rapid assessment and wound cleaning can save lives. Diversion of bowel content in large perianal necrotizing fasciitis should be considered in early stages.

Conclusion

Management of perianal necrotising fasciitis is a considerable challenge due to the anatomy and proximity to bowel content. This case demonstrates the risk of recurrent severe sepsis, secondary to faecal contamination. Although challenging, the NPWTi is the treatment of choice.