Retroperitoneal Necrotizing Fasciitis Mimicking Fournier Gangrene: A Rare and Severe Diagnostic Entity

Introduction

Fournier gangrene, a life-threatening, severe infectious disease, is categorized as a necrotizing soft tissue infection. It arises from polymicrobial infections involving the perineal, genital, or perianal regions [1]. The origins of these infections can be traced to the anorectal, urogenital, or cutaneous systems, or sometimes remain idiopathic [2]. Retroperitoneal extension of Fournier gangrene is rarely reported, with only a few cases described in the literature, and its exact incidence remains unknown. Retroperitoneal involvement in Fournier gangrene indicates deeper and more extensive necrosis involving vital anatomical structures, such as major vessels or ureters. This significantly increases the complexity of surgical debridement and poses a higher risk of intraoperative injury and systemic complications. As a result, patients with retroperitoneal extension are more likely to experience delayed recovery, higher morbidity, and increased mortality. These factors make retroperitoneal involvement a clinically important determinant of management strategy and prognosis.

Although several cases of retroperitoneal involvement have been documented [3], the current literature often lacks detailed descriptions of the clinical progression, anatomical spread, surgical decision-making, and long-term outcomes in such advanced presentations. Furthermore, most reports are limited to brief summaries without comprehensive imaging, intraoperative findings, or multidisciplinary management insights.

In this case report, we detail a rare and complex presentation of Fournier gangrene extending into the retroperitoneum, originating from a perianal source. By providing a thorough account of the diagnostic process, radiological findings, surgical approach, and postoperative care, this report fills a critical gap in understanding the full clinical trajectory and management strategies required for such severe forms of Fournier gangrene.

Case Report

A 45-year-old man with a history of poorly controlled type 2 diabetes mellitus presented with a 3-day history of severe perineal and lower abdominal pain, fever, and scrotal swelling. Upon admission, he had fever (39°C), tachycardia (127 beats per min [bpm]), and hypotension (90/60 mmHg). The physical examination revealed erythematous necrotizing plaques on the perianal region, scrotum, and lower abdominal wall, with woody induration. Palpation of the affected areas caused severe tenderness but no rebound tenderness. The scrotum was markedly swollen (Figure 1), and the skin over the affected regions appeared discolored. Rectal examination revealed tenderness but no obvious fluctuance or mass.

Laboratory test results showed an elevated white blood cell count (18 500/μL), high C-reactive protein level, and mild elevation in serum creatinine level. The patient was considered to have acute kidney injury (stage 1). Contrast-enhanced computed tomography (CT) revealed extensive necrotizing fasciitis involving the perianal and lower abdominal regions. The infection extended cephalad along the psoas fascial planes into the retroperitoneum, reaching the periphery of both kidneys and the infrahepatic region (Figure 2). Gas formation within the fascial planes confirmed the diagnosis of necrotizing fasciitis with retroperitoneal infection.

We suspect the infection originated from the posterior perirectal region and extended cephalad via the fascial planes to the retroperitoneum. The anatomical communication likely followed the psoas fascia and perirectal fascial planes, as supported by CT findings.

The patient received a diagnosis of Fournier gangrene, complicated by retroperitoneal infection and sepsis. Empirical broad-spectrum antibiotic therapy with meropenem (1 g every 8 h) was initiated. Given the severity of the condition, a multidisciplinary team recommended urgent surgical intervention. Preoperatively, a urinary catheter was placed to prevent urethral injury during surgery.

Surgical debridement revealed extensive necrotic tissue within the subcutaneous and fascial layers, including the retroperitoneum. The infected tissue, with pus and gas accumulation, was excised, and the retroperitoneal and bilateral ischiorectal spaces were drained (Figure 3). Wound swab cultures grew mixed aerobic and anaerobic flora, including Escherichia coli and Bacteroides fragilis. Blood cultures collected at admission returned negative, and no systemic microbial findings were detected, indicating that the infection remained localized at presentation. Postoperative care included irrigation with saline and broad-spectrum antibiotics, with antibiotic therapy adjusted based on the bacterial culture results.

Postoperatively, the wound was managed with conventional iodine-soaked gauze packing and daily dressing changes. Additionally, ozonated saline irrigation was used to enhance wound decontamination and promote granulation. The patient also received structured education on wound care techniques, personal hygiene, glycemic control, and signs of infection recurrence to support long-term recovery and prevent complications.

The patient’s symptoms gradually improved, with inflammatory markers normalizing and wound healing progressing well. The patient was discharged 1 month after surgery, with no significant pain and stable condition. A follow-up CT at 1 month confirmed complete resolution of the retroperitoneal infection (Figure 4). At the 3-month follow-up, imaging showed substantial wound healing, indicating near-complete recovery (Figure 5).

Based on clinical and laboratory findings at admission, the patient’s Fournier Gangrene Severity Index (FGSI) score was 10. The individual scores were as follows: heart rate of 127 bpm (2 points), temperature of 39 °C (2), respiratory rate of 26 breaths/min (2), serum sodium of 130 mmol/L (1), potassium of 4.2 mmol/L (0), creatinine of 180 μmol/L (2), bicarbonate of 20 mmol/L (1), and hematocrit of 35% (0). An FGSI score ≥9 has been associated with increased mortality risk, which further underscored the urgency of surgical and supportive management.

Discussion

This case illustrates a rare and severe presentation of Fournier’s gangrene with retroperitoneal extension. The patient presented with acute perineal and lower abdominal pain, scrotal swelling, and systemic inflammatory response syndrome. Rapid progression led to retroperitoneal involvement, emphasizing the need for early recognition, aggressive surgical debridement, and appropriate antibiotic therapy.

Retroperitoneal dissemination in Fournier gangrene is uncommon but highly lethal due to diagnostic challenges and the anatomical complexity of the retroperitoneal space [4–6]. Possible pathways for spread include direct fascial extension, lymphatic or hematogenous dissemination, and contiguous invasion [7]. CT remains indispensable for early diagnosis, assessing disease extent, guiding surgical planning, and monitoring treatment response [8]. In the present case, CT revealed cephalad spread along the psoas fascia to the left adrenal region, prompting immediate surgical intervention.

Although similar cases have been reported, the rapidity and extent of progression in our patient were exceptional [9–11]. Alternative management strategies, such as negative pressure wound therapy or diverting colostomy, can be considered, although they were not required in this case. Timely surgical debridement – long recognized as the cornerstone of Fournier gangrene management – was crucial for infection control in the present case [12]. While the role of fecal diversion remains debated [13], our patient recovered well without colostomy, likely due to early multidisciplinary intervention.

Scoring systems such as the FGSI and Sequential Organ Failure Assessment (SOFA) score can aid in prognostication. In this case, the patient had a high-risk profile (FGSI=10, SOFA=2), warranting aggressive management. An FGSI score of 10, derived from vital signs, laboratory parameters, and acid-base status, has been associated with high mortality risk in previous studies. This score further justified our decision for urgent surgical debridement and close monitoring.

In our case, conventional iodine-soaked gauze dressings were combined with ozonated saline irrigation, which – together with structured patient education, including guidance on hygiene, wound care, and glycemic control – may have contributed to the favorable outcome. These measures are consistent with recent evidence suggesting that ozonated saline has antimicrobial and anti-inflammatory properties and can promote granulation, while structured patient education improves adherence, glycemic control, and wound care practices in patients with diabetes [14]. Together, our experience and that of prior studies highlight that integrating such adjunctive approaches into standard surgical and antibiotic treatment can enhance recovery and reduce the risk of complications in complex soft tissue infections.

Few cases of Fournier gangrene with retroperitoneal extension have been documented, and most are associated with poor prognosis and high mortality due to delayed diagnosis and inadequate infection control. Previous cases often required multiple surgical debridements or prolonged ICU stay, or even resulted in mortality despite aggressive intervention. For example, Basukala et al reported a 70-year-old patient requiring emergency laparotomy and drainage within 6 h, highlighting the importance of early surgery [3]. Molla et al described a young otherwise healthy patient who needed multiple debridements and intensive care [9]. Similarly, Baig et al emphasized that immediate operative management, without delaying for imaging, contributed to survival in a patient with perianal necrotizing fasciitis extending into the retroperitoneum [15]. Compared with these reports, our case achieved a favorable outcome through early multidisciplinary intervention, adjunctive ozonated saline irrigation, and structured patient education, highlighting the benefit of comprehensive individualized management.

Our patient’s postoperative recovery was uneventful, with resolution of infection and no serious complications. As supported by previous studies, favorable outcomes in such cases are strongly associated with early diagnosis and intervention [16,17]. This case also underscores the need for individualized management strategies, including incision planning, retroperitoneal drainage, and tailored antimicrobial therapy.

Despite its clinical value, this report is limited by its single-case nature, precluding comparative evaluation of management strategies. Further research is warranted to develop evidence-based protocols for retroperitoneal involvement in Fournier gangrene, alongside long-term outcome studies and preventive care frameworks.

Conclusions

This case highlights the importance of early diagnosis, prompt surgical intervention, and tailored antibiotic therapy in managing Fournier gangrene with retroperitoneal infection. Timely and aggressive treatment led to a favorable outcome.