Ultrasound in the diagnosis of Fournier's gangrene.

Fournier's gangrene (FG) is a life-threatening, rapidly progressive necrotizing infection. If not recognized and treated early, it is associated with high morbidity and mortality. The classic physical exam findings of crepitus are seen in approximately two-thirds of patients during the early stages of FG. Focused bedside sonography performed in cases of suspected gangrene represents an excellent adjunct in confirming the presence of subcutaneous gas and other signs of necrotizing infection. We present an illustrative case of a patient with FG who was evaluated with focused bedside ultrasonography.

INTRODUCTION

Fournier's gangrene (FG) is a life-threatening, rapidly progressive necrotizing infection of the perineal, perianal, and genital regions.[1] The mortality of FG ranges between 7.5% and 88%, depending on patient risks, comorbidities, and severity of presentation, with most reports citing 20–40% mortality.[23] Prompt diagnosis is essential in order to facilitate immediate operative debridement because the sequential progression of tissue necrosis can reach 2–3 cm per hour.[4] Consequently, diagnostic and therapeutic delays have been shown to increase morbidity, extent and number of surgical intervention(s), as well as mortality.[5] Although clinical examination in conjunction with confirmatory imaging (usually computed tomography) constitute the traditional diagnostic approach to FG,[6] increasing number of clinical reports advocate the use of focused bedside sonography as an adjunctive imaging method in the setting of suspected FG.[57-9]

CASE REPORT

A middle-aged man with a history of metastatic adenocarcinoma of the colon presented to the Emergency Department complaining of vomiting, severe testicular pain, and scrotal edema. His vital signs on arrival showed a blood pressure of 78/45 mmHg, a heart rate of 124 beats/min, and a temperature of 97.6 F. Initial laboratory evaluation featured an elevated serum lactate of 3.5 mg/dL, leukocytosis (white blood cell count 14,900), and acute renal failure (creatinine 3.14 mg/dL). His physical exam revealed acute edema and erythema of the scrotum, with crepitus and exquisite tenderness to palpation extending from the left scrotum to the left lower abdominal wall.

Immediate intravenous fluid resuscitation and broad-spectrum antibiotic administration were initiated. Emergency surgery and urology services were promptly consulted. Following initial IV hydration, his blood pressure improved to 100/62 mmHg, with a heart rate of 106/min. Bedsides, ultrasonography was performed to evaluate gas in the subcutaneous tissue of the scrotum and lower abdominal wall. The ultrasound showed small foci of gas within the tissues of the scrotum, with posterior acoustic shadowing [Figure 1]. Concurrently, the patient underwent computed tomography of the pelvis and scrotum, which showed foci of subcutaneous air [Figure 2]. Given these findings, the patient was immediately taken to the operating room with general and urological surgery services where he underwent extensive debridement of necrotic tissue of his scrotum and abdominal wall.

Figure 1

Scrotal ultrasound with subcutaneous gas bubbles and associated hyperechoic shadowing

Figure 2

CT scan transverse showing subcutaneous air tracking from the left scrotum into the abdominal wall

The patient recovered well postoperatively. His initial hospital care took place in the surgical intensive care unit, mainly due to the need for conscious sedation during serial wound-dressing changes and initial hemodynamic resuscitation related to underlying infection/sepsis. Following the acute phase of his wound care, he underwent subsequent split-thickness skin grafting of the scrotum at approximately 2 weeks postadmission. He was discharged from the hospital 20 days after the initial presentation.

DISCUSSION

Physical exam findings of FG include scrotal edema and tenderness. However, these findings can be present with other processes such as epididymitis or cellulitis. The hallmark of necrotizing infections is gas production by the bacterial organisms, which can sometimes (but not always) be appreciated on physical exam. In fact, estimates are that crepitus may not be detectable in as many as one-third of patients with the diagnosis of necrotizing infection.[10] This may be especially relevant at the early infection stage when surgical intervention is least extensive.

In addition to the physical exam, there are several diagnostic studies that can be used to evaluate necrotizing infections. Plain radiography of the pelvis may reveal subcutaneous emphysema in the involved tissue planes. Computed tomography (CT) may demonstrate adipose “stranding”, fascial thickening, as well as trace amounts of subcutneous gas. CT scan may also help in delineating the etiology of any associated and/or underlying infection, such as a perirectal abscess or other abdominal/pelvic processes.[11] Imaging evaluation in patients with FG may be limited by the frequent presence of concurrent acute renal failure (thus precluding the use of intravenous contrast material) or patient hemodynamic instability making transport to the imaging department unsafe [Figure 3]. Ultrasound constitutes an excellent minimally invasive alternative in such situations because it allows for bedside evaluation for any associated scrotal pathology or soft tissue collection/abscess, and has been shown to identify subcutneous gas, even prior to the overt development of crepitus on physical exam.[5] The characteristic ultrasonographic features of necrotizing infections include the presence of gas in the tissue, which will be bright (hyperechoic) with hyperechoic shadowing distally. The ultrasound may also show evidence of scrotal skin thickening and peritesticular fluid.[8]

Figure 3

CT scan showing subcutaneous air tracking from the left scrotum into the abdominal wall

CONCLUSION

This report highlights a case in which focused bedside ultrasonography was used in a critically ill patient to help delineate the etiology of his illness and expedite appropriate treatment. The diagnosis of FG is certainly a lot easier to make in the setting of advanced disease, when the patient has crepitus on exam, but these findings may only be seen in 19–64% of cases on early presentation.[5] It is in these cases where one needs to maintain a high index of suspicion for necrotizing infection and consider further diagnostic evaluation to determine the etiology. Multiple imaging modalities may be used[612] and it is up to the provider to balance time constraints, comfort with bedside diagnostics, and the role of imaging in their management of the emergent conditions at hand. Ultrasound can easily be used at the bedside to evaluate for subcutaneous gas as well as other possible etiologies associated with similar clinical presentation, including testicular, scrotal, and soft tissue pathology.