infection belongs to the most common complications after human stem cell transplantation ( hsct ) and constitutes one of the major causes of transplantation - related mortality . immune deficiency , which persists after hsct for over a year , can be the cause of an atypical and sometimes abrupt course of infectious diseases , characterized by rapid multi - organ spread of pathogens and their resistance to treatment . severe infections at later stages after transplantation ( 100 days after hsct ) are observed in 4080% of patients . infections caused by atypical intracellular opportunistic bacteria ( including listeria spp . , nocardia spp . or bartonella spp . ) , which are usually responsible for late post - transplantation infections , pose a diagnostic challenge . since their culture is difficult , the results are usually negative . serological tests are not suitable due to insufficient antibody production , and molecular assays are of limited sensitivity which additionally decreases with the duration of infection . this article presents the crucial role of ultrasound imaging in the establishment of a clinical diagnosis of bartonellosis ( i.e. cat scratch disease ) and implementation of effective therapy in a patient after allogenic hsct with severe atypical infection involving multiple organs . a seven - year - old girl received hsct from an unrelated donor due to severe aplastic anemia . after five months , during which the patient received immunosuppressive therapy , she was admitted to hospital due to fever with no other significant signs . multiple bacterial cultures , microbiological and parasitological tests as well as molecular tests for infections with pneumotrophic viruses , cytomegalovirus or epstein - barr virus were negative . imaging examinations of the chest , abdomen and paranasal sinuses ( us , ct , mri ) revealed no changes . empirical broad - spectrum antibiotic therapy , which was modified several times , and anti - fungal treatment were ineffective . hectic fever with 34 peak episodes up to 3940c daily persisted for 4 weeks and crp reached 195 mg / l . repeated microbiological and molecular tests extended to detect atypical pathogens were still negative . in the fourth week of hospitalization , abdominal us , ct and the lesions were round or oval , homogeneously hypoechoic / hypodense with the size from several to several dozen millimeters ; they were not found to be vascularized . us showed deformation of vessels around the foci and hyperechoic contrasting intrusions within the lesions , which grew and multiplied over time ( fig . exclusion of other infections , no response to antibacterial and antifungal treatment , information about pet exposure provided by the parents as well as a typical radiological image of the lesions led to a probable diagnosis of bartonellosis . ultrasound image of the splenic manifestation of suspected bartonellosis : a. disseminated , oval , anechoic and non - vascularized lesions 4 weeks after the onset of fever ; b. more numerous lesions , most of which contain hyperechoic intrusions ; some neighboring lesions fuse  16 day of treatment ; c. regression of the lesions with residual irregular calcifications  after 12 months of treatment long - term combined treatment was implemented : azithromycin and amikacin , followed by doxycycline and amikacin as well as ciprofloxacin and co - trimoxazole . fever subsided , crp was observed to normalize and the lesions within organs regressed gradually . within the subsequent weeks , the patient developed similar painless and non - inflammatory nodules in the cervical lymph nodes , subcutaneous tissue of the arm and thyroid gland ( fig . us revealed that lesions in the organs and soft tissues showed a typical evolution pattern : their size increased to 1020 mm and sometimes they fused with one another . subsequent treatment with azithromycin alternately with cotrimoxazole , which lasted for approximately a year , led to the regression of all organ and subcutaneous foci leaving multiple calcifications . after a year from the conclusion of the therapy , the girl was healthy and remained in a very good physical condition ultrasound image of thyroid involvement in the course of suspected bartonellosis : a. a single oval , anechoic lesion that alters the outline of the gland in the 15 week of treatment ; b. presence of a hyperechoic intrusion in the center ; no new lesions  28 day of treatment ; c. calcification of the lesion after 12 months of treatment cat scratch disease , caused by bartonella henselae , is typically manifested by localized skin lesions , enlarged regional lymph nodes and fever . in immunocompromised patients , the disease can have a severe , systemic course and affect internal organs , usually the liver , spleen and subcutaneous tissue . the multi - focal proliferation of capillary endothelia with the formation of cavernous spaces filled with blood and necrotic tissue results in the development of multiple disseminated nodular lesions in affected organs , which is referred to as peliosis hepatis / lienalis . in imaging , these lesions are multiple , homogeneous and hypoechoic / hypodense , and resemble abscesses or granulomas . the detectability of bartonella infection in immunocompromised patients can be significantly underestimated , which is indicated by the common occurrence of this pathogen . antibodies against b. henselae are found in 81% of cats and in 1948% of people in the general european population . life - threatening multi - organ infection after hematopoietic stem cell transplantation requires rapid therapeutic intervention even when the microbiological confirmation of its etiology is not possible . a probable infection with bartonella can be suspected if at least two of four criteria are met : 1 ) history of cat exposure ; 2 ) detection of antibodies against bartonella ; 3 ) presence of multiple hypoechoic/ hypodense hepatic lesions in imaging ; 4 ) granulomatous or angiomatous lesions with additional positive staining for bartonella 
 . a certain diagnosis requires isolation of bartonella from cultures or detection of its genetic material . these patients presented disseminated organ lesions with similar features to those observed in our patient . b. henselae infection was confirmed in only 13 cases . in the remaining 16 patients , rostad et al . have reported the presence of the same ultrasound image of hepatic or splenic involvement in bartonellosis in 24 organ transplant recipients . moreover , other authors have also presented a similar manifestation of multi - organ bartonellosis . we have not found comparable descriptions of hepatic and splenic imaging that could be observed in the course of other bacterial or parasitic infections . such lesions could be present in candidiasis , which was unlikely in our patient considering the progression of the disease despite intensive anti - fungal therapy , negative microbiological tests and effective treatment targeted to atypical bacteria . since it is difficult to conduct microbiological tests in the course of infections caused by atypical pathogens in immunocompromised patients , repeated ultrasound examinations are useful in the diagnostic process of infective changes in organs . in the case presented above , a clinical diagnosis of bartonellosis was established on the basis of an ultrasound image , which enabled effective therapy .
infections in immunocompromised patients after hematopoietic stem cell transplantation can have a severe and atypical course . 
 some opportunistic pathogens are difficult to detect in microbiological tests , and that is why treatment success depends on an accurate clinical diagnosis . 
 this article presents a case of a 7-year - old girl with severe aplastic anemia treated with bone marrow transplantation with post - transplantation period complicated by persistent , hectic fever , with peak episodes of 3940c , lasting several weeks . 
 repeated microbiological tests failed to reveal the etiological agent , and empirical anti - infective treatment was ineffective . in the fourth week of fever , imaging showed multiple foci resembling abscesses in the patient 's internal organs and , subsequently , in soft tissues . 
 the characteristics of these changes and data concerning environmental exposure led to the clinical diagnosis of cat scratch disease ( bartonellosis ) with multi - organ involvement and enabled the targeted treatment to be implemented . 
 fever subsided and organ lesions regressed . in this case , 
 repeated ultrasound imaging was the basic diagnostic tool that helped arrive at a correct diagnosis and implement effective treatment of this life - threatening complication after hematopoietic stem cell transplantation .