Introduction

Fever in a post renal transplant setting is a challenging medical problem. Nuclear methods using scintigraphy with Indium or Technetium labelled leucocyte scan or Gallium citrate have been validated for the diagnosis and detection of inflammatory processes. Recently, positron emission tomography with 18F-fluorodeoxyglucose (FDG) has been shown as a promising imaging method, especially for fever with undiagnosed aetiology. We report the use of FDG-PET in a post renal transplant patient.

Case Report

A 22 year old man, 6 years post renal transplant (donor being mother), on Prednisolone 5 mg/day and Mycophenolate mofetil 2 gm/day, presented with a 2 day history of fever with chills.

Serum creatinine on admission was 1.8 mg%, baseline being 1.5 mg%. The patient showed no response to empirical antimalarial and broad spectrum antibiotic.

On the 5th post admission day, he developed altered behaviour including sexual disinhibition. EEG, CT and MRI Brain, and CSF studies were all normal. Fever workup, including cultures and CMV PP65 antigen, was negative.

A dual phase (early and late) whole body PET scan with 18F-FDG was performed to localize the source of fever as Indium or Technetium labelled leucocyte scan and Gallium scan were not immediately possible due to logistic reasons. Early and delayed phase of the whole body PET scan revealed two hypermetabolic foci in jejunum and one at the ileocaecal junction, which did not change position in the delayed phase, suggesting the possibility of infective foci. A long colonoscopy revealed a friable and oedematous mucosa of the terminal ileum. The biopsy revealed nodular rather than monomorphic dense lymphoid infiltrate in the lamina propria of the terminal ileum. The immunohistochemistry was positive for CD20 and CD3 but negative for CD10 - all suggestive of a reactive lymphoid process rather than Post transplant lymphoproliferative disorder, which was the alternative diagnosis.

The bone marrow biopsy revealed a solitary non caseating granuloma.

The fever persisted and the patient developed melaena which was severe and haemoglobin kept dropping despite transfusions. Therefore videoendoscopy was done which revealed diffuse small intestinal bleeds.

A laparoscopy assisted enteroscopy was performed under general anaesthesia. 3 inches of distal ileum were resected and end to end anastomosis was performed.

The biopsy of resected ileum showed extensive mucosal ulceration with distinct granulomas in one lymph node – all suggestive of Tuberculous Ileitis. Hence, anti tuberculous treatment was started – Isoniazid, Rifampicin, Ethambutol and Ofloxacin.

Fever promptly subsided, but melaena persisted for a week.

Meanwhile, the patient developed thrombocytopenia, which was refractory to platelet transfusions. However, when Rifampicin was withdrawn, the platelet count recovered.

Serum creatinine reduced to 3.5 mg% from a highest value of 3.7 mg%, fever and melaena subsided and the patient was discharged.

His serum creatinine was 1.9 mg% on last follow up, 2 months after being discharged.

Discussion

The points of interest in this case are:

Fig: 1

1. That a PET Scan was used to localize a focus of Chronic Infection.
FDG has been shown to accumulate in malignant tumours but also in inflammatory processes. This case suggests that FDG-PET is a valuable tool for the detection of occult inflammatory/infective foci, especially when factors like time needed for examination and exposure to intravenous contrast are to be considered. It is also proposed that in the context of undiagnosed fevers, FDG-PET may be superior to Gallium citrate SPECT. This seems to be the consequence of superior tracer kinetics of FDG compared with those of Gallium citrate and of a better spatial resolution of a PET system compared with SPECT imaging.
2. Intestinal Tuberculosis manifested in an unusual way in the form of melaena, which was extremely difficult to manage because the bleeding was diffuse and compounded by Rifampicin induced thrombocytopenia.

References

1. Juri Ruf, Boris Griebenow, Brigitte Stiller, Nanette Sarioglu, Peter E Lange, Holger Amthauer. Detection of infectious colitis by 18 F-fluorodeoxyglucose-positron emission tomog-raphy in a child receiving intensive care after cardiac surgery. Pediatric Radiology 2005; 35 : 7.
2. Andreas Kjaer, Anne-Mette Lebech, Annika Eigtved, Liselotte Hojgaard. Fever of unknown origin: prospective comparison of diagnostic value of 18F-FDG PET and 111indium-granulocyte scintigraphy. European Journal of Nuclear Medicine and Molecular Imaging 2004; 31 : 5.
3. Meller J, Altenvoerde G, Lehmann K, Sahlmann C, Becker. Fever of unknown origin: Prospective comparison of 18F-FDG imaging with a double head coincidence camera and 67Ga citrate SPECT. Nuclear Medicine Communications. 2001; 22 (10) : 1158-9.

*Department of Nephrology; **Department of Nuclear Medicine; ***Department of Gastroenterology; +Department of Surgery; ++Hon. Haematologist, Bombay Hospital and Medical Research Centre, Mumbai 400 020.