The term of FG refers to necrotizing fasciitis that involves perineum and perianal region due to the pathognomonic features. Existing studies have revealed a predominance among the elderly with a mean age of over 50 years, which coincides with this paper. Martinez found that old age was not a direct factor affecting survival . However, this aging trend seems to be related to the incidence of FG with an increasing number of predisposing disease. Similar to our results, males are more common to suffer from FG than females, with the reported male-to-female ratio of 5.3:1 . This sex distribution appears to be associated with the anatomical difference. Infection spreads along the fascial plane, but due to the anatomic protection of the envelope of urethra and corpora cavernosa, scrotum is more common to be affected. It is considered that females are less susceptible to this infection, because of the better drainage of secretion in the female pelvis. Testicular necrosis is rare as a result of the independent blood supply of internal spermatic artery. Therefore, if an infection involves the testis, it should be wary of intraperitoneal or retroperitoneal infections . However, in the case of females, it may cause severe extension to the anterior abdominal wall, as Colles’ fascia is not anteriorly attached.
The underlying pathogenesis of FG is the spread of local infection in the broad sense, only 10% cases are considered idiopathic . The bacteria isolated from FG wound are consistent with normal flora in the urogenital and anogenital regions, which include Gram-negative, Gram-positive pathogens and anaerobic bacteria, although anaerobes are less frequently isolated . As reported in studies, the most susceptible bacteria are Escherichia coli, Pseudomonas aeruginosa, Enterococcus faecium and Staphylococcus aureus . Besides, FG presents a combination of mixed bacteria infection, which may be related to the rapid disease progression and severity. Such complex polymicrobial infection is another feature of FG compared with necrotizing fasciitis in other area. So broad-spectrum antibiotics should be chosen as the basic antibacterial therapy. Generally, double- or triple- combination is recommended as the basic criterion, including third-generation cephalosporins, aminoglycoside antibiotics, metronidazole or ornidazole . Furthermore, new drugs, such as meropenem and piperacillin-tazobactam, are also advocated for the sake of larger distribution and less renal toxicity. In early admission, the regimens are applied empirically in this series, but antibiotics must be modified as appropriate according to the culture results.
The predisposing disease is not only important in the occurrence of FG, but also in its mortality. Among these predisposing diseases, DM is identified as the most common comorbidity involved in FG, which may increase the possibility of bacterial infection. It is found in the literature review that, the percentage of DM reaches up to 76.9% in patients with FG . Moreover, the degree of DM control has also been demonstrated to be correlated with disease progression and extent, therefore, patients with uncontrolled DM may be associated with dismal prognosis . It should be noted that, DM control is difficult in the early progression of FG because of the severe inflammatory response and immune disorder. As discovered from the clinical observation in this study and previous reports, insulin pump is more convenient and efficient than normal insulin injection for the unruly blood glucose . Other predisposing diseases include abscess in perineum and perianal region, hypertension, local trauma, chronic catheterization, tumor, and organ failure. In a sense, Chen considered FG as a complication of colorectal or urological diseases . While, among these predisposing diseases, organ failure should be paid special attention, especially for renal failure. Because deteriorated renal function can not only greatly increase the incidence of FG, but also have an impact on mortality. Moreover, multiple predisposing diseases are a direct indicator for the prediction of mortality .
Early diagnosis plays a crucial role in the management of FG, but the diagnosis of FG is particularly challenging for clinicians in two aspects. On the one hand, early clinical symptoms, including erythema and swelling, can be confused with other infections, such as abscess, fistula or local trauma. Besides, skin necrosis due to vascular thrombosis often falls behind the progression of fascial infection. As demonstrated by Chawla, the necrotic area showed no direct relationship with the disease severity or prognosis . Therefore, it is difficult to make a definite diagnosis in the absence of pathognomonic manifestation at the early stage. On the other hand, delayed diagnosis is fatal, which is correlated with a much higher mortality rate, since the infection progression rate can reach up to 2-3 cm/h. Particularly, septicemia can occur within an hour after the disease outbreak.
In this series, early diagnosis depends on the combination of clinical symptoms, imaging findings and laboratory tests. Apart from the typical symptoms of infection, crepitus caused by gas bubbles can also be found within the infected area as a special feature, and gas in scrotal wall can be detected on ultrasound even before the presence of clinical crepitus. In a literature review, about 54.3% cases are complicated with the symptom of crepitus . The gas on the fascial plane shows dirty shadowing and discrete hyperechoic focus in ultrasonography. While it should be noted that the absence of soft tissue gas does not exclude FG. Other laboratory tests, including acidosis, leukocytosis, sudden thrombocytopenia, and anemia, may be helpful for the early diagnosis. The LRINEC score, which is a combination of indicators, is more practical, and a score≥8 is strongly predictive of FG. Nonetheless, it is demonstrated that LRINEC is only helpful for diagnosis, but fails to predict the clinical outcome. Moreover, the LRINEC score is more sensitive for patients with electrolyte variation and renal impairment .
Aggressive surgical treatment is advocated for the highly suspected cases. A definite diagnosis can be made based on the intraoperative manifestation that invasive infection is observed to spread along the deep fascia. Surgical debridement is conducted to remove the necrotic tissue and make adequate drainage. Typically, the debridement boundary should reach the normal fascia, rather than the normal skin. The following repeated surgical interventions are necessary in the case of infection progression or abundant necrotic tissue. In the meantime, worries about the relationship with mortality may also exist. According to an analysis of 19 FG patients, the average number of repeated debridement was 3.5 times/case, which appeared to have no impact on the patient outcome . It is also demonstrated that, those who are destined not to survive cannot tolerate the repeated debridement necessary for survival.
As for wound management, granulation tissue is cultured for further reconstructive treatment. Typically, NPWT is the most commonly applied method, which is advantageous in wound healing with physiological effects . The superiorities of NPWT have been approved by several studies, yet there are still shortcomings, including high expense, fixed difficulties and skin irritation. Further, NPWT is fittable for cases receiving colostomy. In the absence of fecal diversion, NPWT often leaks due to the fecal excretion. In this series, NPWT was applied in the wound located in scrotum, penis, abdomen, thigh, and perianal region with colostomy. For the perianal cases without ostomy, normal dressing changes were adopted. However, the necessity of fecal diversion is still controversial at present. On the one hand, fecal diversion changes the excretion pathway and facilitates nutrition support; on the other hand, it remains unclear whether it can reduce the risk of infection . In our opinion, the decision of fecal diversion should be made after taking patient conditions and disease progression into full consideration. There is no need to perform forced ostomy for the convenience of NPWT.
Diverse ways can be selected for wound closure, including secondary healing or suture, flaps and skin grafts. But a primary concern is focused on the closure of scrotal defect, given the long-term function of testicle and spermatogenesis. Skin graft is denounced for contraction and abrasion, regardless of its simple procedure and fewer complications. At the same time, the flap derived from the disruption of scrotal thermoregulation with thick flap or thigh testicular transposition is also a source of concern . At present, robust evidence and long-term observation are warranted to conclude an ideal way for scrotal defect closure. An advisable choice of reconstructive procedure should be made based on the individual characteristics, patient preference and surgeon experience. As shown in Table 1, for small scrotal defect (less than 50%), advancement flap or secondary suture was adopted because the scrotal skin was elastic and stretchable. By contrast, the split-thickness skin graft was adopted for larger defect, and pudendal-thigh flap was used in the presence of deep dead space, so as to eliminate the dead space in scrotum.
The mortality in this paper seemed to be much lower than that in previous report. However, this mortality rate was underestimated, since the abandoned cases were excluded according to our inclusion criteria, while they were suspected with a high probability of death. Up to the present, the mortality is considered to be stable, since no obvious evolution is attained in the existing treatment measures for infection control. It is advisable to make efforts to prevent and diagnose FG early. Moreover, the multidisciplinary cooperation model should be adopted in future treatment, including anorectum surgery, urology, infection department and critical care medicine.
Obviously, the shortage of this study is the limited cases, which is much attributed to the lower incidence rate of FG compared to necrotizing fasciitis in other regions. While our aim is to summarize the treatment experience, and make improvement for further treatment. Moreover, adjunctive hyperbaric oxygen was not applied in this study. Although it was reported with a decrease of mortality rate in FG patients after hyperbaric oxygen therapy, the studies were mainly case reports. Due to the shortage of randomized controlled trials and robust theoretical support, further application of hyperbaric oxygen therapy is still limited .