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Year : 2018  |  Volume : 12  |  Issue : 2  |  Page : 152-155

Prostatic abscess as a cause of pyrexia of unknown origin in posttransplant recipient detected on F18 Fluorodeoxyglucose positron emission tomography/computed tomography

1 Department of Nuclear Medicine and PET CT, Sri Venkateswara Institute of Medical Sciences, Tirupati, Andhra Pradesh, India
2 Department of Radiology, Sri Venkateswara Institute of Medical Sciences, Tirupati, Andhra Pradesh, India
3 Department of Nephrology, Sri Venkateswara Institute of Medical Sciences, Tirupati, Andhra Pradesh, India

Date of Web Publication29-Jun-2018

Correspondence Address:
Dr. V S Krishna Mohan
Senior Resident, Department of Nuclear medicine and PET CT, Sri Venkateswara Institute of Medical Sciences, Tirupati - 517 501, Andhra Pradesh
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/ijot.ijot_5_18

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Renal transplant recipients are at an increased risk for opportunistic infections especially in the first year post transplant. Ascertaining the cause of infection requires an extensive clinical and diagnostic evaluation. Here we report a case of pyrexia of unknown origin (PUO) in a renal transplant recipient, who after extensive conventional evaluation was negative. Later F18 FDG PET/CT detected the cause of fever focus as prostatic abscess. This case has been reported to highlight the utility of F18 FDG PET/CT in post renal transplant setting to evaluate the cause of fever.

Keywords: F18 fluorodeoxyglucose positron emission tomography/computed tomography, prostatic abscess, pyrexia of unknown origin, renal transplant recipient

How to cite this article:
Lolla DP, Krishna Mohan V S, Manthri R, Kalawat T, Lakshmi AY, Kumar V S. Prostatic abscess as a cause of pyrexia of unknown origin in posttransplant recipient detected on F18 Fluorodeoxyglucose positron emission tomography/computed tomography. Indian J Transplant 2018;12:152-5

How to cite this URL:
Lolla DP, Krishna Mohan V S, Manthri R, Kalawat T, Lakshmi AY, Kumar V S. Prostatic abscess as a cause of pyrexia of unknown origin in posttransplant recipient detected on F18 Fluorodeoxyglucose positron emission tomography/computed tomography. Indian J Transplant [serial online] 2018 [cited 2021 May 19];12:152-5. Available from: https://www.ijtonline.in/text.asp?2018/12/2/152/235596

  Introduction Top

Solid organ transplant (SOT) recipients are at higher risk of developing infections and malignancies. This is mainly attributed to the lifelong intensive immunosuppressive therapy the patients receive during and after transplantation, which on the one hand enables survival of graft but on the other hand hampers host immunologic surveillance.[1] The most severe consequences of weakened immune system are severe opportunistic infections and comorbidities, resulting in higher rates of morbidity and mortality.[2]

Although fever is a common clinical condition, it sometimes can be challenging when the patient does not respond appropriately despite standard antibiotics and antipyretics. Under these circumstances, an elaborate search for the underlying pathology is initiated. Pyrexia of unknown origin (PUO) or fever of unknown origin (FUO) was first defined in 1961 by Petersdorf and Beeson as recurrent fever of 38.3°C or higher, lasting 3 weeks or longer, and undiagnosed after 1 week of hospital evaluation.[3]

Imaging with F18 fluorodeoxyglucose positron emission tomography/computed tomography (FDG PET/CT) can detect metabolic changes in malignant and inflammatory cells and is widely used in localizing, staging, and evaluating treatment of malignant diseases. F18 FDG PET/CT is also valuable in diagnosing and monitoring lymph proliferative disorders and a number of nononcologic diseases such as aseptic inflammation and infection.[4],[5]

  Case Report Top

A 33-year-old male with end-stage renal disease, underwent live-related renal transplantation with his father as donor, had an uneventful posttransplant course with a normal graft function. The patient was on triple immunosuppression with cyclosporine, azathioprine, and prednisolone. After 8-month posttransplantation, he presented with fever of 3-week duration, which was of low grade and intermittent. In addition to fever, the patient had significant weight loss. He had no other history of cough, expectoration, loose stools, dysuria, or increased urinary frequency. He had no history of tuberculosis in the past and no contact history.

On examination, he was febrile and pallor. There was no lymphadenopathy, his chest examination was unremarkable, and his abdominal examination did not reveal any tenderness over the allograft.

Laboratory investigations revealed anemia (Hemoglobin (Hb)– 5.6 g/dl), leukocytosis (Total Leukocyte Count (TLC) – 15,100 cells/cubic.mm), graft dysfunction (serum creatinine: 1.62 mg/dl), mild jaundice (serum bilirubin: 1.6 mg/dl), thrombocytopenia with platelet count 0.57 lakh/cubic.mm, erythrocyte sedimentation rate 110 mm/1 h. Other laboratory investigations like serum electrolytes, liver function tests, urine and stool analysis, MP QBC, blood and urine cultures were unrevealing. HBsAg and anti-HCV antibody were negative, and HIV serology was nonreactive.

Chest X-ray was normal, and ultrasonography of abdomen showed mild renal parenchymal disease changes in transplant kidney. Noncontrast CT done was negative (contrast-enhanced CT [CECT] avoided in this case due to contrast-induced nephropathy). In spite of an extensive evaluation, we were unable to detect the cause of fever, which was unremitting for 3 weeks – a classical PUO. Later, F18 FDG PET/CT was done to localize the fever focus.

F18 FDG PET/CT showed the focal area of moderately increased FDG uptake in the left lobe of prostate with no corresponding morphological abnormality on CT with maximum standardized uptake value uptake of 6 [Figure 1].
Figure 1: (a) F18 fluorodeoxyglucose positron emission tomography/computed tomography maximum intensity projection image, (b) Computed tomography, (c) Positron emission tomography, and (d) Positron emission tomography-computed tomography axial images show moderately increased fluorodeoxyglucose concentration involving the left lobe of prostate suggestive of focal abscess

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Considering the diagnosis as prostatic infection patient has been put on broad-spectrum antibiotics (ciprofloxacin 400 mg intravenous (IV) bid and also received metronidazole 500 mg IV qid) within a week, there has been subsidence of fever and the serum creatinine levels returned to normal (serum creatinine- 1.1 mg/dl), indicating the cause of raise in serum creatinine levels to be due to infection.

  Discussion Top

F18 FDG PET/CT detects the metabolic changes far ahead of the morphological changes which are delineable by other modalities, thus aiding early detection of the lesions which may not be apparent on CT. Hypermetabolism in normal-sized diseased lymph nodes can be demonstrated only on PET/CT.[6]

Early identification of metabolic changes by PET before the morphological changes manifested on CECT could explain the relatively low sensitivity of the CECT as compared to F18 FDG PET/CT. Although CECT is the conventional imaging modality of choice, further it is not indicated in postrenal transplant setting due to the risk of contrast-induced nephropathy.

F18 FDG PET/CT has gained importance for the detection of infection in renal transplant patients as activated inflammatory leukocytes show increased FDG uptake in which makes FDG PET a very sensitive imaging modality for diagnosis of infection.

Originally, F18 FDG PET/CT was well-accepted clinical tool for routine assessment of cancer. FDG is a marker of increased intracellular glucose metabolism. Nonspecific 18F FDG accumulation can be observed at the sites of inflammation during PET imaging of patients and evolved into a promising imaging tool for diagnosis of inflammatory and infectious causes. The nonspecificity of 18F FDG is an asset in evaluating patients with FUO because the tracer accumulates in infections, malignancies, and inflammatory diseases – the three principal causes of FUO.

F18 FDG PET/CT has about 90% sensitivity in diagnosing abdominopelvic abscesses, active tuberculosis, atypical pneumonias, renal abscess, focal nephritis, bacterial colitis, diverticulitis, and infected vascular grafts.[7]

Recipients of SOTs have a 6%–10% incidence of opportunistic infections in the Indian subcontinent as against 1.4%–9.4% in the Western countries. The mortality rate in the Indian subcontinent is also very high, ranging from 70% to 100%.[8] This is because of intense immunosuppression, delay in diagnosis and treatment, and overcrowded environment. About 87% of the febrile episodes occurring in the transplant patients hospitalized in the Intensive Care Unit were due to infections.[9] F18 FDG PET/CT has been shown to be clinically useful in up to 70% of these cases with a high negative predictive value of up to 100%.[10]

In the present case of renal transplant recipient, the patient had fever for >3-week duration, and he was evaluated using all the conventional imaging modalities which did not reveal any significant clue in diagnosis.

Finally, he was referred for F18 FDG PET/CT where an infective focus was localized in the left lobe of prostate which is supposed to be an unusual site.

Prostatic abscess is a rare clinical entity in this antibiotic era where diagnosis is difficult from clinical presentation as it mimics several other diseases of lower urinary tract such as dysuria, urgency, and frequency. Prostatic abscess mainly affects diabetic and immunosuppressed patients.[10] Two different etiologic patterns have emerged with effective antibiotic therapy. The first is primary abscess in elderly patients with underlying lower genitourinary tract diseases, predominantly Gram-negative bacterial infection. The second pattern is metastatic abscess to the prostate from a septic focus elsewhere. This group is characterized by Gram-positive bacterial infections, often Staphylococcus aureus.

The signs and symptoms of prostatic abscess are highly variable. The classical findings include dysuria, frequency, and urgency (96%); fever (72%); acute urinary retention (36%); and perineal pain (32%). In our case, the patient did not have any of these symptoms except for fever. Complications of prostatic abscess include spontaneous rupture into the urethra, perineum, bladder or rectum, chronic prostatitis, infertility, and sepsis either due to a late diagnosis or inadequate drainage of the abscess.

Prostatic abscess is an uncommon but relatively serious disease that has the potential for causing problems if not diagnosed at the early stage and treated promptly. Careful clinical examination and imaging modalities may assist in diagnosis. Adequate drainage and effective antimicrobial treatment are the ideal therapy for this disease.

In our case, F18 FDG PET/CT could localize the focus in prostate and aid in the diagnosis. Thus, F18 FDG PET/CT emerges as a valuable technique to manage complications in posttransplant recipient patient, and it can also be considered in patients with FUO and severe unexplained inflammatory syndrome scenarios and where conventional imaging is inconclusive.

The advantage of F18 FDG PET/CT is that it allows for one time whole-body evaluation and multiple foci of infection can be identified on a single scan. Furthermore, functional data with F18 FDG PET/CT are complimentary to anatomical data provided with CT. The other advantage of using F18 FDG PET/CT in patients of renal transplant is the avoidance of CECT preventing contrast-induced nephropathy. F18 FDG PET/CT scan has several advantages over conventional imaging techniques including high spatial resolution and the ability to secure results within a short period of time.[11]

The experience with F18 FDG PET/CT scan should eliminate application of many unnecessary invasive and noninvasive diagnostic techniques for the detection of main disease underlying FUO etiology. Moreover, the availability and cost of PET/CT have suited for making it a modality of choice at our institute with a cost of around 13,000.

  Conclusion Top

F18 FDG PET/CT is better than conventional imaging modalities in making a specific diagnosis in the evaluation of PUO. It also helps in deciding the best possible site for biopsy. From our study, we can infer that F18 FDG PET/CT may be used as an initial noninvasive diagnostic tool for the assessment of patients with PUO, especially in posttransplant recipients. Further, F18 FDG PET/CT study could be cost-effective noninvasive diagnostic modality in the FUO, if used at an early stage, helping to establish an early diagnosis, reducing hospitalization days due to diagnostic purposes, and the repetition of unnecessary tests.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.

  References Top

Denton MD, Magee CC, Sayegh MH. Immunosuppressive strategies in transplantation. Lancet 1999;353:1083-91.  Back to cited text no. 1
Fishman JA. Infection in solid-organ transplant recipients. N Engl J Med 2007;357:2601-14.  Back to cited text no. 2
Petersdorf RG, Beeson PB. Fever of unexplained origin: Report on 100 cases. Medicine (Baltimore) 1961;40:1-30.  Back to cited text no. 3
Vaidyanathan S, Patel CN, Scarsbrook AF, Chowdhury FU. FDG PET/CT in infection and inflammation – Current and emerging clinical applications. Clin Radiol 2015;70:787-800.  Back to cited text no. 4
Münster S, Zustin J, Derlin T. Atypical mycobacteriosis caused by Mycobacterium haemophilum in an immunocompromised patient: Diagnosis by (18)F-FDG PET/CT. Clin Nucl Med 2013;38:e194-5.  Back to cited text no. 5
Mittal B, Kuruva M, Harisankar C, Kashyap K, Singh B, Bhattacharya A, et al. Role of 18F-FDG PET/CT in evaluation of patients with pyrexia of unknown origin. J Nucl Med 2011;52:1371.  Back to cited text no. 6
Meller J, Sahlmann CO, Scheel AK. 18F-FDG PET and PET/CT in fever of unknown origin. J Nucl Med 2007;48:35-45.  Back to cited text no. 7
Gandhi BV, Bahadur MM, Dodeja H, Aggrwal V, Thamba A, Mali M, et al. Systemic fungal infections in renal diseases. J Postgrad Med 2005;51 Suppl 1:S30-6.  Back to cited text no. 8
Singh N, Chang FY, Gayowski T, Wagener M, Marino IR. Fever in liver transplant recipients in the Intensive Care Unit. Clin Transplant 1999;13:504-11.  Back to cited text no. 9
Jang K, Lee DH, Lee SH, Chung BH. Treatment of prostatic abscess: Case collection and comparison of treatment methods. Korean J Urol 2012;53:860-4.  Back to cited text no. 10
Tek Chand K, Chennu KK, Amancharla Yadagiri L, Manthri Gupta R, Rapur R, Vishnubotla SK, et al. Utility of 18 F-FDG PET/CT scan to diagnose the etiology of fever of unknown origin in patients on dialysis. Hemodial Int 2017;21:224-31.  Back to cited text no. 11


  [Figure 1]

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1 Azathioprine/ciclosporin/prednisolone
Reactions Weekly. 2018; 1713(1): 54
[Pubmed] | [DOI]


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