A Neglected Flexor Sheath Infection in an Immunosuppressed Transplant Recipient

All four Kanavel signs are present: fusiform swelling, the finger held in slight flexion, tenderness along the whole flexor sheath, and pain on passive extension. This is pyogenic flexor tenosynovitis of the index finger, a closed-space infection in which raised sheath pressure rapidly compromises the flexor tendon's blood supply. The differential includes a superficial cellulitis, a deep-space infection, a paronychia or felon, and, given the aquatic exposure, atypical infection with Mycobacterium marinum or Erysipelothrix; herpetic whitlow is unlikely without vesicles.

A 14-hour delay to a morning clinic is unacceptable. The critical determinants here are the immunosuppression and the diabetes. Prednisolone and mycophenolate blunt the classical signs of sepsis and impair phagocytosis and lymphocyte function, and poorly controlled diabetes adds microangiopathy and a high risk of rapid necrosis. His temperature of 38.3 °C with a normal blood pressure does not mean he is stable; in an immunosuppressed patient this can be an early picture before a rapid decline. There is a real risk of tendon necrosis, digital stiffness, osteomyelitis and amputation.

The correct action is admission and intravenous antibiotics started after blood cultures and, ideally, sheath aspirate for Gram stain and culture, with surgery on the next available emergency list and certainly within hours. As the registrar, I would escalate to the consultant on call for hand surgery and to the transplant team, book an emergency theatre slot, and not accept an elective list as a reason for delay. I would also take wound swabs before antibiotics and ask specifically about fish-tank exposure and any prior similar infection, since atypical organisms change the whole antibiotic strategy.

The operative aim is to decompress the sheath, obtain tissue for culture and remove necrotic material. I would use a mid-axial or Brunner incision over the whole sheath, open the sheath along its length, send fluid and synovium for Gram stain, bacterial culture, fungal and mycobacterial culture, and inspect the tendon for loss of gliding, discolouration and rupture. Frankly necrotic tendon should be excised and the rest left in continuity. The sheath should be left open or loosely closed with a drain rather than tightly closed, and the wound managed with dressing changes. I would not rely on percutaneous catheter irrigation alone in an immunosuppressed diabetic with four Kanavel signs, because it does not allow direct inspection of the tendon.

Antibiotic choice must cover staphylococci, streptococci, Gram-negative organisms and, because of the fish-tank injury, atypical organisms. A pragmatic empirical regimen is intravenous flucloxacillin or vancomycin if MRSA is prevalent, plus piperacillin–tazobactam or ceftriaxone with metronidazole, with doses adjusted to his creatinine clearance of around 30 mL/min. Mycophenolate should be held in discussion with the transplant team to allow lymphocyte recovery, but tacrolimus should usually be continued and the level monitored, because dialysis or rejection is a far bigger threat than the finger. Prednisolone should not be stopped abruptly and should be continued at least at his maintenance dose, with consideration of stress dosing for surgery.

The antimicrobial plan should be narrowed as soon as cultures are available, and mycobacterial infection needs weeks of combination therapy, usually with clarithromycin and ethambutol, so a negative standard culture at 48 hours does not exclude it.

After the infection is controlled, the tendon will adhere and the finger will be stiff unless movement is restored early. The classic reason for poor results is immobilisation. Once the wound is clean and the tendon is intact, I would involve a hand therapist for early controlled active range of motion, with the finger splinted in extension between exercises and never left in flexion. If the tendon is not intact, it needs a staged approach with a silastic rod and later grafting. Oedema control, elevation, and management of the diabetic control with the medical team are part of the plan. Stiffness is likely, and he should be told that the finger will probably not be normal.

Counselling must be honest about the risks: amputation of the digit, need for repeat debridement, spread to the deep spaces of the hand, and a 1–2% mortality for established flexor sheath infection that rises in immunosuppressed and diabetic patients. He should also be warned that atypical organisms can present weeks later, so he must return if the finger becomes red again after apparent recovery.

The pathway change is the most important part of this case. An immunosuppressed diabetic with four Kanavel signs should be directed straight to a senior hand surgery opinion, not to a routine clinic. I would propose a documented referral standard, teaching for emergency staff on the four signs, a nurse-led telephone hotline for hand infections, and an audit of time to theatre, reporting the results to the department. The finger may still be saved, but the process is what determines the next patient's outcome.