Dr Víctor Lorenzo Sellarés Division of Nephrology University Hospital of Canary Islands Santa Cruz de Tenerife Spain

 

A 55-year-old woman, with chronic renal failure secondary to diabetes nephropathy who has been on haemodialysis (HD) for 7 months, presented with fever, back pain, and progressive paraparesis.

The patient had initiated HD using a temporary non-cuffed double-lumen jugular catheter. A brachial arteriovenous fistula was created in the left arm 3 weeks later, but maturation was slow. Soon after HD initiation the patient presented fever and chills. Catheter-related bacteraemia was considered, and the catheter was removed after the administration a single dose of vancomycin (20 mg/kg). Rapid clinical improvement was observed. A tunnelled-cuffed catheter was placed on the same side. Three weeks later the patient had to be hospitalised due to fever and bacteraemia. Blood and catheter cultures were positive for S. aureus. Catheter salvage was attempted with appropriate antibiotic therapy. Fever persisted and the catheter was exchanged for a new catheter at the same site. Fever and bacteraemia reappeared 3 days later, and the catheter was removed and a single dose of vancomycin was administered. A new tunnelized catheter was placed 2 days later. Thereafter, the outcome was apparently good.

Question 1

Comment to Question 1

Seven months after HD initiation, the patient manifested an insidious low-grade fever. She complained of back pain localized in lumbar spine, and progressive paraparesis. Local tenderness to gentle L2-L3 percussion was observed.
There was no recent history of trauma and no other known precipitating factors or constitutional syndrome. No urinary, lung or digestive focus of infection was detected. Blood biochemistry showed mild leucocytosis with neutrophilia and moderate anaemia (haematocrit 28 %) in spite of high doses of erythropoietin (15000 units per week), and elevated erythrocyte sedimentation rate. Albumin was 3.3 g/L, calcium 9.3 mg/dl, phosphorous 5.6 mg/dl and PTH 257 pg/ml. Transesophageal echocardiography demonstrated no cardiac valvular compromise. The patient received 4 hr, thrice weekly bicarbonate HD using a high-flux dialyser.
Plain film identified destructive changes at the L2 and L3; the endplates of the adjacent vertebral bodies were irregular and poorly defined. The intervertebral disc space appeared severely narrowed. Mild signs of spine arthrosis were detected but there were no other signs of osteopenia. CT scan confirmed vertebral destruction and fragmentation of vertebral endplates.

Question 2

Comment to Question 2

 

Question 3

Comment to Question 3

The following imaging studies were performed in this case:
Gallium imaging (Figure 1) showed a dramatic increase of activity involving the affected vertebral bodies.

Figure 1

MRI demonstrated the following (Figure 2): Decreased signal intensity on T1-weighted images (secondary to oedema) in the vertebral bodies and disc, and loss of the margin between the disc and adjacent endplate. Increased signal on T2-weighted images in the vertebral body and disc. Enhancement of the disc in sagittal post-contrast T1.

Figure 2

Along with the patient history, physical examination and imaging to test the diagnosis of SPONDYLODISCITIS were performed.

Question 4

Comment to Question 4

Follow-up: The patient was hospitalised and initially treated with intravenous antibiotics, including vancomycin and tobramycin. Blood culture proved positive for S. aureus and sensitive to vancomycin. After 6 weeks with weekly i.v. vancomycin the patient experienced a progressive recovery.
MRI was performed one month after completion of antibiotic therapy. Signal and enhancement changes gradually decreased over 8 weeks. She had no recurrence of bacteraemia thereafter, and remains alive and doing well on HD.

Comments
The present case illustrates that silent infection originating from repeated catheter infection can lead to late and distant serious complications. Spondylodiscitis, defined as the combined infection of the vertebral structures and disc space, is a rare but severe late complication of infected intravenous catheter, and the incidence is probably underestimated. Its presence should be suspected in patients with back pain, neurologic symptoms, and the antecedent of infected venous catheters, but requires a high degree of clinical suspicion. Differential diagnosis should include non-infectious inflammatory bone disease and, although rare, metastatic cancer.
Spondylodiscitis is usually caused by haematogenous spread of bacteria from an infectious focus at some distance from the spine. Latency time (the time between catheter removal and symptom appearance) is very variable in our experience, ranging from a few days to nearly one year.
The clinical presentation commonly commences with the insidious development of localized back pain combined with non-specific symptoms such as malaise, fever, or weight loss, and progressive neurological deficit. The routine laboratory tests are usually non-specific. Fever and leukocytosis may be absent. The erythrocyte sedimentation rate is usually elevated. Blood cultures may be negative in 50% of the cases.
The combination of gallium bone scan and MRI, associated with a favourable antibiotic course, indicate spinal infection most reliably. The contiguous involvement of the disc space is the hallmark of pyogenic infection. In degenerative disc disease the end plates are preserved. The signal intensity of a degenerative disc is almost always decreased in T2-weighted images; the reverse of that seen with infection.
Prolonged antibiotic treatment and immobilization of the spine result in the resolution of spondylodiscitis in the majority of cases.
This serious complication is an additional reason to avoid, if possible, temporary venous central catheters for HD.

References (Date of publication order)

Correspondence to:
Víctor Lorenzo
Division of Nephrology
University Hospital of Canary Islands.
38320 Ofra. La Laguna
Santa Cruz de Tenerife, Canary Islands.
Spain
Fax: +34-922-64 43 13
E-mail: lorenzovictor@terra.es