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Atypical cellulitis

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Q1: What are the computed tomography findings in figs 1 and 2? (see p 434)

Figure 1 is a section through the perineum and upper thigh showing a right vaginal hydrocoele with normal testis.

Figure 1

Barium enema showing polypoidal growth in the caecum.

Figure 2 is a section through the lumbar area showing retroperitoneal gas, fluid, and necrotic tissue displacing the right kidney anteriorly but both kidneys look normal.

Q2: What is the most likely diagnosis?

Right sided retroperitoneal abscess/necrotising infection, which is extending into right groin with secondary hydrocoele.

Q3: What should be the next step of management?

The patient should be rehydrated and should receive intravenous high dose combination antibiotics to start with and then should be taken to theatre for radical surgical debridement and drainage of pus/necrotic tissue. Finally further investigations are required to identify the source of infection.

Discussion

We treated this patient initially with high dose broad spectrum antibiotics and intravenous fluid therapy with a provisional diagnosis of pyonephrosis and right epididymo-orchitis. The plainx ray film of the abdomen was unremarkable and there was no evidence of any renal stones. The next morning computed tomography (with intravenous contrast but no oral contrast) revealed retroperitoneal necrotising infection but without any definite source. The patient was taken to theatre and underwent a right orchidectomy along with debridement of retroperitoneal necrotic tissue extraperitoneally via a separate lumbar incision. During operation we found more necrotic tissue and milky fluid rather than frank pus. Urgent Gram stain showed the presence of Gram positive cocci and bacilli. He was started on high dose benzylpenicillin, metronidazole, and flucloxacillin along with parenteral feeding. Subsequent intravenous urography was normal but a barium enema (fig 1, right) revealed a polypoidal growth in the caecum. Laparotomy and right hemicolectomy was performed for a locally invasive adenocarcinoma of caecum with small intraperitoneal tumour deposits. Eventually he was discharged home after two months of hospital stay.

In summary, this man had retroperitoneal necrotising fasciitis (RNF) due to locally perforated carcinoma of the caecum. RNF is a rare variety of synergistic soft tissue infection of retroperitoneum. Bowel perforation (carcinoma, perforated diverticular disease, or undiagnosed strangulated hernia) and urinary extravasation are commonly found as predisposing pathology. RNF is very difficult to diagnose in its early stage. A Medline search has revealed only three published articles on RNF.1-3 Almost all of the patients presented with abdominal wall, groin, and/or inner thigh cellulitis with or without cutaneous gangrene. All of their patients were very ill systemically with severe pain being a key diagnostic symptom. Computed tomography has been found to be a very useful diagnostic tool and if any bowel lesion is not evident on computed tomography, patients should have a barium enema or colonoscopy. When in doubt, aspiration of tissue fluid and urgent Gram stain can be very useful. Frozen section biopsy of the necrotic area has been found to be of good value for early diagnosis.4 Bacteriology usually reveals mixed growth of aerobic and anaerobic organisms, of which commonly found organisms areStreptococcus faecalis,S milleri, coliforms, and bacteroides spp. Prompt and radical surgical debridement of retroperitoneal tissue is the key treatment and quite often repeat debridement is required.2 High dose combination antibiotics are life saving. Hyperbaric oxygen has been found to reduce the mortality and need for repeat debridement,5 6 but its role is still controversial.

Mortality is very high (range 37%–80%) depending on the extent of infection. The great majority of patients, who had laparotomy to deal with bowel pathology and retroperitoneal necrosis at the same time, died in the early postoperative period because of septicaemia and subsequent multiorgan failure.1 Our patient went home and is still alive and well six months after surgery. We believe this is because in first stage we debrided retroperitoneal tissue extraperitoneally and subsequently we dealt with the primary pathology intraperitoneally.

Learning points

  • Retroperitoneal necrotising fasciitis (RNF) is a rare but fatal condition.

  • Any atypical cellulitis of the abdominal wall, groin, and inner thigh should be treated suspiciously.

  • If in doubt computed tomography is a very good tool to diagnose RNF.

  • Early and radical surgical debridement is essential with a view to redebridement.

  • If RNF is diagnosed, a bowel lesion should be sought for.

Final diagnosis

Retroperitoneal necrotising fasciitis due to locally perforated carcinoma of the caecum.

References

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