Cellulitis of the right thigh, with gas

Cellulitis involving the lower limb is a common cause of admission to hospital. In instances where cellulitis affects the thigh and groin region, anorectal causes should be sought.

CASE HISTORY

A woman of 69 was admitted after four weeks of rigors, low backache and anorexia. In addition her right hip had been painful for three weeks. There had been no change of bowel habit or abdominal pain. Three days before admission she had been started on trimethoprim by her general practitioner for a possible urinary tract infection. The medical history included hypertension, a pleomorphic salivary gland adenoma (excised one year previously) and rheumatoid arthritis. She was taking co-codamol, lansoprazole, lisinopril and prednisolone (15 mg once daily); she had recently stopped taking methotrexate.

On examination she was pyrexial (temperature 38.4°C) and mildly jaundiced. Her abdomen was soft and non-tender, but the right thigh was erythematous, warm and swollen on the anteromedial aspect from just below the inguinal ligament to the mid thigh. Haemoglobin was 11.5g/dL, white cell count 18.0 × 10⁹/L, bilirubin 41 μmol/L. Cellulitis was diagnosed and she was started on intravenous benzylpenicillin 1.2 g four times daily and flucloxacillin 1 g four times daily. After 48 hours the thigh was slightly less erythematous but the fever persisted. Blood cultures were negative as were antistreptolysin titres. The treatment was changed to intravenous metronidazole 500 mg three times daily and clindamycin 600 mg four times daily and hyperbaric oxygen. After a further three days the cellulitis had spread over the whole thigh, her temperature was 39°C and there was evidence of an underlying soft tissue collection with crepitus. An ultrasound scan revealed gas in the soft tissues from the thigh to the ankle, confirmed by a plain X-ray. On clinical examination of the abdomen and perineum there was still no evident septic focus. Drainage of the thigh abscess yielded a large volume of foul smelling gas and pus, and the incision was extended from the groin to the knee. Most of the pus was subcutaneous; a small amount extended between the muscle groups but there was no evidence of myonecrosis. A tract was seen to be extending extraperitoneally up the femoral canal, with pus coming from above. A drain was placed up the femoral canal and the thigh wound was left open. On culture the pus gave a mixed growth of coliforms, anaerobic flora, streptococcus species and Pseudomonas aeruginosa. A CT scan showed extensive diverticular disease and a gas collection in the region of the right femoral canal closely related to a loop of bowel (Figure 1). At this stage faeces began to emerge from the thigh wound. At laparotomy there was a perforated diverticular mass in the right iliac fossa which had tracked down the femoral canal without contamination of the peritoneal cavity. A Hartmann's procedure was performed, with resection of about 15 cm of diseased sigmoid colon. After sixteen days she underwent debridement of the right thigh wound which was then closed with deep tension sutures. A lymphocutaneous fistula developed but this settled spontaneously. Five months later the colostomy was reversed without complications.

Figure 1.

Axial CT slice at level of hip joint, demonstrating air in soft tissue and tracking in the femoral canal

COMMENT

A possible cause of the gas tracking in the soft tissue was necrotizing fasciitis. However, no debridement of necrotic tissue was necessary during the initial procedure; moreover, necrotizing fasciitis is usually associated with a thin brown exudate rather than a large amount of frank pus.¹ A largebowel origin is more likely, and the perforation might have occurred several weeks earlier, with partial walling off in the right iliac fossa. The patient was insistent about her lack of gastrointestinal symptoms, but the manifestations could have been limited by the steroid she was taking.

Although femoral hernias usually contain omentum or small bowel, occasionally they contain appendix, caecum, testicle, ovary, a Meckel's diverticulum or a caecal diverticulum.²

Previous workers have described necrotizing fasciitis of the abdominal wall secondary to a strangulated femoral hernia containing a perforated sigmoid diverticulum in the presence of a rectosigmoid cancer, though this involved the left femoral canal.³ Necrotizing fasciitis has also been described in the abdominal wall over the right iliac fossa secondary to perforation of a sigmoid diverticulum.⁴ We have not found any previous report of a perforated sigmoid diverticulum presenting with cellulitis and abscess formation in the right thigh.