The presence of visible gas on radiographs is associated with various
pathological conditions, ranging from severe infections caused by
gas-producing organisms to cutaneous and subcutaneous tissue disruption that
allows an interface with the air. A high index of suspicion surrounds the
finding of gas on radiographs because of the virulence of conditions such as
gas gangrene and necrotizing fasciitis.
We report a case in which proximal spread of gas in the soft tissues was
not due to a spreading infection but rather to a cutaneous ulcer that, during
walking activity, possibly acted as a one-way valve, allowing air to dissect
proximally. To our knowledge, this mechanism of gas spreading in the soft
tissues has not been reported previously. Our patient was informed that
information concerning the case would be submitted for publication.
Afifty-nine-year-old man with type-1 diabetes mellitus presented to our
clinic for the treatment of a forefoot ulcer, under the area of the great toe,
that had been present for more than five months. There was a history of a
continuing serous discharge and increasing erythema during the week prior to
presentation. Physical examination demonstrated swelling with erythema on the
dorsum of the forefoot. The ulcer, located under the area of the first
metatarsophalangeal joint (Fig.
1), was approximately 4 × 2 cm in size and exhibited no
malodor or frank pus. Testing with a 5.07-g monofilament revealed a lack of
protective sensation distal to the level of the ankle, but the patient had a
palpable dorsalis pedis pulse and good capillary refill in the toes. Movement
of the great toe at the metatarsophalangeal joint caused bubbles to appear at
the base of the ulcer. The patient had no systemic symptoms, and the body
temperature was 98.6°F (37°C). Blood tests revealed a hemoglobin level
of 12.9 g/dL (129 g/L); a total white blood-cell count of 6.3 ×
109/L with 45.3% granulocytes, 37.5% lymphocytes, 9.4% monocytes,
6.5% eosinophils, and 1.3% basophils; a serum sodium concentration of 139
mmol/L; a serum potassium level of 4.2 mmol/L; a serum urea nitrogen level of
15 mg/dL (5.4 mmol/L); and a serum glucose level of 198 mg/dL (10.99 mmol/L).
Radiographs and magnetic resonance imaging revealed gas in the soft tissues
not only in the vicinity of the ulcer but also much more
proximally—i.e., in the soft tissues of the midfoot dorsally and at the
level of the ankle anteriorly (Figs. 2-A
and 2-B).
Because of the possibility of gas gangrene or necrotizing fasciitis, the
patient underwent surgical débridement and irrigation of the ulcer in
the operating room. He was managed with intravenous administration of
clindamycin and levofloxacin and with inpatient observation. Cultures of
specimens taken from the wound were evaluated for both aerobic and anaerobic
bacteria and revealed a moderate growth of coagulase-negative Staphylococcus
species only. Throughout the admission, the patient remained afebrile and
exhibited no constitutional signs relating to a systemic infection, and the
ulcer continued to heal over the course of the hospital stay. A weight-bearing
total-contact cast was applied, and the patient was discharged on the third
postoperative day. By four weeks, uneventful healing of the ulcer had
occurred, and no more gas was seen in the soft tissue on subsequent
radiographs.
This case demonstrates the need to correlate the radiographic finding of
gas with the clinical findings at the time of presentation. Automatically
associating radiographic evidence of gas with gas gangrene or necrotizing
fasciitis in the presence of an infected foot ulcer is unwarranted if the
patient does not exhibit the appropriate constitutional symptoms and if the
ulcer or wound does not exhibit other features of an acute infection locally.
Several investigators have defined the presenting characteristics of
necrotizing fasciitis in an effort to increase the accuracy of diagnosing
myonecrotic gas-producing
infections1-4.
Fisher et al. reported that 80.7% of patients with a diagnosis of necrotizing
fasciitis were
febrile1. Tang et
al. found that 79.2% of patients who were diagnosed with necrotizing fasciitis
were in toxic shock and that all patients had severe pain at the wound
site2. Schmid et al.
showed that the absence of a hyperintense signal on T2-weighted magnetic
resonance images excluded the presence of necrotizing
fasciitis3. Wall et
al. found that patients admitted with a diagnosis of necrotizing fasciitis who
had a white blood-cell count of =15.4 × 109 /L or a serum
sodium concentration of <135 mmol/L had only a 1% chance of exhibiting
necrotizing fasciitis. They recommended observation without surgery in such
cases4.
Our patient was afebrile throughout the admission and exhibited no
constitutional signs of infection. The blood tests revealed a normal white
blood-cell count of 6.3 × 109/L and a serum sodium
concentration of 139 mmol/L. Cultures of specimens from the wound demonstrated
the growth of coagulase-negative Staphylococcus species only, which has not
been reported to be associated with gas-forming sequelae.
The clinical presentation of our patient was not typical of that seen in
patients with a diabetic ulcer associated with gas gangrene. No malodor or
substantial local purulence was seen at the time of the physical examination.
We did observe air bubbles at the ulcer when the first metatarsophalangeal
joint was moved; however, we postulate that the ulcer in this patient was
acting as a one-way valve, entrapping air and causing it to spread along the
tissue planes proximally, to the level of the ankle.
Gas dissecting into the soft tissues as a result of bacterial activity,
especially in a diabetic patient, is an extremely serious situation that can
threaten both life and
limb5. Gas gangrene
and necrotizing fasciitis can cause necrosis of tissues in the limb and
systemic shock with multiorgan failure within a matter of hours. Diligent
examination and close observation are therefore important. If there are other
signs of infection in addition to gas in the soft tissues (e.g., cellulitis
surrounding or spreading from an ulcer, malodor, a foul discharge, necrotic
tissue, or signs of systemic illness), then the gas should be considered to be
due to bacterial activity and urgent aggressive treatment should be initiated.
Management of a patient with such symptoms may require hospital admission for
intensive care, resuscitation, intravenous administration of broad-spectrum
antibiotics, and surgical débridement of all necrotic tissue,
fasciotomies, or even, on occasion, a life-saving
amputation6-8.
Although a high index of suspicion should accompany the detection of gas on
radiographs, the case of our patient illustrates the importance of correlating
this finding with the clinical presentation to avoid unnecessary radical
treatment. It is important to bear in mind that gas detected in the soft
tissues may not necessarily indicate bacterial activity but may instead
represent gas that has spread by way of a mechanical means from an ulcer.
?