Department of Nephrology, Kent and Canterbury Hospital, Canterbury, UK
Case
A 46-year-old Caucasian male presented to casualty with a 3-day history of sweats, diarrhoea, vomiting, fainting episodes and increasing breathlessness. On the day of admission, he awoke with bilateral leg pain associated with a rash affecting his lower limbs. Past medical history included peripheral vascular disease, hypercholesterolaemia and a bipolar affective disorder. Medication prior to admission was dothiepin, simvastatin and aspirin. He smoked 10 cigarettes per day and consumed up to 36 units of alcohol per week. On admission, clinical examination revealed him to be alert and orientated though dyspnoeic, febrile 37.6°C, centrally and peripherally cyanosed with a coalescent purpuric rash on his legs. He had a sinus tachycardia at 120 per min, blood pressure 80/60 mmHg, no pulses palpable below his femoral arteries and no peripheral oedema. Respiratory rate was 15 per min, chest auscultation revealed good bilateral air entry with no added sounds. Abdominal examination was unremarkable.
Initial laboratory investigations were as follows: sodium 137 mmol/l, potassium 3.7 mmol/l, urea 20.8 mmol/l, creatinine 483 µmol/l, glucose 4.7 mmol/l, albumin 22 g/l, total bilirubin 22µmol/l (<22 µmol/l), aspartate aminotransferase 930 IU/l (<50 IU/l), alkaline phosphatase 55 IU/l (<126 IU/l), amylase 50 IU/l (<110 IU/l), corrected calcium 1.84 mmol/l, phosphate 2.32 mmol/l, CPK 2273 IU/l (<170 IU/l), CK-MB fraction <7%, haemoglobin 14.8 g/dl, white cell count 20.6x109/l (92% polymorphs) and platelets 27x109/l. A blood film failed to demonstrate schistocytes, clotting was mildly deranged with prothrombin time 13 s (control 13 s), activated partial prothrombin time 56 s (control 31 s) and fibrinogen 0.5 g/l (<0.4 g/l). Chest X-ray was normal.
A provisional diagnosis of acute renal failure secondary to septicaemia was made. He was admitted to ICU where despite fluid resuscitation, inotropic support and broad-spectrum antibiotic treatment (cefotaxime, benzyl penicillin and metronidazole) he remained hypotensive, developed oligoanuria and required haemofiltration within 24 h of admission. There was further deterioration with development of lower limb digital gangrene and ARDS requiring ventilatory support 72 h after admission. A Gram-negative bacillus was grown from the initial blood cultures 48 h post-admission. Recovery was delayed though the inotropes and ventilatory support were eventually discontinued 25 and 28 days post-ICU admission respectively. He remained dialysis-dependent. Six months after this admission he remains stable and is maintained on continuous ambulatory peritoneal dialysis.
Questions
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This patient presented with acute renal failure secondary to septic shock. A wide range of pathogens are implicated in septicaemia which in order of decreasing frequency are: Gram negative, Gram positive, and anaerobic organisms. The aetiological factor in this case was a Gram-negative bacillus. Common potential pathogens that one should therefore consider in rank order of frequency are; Escherichia coli, Klebsiella, Pseudomonas aeruginosa, Serratia, Enterobacter and Proteus. The association of cutaneous manifestations with Gram-negative septicaemia are most commonly associated with P. aeruginosa which may produce a bulls eye type lesion with a rim of indurated erythematous tissue and a central vesicle or necrotic ulcer. A wide range of cutaneous lesions may be associated with E. coli, Klebsiella, Enterobacter and Serratia such as ecthyma lesions, vesicular or bullous lesions, cellulitis and occasionally diffuse erythematous reactions or showers of petechial lesions. Additional information is required from the patient to assess risk from such infections. Thus, an assessment of alcohol history, sexual history and transfusion history might be indicated. A contact history should be sought including occupation, pets and recent injuries.
The diagnosis in this case was obtained by characterization of the Gram-negative bacillus isolated from blood cultures as Capnocytophaga canimorsus, formerly designated Dysgonic fermenter 2 (DF-2) which is a commensal bacterium of dogs and cats saliva. Further questioning of the patient revealed that he had been licked by his dog on an open hand wound approximately 1 week prior to presentation.
Infection with C. canimorsus usually results following a bite (54%), scratch (8.5%), or mere exposure (27%). Infection can occur in all individuals although immunocompromised individuals such as asplenics (33%), alcoholics (24%) and immunosuppressed (5%) are more susceptible. Up to 40% of septicaemic patients may have no such predisposing factors [1]. Capnocytophaga canimorsus infection can produce a wide range of clinical illness from eye involvement to fulminant septicaemia [24]. Clinical presentation includes non-specific symptoms such as fever, chills, abdominal pain, diarrhoea, and vomiting. Common clinical and laboratory findings include a rash, which may be macular, maculopapular or purpuric in nature, leukocytosis, features of disseminated intravascular coagulation, and renal failure [1]. Haemolytic uraemic syndrome and thrombotic thrombocytopenic purpura have also been described [5,6]. Capnocytophaga canimorsus is sensitive to a wide range of antibiotics including penicillins, cephalosporins, chloramphenicol, and clindamycin. Nevertheless infection continues to carry a high mortality.
In the case of this patient despite receiving initial appropriate antibiotic therapy, he still progressed to acute renal failure with the development of lower limb digital gangrene. The latter may have been aggravated by his pre-existing peripheral vascular disease. At presentation he had septic shock with a developing coagulopathy. The acute renal failure was most likely due to acute tubular necrosis secondary to pre-renal insult and sepsis. The lack of recovery of renal function probably indicated concomitant cortical necrosis.
Notes
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References